Navitron Renewable Energy and Sustainability Forum

HEAT PUMPS & Geothermal Energy => Heat Pumps => Topic started by: benseb on May 31, 2019, 09:34:25 PM



Title: Quote for GSHP
Post by: benseb on May 31, 2019, 09:34:25 PM
Hi

We have a period house, 1800s construction with rubble filled solid walls. We have ok insulation- walls are insulated internally, ceilings insulated and double glazing. We have solid floors which arenít insulated and lots of timber double glazed doors. Have done lots of draught proofing and added velux which helps with solar gain.

Our oil boiler is 16 years old and as we have some cash would like to replace it with something more efficient and green.

Oil bills range between £1500 and £2500 per year and we heat to about 19c but only for about 2.5 hours per day to keep costs low.

EPC is C. Energy usage 30,000Kwh. Heat loss calculator by installers estimates as 60,000kwh but they have warned this is overkill as SAP greatly underestimated the U values of stone walls but they have to spec to provide this. (We used about 30,000kwh of oil last year)

Weíve just had a quote for a GSHP with boreholes (trenches would be too disruptive outside, and probably not enough room)

Heat pump is a 3 phase 24Kw Heliotherm

Cost is approx £30k for boreholes,  the heat pump installation, water tanks, ground works etc.

RHI basically covers this cost over 7 years but no extra return. Then we save on fuel

What Iím struggling with is that estimate show our elec cost will be about £2200 compared to oil at £4000

I get that this will be much more comfortable at 21c 24/7 but if we decide to heat to just 19c which weíd be happy with, we wonít see as much benefit from the fuel savings...

Are there likely to be any alternatives?  Was hoping to spend some more on insulation then have a cheaper GSHP install and running costs but Iím struggling to know what we can retrofit without masses of disruption

Thanks




Title: Re: Quote for GSHP
Post by: RIT on May 31, 2019, 10:03:52 PM
Have you talked to anyone about an ASHP unit? A unit would not be as efficient as a GSHP, but the installation cost would most likely be a lot less.

The RHI payment for ASHP is about half of that for GSHP so it's not a simple choice - you would need to talk to an expert.


Title: Re: Quote for GSHP
Post by: brackwell on May 31, 2019, 10:27:16 PM
that estimate of elec cost to be about £2200 compared to oil at £4000 is based on the 60,000kwh fig. so if you have 30,000kwh then those figs will be 50% (30K kwh with a COP of 4 = 7500kwhx 0.15 kwh leccy = £1125 so about correct). This sounds a little optimistic for a retrofit system compared to your oil system to me.

However has no one mentioned that HP like to run at low water temps in order to get the efficiency and this usually equates to using under floor heating or doubling the size of your rads!


Title: Re: Quote for GSHP
Post by: benseb on June 01, 2019, 08:15:24 AM
Hey

Yes considered ASHP but it can get cold and damp here which is their weakness so GS appeals a lot more. Plus the higher RHI!

I replaced our radiators downstairs recently and generally added 50-100% to their output by oversizing and getting higher output column rads. UFH isnít possible due to floor heights and low ceilings.

Saying that the new heat loss calcs would say our existing rads are massively undersized even for oil, which again points to the heat calcs being on the high side as we have no issues with them now.

So hard to do heat loss on an old building with stone walls, doesnít tick any boxes!!

Anyone got experience of HelioTherm or MasterTherm heat pumps?


Title: Re: Quote for GSHP
Post by: gnarly on June 01, 2019, 09:18:34 AM
Is your oil boiler condensing?  Apparently they only became mandatory in 2007 (12 years ago) so it might not be.

Agree that ASHP would be a concern with that heat load... keeping warm during a super cold spell would be difficult and seems sure to involve expensive electric back up heat.

Another option is an oil / ashp hybrid system, with both oil and ashp feeding the same heating circuit but not at the same time.
  * heat is additive so any ashp heat comes directly off the oil requirements
  * provides backup heating so boiler or ashp going wrong doesnít leave you totally without any heat
  * ashp gets used more in the shoulder seasons and the radiators wonít need to be super oversized
  * ashp is much more efficient in shoulder seasons too
  * should still get RHI with a heat meter

Anyway just a thought as a half way house.  If more people could do hybrid heating systems it would really reduce fossil fuel use...
 


Title: Re: Quote for GSHP
Post by: benseb on June 01, 2019, 10:17:22 AM
That could be a good shout. Although to be honest I'd rather get rid of the nasty dirty oil if possible. It leaves us open to replacing the oil boiler too which I don't really want to spend money on a fossil fuel

I was hoping to find a way of adding more insulation to reduce down the heat load of the house, bu really it's only the floors and that sounds like a horrible job.

We do have lots of barn doors which are double glazed but timber (and thin in places), so perhaps either replacing the doors or getting some hefty curtains might be a big help...


Title: Re: Quote for GSHP
Post by: Tinbum on June 01, 2019, 12:03:13 PM
I have an old barn/ Methodist chapel that I have planning to convert to a dwelling but building control is a nightmare and is putting me off. Never use NHBC for conversions- they want everything replaced!!  The walls are really thick stone and they want me to cover them all in insulation! The house I lived in there is the same construction, with no wall insulation, and was the cosiest house ever and the bills weren't at all high. It was a loverly temperature all year round. Calcs for heat loss through stone walls are all wrong.


Title: Re: Quote for GSHP
Post by: benseb on June 01, 2019, 01:42:51 PM
Yes agreed. I just double checked the heat loss calcs...

The exterior walls were quoted with a U value of 1.75 - thats for a hefty external limestone wall, cavity, brick inner layer, plus 50mm of EPS internally. Putting this into a calculator myself I got a U of 0.6 - which changes our heat loss by about 20,000Kwh/year!!

Very difficult to trust a quote on those calculations. Makes the difference between an 18Kw and a 30Kw heat pump requirement. It would also mean my radiators would need to be humongous! And I thought 1500mm x 600mm x triple was enough.

I was watching a very interesting talk about GSHP and they guy said his house was full stone, very little insulation. Once he had it up to temperature, the thermal mass kept it very cosy. His thoughts were you either have high thermal mass OR you need lots of insulation, but high thermal mass AND lots of insulation isn't needed.

As long as you don't have lots of draughts!

So draught proofing will be my focus for now I think, and getting another quote on the heat loss as I dont want to be getting a 30Kw GSHP if an 18 will suffice!


Title: Re: Quote for GSHP
Post by: Countrypaul on June 01, 2019, 02:02:39 PM
If you are putting in lots of draught proofing and making the whole house much more airtight, then you need to be aware that lack of ventillation can cause problems such as increased dampness and mould. you might want to look at an MVHR system if you go for a high degre of air tightness, but retro-fitting could be a nightmare.

You have another option concerning the GSHP and or ASHP and that is to put a small one in (or even one of each) and keep the oil burner for the time being. As you increase the air tightness and insulation (including fitting big thermal curtains) you should then see a drop in the use of the oil burner, to the point it is no longer used and can be retired, or choose to put in a second heat pump and use two smaller one rather than one large one.  Probably much less popular with installers though as they cant sell you as much.

Thermal mass works well if it is inside the thermal envelope, if outside the thermal envelope then it is much less beneficial - hence one reason why EWI is used.

An older oil burner whilst not as efficient as a modern one is likely to be more reliable and can last much longer than 16yrs. Ours was 25yrs old and still going strong, though we only used about 1500L per year (small house with solid brick walls). We moved house into a larger renovated property where we put in lots of insulation and effort into air tightness (and installed an MVHR system) so left the old boiler behind.  The cost of replacing the old oil boiler with a modern one indicated that we would never get close to recuperating the cost by a long way.

You also don't mention whether you have PV installed which could also help reduce the costs of the HPs during the shoulder seasons.

Several on here have also installed air to air heat pumps to help hea the house - and also cool in in summer, these tend to be much less expensive to install and can make a significant contribution.

Don't think that you have to change from one single source of heating to a single other source, a mixture of different heat sources can make a more efficient solution in some cases.  Also running a heat pump at night and loading a thermal store (or thermal mass in the property) off E7 might be less espensive that running a HP 24/7. With more variable rate electricity tariffs appearing selecting when to run a HP may also give more options.


Title: Re: Quote for GSHP
Post by: brackwell on June 02, 2019, 07:34:53 AM
If i understand correctly the decsion is not about whether to have GSHP or not but what size of HP is required.
Well,i think this is a non decision because

1) Tests with modern condensing modulating gas boilers showed that the boilers efficiency had very little correlation with size. This is obvious really because their output modulates up /down to suit and achieve optimum eficiency in nearly all cases. This is also true of the modern inverter type HPs.  So whether you choose 15kw or 30kw is irrelevant except you might need 3ph leccy for 30kw ?  but the cost differential of the heat pump must be small in the total cost ?

2) If you were to choose a system 50% the size of max winter it would still cater for 75% of your heat requirements.

3)  The RHI payment is based on haveing a system which meets the efficiency requirements. This is not based on what you think is necessary but what the calculations deem to be necessary and has to be done by a MCS installer (more expense). This may be a very expensive or impossible requirement to meet.  You would end up gaming the system however as the RHI payments would be based on theoretical requirement not your actual requirements.

4) the very important and essential difference with heat pumps is they are best to leave ticking over for long periods and even 24/7 if necassary to gain max efficiency and therefore least cost. This is a completly different mind set to FF boilers and takes a bit of getting used to but it does make for a very flexible system and so whether its a 15 kw HP working 24/7 in depths of winter or a 30kw working for less hrs is largely irrelevant.

5) trust you have the correct soil/rock conditions

With or without RHI this GSHP would be a great system.


Title: Re: Quote for GSHP
Post by: benseb on June 02, 2019, 08:52:01 AM
Thanks for the replies

Yes I guess it depends on how much difference the Hp cost. Initially this was going to be quite a lot as on Single Phase it would mean 2 HPs but luckily we have 3P so the incremental cost for a single larger unit is probably not as big

I like the idea of a bivalent system as the oil boiler still works, but itís just size restrictions as our current huge  boiler and huuuge 500l tank are in our downstairs toilet. I think weíll be ok replacing with a smaller DHW tank, buffer and GSHP  but no room for the big 50Kw oil boiler!

I guess whatís thrown me is having the heat loss calcs so wildly different from real life as the walls were t species correctly. I think Iíll get another company to run some too and see what they come back with

I do love the idea of GSHP but the price is stacking up. At £30k thereís not really any RHI return over the cost of the system but at least it will pay that back


Title: Re: Quote for GSHP
Post by: brackwell on June 02, 2019, 09:05:01 AM
The bivalent system will make it very difficult with RHI as you would then need to fit measuring equipment on the GSHP and this is all you would get paid for.  I suspect this would get even more uneconomic.


Title: Re: Quote for GSHP
Post by: benseb on June 02, 2019, 09:48:48 AM
Ok, so plan then is to get another set of heat loss calcs so I can see whatís realistic and get a couple of ideas on which heat pump weíd need

I have land which I could put a strip of solar PV on (sadly not enough for ground loops!) so that will get some consideration too

I was a bit anti solar since the FIT was removed but I guess with a heat pump it will certainly help in the shoulder months. Although I have quite a cool house in the summer it could power some GsHP cooling too to recharge the borehole if plenty of PV generated.


Title: Re: Quote for GSHP
Post by: Countrypaul on June 02, 2019, 10:33:08 AM
Whether it is worthwhile to "recharge" the borehole with the PV will depend significantly on the geology. If there is significant turnover of water in the borehole you might find that the temperature evens out over relatively shot periods of time regardless of how much heat you put in or take out.


Title: Re: Quote for GSHP
Post by: Bodidly on June 02, 2019, 10:38:45 AM
Is it a good idea to have a GSHP without UFH? From what you describe of the insulation and the radiators I would expect a poor COP but maybe GSHPs have come on in recent years. Ours has ground loops, we are well insulated all around combined with UFH and it's good but not miraculous.


Title: Re: Quote for GSHP
Post by: benseb on June 02, 2019, 11:52:10 AM
The radiators are oversized so will work at 45-50c  in deep winter. Less at other times.

COP at 50c is around 4 according the MCD website


Title: Re: Quote for GSHP
Post by: Bodidly on June 02, 2019, 11:55:46 AM
The radiators are oversized so will work at 45-50c  in deep winter. Less at other times.

COP at 50c is around 4 according the MCD website

Hmmm I would be very skeptical of that figure. Ours never runs over 30C and I doubt we get over a COP of 4 but as I say I am not familiar with the latest models

Might be worth having a read through some of John Cantor's info. There is a good graph of output V COP on here http://johncantorheatpumps.blogspot.com/ and more info on his site. A salesman will tend to try to baffle with BS


Title: Re: Quote for GSHP
Post by: benseb on June 02, 2019, 12:05:17 PM
Will do thanks

These are Heliotherm units. Investor driven so do have better efficiencies

Iíve ignored figures on their website and just used MCS figures. But hey, who knows!


Title: Re: Quote for GSHP
Post by: Countrypaul on June 02, 2019, 12:44:08 PM
Will do thanks

These are Heliotherm units. Investor driven so do have better efficiencies

Iíve ignored figures on their website and just used MCS figures. But hey, who knows!

Investor driven heat pumps, do they pedal them?  ;D


Title: Re: Quote for GSHP
Post by: benseb on June 02, 2019, 01:08:17 PM
Haha. The ultimate in efficiency!


Title: Re: Quote for GSHP
Post by: billi on June 03, 2019, 12:04:48 AM
Quote
EPC is C. Energy usage 30,000Kwh. Heat loss calculator by installers estimates as 60,000kwh but they have warned this is overkill as SAP greatly underestimated the U values of stone walls but they have to spec to provide this. (We used about 30,000kwh of oil last year)

Weíve just had a quote for a GSHP with boreholes (trenches would be too disruptive outside, and probably not enough room)

Heat pump is a 3 phase 24Kw Heliotherm

Cost is approx £30k for boreholes,  the heat pump installation, water tanks, ground works etc.

RHI basically covers this cost over 7 years but no extra return. Then we save on fuel

What Iím struggling with is that estimate show our elec cost will be about £2200 compared to oil at £4000
  as far as i am aware ,    one can get RHI payment,  even from 2 sources   , if thats still true,  i would consider,  if space is there, a lot of solar thermal and  connect the  heatpump to it too  .  30  GBP will cover a lot .....

https://www.consolar.de/en/press/press_releases/news/article/consolar_starts_mass_production_of_the_pvt_heat_pump_collector_solink.html

Billi


Title: Re: Quote for GSHP
Post by: DonL on June 03, 2019, 04:14:36 PM
When I addressed the same question of whether the calcs were realistic, I turned the recirculating temperature from the oil boiler as low as it would go and waited to see under what conditions it could not maintain temperature. Unfortunately you can't try this until next winter.


Title: Re: Quote for GSHP
Post by: jtp10000 on June 03, 2019, 05:59:30 PM
It is worth considering that if the cheaper / simpler option covers you for 80-90% of the year it isn't a bad set up at all. On the coldest days you may need your log burner (an MVHR will circulate the extra heat nicely) and if your mother in law needs it you can always plug in a leccy heater when she comes to stay.  A good 15kw log burner is a huge boost to the overall requirement on a cold day if you are draft free. I think the official calcs are all based on worse case scenario which is requiring you to be guaranteed 23degress or something absurd.  A house at 'only' 18 degrees, as we all know on this forum, is usually fine.


Title: Re: Quote for GSHP
Post by: benseb on June 06, 2019, 05:50:14 PM
Yes I think we've sort of planned by that as we've upgraded our two WBS to 7kw in the main rooms downstairs, so plenty of umpf on a cold day on top of the heating.

I think unfortunately with MCS, you have to spec the system to fit ALL heating demand down to design temps which is like -3c. I'll have a word and see if they are willing to take these into account for the very coldest days, but I'm hoping when we have another set of heat loss calcs done tomorrow by a different company they will come back a bit less.

118w/m2 does seem very high and they have said that's crazy high considering we have insulation and we're not living in a cave.


Title: Re: Quote for GSHP
Post by: benseb on July 06, 2019, 10:03:59 AM
So quick update...

We had another set of heat loss calcs completed (paid for) which make a lot more sense

Overall peak heat loss 13kw with annual heat demand 30,000Kwh

This matches our current oil spend thereabouts.

Weíre also in the middle of laying new tiles in 50% of our downstairs so have taken the opportunity to lay a retrofit UFH system. It uses 25mm XPS with 16mm pipes laid in. So not loads of insulation but the best we can do without digging the floor up (no chance!)

So I think I we have a fairly good basis for proceeding now. Thereís an oversized rad in our hallway that will now have UFH too so may just leave that in initially then cap it off if we never need it.

So now I just need to work on the quote and try to get it down (new company suggest 11-15kw GSHP), just a shame boreholes are nearly £13k!!

There is an option that Kensa have suggested of sharing a ground loop with our new holiday let (60m2) to get the non domestic/20yr RHI which could be quite lucrative but 20years is a long time to wait. I think due to lower payout per year breakeven is about 11yrs rather than 6 on domestic.

Just depends if weíll ever move house!


Title: Re: Quote for GSHP
Post by: GarethC on July 06, 2019, 06:33:29 PM
I believe that UK field trials (Energy Saving Trust?) demonstrated that GSHPs do only marginally better than ASHPs. Certainly nowhere near enough to justify the hugely higher capital cost. Differing subsidy rates may make GSHPs  financially worthwhile to the householder (while being a silly use of subsidies, but anyway), but you would still incur a much smaller initial outlay with an ASHP, and wouldn't have to faff around with a borehole or slinky.


Title: Re: Quote for GSHP
Post by: benseb on July 06, 2019, 06:49:45 PM
I believe that UK field trials (Energy Saving Trust?) demonstrated that GSHPs do only marginally better than ASHPs. Certainly nowhere near enough to justify the hugely higher capital cost. Differing subsidy rates may make GSHPs  financially worthwhile to the householder (while being a silly use of subsidies, but anyway), but you would still incur a much smaller initial outlay with an ASHP, and wouldn't have to faff around with a borehole or slinky.

Yes Ive been weighing up the options. But ultimately both will be paid off in full by RHI. Then Iím left with a system with lower running costs if going the GSHP route. With it being a fairly big house that COP difference does add up especially with winters seeming to get colder and more extreme  as this planet warms up

We also live at the bottom of a big fell which tends to be quite foggy  at times (not great for ASHP) and itís a very quiet area (AONB) that Iíd prefer not to have an outdoor unit,  so thereís a few reasons to go GSHP over AS.

Without the RHI it would be a no brainier for AS but as both seem to come out about equal after payments itís only really the ďloanĒ of the capital for a few years and Iíd rather stump up the cash and have a more economic system thatís less likely to have issues in the 0-10c damp conditions.

Iíll be getting something for a small holiday let too, 60sqm so probably ASHP unless the ďmom domestic shared ground arrayĒ makes it worth doing GSHP


Title: Re: Quote for GSHP
Post by: andrewellis on July 07, 2019, 11:59:15 AM
From my experience the field trials resulted in stricter MCS rules.  Although no formal cop calcs our system has outperformed my calculations which included running an oil boiler at the same flow temp as a gshp to measure energy usage. It is important to do the measurements right and upgrade radiators as required. As mentioned, without the RHI it would make no sense. Coupled with the solar panels it is doing very nicely in an old property with some insulation in the north east of Scotland up a windy hill.


Title: Re: Quote for GSHP
Post by: benseb on July 07, 2019, 12:11:38 PM
Thanks Andrew

Always good to hear from someone whoís had a good experience!

I did all our heat calcs to work our rad sizes. A couple of rooms I was a bit hesitant about as I was struggling to fit enough in, but weíve decided to add retrofit UFH in those rooms now with an output of 120W/m2 so weíre more than covered now

Would you mind sharing what your EPC rating was compared to what you pay in bills now with the GSHP and solar?

Ben


Title: Re: Quote for GSHP
Post by: andrewellis on July 07, 2019, 02:14:21 PM
The EPC shows 30277 for heating and 2982 for hot water. 150 sqm. Iíd say in reality from my calculations we are more like 25000-27000 for heating and an easy 6000-6500 for hot water (kids like a bath!).   Our electrity on the GSHP was 6100 which with economy 10 gave a cost of about 800 GBP for the rolling year. This included a radiator in the garage (not in calculations) to stop my tools rusting.

One thing that works in our favour is that if it is windy there are quite a few air changes per hour.  However, when it is really cold the air is still so the heat pump doesnít work any where near as hard as the calculations suggest.  We had all the calculations done for -5.6 degrees.  The coldest we had last year was -10C and we hit about 53ļC on the radiator loop working about 80% on the compressor (12kw nibe inverter driven).

The borehole is more expensive but for us with granite a much better solution. When we factored in the upheaval of digging it wasnít much more for the borehole (150m*2=300m).  After the winter, the temperature has already recovered to the same as last year. 

From what I can tell the Kensa are not as efficient as the newer inverter driven pumps.

We have a wood fire which used to be on from morning to late evening.  However it is too hot to put it on most of the year for more than a few hours at a time.  The solar PV use in the spring/autumn months is very good making for a much quicker payback on them as well.

Iíd say as long as you are paying attention to the numbers a GSHP is a very doable solution.


Title: Re: Quote for GSHP
Post by: andrewellis on July 07, 2019, 02:17:23 PM
Send us a pm if you want a chat.  I just read your first post and it sounds like a similar setup.


Title: Re: Quote for GSHP
Post by: benseb on July 07, 2019, 04:49:53 PM
Cheers Andrew 👍🏻

Sounds like a well planned and designed system. A slightly smaller heat pump than ours but our EPC are similar.

Have dropped you a message.


Title: Re: Quote for GSHP
Post by: benseb on July 09, 2019, 08:40:30 AM
Iím on holiday at the moment with far too much time to think and have started to doubt myself whether ASHP might be a better option!

Itís so hard when many companies are either very pro or anti each type of heat pump so youíre stuck between various opinions.

Going to get a couple more companies round for a chat when I get back.

Itís mainly the £13k or so tied up for a few years for boreholes. Could replace all our downstairs doors (x6!) with nice low U triple glazed versions and have plenty of change! Might well cover the difference in COP from lowered fuel consumption.   wackoold


Title: Re: Quote for GSHP
Post by: Tinbum on July 09, 2019, 09:18:04 AM
I would think GSHP would be better for winter heating than ASHP but as you say cost!!


Title: Re: Quote for GSHP
Post by: titan on July 09, 2019, 11:14:47 AM
Heat pumps are not really suitable for retrofitting in old dwellings. The Energy Saving Trust clearly showed that in their report some years ago. Water at 35 deg C will have a difficult or even impossible task of heating an old building with poor insulation, and higher than this the COP reduce significantly and costs proportionally. It has been suggested 19 deg C is comfortable, it may be in a well insulated sealed dwelling but won't be in anything else and 19 deg C won't meet the requirements of the RHI. The RHI requires that the installed renewable system will provide full heating and DHW all year. Which in your case will mean a big heat pump maybe a three phase supply. It may be worth considering a hybrid system with an ASHP providing some heating and oil/lpg/pellet/solar/wood/biomass etc. ASHP can be in a shed/building to reduce the noise if it it is a potential problem. Air to air ASHP are popular in colder climates and possibly better in an older dwellings and gets rid of radiators and the problem of retrofitting underfloor, also for reducing humidity often a problem in older properties with solid stone walls.


Title: Re: Quote for GSHP
Post by: benseb on July 09, 2019, 11:48:03 AM
Heat pumps are not really suitable for retrofitting in old dwellings. The Energy Saving Trust clearly showed that in their report some years ago. Water at 35 deg C will have a difficult or even impossible task of heating an old building with poor insulation, and higher than this the COP reduce significantly and costs proportionally. It has been suggested 19 deg C is comfortable, it may be in a well insulated sealed dwelling but won't be in anything else and 19 deg C won't meet the requirements of the RHI. The RHI requires that the installed renewable system will provide full heating and DHW all year. Which in your case will mean a big heat pump maybe a three phase supply. It may be worth considering a hybrid system with an ASHP providing some heating and oil/lpg/pellet/solar/wood/biomass etc. ASHP can be in a shed/building to reduce the noise if it it is a potential problem. Air to air ASHP are popular in colder climates and possibly better in an older dwellings and gets rid of radiators and the problem of retrofitting underfloor, also for reducing humidity often a problem in older properties with solid stone walls.

I have a feeling this is rather old thinking Titan

The EST did that trial before the MCS standards were out. They did another some since that fared very well. Retro fit and new build. UFH and rads.

https://www.icax.co.uk/pdf/The_heat_is_on_EST_report.pdf


As long as the heat emitters are large enough to support lower water temps then itís fine. Ours have been designed for 45c flow at -2c outside so generally lower than that for most of the year. COP around 3.7

So really itís more a question whether the extra £12-13k, that will be recovered over 7 years from RHI is worth it for a more efficient system.

I will post more once Iíve spoken to a few more companies


Title: Re: Quote for GSHP
Post by: titan on July 10, 2019, 09:58:12 AM
[
I have a feeling this is rather old thinking Titan

The EST did that trial before the MCS standards were out. They did another some since that fared very well. Retro fit and new build. UFH and rads.

https://www.icax.co.uk/pdf/The_heat_is_on_EST_report.pdf


As long as the heat emitters are large enough to support lower water temps then itís fine. Ours have been designed for 45c flow at -2c outside so generally lower than that for most of the year. COP around 3.7


I will post more once Iíve spoken to a few more companies



Interesting that you think this is old thinking, since there has been no significant improvements in heat pumps since I did my install five years ago. I think I understand what is involved in a domestic installation since I did all my own heat loss calcs designed my complete system  installed the UFH, ground array,gshp, unvented DHW system. Stating the obvious all the companies you are contacting are in business to sell heat pumps. All the poor performing installs from the report are in old dwellings, (I can't get your link to open) they were all mis-sold systems. Old dwellings with  sub optimal insulation,large air loss  and sub optimal low temperature heat emitters (compare whole floor with rad area)  . I will be amazed if you ever see a COP of 3.7.


Title: Re: Quote for GSHP
Post by: brackwell on July 10, 2019, 11:40:43 AM
I have always been mystified why a HP should be efficient in one set up and not in another. Surely just because it runs longer in one stuation than another does not alter the efficiency.  I think the problem is that the people in large demand homes do not fit a big enough system,they dont want the large spend in the first place and the sellers quote for to small a system so as not to scare the customer off.  The OPs first question seems to be whether to fit this size or that.  The answer must be to fit the bigger of the two as the big one will always provide enough efficiently if the emitters are sized for the heat loss.  On the other hand the smaller one if too small may on occasions have to run out of optimum in mid winter when the heat requirement is greatest and the COP drop to 2 say.  On top of this for ASHP you have the problem of condensation/icing which has to be less in the bigger unit as it does not need to drop the air temp as much due to the larger volume of air going through.  I suspect that a lot of the old data included non inverter types of old which were either off or on, a bit like the old non modulating boilers v newer modulating ones.

PS It is quite rare for machines to be at optimum efficiency at max output so again i suspect that a HP opperating a max output can never be optimum efficiency but then....


Title: Re: Quote for GSHP
Post by: TT on July 10, 2019, 01:15:29 PM
If you can use electric point of use for water heating that's a bonus.



Title: Re: Quote for GSHP
Post by: titan on July 10, 2019, 04:37:49 PM
 I suspect that a lot of the old data included non inverter types of old which were either off or on, a bit like the old non modulating boilers v newer modulating ones.


Inverter driven heat pumps are not comparable with modulating boilers which can have a modulating range greater than a heat pump max output. The temperatures are much higher, over double, and there is considerable lag with a heat pump especially with UFH. For the same reason weather compensation is useless for controlling a heat pump system. For maximum COP the flow temperatures need to be low and the whole system designed for these low temperatures, which includes a suitable building. Fancy controls don't change the basic facts, lipstick on a pig comes to mind. 


Title: Re: Quote for GSHP
Post by: benseb on July 10, 2019, 05:53:00 PM
Iíve designed my system to run at 45c max when -2c outside. The UFH and rads will all work at this temp (lower for UFH) and the corresponding COP is about 3.7 on a GSHP or lower on a ASHP

So no matter how big or old my house, as long as I can run the heat pump at say 35-45c I will see an efficient system.

The issues come when people undersize the emitters or heat pump or run times and try to heat a house at 55-60c with awful COP

And just because UFH is involved doesnít necessarily mean very slow response times. That depends how big of a slab youíre heating. You can still get a decent output with lots of pipe and less screed, you just have less thermal mass.

Ultimately a older house with higher heat loss is only the same  as a very well insulated but very big house. Itís just overall heat demand that needs to be matched by the HP and the emitters.

Our house has an EPC C rating so itís certainly not a cave.

Going back to the report there were actually more retro fits I believe. There was a conclusion that using UFH vs rads have no difference in efficiency as long as both were correctly sized.

The report concludes that the one factor that makes a difference is the quality of spec and install.

It did say more owners of GSHP were happy than ASHP and I presume this is due to it being more niche so you get less cowboy ďplumber turned ASHP expertsĒ

I keep crunching numbers and it does seem GSHP has the edge as the RHI cap is 10,000kWh higher so once everything is calculated Iíd get more of the GSHP paid off, despite it being approx 2x the cost.


Title: Re: Quote for GSHP
Post by: titan on July 10, 2019, 08:58:38 PM
Hi

 added velux which helps with solar gain.

oil bills range between £1500 and £2500 per year and we heat to about 19c but only for about 2.5 hours per day to keep costs low.

EPC is C. Energy usage 30,000Kwh. Heat loss calculator by installers estimates as 60,000kwh

We used about 30,000kwh of oil last year


Heat pump is a 3 phase 24Kw Heliotherm

Cost is approx £30k for boreholes,  the heat pump installation, water tanks, ground works etc.


Are there likely to be any alternatives?  Was hoping to spend some more on insulation then have a cheaper GSHP install and running costs but Iím struggling to know what we can retrofit without masses of disruption



I am just trying to provide some feedback for you as asked for in your original post. yes Velux does provide some solar gain but when there is no sun it is similar to a hole in the roof. The massive difference between your EPC calculated energy requirement and the installers quote should ring some alarm bells, the difference is 30,000 kWh my total yearly actual use is 2000kWh for a 300m2 house at 21 deg C. You don't mention if you have access to 3 phase if not additional costs. With such large costs involved it would be worth developing a spreadsheet with an accurate heat loss calculation so at least it is not guess work. then calculate how you will distribute the heating. From the estimated heating requirement the rads will need to be doubled at least. What you are posting is theory based on what, 30,000kWh or 60,000 kWh you need to start with some accurate data. Saying you will be getting a COP of 3.7 is unrealistic.


Title: Re: Quote for GSHP
Post by: TT on July 10, 2019, 10:18:36 PM
ASHP for me.
Manage 2 large commercial buildings, 1 started off as GSHP
And was ripped out after 10 years, the other was ASHP from initial design with an air test of 9.99.

Location NE Fife.

ASHP Works well, I use an air con company for installation and yearly maintenance as they know this technology.


Title: Re: Quote for GSHP
Post by: todthedog on July 11, 2019, 06:28:41 AM
Air/air ASHP both here Wales and Sweden.  The Swedish house was well but not super insulated (as new builds are now), most houses had one, only one person had a GSHP.  The 'village ' thought that he was very rich, cost was over 30000 euro for a 120m2 house.   Against our ASHP install of 2500 euro.  Winter temps dropped to -15c.


Title: Re: Quote for GSHP
Post by: benseb on July 11, 2019, 06:33:35 AM
Titan - I did heat loss calcs and they came out around 30,000

I then paid Nother company to do some and about the same. Never going to be 100% as thereís some guesswork as to whatís under some old walls but I think itís fairly close based on old plans from renovation

The issue with the initial quote was they had done the calcs and given the external walls a U value of 2. We have 600mm of sandstone, a double brick inner leaf, 50mm of XPS or Kingspan then plasterboard. Which is closer to 0.6. Makes a big difference. I think they had done 10 air changes per hour too which is just from guesswork and much too high.

We know itís wrong as our fuel costs would be much higher on oil if so

I appreciate your warnings but I think we just need to disregard that first quote
Ps, our Velux gave a U cal of 1.0 so certainly not the same as a hole in the roof!


Title: Re: Quote for GSHP
Post by: benseb on July 11, 2019, 06:36:43 AM
ASHP for me.
Manage 2 large commercial buildings, 1 started off as GSHP
And was ripped out after 10 years, the other was ASHP from initial design with an air test of 9.99.

Location NE Fife.

ASHP Works well, I use an air con company for installation and yearly maintenance as they know this technology.

How come the GS was ripped out TT?

I think my main concern with GS is that the capacity is fairly fixed by the ground array. If itís underspecced thereís no real solution except more drilling

At least if an AS is underspecced itís much easier to pull the unit out and replace with a bigger one. Plenty more air to go around!

We live at the bottom of a hill which does have its fair share of fog tho, so just need to ensure that doesnít lead to it icing up a lot


Title: Re: Quote for GSHP
Post by: benseb on July 11, 2019, 06:37:38 AM
Air/air ASHP both here Wales and Sweden.  The Swedish house was well but not super insulated (as new builds are now), most houses had one, only one person had a GSHP.  The 'village ' thought that he was very rich, cost was over 30000 euro for a 120m2 house.   Against our ASHP install of 2500 euro.  Winter temps dropped to -15c.

How did the Wales unit fair? What sort of size property/HP?

Cheers


Title: Re: Quote for GSHP
Post by: benseb on July 11, 2019, 06:43:23 AM
Iím definitely coming around to the ASHP I think

Any recommended installers in the NW of England?

Also what brand heat pumps have people used?

Our HL now says peak loss of 13kW at design temps (-2) so is it best to go one step up - 15kW just to ensure the emit doesnít work too hard at the low temps?

In reality we have a 4kW and a 8kW WBS downstairs we would crank up at low temps to ensure we donít need to run the system at too high a temp but I think Iíd feel happier with a bit of margin



Title: Re: Quote for GSHP
Post by: brackwell on July 11, 2019, 08:17:17 AM
"In reality we have a 4kW and a 8kW WBS downstairs we would crank up at low temps to ensure we donít need to run the system at too high a temp but I think Iíd feel happier with a bit of margin"

After all this time we eventually get there.  These stoves are the reason why the original cals catered for large air changes which presumably you have ignored?   To go with these stoves you must have large air ingress otherwise you would not be able to run the stoves adequately.   If you are unable to completely close off these stoves you need to replace them perhaps with ones that take outside air directly,  or remove them, or use them more 24/7.  Stoves and more so open fires and the attendent draughts are possibly the biggest heat loss in a building.

PS as your oil boiler got a balanced flue? or another big draught/


Title: Re: Quote for GSHP
Post by: benseb on July 11, 2019, 09:24:57 AM
Iíd like to give them credit for thinking about the stove air changes but in reality that first HL didnít. It had 10 air changes per hour in every room. Thatís an entire house air change every 6 mins!

They had also specced all the doors/windows as single glazed when they are double. Etc etc.

The stoves are sealed, with twin wall flue which heats upstairs. The one without an air intake kit has a closable vent (naughty!)

The oil boiler is old so thereís a vent in the wall but that will be going when the oil boiler is ripped out.

Hereís the new heat loss if anyoneís interested. Seems to make sense. Also great to see which rooms to improve first.

(https://i.postimg.cc/D84Nwt3w/5-C1-D6923-5-A3-A-4-DF5-98-BC-2808-E0-C56-EB3.png) (https://postimg.cc/D84Nwt3w)


Title: Re: Quote for GSHP
Post by: todthedog on July 11, 2019, 07:46:43 PM
Welsh install was for the kitchen/lounge about 35m2, this is where we live. The idea was to take over heating into the shoulder months and perhaps into the winter if it's mild. We went with Mitsubishi based on reputation and previous installs. It was also the Swedish consumer organisation choice.

3.5kW cost about £650 install £650 of which £500 for refrigeration  engineer,£150 for electrician to run dedicated line and circuit breakers etc.
Bonus to run it in aircon mode if we have a really hot evening powered by the pv.


Title: Re: Quote for GSHP
Post by: JonG on July 12, 2019, 08:08:22 AM
Hi Ben, we are installers and have worked in the industry for around 12-13 years, vast bulk of our work is retro and we have installed in everything from 400 year old farmhouses to semis and heat pumps can often be made to work and work well in a wide range of applications.

With your heat loss, you are right on the cusp of what a single phase unit can deliver and as I am sure you will know the MCS cannot take into account other forms of heating if the heat pump does not directly control them.

Generally the MCS fabric heat loss calculations do come up above requirements by circa 20-30% if completed correctly but the paperwork has to be in order for the MCS/RHI.

Havent read the whole thread, but main options could be to improve air tightness or insulation to bring the heat loss down, or consider a hybrid perhaps, this is our least favoured option though.


Title: Re: Quote for GSHP
Post by: benseb on July 12, 2019, 11:41:05 AM
Hi JonG

For this sort of install would you recommend GSHP (would need to be borehole) or ASHP?

We do have three phase so can get whatever size unit we need. Itís looking like about 15Kw



Title: Re: Quote for GSHP
Post by: JonG on July 12, 2019, 01:01:16 PM
Efficiency wise in a direct comparison there isn't a significant difference between the 2 now in all honesty with inverter driven ASHP and GSHP (fixed speed GSHP actually operate slightly more efficiently than inverters). The main differences are infrastructure cost, lifecycle cost (i.e. outdoor unit degrades quicker than GSHP) and tariff. On boreholes though the additional revenue will soon be offset by the up front cost.

That said choice is an issue, in so far that 3 phase 16kw GSHPs are easily available but you are stretching the envelope on a single phase ASHP at the same duty, many manufacturers are now only offering the single phase range and then there is a jump up to larger outdoor units or a preference for cascades of singles, which are not a bad option given the higher turndown ratio/reducndancy, but at a higher initial infrastructure cost.

There is at least 1 high temp capable of around 16kw from memory, using a cascade of refrigerant that could be an option, it runs on low temp unless bivalent is reached and then fires the 2nd compressor to achieve higher temps and outputs. This does increase complexity and failure points though.

The 14-16kw area is a bit tricky from a specification POV and it can be that if the calcs are correct a hybrid may make the most economic sense.



Title: Re: Quote for GSHP
Post by: JonG on July 12, 2019, 01:05:13 PM
At 30,000kwh u are over the cap for ASHP so a hybrid becomes more of an option because you will only be remunerated for the value stated on the EPC, which will be lower than the 30k that the heat loss suggests.


Title: Re: Quote for GSHP
Post by: benseb on July 12, 2019, 01:08:54 PM
Thanks Jon

We had originally been looking at a 15Kw Heliotherm GSHP which looked quite good but the company kept messsing us around and not returning calls etc.

I was thinking GS would be better as our cap would be 30,000 rather than 20,000. We have n old EPC which states approx 33,000 for heating.

We do still have a working oil boiler but presumed this would just get messy from an RHI point of view and with it being old we didnít really want to spend extra on oil in the future.

I think going forward we just need to know what options are available so will drop you a message


Title: Re: Quote for GSHP
Post by: JonG on July 12, 2019, 02:09:20 PM
Strangely enough we were the first to bring Heliotherm into the UK!

Think we still have the partner rights for distribution but would have to check, we installed one back when fixed speed were easy enough to route through DNO's so didnt fit another, with the creaking grid now, pretty much everything is inverter.

It's a dear option, very well made, I trained at their plant in Austria on it, but the costs don't reflect in higher savings against other units IMHO.

EPC has to be 2 years old to qualify now.

Oil is harder to integrate due to usually high, fixed output, fixed flow temp (and has to be high enough to avoid condensation at the boiler) but is doable with BEP and a mixer, also a heat meter is needed for a hybrid, but this can be a blessing plus you can MMSP if you want.