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Author Topic: Quote for GSHP  (Read 5072 times)
andrewellis
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« Reply #30 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.
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6.48kw Solar PV JA (300W)Panels, SolarEdge inverter
Borehole -> Nibe F1255 12kw GSHP -> Radiators
Nissan Leaf
benseb
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« Reply #31 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.
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benseb
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« Reply #32 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
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Tinbum
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« Reply #33 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!!
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85no 58mm solar thermal tubes, 28.5Kw PV, 3 x Sunny Backup 5048, 3x Sunny Island 5048, 2795 Ah (135kWh) (c20) Rolls batteries 48v, Atmos wood gasification boiler, Brosley wood burner, 2000lt buffer tank and 250lt DHW
titan
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« Reply #34 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.
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benseb
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« Reply #35 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
« Last Edit: July 09, 2019, 11:59:13 AM by benseb » Logged
titan
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« Reply #36 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.
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brackwell
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« Reply #37 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....
« Last Edit: July 10, 2019, 11:47:56 AM by brackwell » Logged
TT
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« Reply #38 on: July 10, 2019, 01:15:29 PM »

If you can use electric point of use for water heating that's a bonus.

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titan
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« Reply #39 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. 
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benseb
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« Reply #40 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.
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titan
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« Reply #41 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.
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TT
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« Reply #42 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.
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todthedog
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« Reply #43 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.
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'In a time of universal deceit, telling the truth is a revolutionary act'
benseb
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« Reply #44 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!
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