Quote for GSHP

[benseb]

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

[Bodidly]

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

[benseb]

Will do thanks

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

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

[Countrypaul]

Will do thanks

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

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

Investor driven heat pumps, do they pedal them? 

[benseb]

Haha. The ultimate in efficiency!

[billi]

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)

We’ve 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 I’m 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

[DonL]

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.

[jtp10000]

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.

[benseb]

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.

[benseb]

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.

We’re 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. There’s 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 we’ll ever move house!

[GarethC]

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.

[benseb]

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 I’m 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 it’s a very quiet area (AONB) that I’d prefer not to have an outdoor unit,  so there’s 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 it’s only really the “loan” of the capital for a few years and I’d rather stump up the cash and have a more economic system that’s less likely to have issues in the 0-10c damp conditions.

I’ll be getting something for a small holiday let too, 60sqm so probably ASHP unless the “mom domestic shared ground array” makes it worth doing GSHP

[andrewellis]

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.

[benseb]

Thanks Andrew

Always good to hear from someone who’s 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 we’ve decided to add retrofit UFH in those rooms now with an output of 120W/m2 so we’re 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

[andrewellis]

The EPC shows 30277 for heating and 2982 for hot water. 150 sqm. I’d 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 doesn’t 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 53ºC 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 wasn’t 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.

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