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HEAT PUMPS & Geothermal Energy => Heat Pumps => Topic started by: StationHouse on August 30, 2011, 10:37:33 AM



Title: New ASHP Install
Post by: StationHouse on August 30, 2011, 10:37:33 AM
First post so be kind...

Last year we moved to our dream house the sticks which turned out to be a miserable experience over winter...

We inherited an elderly bulk LPG CH system, an LPG gas stove and an LPG flame effect fire. Little did we realise at that point just how expensive LPG is and that the old potterton CH boiler/rads were past it. Could not get the rads hot which meant big bills with no heat to show for it. And the two fires were more for effect only. I did try to flush the system and despite lot's of sludge coming out it made no real difference.

If we had not installed a new Stovax multifuel stove last October I think we would have moved back to our parents until spring! Needless to say the stove was never off but as it was at one end of the house the other end did not benefit from the heat where we had to use oil filled rads to bring the temps up to 16c or so. Despite having a woodland we had to buy in wood and coal as we were not prepared for winter, not cheap...

Anyway after a huge amount of research rightly or wrongly we plumped for and ASHP for the following reasons. It's always on (though temps are set to vary during the day) so the fabric of the house is nice and warm which has transformed it, the wife can work it, we just have the one heating bill now instead of four (LPG, Electric, Wood and Coal), loads of DHW and we can shop around for the cheapest electricity deals. GSHP was out as the garden was not suitable, pellet boilers were pricey and you have to house it somehow, a boiler stove connected to rads/dhw was out as installers never came back to us with quotes...

As we were starting again and combining it with renovations it did not make sense to continue with LPG and oil was out to as we did not want a oil tank at the front of the property and friends who have oil want to get rid of it for something else, again due to cost. Renovations included much more insulation in the property for the ASHP.

The ASHP heats the house through fan convectors, UFH and a towelrail radiator which is more for effect than heating due to very low flow temps.

Though the ASHP is cheap to run at the moment I'm fully aware it will be more expensive over winter but should still be cheaper than last years combination of wood, coal, LPG and electricity. Plus there's the 850 RHI payment on it's way and possible RHI payments for 18 years which would be a nice bonus but in no affected our decision to go ASHP. At the end of the day the system was chosen and designed for comfort/easy of use in a property occupied throughout the day not for the cheapest running costs. I'll be able to publish running costs if anyone is interested once I have recorded more electricity readings over the next winter. The only problem is the readings will include household use as well.

The future... I would love to have some fun having a bodge at generating electricity from our river to perhaps powering outdoor/shed/garage lights and have solar PV installed. Solar thermal is out as we made no provision for it with the new tank for the ASHP install though we did seriously look into it.
(http://s2.postimage.org/16zedc3tw/IMG00004_20110720_0721.jpg) (http://postimage.org/image/16zedc3tw/)


Title: Re: New ASHP Install
Post by: billi on August 30, 2011, 10:56:18 AM
Hi  and welcome

Quote
The future... I would love to have some fun having a bodge at generating electricity from our river to perhaps powering outdoor/shed/garage lights and have solar PV installed

hopefully you supply more details about your river and we make your Heatpump  one of the best in the UK  ;D


looks like a nice spot by the way


Title: Re: New ASHP Install
Post by: brackwell on August 30, 2011, 11:19:55 AM
Welcome Stationhouse,

We all like to hear what people are doing and particularly how the plan turns out.

ASHP are always a point of discussion particularly as to how effective they are in deep winter in the UK where the high humidity levels can cause the build up of ice on the outsde unit. This is normally removed by a electrical heating element when of course the COP becomes close to 1 . I would love someone to actually put nos and quantity to this phenomenon.

I fear that most people spend time and money on looking at power input to the building and not enough on insulation and reducing power outputs.   Insulation is one of those kind of vague subjects which most people dont really have a feel for. Switch on a boiler yes -insulate so you dont need the boiler no.  Just imagine the effect of cutting out those vents and chimney for the fires! as a starter.

 I have a 5 Kw Stovax but really only use it in the evenings (dont believe in keeping it in overnight ).  I am sure it would heat the whole house if necessary.  Well with the LPG,ASHP,Stove you now have a good range of tools available and over the course of time will work out the best combination that suites you.

But a water turbine is something else again. Of all the renewables this has to be the most cost effective/productive.  If you have a decent river to access then thats like the jackpot. How big/flow rate is this river ?  Big enough to drive a ASHP ?

Ken


Title: Re: New ASHP Install
Post by: rondurrans on August 30, 2011, 11:30:41 AM
StationHouse you might like to try a book entitled 'Going with the Flow' (small scale water power) published by the Centre for Alternative Technology for 12 (try online store see link below) - Billy Langley & Dan Curtis

http://store.cat.org.uk/product_info.php?cPath=104_253&products_id=767


Title: Re: New ASHP Install
Post by: StationHouse on August 30, 2011, 11:56:34 AM
Thanks for the helpful replies and being kind.

From speaking to other ASHP owners they seemed to get through the winter fine though the odd one did have large leccy bills but not as bad as others who were on oil. Very hard to compare different households heating costs though... With this in mind we did our best to size the pump correctly, run at much lower flow temps (when compared to oversized rads)  and insulate everything inc CWI, under floors, loft, quality external doors and DG, thick underlay and carpets... House has never felt so warm though there is still more to do to the last two rooms.

Very happy to share information as when we were doing research there is not much on the web so we spent the best part of a year looking into all the options, viewing installed systems and speaking to the owners
and lots of installers to build up our knowledge. One thing is for sure there are installers out there that seem to know little about them so it's finger in the air stuff...

Will look through previous hydro posts and if you like can post pics of the river?

Cheers


Title: Re: New ASHP Install
Post by: billi on August 30, 2011, 12:01:51 PM
Quote
Will look through previous hydro posts and if you like can post pics of the river?


 exhappy:  yes please    se)(y  pics please


Title: Re: New ASHP Install
Post by: StationHouse on August 30, 2011, 01:29:04 PM
I'll grab the camera and stick the wellies on tonight  ;)


Title: Re: New ASHP Install
Post by: StationHouse on August 30, 2011, 10:25:41 PM
Update - I've been tracking electricity usage since install it is working out at approx 20 per month for heating and DHW  :) Total leccy bill for house is around 50 per month. As this is Scotland and summer has been cr@p (as usual) it is heating... Water temp is boosted to 65c every 14 times i.e. once a week.

No doubt winter will be more expensive  :winter Hence why i'm overpaying on the direct debit so there are no shocks  :o

ASHP is a single phase 14kw Mitsubushi EcoDan connected to UFH and Dimplex SmartRads.

The wife is really keen on the hydro generation stuff so will head over to these boards too  ;D


Title: Re: New ASHP Install
Post by: Countrypaul on August 30, 2011, 11:36:30 PM
As you have a river did you consider a water source heat pump ie. a ground source heat pump but with the source being the water in the river rather than dug into the ground?

Paul


Title: Re: New ASHP Install
Post by: StationHouse on August 31, 2011, 12:12:53 AM
Yes it was an option but was much more complex and expensive than the ASHP to install. Plus the heat pump, due to size, would have needed to into the garage, then get insulated/buried pipes into house etc

Cheers


Title: Re: New ASHP Install
Post by: dullnote on November 07, 2011, 10:11:28 PM
Hi StationHouse, I see your name pop up all over this site, and you still appear to like your ASHP, I too stay in Scotland and thinking about a pump, read about the horror stories all over the place.

at present I am paying for LPG, last week it cost me 6.06 a day thats a lot of Leccy I could buy, since the start of Sep when the heating went on average cost is 3.97 a day approx 30kw.

Please keep us posted throughout the winter I am very interested, to see how the pump performs.

I read somewhere you have missed out on the solar PV, I was fortunate to get my system in on time

Dullnote


Title: Re: New ASHP Install
Post by: StationHouse on November 07, 2011, 10:34:27 PM
Very happy with ASHP especially now it's freezing outside... Had to scrape the car this morning!  freeeze

House is lovely and warm all the time and system just does what it needs to do so don't worry about heating anymore.

I'd almost blanked out this time last year, LPG and going through renovations...

PV going on this week, it's such a big thing i dunno what to expect or changes it will make...

If this was a money saving house i'd still be living in a Wimpey box  ;)

Tis only money, comes and goes...


Title: Re: New ASHP Install
Post by: StationHouse on December 05, 2011, 11:46:38 AM
After a few very mild weeks the temp has d
                                                              r
                                                               o
                                                                p
                                                                 p
                                                                  e
                                                                   d big time...

So far the ASHP is heating without breaking a sweat and no defrost cycles yet. Still cheap to run when compared to Oil/LPG etc

Early days but so far very happy :crossed


Title: Re: New ASHP Install
Post by: bassman on December 05, 2011, 01:09:36 PM
Glad to hear your ASHP is performing well, as you know I had a ASHP installed in September and all is well so far.

Electric consumtion is gradualy rising as can be expected but not to the level (cost wise) that oil would have cost.

Surprised you have not had a defost cycle yet (you might have been sleeping at the time) as I have seen 3 recently since we have had sub zero temps and heavy frost.  Dusting of snow last night led to a defost this morning

I will be posting a link to my energy consumption for November soon


Title: Re: New ASHP Install
Post by: StationHouse on December 05, 2011, 01:58:16 PM
Glad to hear your ASHP is performing well, as you know I had a ASHP installed in September and all is well so far.

Electric consumtion is gradualy rising as can be expected but not to the level (cost wise) that oil would have cost.

Surprised you have not had a defost cycle yet (you might have been sleeping at the time) as I have seen 3 recently since we have had sub zero temps and heavy frost.  Dusting of snow last night led to a defost this morning

I will be posting a link to my energy consumption for November soon

Great to hear your reply  :) I've been watching a gradual rise in electricity too and log it on excel but need to find a better way as it only really makes sense to me.

ASHP only really runs during the daytime unless the temp in the house drops to 17c or below during the night so fingers crossed defrost cycles will be few and far between...

From your description it's the same weather here.

There is a downside to fan convectors... Got a call from the wife... the cat just puked on one  facepalm  Can wait to clean that when I get home tonight...


Title: Re: New ASHP Install
Post by: dullnote on December 06, 2011, 03:06:22 PM
Hi Stationhouse and Bassman I would be grateful if you could keep us up to date with the ASHP over the winter. I am looking into these I have 4 bed detached house two years old, full underfloor heating running a LPG boiler. Last year at this time casting me approx 10 a day to run, I have fitted a woodburning stove this year and now have the gas bill down to 5 to 6 per day. (at present time due to cold weather) last year worst was 12 a day but it was never above -5 degrees.

I would like to see the running costs, also info on any noise issues

Thanks

Dullnote


Title: Re: New ASHP Install
Post by: StationHouse on December 06, 2011, 03:24:00 PM
Can do.

My meter readings are bit adhoc as I do it as and when I get a min but at least once a week. From that I try to calculate averages over the year as with any heating sytem. The thing to bear in mind are my readings are for whole house usage not just the ASHP.

I don't think I've built a big enough balance with nPower for winter useage but hoping the lighter nights next year will pull things back with the PV.

On my tariff over the last four months I'm using about 65 a month for everything.

As we are all on different tariffs I'll just give you the units used with a note of our useage patterns etc.

Cheers.


Title: Re: New ASHP Install
Post by: mpooley on December 06, 2011, 05:28:48 PM
I am very interested in hearing you opinion on your fan convectors as I am in a situation where i cant have underfloor heating installed.
which ones did you use?



thanks

Mike

 


Title: Re: New ASHP Install
Post by: StationHouse on December 07, 2011, 08:13:30 AM
I am very interested in hearing you opinion on your fan convectors as I am in a situation where i cant have underfloor heating installed.
which ones did you use?



thanks

Mike

 

Hi,  we went for the white glass fronted Dimplex SmartRads. Size them at the lowest fan speed to the room so they run at their quietest. We went for them to keep the cop/efficiency as good as it could be as they run at pretty much UFH temps. An oversized rad system needs a much higher heat curve plus the rads need to be huge. SmartRads are similar size to GCH rads. One thing to note is they need their own electrical circuit but as we were decorating it was no big deal. They are not cheap as we needed 13 but was hugely cheaper than retro fitting UFH. In saying that we put wet ufh in the bathroom as it was a small space. The beauty of fan convectors is unlike normal rads they hold very little water, about 1lt, so you get very fast warm up/response times and less work for the ASHP to do. Although we have a stat for the UFH in the bathroom and a wireless stat for the fan convectors when the house is pretty much at temp its cool air they are blowing which seems mad that the house is sitting 20c as a result. You only ever feel them blow warm air if the system is say changing from 17c to 20c in the morning then it settles back to blowing cool air. Conversely if the system goes from 20c to 17c at night the fan convectors all automatically turn off as they no longer sense warm water flowing to them... Warranty support has been great as we had a couple of noisy ones.

Cheers


Title: Re: New ASHP Install
Post by: mpooley on December 07, 2011, 10:10:03 AM
Thanks!
What does "An oversized rad system needs a much higher heat curve" actually mean ?
sorry but im a bit thick lol

One worry I have would be the fan noise? but more worryingly my wife wont have our under kitchen fan rad on at all, as unless the air is coming out hot she reckons it's just a draught ! so i think she might hate having cool air blown about in the lounge!

Mind you she is bonkers but what can i do lol

mike


Title: Re: New ASHP Install
Post by: StationHouse on December 07, 2011, 10:19:02 AM
You only feel the cool air if you are right inches from them otherwise the rooms feel nice and warm with no draft.

Heat curve is simply this.

Very briefly with arbitary figures as i cant remember what mine are. When the outside temp is say for example -10c the ASHP heats water to 40c and when the outside temp is 15c it heats water to 20c. 

Cheers


Title: Re: New ASHP Install
Post by: mpooley on December 07, 2011, 04:42:23 PM
thanks  :cross


Title: Re: New ASHP Install
Post by: JonG on December 07, 2011, 10:50:53 PM
Hi Mike whilst fan coils are great for getting flow temps low, a heat pump runs better with big thermal masses. This is why UFH in a screed is so good. It takes time to warm it gently with a low flow temp and then gives it off slowly over time. This means that the HP runs long and low to achieve temperature in the screed and in the shoulder periods it will then be held off for longer whilst the screed acts as a large radiator.

With a reduced system volume there is a potential for cycling because the low volume of water will reach temp quickly and then cycle the heat pump as the temp fluctuates, because just as the system will heat quickly it will also cool quickly where ideally the HP would run for longer to achieve temperature and then the mass in the system would damp out short on off periods.

UFH in screed is great, cast iron rads are OK but we also get reasonably good results with standard oversized panels. K3 units are now available that are triple panel, triple convector, which reduce the overall footprint but stand further off the wall.

A competent installer should heat loss each room and then apply radiator manufacturer factors to the heat loss to calculate the size of radiator based on the flow temp and design internal temp of the room.   

Seriously consider a buffer too, this increases system volume and therefore mass and also introduces a host of other benefits that I have referred to in another post.

Cheers

Jon


Title: Re: New ASHP Install
Post by: mpooley on December 07, 2011, 11:14:59 PM
Thanks Jon - Yes I have noticed your other posts
You seem to know what you are talking about.

I assume you are an installer but I bet you don't live anywhere near me  :snow

Mike


Title: Re: New ASHP Install
Post by: bassman on December 12, 2011, 01:24:03 PM
Hi

Just added a link to my post

https://picasaweb.google.com/108455921836178416144/October262011?authuser=0&authkey=Gv1sRgCM-0qfuOjc_9ew&feat=directlink

November 2011 power input


Title: Re: New ASHP Install
Post by: mpooley on December 12, 2011, 01:39:27 PM
Hi

Just added a link to my post

https://picasaweb.google.com/108455921836178416144/October262011?authuser=0&authkey=Gv1sRgCM-0qfuOjc_9ew&feat=directlink

November 2011 power input

Looks low compared to my oil consumption costs !
what size approx house is it ? and is it well insulated?

thanks
Mike


Title: Re: New ASHP Install
Post by: bassman on December 12, 2011, 03:13:47 PM
185sq m
200mm loft insul
Cavity wall bead filled
UFH all tiled floor

I have 80% of the building on "heat" at present - with oil it was more like 50%
I was using on average 3000l of oil per year for the last 7 years so I will have accurate figures to compare to


Title: Re: New ASHP Install
Post by: dhaslam on December 12, 2011, 03:36:09 PM
Was the same insulation in place  when you were using 3000 litres of oil per annum?


Title: Re: New ASHP Install
Post by: bassman on December 12, 2011, 04:26:08 PM
Yes, all that has changed is the heat source


Title: Re: New ASHP Install
Post by: mpooley on December 12, 2011, 04:44:31 PM
Yes, all that has changed is the heat source

wow that's a lot of oil for such a reasonably well insulated house.

my loft area is over 300sq meters - 2 story house
with some solid flint walls but mostly brick /cavity/block with insulation and flint/block/cavity/block - again filled.
270mm loft insulation soon to be topped up to 400mm !!
I have averaged about 3200litres but last year was 3600L

but we don't heat all of it as only use 2 of the 5 bedrooms and its got a huge solid flint walled dining room which we don't bother with in the winter.

hope this winter will be a mild one lol

mike


Title: Re: New ASHP Install
Post by: JonG on December 12, 2011, 09:55:25 PM
Hi Mike, whereabouts are you, we are indeed installers and in the North West. The only reason I sound like I know what I am talking about is having made mistakes and learned from them the hard way!

In fairness there are quite a lot of issues which crop up due to ignorance and ill advice from manufacturers who don't really know how best to apply the technology.

Jon


Title: Re: New ASHP Install
Post by: mpooley on December 13, 2011, 08:22:07 AM
ah I'm in sunny Norfolk mate. what a shame.

one thing you may be able to comment on though is that all the installers I have had give me quotes said that i should not change any of my rads! just suck it and see! they reckon that most of their customers are happy and find out that the system works fine.

I'm afraid I don't believe it really- I want to - but i don't.
No one has offered to do a proper survey and calculate individual heat requirements for each room!

Fortunately I have! 
I have also tried to work out the heat output from normal rads at different water temps.
I am pretty unsure of this as I couldn't find much info on it but I made a little spreadsheet where I estimate the size needed for various temps.
At 35c it was  8 times the size of a rad at 75c water

I am assuming though that having the system on 24/7 will make a big difference to that but am not sure how to work it out.

thanks]

Mike


Title: Re: New ASHP Install
Post by: StationHouse on December 13, 2011, 08:49:52 AM
I got installers with that 'suck it and see' attitude too...

'We will just connect the ASHP to the existing pipework and radiators'

1) It clearly stated that the EcoDan required 15mm for the high flow rates required, we had microbore!!!

and

2) the existing sluged up rads were undersized for LPG GCH never mind the low grade heat from an ASHP!!!

Installers with this attitude are chancers clearly not qualified in any way whatsoever and should be shown the door and told why...

Do you really think they will come back to rectify once they have your cash....?

I'd love to name names but probably not the done thing as one company quoted me 14k to install a Daikin Altherma connected to existing rads/pipework when the ASHP itself was about 6k. So thats 8k to install an ASHP!!!!!!!!!!!!!!!!



Title: Re: New ASHP Install
Post by: bassman on December 13, 2011, 09:06:39 AM
14K was "day light robbery" - my Daikin 16kW monobloc was supplied and installed for 6300 and that included extra pipework to retain my existing oil boiler that I wanted to keep for "backup" purposes.

I supplied the concrete base and put a hole through the wall for the pipework etc.


Title: Re: New ASHP Install
Post by: StationHouse on December 13, 2011, 09:14:21 AM
It's not just ASHPs, one of my solar quotes specified completely the wrong grade of wiring for the proposed panels so they don't even know the spec what they were installing  facepalm

No point in naming them as I doubt they'll still be in business following the FIT change  :)

Cheers


Title: Re: New ASHP Install
Post by: titan on December 13, 2011, 09:15:40 AM

one thing you may be able to comment on though is that all the installers I have had give me quotes said that i should not change any of my rads! just suck it and see! they reckon that most of their customers are happy and find out that the system works fine.


While not defending  misleading advice, they may have a point. Most so called heating engineers ( plumbers) usually grossly oversize carbon fuelled  systems including the rads and boiler ( unless they are working to a fixed price cheap quote) so you have nothing to lose trying your existing system which may have also been installed before other improvements like cavity wall insulation etc.


Title: Re: New ASHP Install
Post by: mpooley on December 13, 2011, 09:38:40 AM

one thing you may be able to comment on though is that all the installers I have had give me quotes said that i should not change any of my rads! just suck it and see! they reckon that most of their customers are happy and find out that the system works fine.


While not defending  misleading advice, they may have a point. Most so called heating engineers ( plumbers) usually grossly oversize carbon fuelled  systems including the rads and boiler ( unless they are working to a fixed price cheap quote) so you have nothing to lose trying your existing system which may have also been installed before other improvements like cavity wall insulation etc.

Yes I can see your point on that one but they probably at least make an effort lol

in my case the house is a renovated barn which was basically derelict so most walls are new and had a good standard of insulation by 1990 standards.
in fact the rads seem undersized for a normal high temperature system to me.
The pipe work is very poorly sized - some rads just would not get any flow until i re sized some of the pipes.


thanks

Mike


Title: Re: New ASHP Install
Post by: titan on December 13, 2011, 09:53:07 AM
Jaga do some nice low temperature rads,  www.jaga.co.uk/products/catalogue/energy-savers        I was considering the mini trench rads for upstairs ( new build) but in the end didn't put any in as my calcs say the ground floor ufh is enough for the whole house, time will tell :).


Title: Re: New ASHP Install
Post by: StationHouse on December 13, 2011, 09:53:32 AM

one thing you may be able to comment on though is that all the installers I have had give me quotes said that i should not change any of my rads! just suck it and see! they reckon that most of their customers are happy and find out that the system works fine.


While not defending  misleading advice, they may have a point. Most so called heating engineers ( plumbers) usually grossly oversize carbon fuelled  systems including the rads and boiler ( unless they are working to a fixed price cheap quote) so you have nothing to lose trying your existing system which may have also been installed before other improvements like cavity wall insulation etc.

Never seen an oversized GCH rad system, indeed rads in newer builds rads are so teeny that once when heating a brand new house from cold [bristol] I just could not get the house up to temp for a whole day... I even pushed the bed up against the rad! Strangely I find most new builds cold, some just go cold as soon as the GCH is off...

Proper heating engineers are just that... engineers. Each room needs to be calculated appropriately taking into account age of building, celing heights, glazing, insulation etc. Pipework and flow rate can also make or break a system especially with ASHP as all the pipework needs to be insulated too.

No wonder there are so many bad ASHP installs out there...


Title: Re: New ASHP Install
Post by: mpooley on December 13, 2011, 09:59:40 AM
mmh i never thought about pipe runs being insulated!

in the loft etc they are of course but not in the floor .

will that really make much difference though ?
wouldn't it be just like a little underfloor heater

I will try and run the boiler at 45c - 24/7 for a week maybe and see how it works.
That should test it i suppose?

Mike



Title: Re: New ASHP Install
Post by: StationHouse on December 13, 2011, 10:30:24 AM
My flow temp over this winter so far is usually around 37c so over long pipe runs the insulation is essential being a suspended timber floor. Tis cold under there... There is the usual insulation between the joists which helps too.

Hope this helps

Cheers


Title: Re: New ASHP Install
Post by: titan on December 13, 2011, 10:51:25 AM

one thing you may be able to comment on though is that all the installers I have had give me quotes said that i should not change any of my rads! just suck it and see! they reckon that most of their customers are happy and find out that the system works fine.


While not defending  misleading advice, they may have a point. Most so called heating engineers ( plumbers) usually grossly oversize carbon fuelled  systems including the rads and boiler ( unless they are working to a fixed price cheap quote) so you have nothing to lose trying your existing system which may have also been installed before other improvements like cavity wall insulation etc.

Never seen an oversized GCH rad system, indeed rads in newer builds rads are so teeny

A developer build would be covered by the bold bit above


Title: Re: New ASHP Install
Post by: JonG on December 13, 2011, 09:25:25 PM
Just to put a slightly different perspective on things, the approach where existing rads are used stems directly from training that I undertook years ago with Mitsubishi and Ice Energy who's stock in trade approach was just that. If the installers have not moved on from this they will still approach projects from this perspective until Feb next year. Both companies took the view that cold spots could be tackled post installation and flow temps that were recommended were far too high for true efficiency. We are now very wary of the Japanese units, mainly because of the lack of hydraulic design and knowledge that is exhibited by the manufacturers.

It was and is to a degree also commonplace and accepted practice to oversize boilers though, simply because they were sized to be able to deliver a rapid ramp up of heat in a property from a standing start and percentage uplifts were often included on the heat loss to achieve this which then impacted radiator size too. Modern units will also ramp down significantly way below what an inverter driven HP will do, so gas usage is matched against load much better. Oil boilers are on off though and rely on the mini buffer of their jacket to reduce cycling.

Rarely though are the sizings sufficient to cope with the low flow temps required to run a HP efficiently. Mike if you want to work out your own rad sizings you need to heat loss each room, find out the rad manufacturers factor for the mean water temp that will be circulating against the design temp for the room, apply this to your heat loss and then choose a rad from their existing (Delta-T 50) schedule to meet your revised heat loss.

The mean water temp is dictated by the delta-t that your chosen HP needs, which may be between 5 and 10 degrees depending on the unit.

If you have a look on the Microregeneration Website under the installers section the new standards (MCS3005v3) confirm exactly how the heat loss will be calculated after Feb, what the design outside temp should be for your location to achieve 100% coverage and there are some look up tables for heat emitters because installers will have to give a star rating for efficiency based on the flow temp required to achieve design temp in the worst performing room with the emitter selected.

In terms of pipework insulation, this is very important, you can get away without it but why lose heat to a space that you do not need to heat, plastic has a lower level of heat loss so is a good choice under floors, it also requires less elbows so all important flow rate is improved.

I've said it before but seriously consider a buffer to preserve the flow rate, we just about hit nominal on Daikin's with 35mm into a buffer, so imagine how tricky it is through an entire system and rad valves. Throw in some sludge a few years on, and what might work day 1 won't be quite as good later on. As I said before though although a buffer is a good addition to any ASHP, you cannot integrate them properly with a Japanese unit, because they are looking for an on/off signal as opposed to a resistance based thermistor measurement, so you can't weather compensate the buffer. Daikin's will load compensate but compressor wear is still a concern because it samples from the base of the buffer where the return is coolest and does not allow the buffer to decay before being called back in.

Unfortunately the HP industry is hugely technical and errors are very easily made, often in complete ignorance. Just try and arm yourself with as much info as possible and pick your installer wisely. A good source of info is also the Refrigeration Engineers Forum which gets a bit techy but is a good place to lurk and learn. If you have an idea of which unit you are interested in I may be able to get an installer recommend from 1 of the reps we deal with locally.



Title: Re: New ASHP Install
Post by: mpooley on December 13, 2011, 10:30:00 PM
Thanks Jon
I have downloaded the PDF's and when i get a minute or hour or day or two will try to understand it ;)

It looks like it's going to be a difficult choice !

Mike


Title: Re: New ASHP Install
Post by: StationHouse on January 18, 2012, 05:22:43 PM
850 RHI payment finally been recieved  :)

And I thought registering for FITs was slow  ;)


Title: Re: New ASHP Install
Post by: Solal on January 19, 2012, 11:23:44 PM
, you cannot integrate them properly with a Japanese unit, because they are looking for an on/off signal as opposed to a resistance based thermistor measurement, so you can't weather compensate  

Is it not possible  to fit a bespoke retrofit  weather  compensator controller    with the buffer  in a parallel  circuit  like the way Viessmann  do with  thier Mono-energetic system?
With  the heat  pump interlocked   from   the twin stats  on the   buffer  which track  the compensated set point.