Navitron Renewable Energy and Sustainability Forum

HEAT PUMPS & Geothermal Energy => Heat Pumps => Topic started by: marshman on September 21, 2015, 03:52:49 PM



Title: GSHP Install - opinions please
Post by: marshman on September 21, 2015, 03:52:49 PM
Been considering this for a while. 

House approx 240 sq m,  well insulated (12"+ insulation in loft, double glazed, cavity wall insulation) currently heated by woodburning boiler stove (14kW to water & 8kW to room) driving underfloor heating upstairs and downstairs. Surrounding land of approx 1 acre with good access. Woodburner burns any wood I can find - mainly old pallets.

Looking at changing system because a) woodburner is now 30 years old, b) its getting harder to get the wood and chop it up and c) it would be nice to put the heating on a timer so you don't come home to a cool house in the middle of winter.

Had an EPC done which laughingly quoted space heating requirement of 30546 kWh per year & 3772 kWh per year.

Rang round and got a whole range of quotes up to 30k but one local guy came round and seemed to talk sense his quote is as follows:

21157.50  for

5 ground loops (no slinkies but a total run of 1100m)   -  overdone because we are on a shingle bank and he is concerned ground conditions.

Thermia Diplomat Optimum G2 10 SP  heat pump with built in hot water tank    (predicted heat output 21163 kWh/year heat + 3300 kWh per year to water) SPF 3.97

120ltr buffer tank

Lowara inverter driven booster pump to increase hot and cold water pressure throughout the house

Powerflushing existing UFH ssytem

Includes commissioning and all electrical work.

Questions:

1. Does the price sound right?   - should be straight forward install as easy access to everything with little or no making good to do.

2. Buffer tank and hotwater tank don't seem very big to me. At present we have a massive 500 ltr tank which gets heated once every 2 or 3 days.

3. How reliable will the system be?  (current system is 30 years old and never (never!) given trouble - even got the same circulating pump - it's a simple system!). The pressure booster worries me for a start!

4. Is Thermia a "good" make of GSHP?

Biggest worry is the massive outlay and potential running costs approaching 1000 per year (electric cost) when at the moment the cost is almost 0 - well maybe 100 per year in electric for circulating pump and diesel getting & cutting the wood - my time is free ;)  Also there is the very real danger of the RHI being cut before it is commissioned.

Any info/opinions appreciated.

Roger






Title: Re: GSHP Install - opinions please
Post by: Mostie on September 21, 2015, 04:32:22 PM
Roger, I often wonder if something like this is too complicated for a domestic dwelling and the cost of a failed compressor may frighten you  svengo


Title: Re: GSHP Install - opinions please
Post by: todthedog on September 21, 2015, 04:47:55 PM
What about a new wood burner a tad more efficient, buy in wood. I'm getting too old, and hate chainsawing.
Plus an ASHP, we have one which we use in the shoulder months just in the downstairs about 50m2. Instant heat.
Less fuss and a deal cheaper.


Title: Re: GSHP Install - opinions please
Post by: JonG on September 21, 2015, 05:05:22 PM
That price looks about right pretty much in line with what we would price at for a similar job, but we would offer the NIBE over the Thermia, better control interface, better UK back-up and we have had less issues with NIBE in comparison with Thermia/Danfoss.

NIBE would suggest a 200 litre buffer but it is designed to work differently to your existing system, given that it doesn't store as much energy, more to guarantee flow rate and flow volume and avoid short cycling.

We also fit the Lowara pumps which are very good, you need to keep on top of servicing and especially expansion vessel pressure and integrity.

If the RHI goes it would more than likely be next Spring so could easily be up and running before then?

A good install should last around 20 years but there will be repairs along the way inevitably due to the number of moving bits compared to your existing set up.


Title: Re: GSHP Install - opinions please
Post by: dhaslam on September 21, 2015, 05:50:08 PM
It does seem a little expensive  but  it takes the  away a lot of the work if that is what you want.     The way to keep cost down is to use off peak electricity as far as possible.    It helps if there is a a period of low cost daytime electricity  but  by using your existing tank as a buffer  as well as  the heat capacity  in the floor you should be able to minimize daytime electricity.   My electricity usage   for 2014 was  1278 kWh for the heat pump and  two circulation pumps. Practically all was at off peak rate.   I do use the woodstove as well and that covers about  50% of the heat requirement.  If I was starting again I would  use a non boiler stove  and  bigger heat pump because the stove costs ten times more to run.   

The heat pump you are considering seems to be only available in three phase and has built in immersion which needs to be used with caution.   With a budget of that size it might be better to  use two smaller heat pumps. Applying the  Linbergh rule means double  risk of  failure  with two  but  you would still have sufficient heat in most circumstances with one working while repairs are organized.

           


Title: Re: GSHP Install - opinions please
Post by: brackwell on September 21, 2015, 06:19:08 PM
Presuming you still have your PV then i would use that to power a ASHP via a Immersun programmed to switch a relay when excess leccy exists. A small unit will take a big load of the heating leaving a smaller more efficient wood fire to help with the worst.

The bigger question is how come your EPC threw up such a large heating requirement. Maybe you also need to address this also.

Ken


Title: Re: GSHP Install - opinions please
Post by: marshman on September 21, 2015, 07:56:06 PM
Roger, I often wonder if something like this is too complicated for a domestic dwelling and the cost of a failed compressor may frighten you  svengo

I kind of wonder about this to which is why I am asking for peoples opinions.

What about a new wood burner a tad more efficient, buy in wood. I'm getting too old, and hate chainsawing.
Plus an ASHP, we have one which we use in the shoulder months just in the downstairs about 50m2. Instant heat.
Less fuss and a deal cheaper.

Again have thought about this, a newer more efficient woodburner is a plan "B", one concern is that the logs I can buy in have a lot less heat output than the pallet wood I currently burn - I know I've tried them. see below for comment on ASHP.

Presuming you still have your PV then i would use that to power a ASHP via a Immersun programmed to switch a relay when excess leccy exists. A small unit will take a big load of the heating leaving a smaller more efficient wood fire to help with the worst.

I did get a quote on a ASHP, the saving was not as great as I would have thought. I only got it for comparison. Not overly keen on them as we live right on the coast and I would be worried about corrosion. The only saving is on the ground loops as far as I know. They are not as efficient (though they are  not bad) and the RHI is a lot less. Yes I still have the PV and it's still going really well BUT it's output in the winter when you need the heating is not great - this is not helped by the shallow angle its mounted at. We don't need much heat on the still sunny days, its when the easterly wind gets up and down here that usually means cold and grey and the PV is doing a few hundred watts at best. The other issue with having a wood burner in tandem is the requirement for a heat meter which adds to the cost.

Thanks for the thoughts

Roger


Title: Re: GSHP Install - opinions please
Post by: marshman on September 21, 2015, 07:58:54 PM
That price looks about right pretty much in line with what we would price at for a similar job, but we would offer the NIBE over the Thermia, better control interface, better UK back-up and we have had less issues with NIBE in comparison with Thermia/Danfoss.

NIBE would suggest a 200 litre buffer but it is designed to work differently to your existing system, given that it doesn't store as much energy, more to guarantee flow rate and flow volume and avoid short cycling.

We also fit the Lowara pumps which are very good, you need to keep on top of servicing and especially expansion vessel pressure and integrity.

If the RHI goes it would more than likely be next Spring so could easily be up and running before then?

A good install should last around 20 years but there will be repairs along the way inevitably due to the number of moving bits compared to your existing set up.

Thanks, are you saying the Thermia is less reliable?

Also is the Lowara pump necessary, why not stay with the unvented system - the tanks are already there so why complicate it? - its a question for my guy really but interested to hear other views.

Roger


Title: Re: GSHP Install - opinions please
Post by: marshman on September 21, 2015, 08:09:28 PM

The bigger question is how come your EPC threw up such a large heating requirement. Maybe you also need to address this also.

Ken

Yes, initially not happy about that but its just a number!  It's a stupid quirk of the system. Its a very old property with very thick walls. It has been renovated and has an inner skin of 5" thermal blocks and a 2" filled cavity. However as the EPC guy could not see the blocks or the cavity he has assumed it is a solid wall. The house is also pretty large (240 sq m). I have been told that in a way it is good as the RHI is based on the figure quoted on the EPC and not on reality. As I said in my first post the existing wood boiler keeps the house toasty and in the coldest bits of the winter its going around  6 hours a day, so totally over estimating I get 6 x 20kWh x 180 days = 21000kWh - pretty close to what the estimate from the installer says - not the 30000 odd kWh per year stated in the EPC.

Once I've sorted the heating I will be replacing the windows - currently old wooden (rotten, but draughtproof) 16mm double glazed units with some triple glazed units which will help.

Roger


Title: Re: GSHP Install - opinions please
Post by: brackwell on September 21, 2015, 09:10:57 PM
Roger,

Is it correct that you estimate the electrical cost to run the GSHP at 1000/yr  ie x cop of 3.97 = 3970 worth of heat  ??

I agree a poor EPC is to your benefit if you are claiming RHI but of course the the installation then has to be MCS standard.  The MCS standard is calculated on virtually every room being maintained at 21C so it is easy to reduce your actual requirement below the EPC/MCS value.  I have forgotten now but do you need to have a EPC rating to claim RHI=could this be a problem?

I share your concern regarding ASHP corrosion-bad idea.

Does GSHP work in shingle?  I really dont know but i have some doubts.    If the tubes are packed in heat transmitting material perhaps but does heat travel down from the surface of shingle?

My philosophy is always to reduce the outputs first ie DG and the efficiency ie modern stove perhaps burning half the wood.

Ken


Title: Re: GSHP Install - opinions please
Post by: gravelld on September 21, 2015, 09:43:03 PM
Have you looked into reducing demand? It's all relative of course but I would not call your house "well insulated", it's about the bare acceptable minimum, and that's not talking about air tightness, thermal bridges (sounds like an unusual construction, is the cavity bridged much?) etc. Had a thermal imaging survey done? Can you insulate externally?


Title: Re: GSHP Install - opinions please
Post by: JonG on September 21, 2015, 10:12:31 PM
MCS Standard for a retro is 21 in living and dining, 18 in kitchen, hallways and landings and 22 in bathrooms.

There are differences between NIBE and Danfoss, in terms of the product and the companies. We are installers and service agents for both so have seen them from all sides.

Danfoss had a UK presence which was haemorrhaging cash, Danfoss pulled the plug and a family owned Irish firm (Ashgrove) bought the rights to market Thermia in the UK. They are rebuilding things slowly.

They have brought a better technical knowledge to the product but many installers had lost faith in the interim due to the collapse of the UK support. We have repaired many more Danfoss units than NIBE, but there is a caveat here. Danfoss UK and Ashgrove inherited a stack of 10 year warranty installs from the bad old days which in some cases resulted in premature failure, that said we have had to work on plenty of good installs that also have a high failure rate. Mainly, 3-ports, soft starts, circulators and sadly some compressors.

In all of our NIBE installs we have only had 1 soft start fail and a collapsed flexi on a ground loop circuit. NIBE also offer a 7 year warranty as standard, which you pay for as an option with the Thermia, this is supported by a network of NIBE service engineers, so if your installer is away or busy you still get support.

Performance is very similar, but the Thermia does not allow you to have a set point for HW, it works on a pressure stat on the fridge circuit that cuts out when the HW is at around 48-52 degrees, with the NIBE if you want less than this or higher you can make the choice and/or top it off with the immersion.

If you have a multifunction relay in your inverter you can link it direct to the NIBE and use it to bring it on for HW prep if there is excess generation, I am not aware that this is feasible on the Thermia, a MF relay is about 140 so much cheaper than an Immersun. This is also possible with an IDM unit if you fancy some Austrian bling instead. 

Thermia do have some interesting stuff in the pipeline though like an inverter driven single phase unit,they already have this in the 3-phase products but haven't reworked for 1 phase yet.

In terms of the cylinder you could stay with a vented option fed from header tanks, but you would need an up-sized coil sized to match the flow rate and heat output from the heat pump, but there is a fair chunk of wasted heat in a vented installation due to peculation of heat up the vent, you would also want it as close to the HP as possible to avoid distribution losses and flow rate issues across the coil.


Title: Re: GSHP Install - opinions please
Post by: JonG on September 21, 2015, 10:31:03 PM
Sorry meant to say that the cylinder would need 2 sensor pockets for a Thermia install too.

Our clients have experimented with E7 but due to the long run times on heat pumps they end up using too much higher rate leccy during the day which negates the benefit of the lower rate overnight.

If you have a non-RHI system with multiple options it may work OK , but the rules around metering and bivalents under the RHI make it difficult to design systems of this nature.

If you did decide to go ahead in a post RHI world, we would recommend ditching the ridiculous 100% sizing rule and go with a bivalent.


Title: Re: GSHP Install - opinions please
Post by: marshman on September 21, 2015, 10:38:36 PM
Roger,

Is it correct that you estimate the electrical cost to run the GSHP at 1000/yr  ie x cop of 3.97 = 3970 worth of heat  ??

I agree a poor EPC is to your benefit if you are claiming RHI but of course the the installation then has to be MCS standard.  The MCS standard is calculated on virtually every room being maintained at 21C so it is easy to reduce your actual requirement below the EPC/MCS value.  I have forgotten now but do you need to have a EPC rating to claim RHI=could this be a problem?

I share your concern regarding ASHP corrosion-bad idea.

Does GSHP work in shingle?  I really dont know but i have some doubts.    If the tubes are packed in heat transmitting material perhaps but does heat travel down from the surface of shingle?

My philosophy is always to reduce the outputs first ie DG and the efficiency ie modern stove perhaps burning half the wood.

Ken

Hi Ken,

I think so! the illustration quotes an energy use (i.e input) of around 6150 kWh per year.

Share your doubts about shingle and it's conductivity, however most of it is not "big" shingle it's more like wet dirty pea beach with strips of clay in places. It's difficult as the ground varies enormously from chunks of sold grey clay through dirty peabeach to clean free running shingle. Having said that we are not that much above the water table in fact in the winter the pipes will be mostly in the water table which I think could be a good thing.

Agree about reducing outputs first but the stupid RHI discourages this. You want a high number on the EPC to get maximum RHI (needed to pay for the inflated cost of the installation), then reduce the heat requirement after the installation to save on running costs. Having said that the MCS requirement makes the installation more expensive so in the end all that happens is my head explodes trying to work it all out!  The house has an EPC rating of D (59) according to the report and as it already has loft and cavity insulation as far as I know I am eligible for the RHI. You are correct about the requirement for sauna temperatures in all living rooms but the guy has done the calculations and has sized the heat pump accordingly - i.e. oversized. I suspect if I go ahead and the replace the windows as well the running costs will be a lot less than quoted.

It is not a clear cut decision by any means. Perhaps I should get another quote forgetting RHI and MCS etc and see what that runs out at.

Roger


Title: Re: GSHP Install - opinions please
Post by: marshman on September 21, 2015, 10:50:23 PM
Have you looked into reducing demand? It's all relative of course but I would not call your house "well insulated", it's about the bare acceptable minimum, and that's not talking about air tightness, thermal bridges (sounds like an unusual construction, is the cavity bridged much?) etc. Had a thermal imaging survey done? Can you insulate externally?
The figures given are from the EPC - a box ticking exercise where if there isn't the right box you tick the nearest available one. The house has bits dating back to the late 1700's, its a big 5 bedroom detached house in a very exposed location.  It is well insulated, in excess of 12" of insulation in the loft, double glazed, draught proofed, Solid walls 18" thick, then a 2" filled cavity, then 5" thermal blocks inside that. Of course it can be improved but I at the moment I am trying to juggle EPC figures, RHI/MCS requirements and long term running costs and reliability.

I agree the house could be better but its been wet and windy here all day, no sun, and the outside temp is now down to around 11 deg C. Inside the house is still 20 deg C. No heating on - last time the fire was lit was yesterday for about 2 hours to heat the water. I know there is a lot of thermal mass but given the very exposed location its not that bad.

Roger


Title: Re: GSHP Install - opinions please
Post by: marshman on September 21, 2015, 10:54:32 PM
Sorry meant to say that the cylinder would need 2 sensor pockets for a Thermia install too.

Our clients have experimented with E7 but due to the long run times on heat pumps they end up using too much higher rate leccy during the day which negates the benefit of the lower rate overnight.

If you have a non-RHI system with multiple options it may work OK , but the rules around metering and bivalents under the RHI make it difficult to design systems of this nature.

If you did decide to go ahead in a post RHI world, we would recommend ditching the ridiculous 100% sizing rule and go with a bivalent.

Thanks JonG for taking the time to explain still lots to think about and discuss with the potential installer.

The existing cylinder and manifolds for the UFH are all in the same small room where I want to site the heatpump so long pipe runs are not an issue.

Roger


Title: Re: GSHP Install - opinions please
Post by: brackwell on September 22, 2015, 08:20:36 AM
Roger,

You have been a long time member of this forum and therefore i am sure you have most of the issues in hand.

Standing back and looking at the big picture then i would say that if the RHI payments over the 7yrs meet the installation and running costs then what have you got to loose and you should go for it.  If after 7 yrs you do not like it, well so what dont use it.

Ken


Title: Re: GSHP Install - opinions please
Post by: Bodidly on September 22, 2015, 08:51:09 AM
From the maintenance point of view we are around 8 years in using a GSHP for DHW and part of the space heating with total maintenance costs to date being 0. One of the circulation pumps is getting a bit tired so that's 45 when I change it. Pretty good in my book.


Title: Re: GSHP Install - opinions please
Post by: billi on September 22, 2015, 09:09:00 AM
sure if it sums  up with the RHI ....., still  21000 GBP  is hefty  and  equivialent to   25000 kwh of pv units  per year


Title: Re: GSHP Install - opinions please
Post by: Mostie on September 22, 2015, 12:52:01 PM
.. and you can buy a 10kw ASHP for about a grand, at that price if it broke you could just get another, it wouldn't be worth getting someone to fix it.  stir:


Title: Re: GSHP Install - opinions please
Post by: titan on September 22, 2015, 02:10:18 PM
I have just read through the whole thread and clearly you need to do the maths but I would have thought that an ASHP sized for your actual heating requirement instead of the ridiculous RHI requirements may work out more cost effective than an oversized system which will have to be installed by an MSC approved installer ( expensive). just to get the RHI. You say you are by the coast on shingle, unless it is permanently waterlogged I can't see that being very good as a ground array. However the proximity to the sea should give a frost free environment and probably be a good  location for a ASHP in the UK.


Title: Re: GSHP Install - opinions please
Post by: marshman on December 12, 2015, 09:43:08 PM
Thought I would post a brief update.

After much agonising, discussion, to'ing and fro'ing I went for it.

Basic spec of the system was similar to before:

10kW GSHP
120 ltr buffer tank driving existing underfloor heating
1200m gound loops
300 ltr DHW cylinder -  conventional vented system

Guy who installed it did listen to my concerns over the complexity of the original proposal and I am happy with the solution he installed.

Ground loops were put in at around 1.3 to 1.4m in the shingle (the trenching machine does not like shingle!) but luckily when we got to the back of the field we hit lovely wet clay and got the pipes down to 1.5m and into the water table. So I have just over 600m of the groundloops (about half of each of the four loops) in what I think are ideal conditions - wet clay.

The system was fired up for the first time on Thursday afternoon and has been running ever since. After deep and meaningful discussions about heatcurves and integral figures the initial heatcurve was set at 40 deg C. As we have a good underflooor system I have decided to leave it running 24/7 (i.e. heating is on all the time as it has such a slow response and the house is occupied most of the time. I can balance the flow round the underfloor loops to get an even temperature through out the house. Since then I have dropped the heatcurve to 38 degrees C because the house is simply too warm!  At the moment the pump is running for 20 minutes (using 2.4kW) in every 90 minutes - its around 11 degrees C outside (7 last night).  The house is still on the warm side so will see how it's doing in the morning and will back it off some more. but at the moment I am deeply, deeply  impressed. Heats the hot water up in around 20 mins to 55 degrees C, have made sure all auxilliary heaters are off! Have also installed an Apollo Gem PV power diverter to heat the hot water via the immersion when we have excess PV. 

The ground loops seem OK at the moment - incoming is sitting at 13 degrees C and out going drops to 7 or 8 degrees C, we will see what they are at the end of the heating season!

Some pics are attached.

Roger

(http://s8.postimg.org/pdbch8ig1/gshp_Large.jpg) (http://postimg.org/image/pdbch8ig1/)

(http://s8.postimg.org/coh1xkcbl/inside_done_Large.jpg) (http://postimg.org/image/coh1xkcbl/)

(http://s8.postimg.org/t0r3naqn5/PICT0061_Large.jpg) (http://postimg.org/image/t0r3naqn5/)

(http://s8.postimg.org/ju8t00lep/PICT0080_Large.jpg) (http://postimg.org/image/ju8t00lep/)


Title: Re: GSHP Install - opinions please
Post by: Iain on December 13, 2015, 08:38:30 AM
Hi
You say you have dropped the temps for the heating.
I have my hot water cylinder set to 42 deg C (just a normal cylinder,boiler fed) This is quite hot enough for all we need.
So just wondering if the HW temp can come down a bit, without noticing.

Iain


Title: Re: GSHP Install - opinions please
Post by: marshman on December 13, 2015, 10:12:58 AM
Hi
You say you have dropped the temps for the heating.
I have my hot water cylinder set to 42 deg C (just a normal cylinder,boiler fed) This is quite hot enough for all we need.
So just wondering if the HW temp can come down a bit, without noticing.

Iain
Hi Iain, funny you should say that as this is exactly what I have now done. I have reduced the upper limit. Not as low as 42 though. The tank has two temperature sensors, one at the top and the other mid way down. It is the one midway down that triggers a heating cycle when the tank gets down to 41 deg C at the midway point.  The heat cycle will then run until the whole tank is up to the set temperature. It is this set temperature that I am reducing. There is also a weekly Legionella cycle where the tank is heated to 60 degres C. Never bothered about that before, we will see how it goes but I might delete that. When you say your temp is set to 42 deg C is that on the boiler or on a simple tank stat clamped to the side of the tank?

House still too warm this morning so heatcurve now down to 37 deg C and flow in the UFH loops adjusted again.

Roger





Title: Re: GSHP Install - opinions please
Post by: Bodidly on December 13, 2015, 01:01:16 PM
Slightly confused by your use of the term "heat curve".  I thought the heat curve was was the balance to how much the GSHP compensates for external changes in temperature. Is your heating system going up to 40C? Sounds hellishly hot for a well insulated building or is through rads and not UFH?


Title: Re: GSHP Install - opinions please
Post by: titan on December 13, 2015, 01:40:00 PM
I was wondering also about the term heat curve. The control on my GSHP is done via the return temperature setting which Kensa say is 5 deg C lower than the flow. It is currently set at 29 deg C so the flow is 34 deg C which is fine


Title: Re: GSHP Install - opinions please
Post by: Iain on December 13, 2015, 01:54:32 PM
Hi Roger

Quote
.When you say your temp is set to 42 deg C is that on the boiler or on a simple tank stat clamped to the side of the tank?

My boiler has an electronic temp sensor on the tank/cylinder, it cuts in at 40 deg C and cuts out at 42 degC. A lot more accurate than the mechanical thermostats normally fitted. I adjust the set temp on the boiler panel.

Iain


Title: Re: GSHP Install - opinions please
Post by: marshman on December 13, 2015, 03:44:33 PM
Slightly confused by your use of the term "heat curve".  I thought the heat curve was was the balance to how much the GSHP compensates for external changes in temperature. Is your heating system going up to 40C? Sounds hellishly hot for a well insulated building or is through rads and not UFH?

Sorry Titan/Bodidly I'm a bit new to heatpump terminology but trying to learn fast. The heatpump is a Thermia Diplomat Duo G2 10kW, (apparently similar to Danfoss), Yes the heatcurve as far as I can see is a curve which relates the maximum flow temperature (to the buffer tank and hence heating) to the outside temperature. According to the book of words a 40 degree heatcurve sets the flow at 40 deg C when the temperature outside is 0 degrees C. So if its warmer outside the maximum  flow temp will be less if it is colder then it will be more (up to a preset maximum). Thermia seem to base everything around the heatcurve. There is a Room Temp setting which effectively adds an offset to the curve, 3 degrees C on the curve for every 1 degree C increase in the Room Temp. setting.

The way the pump is operating at the moment when the buffer tank, and hence the water circulating in the UFH drops to around 25 deg C, it fires up and heats the water to what appears to be the temperature set by the heatcurve/current outside temperature (I think!). It then shuts off and sits there until the temperature in the buffer has dropped again. So at the moment it is coming on once for 15 to 20 minutes every 90 minutes or so.  I also think it looks at the rate of heat loss from the buffer tank to determine the current heat load of the house (and therefore the current indoor temperature) and varies the start temperature accordingly. Effectively you have to average out the temperature of the water circulating in the UFH, which I guess is averaging around 28 degrees C at the moment. So yes initially the temp of the water crirculating does hit 40 (or so) degrees C but rapidly drops (decays) to much lower temps. I am letting the system just run 24/7 (including the UFH circulating pump) and tweaking the temperature settings down every morning to allow it time to stabilise, the house has a lot of thermal mass, (huge inglenook and chimney stack and 2 foot thick walls),  when the house starts to get too cold I will know I have gone too far and can then step it back up one notch.

The attached pic is of the flow temp graph taken just after install. It shows the flow temp getting up to around 42/43 degrees C then dropping away down to 25 degrees C before another heat cycle. At that time the heatpump was running for 20 minutes in every hour.

Have attached another close up pic of the trenching machine - impressive bit of machinery. They said if it wasn't for the shingle they could have done all 4 x 300m loops in a day.

Roger
(http://s28.postimg.org/nkbg4tg3t/PICT0064_Large.jpg) (http://postimg.org/image/nkbg4tg3t/)

(http://s22.postimg.org/7h4exkwil/PICT0005_Large.jpg) (http://postimg.org/image/7h4exkwil/)


Title: Re: GSHP Install - opinions please
Post by: JonG on December 13, 2015, 04:56:55 PM
The start time for the heat pump is via the value labelled Integral, which looks at the actual flow temp, required flow temp (as predicted by the curve) and the time elapsed between measurements.

As the integral drops at -60 it recruits the compressor at -600 it recruits the back-up source. As the actual flow approaches the required flow it climbs to 0 and the unit switches off.

Anti cycling is also built in in terms of start intervals.

The Danfoss /Thermia curve is built around a required FT at 0, more usually the FT is set to match the design criteria whatever that may be (i.e. -3 or -4 around here).

Ideally a room unit measures internal temp and adjusts the curve in line with internal ambient, otherwise on a cold windless day the curve may be higher than it needs to be because heat loss is lower.


Title: Re: GSHP Install - opinions please
Post by: Bodidly on December 13, 2015, 05:25:05 PM
No need to apologise Roger just interested as I was never quite sure myself what a heat curve is. Got a quick talk through on ours when commissioned and not really done much to it since setting it up as the darn thing is far smarter than me. Ours is set to a heat curve of 1.5 (whatever that means) and this is tied to the weather compensation software. Basically once we got the heat curve right the house stays at a steady temperature not from guidance from an internal thermostat but from the external temp gauge. Apparently running it this way is more efficient but don't ask me why just what I was told :D

Hope your setup works as well as ours has. You sound like you have ample ground loops which should keep you well supplied with lots of cheap trouble free heat.


Title: Re: GSHP Install - opinions please
Post by: titan on December 13, 2015, 05:55:11 PM
From the other posts it looks like the heat curve is actually some form of weather compensation.My unit has this but it is not used, Kensa say the response is too slow with UFH but OK with rads. Any increase in the flow temperature above 35 will drop the COP.


Title: Re: GSHP Install - opinions please
Post by: Bodidly on December 13, 2015, 06:04:31 PM
From the other posts it looks like the heat curve is actually some form of weather compensation.My unit has this but it is not used, Kensa say the response is too slow with UFH but OK with rads. Any increase in the flow temperature above 35 will drop the COP.

Strange they think it would be to slow. Thought it was devised to give the system time to anticipate a potential change in internal temps before they happen. Certainly works for us but we have IVT unit so maybe different brands behave differently.


Title: Re: GSHP Install - opinions please
Post by: marshman on December 13, 2015, 09:52:23 PM
No need to apologise Roger just interested as I was never quite sure myself what a heat curve is. Got a quick talk through on ours when commissioned and not really done much to it since setting it up as the darn thing is far smarter than me. Ours is set to a heat curve of 1.5 (whatever that means) and this is tied to the weather compensation software. Basically once we got the heat curve right the house stays at a steady temperature not from guidance from an internal thermostat but from the external temp gauge. Apparently running it this way is more efficient but don't ask me why just what I was told :D

Hope your setup works as well as ours has. You sound like you have ample ground loops which should keep you well supplied with lots of cheap trouble free heat.

That is what I'm hoping for my system, will gradual tweak it over the coming weeks and see how it performs. The UFH does respond slowly but with the thermal mass of the house I think the weather/outside temp. compensation should work.

Roger


Title: Re: GSHP Install - opinions please
Post by: marshman on December 13, 2015, 10:04:06 PM
The start time for the heat pump is via the value labelled Integral, which looks at the actual flow temp, required flow temp (as predicted by the curve) and the time elapsed between measurements.

As the integral drops at -60 it recruits the compressor at -600 it recruits the back-up source. As the actual flow approaches the required flow it climbs to 0 and the unit switches off.

Anti cycling is also built in in terms of start intervals.

The Danfoss /Thermia curve is built around a required FT at 0, more usually the FT is set to match the design criteria whatever that may be (i.e. -3 or -4 around here).

Ideally a room unit measures internal temp and adjusts the curve in line with internal ambient, otherwise on a cold windless day the curve may be higher than it needs to be because heat loss is lower.


Thanks Jon , That's what I was attempting to say :)

I did think that there should be some internal temp sensor not only to compensate for wind/rain etc but also changes in occupancy.  At the moment there are four people in the house but over Christmas there will be up to 9 (possibly 11) plus Xmas cooking which has to have a big effect. Will be interesting to see if my theory that the heatpump controller senses the heatload by the rate of heat extraction from the buffer tank.

I need to ask the installer about the possibility of a room sensor - other than the one connected to the largely redundant programmer (set to continuous at the moment). Also I have seen mention of "Tarif Control" which I assume means settings to take advantage of economy 7 - however can't find it in any of the menus - service or user.

Also would like to know more about the Brine flow and return temps and temp differentials.  Mine is incoming at about 13 degrees C and out at 8 or 7 degrees C which is a drop of 5 or 6 degrees which seems a bit high. As far as I can tell the Brine pump is running at maximum. Maybe the ground loops are too good??  As I said still on a bit of a learning curve, but very happy so far.


Forgot to say earlier total install took 8 days from start to finish including the weekend. Ground loops were installed by a sub contractor and took 2 1/2 days in total. All the rest was done by 2 guys in 6 working days. (actually it was only 10 man days as one was off for 2 days).

Roger


Title: Re: GSHP Install - opinions please
Post by: JonG on December 13, 2015, 10:50:35 PM
You would usually have a stat to control system side circulation if the buffer is in parallel and a load compensating control back to the heatppump to refine the curve.

Delta on the brine is ideally 3 but 1200 m is a lot of pipe for a 10kw we would have around 600m up here but obviously ground conditions dictate. What is each loop length?

Also not sure which unit u have but the opti pro has some fuzzy logic that settles the delta over time provided pump is man enough.


Title: Re: GSHP Install - opinions please
Post by: marshman on December 13, 2015, 11:13:34 PM
We had lots of discusion on the loops. We are on a shingle bank with pockets of clay.  The installer recomended oversizing the loops as he was worried about running the loops through lots of shingle. There are 4 loops, each 300m. Separation is better than 1m. 150m of each loop is in wet clay, the rest in dirty shingle.  If the ground array is an issue then I guess I could close 1 or even 2 loops off i  the manifold chamber.

Is too much ground loop an issue?

What's the consequence of a temp difference greater than 3 degrees on brine side?

I suspect the controller does learn and has a bit of fuzzy logic, time will tell. It's a diplomat duo g2.

Roger



Title: Re: GSHP Install - opinions please
Post by: JonG on December 14, 2015, 10:16:26 PM
Hi Roger, too much loop can be an issue (see my comments on the other thread about slinkys in Scotland), but provided the coil rating of the cylinder is high enough should be OK.

We experimented with 300m loops on the Danfoss Opti Pro, which I believe is identical to yours in terms of pump head/flow rate etc. and on the 2 units that we used 300m loops we have had similar delta's, and therefore reverted to 200m runs.

The risk is that if the delta gets too wide you can end up with low pressure errors, (refrigerant cooled too much), it hasn't happened on the 2 we have done but I do keep an eye on it at service or routine visits to the property (it is 2x10kw units cascaded), type of glycol used will impact (ethylene based better) just keep an eye on it as the temps drop and the brine gets more sluggish due to the glycol.

The duo g2 does have a modulating pump with some learning ability so it will take time to settle.


Title: Re: GSHP Install - opinions please
Post by: marshman on December 14, 2015, 10:55:18 PM
Hi Roger, too much loop can be an issue (see my comments on the other thread about slinkys in Scotland), but provided the coil rating of the cylinder is high enough should be OK.

We experimented with 300m loops on the Danfoss Opti Pro, which I believe is identical to yours in terms of pump head/flow rate etc. and on the 2 units that we used 300m loops we have had similar delta's, and therefore reverted to 200m runs.

The risk is that if the delta gets too wide you can end up with low pressure errors, (refrigerant cooled too much), it hasn't happened on the 2 we have done but I do keep an eye on it at service or routine visits to the property (it is 2x10kw units cascaded), type of glycol used will impact (ethylene based better) just keep an eye on it as the temps drop and the brine gets more sluggish due to the glycol.

The duo g2 does have a modulating pump with some learning ability so it will take time to settle.


Thanks for the info Jon. I assume the problem is low flow rate, thus the wide delta. I would have thought that 4 parallel loops would be OK though. They added Fernox HP-15C (monopropylene glycol) at around 33% concentration to the ground loops, (about 350 litres iirc). Wouldn't have been happy using an ethylene based glycol as the pipes are mainly in the water table , we are in an SSSI and next to a bird reserve so I would be worried about any leaks. Apparently propylene glycol is less poisonous, if a little more viscous.  I did have a play with the speed of the brine pump but I didn't see any difference in the deltas.

You are correct about it taking time to settle. Every time I change the heat curve by 1 degree it takes all day to "adjust" the start and stop temperatures and settle down. Its easy to see at the moment as the outside temperature has been fairly constant.

Roger


Title: Re: GSHP Install - opinions please
Post by: dhaslam on December 15, 2015, 01:29:51 PM
The temperature drop of about seven degrees  implies that the flow is only something like 1000 litres per  hour  or about the same as an ordinary circulation pump with 22mm pipes.   The input temperature  of 13C does seem very high, pipe surface readings can be influenced  by a degree or two  by the surrounding air temperature.    High input temperatures  greatly increase efficiency and also improves output.     I have a  buffer tank on  the input side of the heat pump as  well as on the output side.   It means having an extra pump but it does allow the option to run  two heat pumps  or mix input  sources.   The buffer tank allows a  high circulation rate and the temperature differential stays  under two degrees.  One option for me  is a small wind generator connected to an immersion  in the  input buffer tank.   


Title: Re: GSHP Install - opinions please
Post by: Gavferg on December 15, 2015, 02:00:57 PM
I tried much the same pantomine for over a year as apart of the planing process for a complete stone walled cottage refubishment and new build extension for a smaller building up here in scotland and after many many quotes and sales visits the lowest i got was 21.000 , not including the bore holes that seem to be the lastest and only option being offered locally which is likegivingthecompany open access to your bank account until they hit the depth required.It Seems groundloops are dropping rapidly in effiecency arond here after a few years. So we gave up and specified a cheap oil boiler into underfloor heating and spending more insulation and waiting for something better to come along. even the calcs for rhi werent very good running costs were very high. :snow


Title: Re: GSHP Install - opinions please
Post by: titan on December 15, 2015, 04:11:24 PM
I am glad I didn't read this thread before I installed my system, bloody hell it makes a simple system complicated. I have to say I don't think  a GSHP with a UFH needs weather compensation. A modulating gas boiler maybe or GSHP with rads even. The costs associated with GSHP installations just seem to be rising which is a big disincentive for potential users. Why are buffer tanks used with UFH they are not needed, just more expense, pipework, standing losses. A GSHP with UFH should be as simple as it gets for heating, direct flow from the GSHP at 35 deg C ( + or - a few deg) to the manifold no blender needed and controlled by zone stats what could be simpler.

The flow from my ground array is 9.5 Deg C which is the sort of temperature to be expected at this time in the heating season.


Title: Re: GSHP Install - opinions please
Post by: marshman on December 15, 2015, 10:15:02 PM
The temperature drop of about seven degrees  implies that the flow is only something like 1000 litres per  hour  or about the same as an ordinary circulation pump with 22mm pipes.   The input temperature  of 13C does seem very high, pipe surface readings can be influenced  by a degree or two  by the surrounding air temperature.    High input temperatures  greatly increase efficiency and also improves output.     I have a  buffer tank on  the input side of the heat pump as  well as on the output side.   It means having an extra pump but it does allow the option to run  two heat pumps  or mix input  sources.   The buffer tank allows a  high circulation rate and the temperature differential stays  under two degrees.  One option for me  is a small wind generator connected to an immersion  in the  input buffer tank.   

I assume the sensors are properly connected to the pipes and not influenced by the outside air - but you never know. My buffer tank also has an immersion fitted, but its not connected to anything yet. I suspect if I did put some heat into it the controller would get confused and its calculations would get even more fuzzy ;D

I checked the flow rate of the ground loops today at the manifold chamber. Each loop is fitted with a crude flow meter. All loops were reading the same level of flow, as you would expect, and all were showing just above 8 litres per minute. So four loops at 8 litres per minute gives a total of 32 ltrs / min = 32 * 60 = 1920 ltrs per hour minimum.

The heat pump can control, modulate as Jon says, the speed of the brine pump. I have set it to max but this is just the start up speed, not sure if it falls back to what the controller is happy with. I'm tempted to dive in with a calibrated thermometer and measure the flow and return temps direct to see if the displayed temperatures are correct, or even monitor the volts on the pump to see if it is running flat out.

I wouldn't be bothered except everyone seems to be saying the differential is quite large and if it is "stressing" any part of the heat pump I would like to get it sorted to ensure it has a long life!

Roger


Title: Re: GSHP Install - opinions please
Post by: marshman on December 15, 2015, 10:48:05 PM
I am glad I didn't read this thread before I installed my system, bloody hell it makes a simple system complicated. I have to say I don't think  a GSHP with a UFH needs weather compensation. A modulating gas boiler maybe or GSHP with rads even. The costs associated with GSHP installations just seem to be rising which is a big disincentive for potential users. Why are buffer tanks used with UFH they are not needed, just more expense, pipework, standing losses. A GSHP with UFH should be as simple as it gets for heating, direct flow from the GSHP at 35 deg C ( + or - a few deg) to the manifold no blender needed and controlled by zone stats what could be simpler.

The flow from my ground array is 9.5 Deg C which is the sort of temperature to be expected at this time in the heating season.
Hi titan,

The weather compensation is really just the cost of the outside sensor and some software in the controller, doesn't really add to the cost of the system. I agree regarding the buffer tank, it is a waste of space & money, but AFAIK the MCS regs call for it to ensure that the heat pump doesn't cycle too often - more for radiators than UFH - the result of a one size fits all policy! My system is simple really, one Grundfos circulation pump moving water round all the UFH loops via two manifolds, one upstairs, one down, and back through the buffer tank. No stats, no valves, no nothing other than the expansion vessel.

The original UFH installed in the mid 1980's had a permanently pumped system with two thermostic valves and a bypass. One thermostatic valve acted to limit the maximum water temperature flowing through the floor to around 45 deg C. The other was the room stat. As the room warmed up it gradually reduced the temperature of the water flowing through the UFH until such time as an equilibrium was reached. This in my opinion, and the opinion of Wirsbo at the time, was the best way to set up and control their UFH. The modern  "conventional" way seems to be the same as with radiators, keep the water temp constant then start and stop the circulation pump. The problem with that is UFH, especially the one in this house has a very slow response time, so the system is very sluggish and is almost never the right temperature.  My "new" heatpump system does the same thing as the my original system. It controls the temperature of the circulating water to achieve a constant temperature in the house. The only difference is that it does it by monitoring the outside temperature, deriving the heat loss from the house and hence its heat requirement. So I end up with it running 24/7, a nice even temperature everywhere and a heat pump that at the moment is cycling once every 90 minutes or so.

The other thing is my heat pump compressor is not inverter driven so as far as I know it is on or off so it couldn't maintain a constant temperature unless it had a massive buffer tank and some form of temperature mixing valve.

Having said all that every house is different, every install is different, heating system and UFH systems are different and have different characteristics, finally, the house occupants needs/objectives are different. So what works well in one situation is no good for another. I've lived with a Wirsbo UFH system for over 25 years and love it. Its basically a 20mm (might be 22mm) PEX pipe sitting in an aluminium spreader plate that is sandwiched under the floor boards against insulation. The contact area between the pipe, the aluminium plate  and the underside of the floorboard is very good. Pipe spacing is about 12" (300mm). I have 4 loops covering about 100 sq m down stairs and a similar amount upstairs.

Time will tell what the long term temperature of the ground loops will be but I appear to be lucky that they are sitting in the ground water for the most part.

Just the mystery of the large delta to solve ???


Roger


Title: Re: GSHP Install - opinions please
Post by: davec on December 16, 2015, 09:24:40 AM
... It Seems groundloops are dropping rapidly in effiecency arond here after a few years. ...

Interesting. Any idea why that might be?


Title: Re: GSHP Install - opinions please
Post by: titan on December 16, 2015, 11:50:19 AM

I'm tempted to dive in with a calibrated thermometer and measure the flow and return temps direct to see if the displayed temperatures are correct, or even monitor the volts on the pump to see if it is running flat out.


I use one of these    http://www.ebay.co.uk/bhp/infrared-thermometer


Title: Re: GSHP Install - opinions please
Post by: dhaslam on December 16, 2015, 11:52:12 AM
It is important to know the flow rate because all of the loops may not be working fully.    Is the feed pipe and the pump large enough to  handle  flow to the separate  circuits?  

Underfloor heating flow temperature should be  fairly low  to avoid overheating  on sunny days.  Mixer valves tend to have the lowest  setting of 35C  but in a well insulated house  circulation temperature  can be ten degrees lower for much of the year.    The outside temperature isn't always a good guide  because  houses with lots of windows can  be warmer  inside  in  frosty weather than on wet  days with  milder temperature.    


Title: Re: GSHP Install - opinions please
Post by: Fionn on December 16, 2015, 12:41:06 PM
With regard to efficiency drop, the only reason that this can happen is if you extract heat each winter at a higher rate than it is replenished in the summer.
Normally this indicates that the ground loops are undersized.
Back feeding solar thermal energy into the ground has a bad reputation on this site.
Notwithstanding this it is undeniable that if you added back the same amount of energy that you extract in winter during the summer you would slow or reverse this trend.
If you had good ground conditions with rapid groundwater movement then you wouldn't get progressive cooling one season after the other in the first place, and dumping heat into the ground in summer would be a fruitless exercise.


Title: Re: GSHP Install - opinions please
Post by: marshman on December 16, 2015, 02:17:47 PM

I'm tempted to dive in with a calibrated thermometer and measure the flow and return temps direct to see if the displayed temperatures are correct, or even monitor the volts on the pump to see if it is running flat out.


I use one of these    http://www.ebay.co.uk/bhp/infrared-thermometer

Yes got one of those. Great for checking the flue temp on the wood burner amongst other things but in this case where where I am looking at just 1 degree or so I'm not sure it will be good enough. Also they are "calibrated" on the emissivity of a certain surface. On the shiny copper pipes I suspect the accuracy will be worse. I would prefer to clamp my own sensor onto the pipes as they enter and exit the heat exchanger but to be honest I don't think that both sensors in the unit will be wrong.

Roger


Title: Re: GSHP Install - opinions please
Post by: Fionn on December 16, 2015, 02:24:28 PM
I find one of these very useful and both accurate and precise.
http://www.ebay.co.uk/itm/171488826237
It's a handheld digital K type thermocouple thermometer with 4 input channels.
You can plug in pipe clamp or probe type sensors into the unit.


Title: Re: GSHP Install - opinions please
Post by: JonG on December 16, 2015, 04:21:50 PM
Hi Roger, a very rough rule of thumb on flow rate across the ground loops is 3 litres per min per kw of heat pump, so in your case 30 lpm. It will settle as the fuzzy logic in the software learns the resistance but with propylene glycol that gets more viscous as it gets colder you will need to keep an eye on things.

In terms of resolution if there does transpire to be an issue, it may be possible to fit an inverter driven pump from a larger Thermia heat pump, or an external pump in parallel to increase flow rate (assuming that the head is sufficient on the existing pump). Pumps in series increases head but not flow rate, pumps in parallel increase flow rate but not head.

There is no inverter on your compressor it is direct on line on/off, any extra capacity is stored in the buffer (but will be marginal given buffer size). Buffers are not mandatory in MCS installations and we quite regularly go straight to screed for simplicity.


Title: Re: GSHP Install - opinions please
Post by: marshman on December 16, 2015, 06:22:33 PM
It is important to know the flow rate because all of the loops may not be working fully.    Is the feed pipe and the pump large enough to  handle  flow to the separate  circuits?  

Underfloor heating flow temperature should be  fairly low  to avoid overheating  on sunny days.  Mixer valves tend to have the lowest  setting of 35C  but in a well insulated house  circulation temperature  can be ten degrees lower for much of the year.    The outside temperature isn't always a good guide  because  houses with lots of windows can  be warmer  inside  in  frosty weather than on wet  days with  milder temperature.    

Flow rate is the same, according to the individual flow meters. Based on JonG's "rule of thumb" my total flow rate of around 32 ltrs/min is about right. So I guess the pump is capable of doing the job - unless it can't hack it as the loop temp drops and the fluid gets more viscous.

Don't have many big windows, and certainly not many that catch the sun so solar gain is not much of a factor.

I agree regarding UFH temps. Mine is  happy to run a very low temps. As I said its's running 24/7 and the average temp is well below 35 deg C at the moment, but then its not exactly cold outside, wet and windy but not cold.


Hi Roger, a very rough rule of thumb on flow rate across the ground loops is 3 litres per min per kw of heat pump, so in your case 30 lpm. It will settle as the fuzzy logic in the software learns the resistance but with propylene glycol that gets more viscous as it gets colder you will need to keep an eye on things.

In terms of resolution if there does transpire to be an issue, it may be possible to fit an inverter driven pump from a larger Thermia heat pump, or an external pump in parallel to increase flow rate (assuming that the head is sufficient on the existing pump). Pumps in series increases head but not flow rate, pumps in parallel increase flow rate but not head.

There is no inverter on your compressor it is direct on line on/off, any extra capacity is stored in the buffer (but will be marginal given buffer size). Buffers are not mandatory in MCS installations and we quite regularly go straight to screed for simplicity.

Thanks Jon, as I said above mine is flowing at over 30 ltrs / min so that would appear to be correct. I know the compressor is on/off with no inverter - Danfoss/Thermia have just announced an inverter driven one. I was referring to the brine pump being variable speed. I will keep an eye on things as you suggest as the temperatures drop.

Interesting about buffer tanks not being compulsory as I have been told by more than one installer that they are, it does allow the option of easily connecting another heat source in the future should it be needed (can't think why though). I would have been happy to do away with my buffer as well as there is enough liquid in the UFH loops for it to all work OK without excessive cycling.

Thanks again for you inputs.

Roger


Title: Re: GSHP Install - opinions please
Post by: marshman on December 18, 2015, 12:54:25 PM
OK I think the "mystery" is solved. The Brine in and out temperature sensors were not reading the correct temperatures - as suspected. There is a sub menu in the installer section for sensor calibration. Believe it or not they were a long way out, just under 3 degrees on the difference. Once set the display now shows the expected difference of 3 deg C, as set in the install menu, confirmed by independent thermometer on pipes in and out of the heat exchanger and the brine pump is no longer running flat out. Flow meters in the chamber now showing just under 8 ltrs / min each (there are 4 loops), which tallies with JonG "rule of thumb" statement of 30 lts/min.  So now all looks a lot more sensible.  I did also use my IR thermometer (as sugested by Titan) on the black manifold pipes in the manifold chamber outside and it confirmed a temp difference of 2.8 deg C.

There is no mention of checking the calibration of the sensors in the installation manual but to me it seems fundamental to the correct operation of the system.

Thanks to all for your input and suggestions.

As a foot note it seems the incoming temperature is really closer to 11 degrees C than the 13 that I originally quoted!

Roger