Ground Source Heat Pumps

[MikeT]

Is any one using this system to heat their homes? I have installed this system, works fine when weather cold but difficult to control as the temperature rises. I would be interest hearing how other people have got on with GSHPs. Mine seams cheap to run and the Renewable Heat incentive Payment is very helpful.

Mike

 

[Gilberdyke John]

Is any one using this system to heat their homes? I have installed this system, works fine when weather cold but difficult to control as the temperature rises. I would be interest hearing how other people have got on with GSHPs. Mine seams cheap to run and the Renewable Heat incentive Payment is very helpful.

Mike

A friend converted his house from oil fired boiler heating to ground source. His electricity costs went up but the savings by not buying oil far outweigh that. He hasn't reported any control problems, maybe your controls need investigation?

 

[oliver90owner]

Should turn off on a thermostat when up to temp? Or are you heating domestic hot water from it as well? That may cause control complications and a reduced COP.

If you have a control problem ask on one of the renewables fora. -------- forum is as good as any.

Any other renewables? Or are you heating during the night on E7?

Regards, RAB

 

[MikeT]

Should turn off on a thermostat when up to temp? Or are you heating domestic hot water from it as well? That may cause control complications and a reduced COP.

If you have a control problem ask on one of the renewables fora. -------- forum is as good as any.

Any other renewables? Or are you heating during the night on E7?

Regards, RAB

RAB

Its really my wife who is complaining about the control. She expects it to perform as an oil system able to get heat by turning up the 'stat. The whole house is under floor heated and therefore there is a considerable amount of heat stored in the concrete raft. Each room has its own thermostat controlling the underfloor loop by an actuator on the manifold. Also the amount of insulation in walls, floor and roof, double and triple glazed windows dose not allow much heat loss.

It heats both hot water and central heating with no other heat source except Rayburn in kitchen and wood burner in the lounge.

The heat comes from 1000m of pipe 1.2m deep (filled with antifreeze) in the field and comes into the house at about 3oC and goes back to the field at -1oC. The temperature is low now because the sun has not had time to warm
the soil after the winter. In the autumn the heat will come in at 12oC and go back at 8oC.

We have a 3 phase heat pump which converts the field heat to 50oC (this is run at a low temp because my wife has MS in case she scalds herself) for the hot water and approx. 39oc for the central heating, This will be higher if the outside temp is below freezing. System is managed by a computer, system is Swedish designed.

The house temp runs at 20 -21oC in the living rooms and bathrooms and 18oC in the bedrooms. The temp drops by approx. 3 -4 oC at night. It has to maintain this as it takes too long to increase the temp as the water temp in the unfloor is relatively low.

I'm glad we installed the system despite my wife's dislike of it at its save us £1000s in not having to buy oil. and we get the RHI payment for the next 7 years.

Mike

 

[Pete D]

Hi Mike, I have a GSHP, installed it myself 5 and half years ago. It great, we have DHW and CH all year from the ground loop via the pump installed in my garage.
Controls have never been a problem. As you know there is a considerable lag compared with conventional boilers when you up the stat for instant heat, trick here is not too. I have not changed our settings for about 4 years except to switch it to summer mode and back to normal yearly. You can offset / compensate for the lag a bit, likewise you can deliberately set it to be cooler at night whilst sleeping.
Mine will of paid for itself next year.

Kettle is on.

 

[user 6228]

RAB

Its really my wife who is complaining about the control. She expects it to perform as an oil system able to get heat by turning up the 'stat.
....
Mike

It's really an issue of underfloor heating and the consequential thermal mass of the system.it takes hours to cool and heat the system. Try shifting the whole cycle of reducing and then restoring the temperature by a few hours if you haven't already done so. E.g move the night time setting to early evening and the day time setting to start in small hours.

 

[Gilberdyke John]

It's really an issue of underfloor heating and the consequential thermal mass of the system.it takes hours to cool and heat the system. Try shifting the whole cycle of reducing and then restoring the temperature by a few hours if you haven't already done so. E.g move the night time setting to early evening and the day time setting to start in small hours.

The friend I mentioned above used his existing radiators, supplemented with extra radiators or changing to larger sizes as required so no long lag response compared to ufh. It's my personal thought but I am not particularly keen on relying upon a system with inherently long time response such as ufh in a concrete slab. Nearly as bad as going back to storage heaters

 

[user 6228]

The friend I mentioned above used his existing radiators, supplemented with extra radiators or changing to larger sizes as required so no long lag response compared to ufh. It's my personal thought but I am not particularly keen on relying upon a system with inherently long time response such as ufh in a concrete slab. Nearly as bad as going back to storage heaters

There you go . UFH is really a lifestyle choice. It really works for houses occupied all day, I.e. Like old style Aga. it isn't a fashion item

 

[MikeT]

There you go . UFH is really a lifestyle choice. It really works for houses occupied all day, I.e. Like old style Aga. it isn't a fashion item

If I was doing this again I would use part UFH and part rads to have more control. The house is occupied 24 hrs a day as my wife is disabled.

The system was commissioned in October 2009 and the calculations were based on oil at 35p/l. The system has now paid for itself and we are now in profit especially with the RHI payment of almost £3000/year.

No major problems except the pump circulating the fluid from the field had an intermittent problem and a valve had to be replaced. I have extended the warranty for a further 5 yrs, just in case the compressor fails as that could be expensive.

 

[user 6228]

If I was doing this again I would use part UFH and part rads to have more control. The house is occupied 24 hrs a day as my wife is disabled.

The system was commissioned in October 2009 and the calculations were based on oil at 35p/l. The system has now paid for itself and we are now in profit especially with the RHI payment of almost £3000/year.

No major problems except the pump circulating the fluid from the field had an intermittent problem and a valve had to be replaced. I have extended the warranty for a further 5 yrs, just in case the compressor fails as that could be expensive.

Radiators need to be bigger becuause of the lower temperature. Other solutions might be better.
e.g Air destratification fans or electric radiant heaters in key places

 

[Pete D]

Should of added that mine runs rads, all oversize by about 40%, all double panel and all pipework that is not on show is 22mm, just upstands that are 15mm. Its all about higher flow rates/ volumes with lower temperatures.

I believe my ground loop is super efficient as I used more space between trenches / pipes (10m) than the minimum recommended (1m).
My additional heat (electric immersion) that can be expensive only ever comes on about 20 minutes per week for 'pasteurisation' of the system. Its clocked less than 170 run hours which is less than 1% of full operation hours.

 

[MikeT]

My efficiency is similar to yours. The usage reading is 8500hour of which only 5 % is using the additional heat facility. This is higher than it should be, but we had an intermittent problem last winter which cut out the compressor several times, this resulted in the 2/3 of the 9kw heater being used. I installed the ground loops which consists of 5 200m lengths of pipe in 100 m trenches. Did not use the slinky method of installation, pipe down one side of the trench and back up the other side.

System bought from Ice Energy, most work done by me except final commissioning by Ice Energy, so as to make it eligible for the RHI payment.

The house is a converted Victorian Cow shed some 3000 sq ft, "L" shaped (long and narrow), so not the most thermal efficient. Our electricity bill is £1600/year includes, lighting cooking etc. I estimated our oil consumption would have been in the order of 3000 -4000l/yr, (heating is on all day).

If I was installing again I would use Rads in the bedrooms, and underfoor in the bathrooms and living rooms. (In the lounge the rads would be too large as the room is big with a vaulted roof and 3 outside walls.

 

[Dusty Rhodes]

This doesn't contribute much to your discussion, but last year, Manchester Cathedral had most of its flooring ripped out to put in ground source heating, with underfloor heating.

http://www.manchestercathedral.org/news/186/manchester-cathedral-invest-in-green-heating-scheme

It's now so toasty, that at the weekend, the floor threatened to soften the huge Easter Candle, as we waited to install it in the stand. Nothing worse than a droopy, four foot long candle.

One disadvantage of the system is that those who work in the cathedral all day - vergers and volunteer guides - find their feet get too hot by the end of the day.

Dusty

 

[Pete D]

Hi Mike, mine has done twice as many run hours as yours but you have had yours longer, which seems an oddity. I don't get RHI payment so would be interested in a chat as last year I tried to get it retrospectly and I was told I had mine installed to early to qualify.
Mine too was Ice Energy and final commissioning was by them after I installed it.
Efficiency wise my additional heat has run for approx. 160 hours out of 16,000.

 

[MikeT]

Sorry Pete, Got the date of Commissioning wrong it was 15/05/10, but was used form the previous October before it was signed off by Ice Energy.

The retrospective applications for RHI have now expired - last date I believe was the 8th April.

Mike

Ps my running may be less because mine is a large system running on a 3 phase supply.

 

[Pete D]

Hi Mike, ah, I see, my installation missed the cut off date by a few months for retro claims as I was told.
Mine is only slightly smaller than yours at 7kw and 400m loop, also on 3 phase supply.
Mine is now supplemented by a 5kw turbine on a 15m mast down the field, good way mark for the bees.
My internal sensor is away from other heat sources so room temperature is maintained at a true 21.5c, but at night it rolls back to 18c and during the summer the whole system rolls back to 16c which means it basically doesn't run frm now through till September ish except DHW.
The rads work fine and instead of warming a slab I warm the well insulated walls and ceilings which mean that it never really drops back. Since about 3 months after installation when I kept playing with it the wife has never said she is cold and as I have no room stat she can't fiddle as its in the garage which isn't her domain and of course I haven't shown her how to adjust the settings.
I haven't touched the settings for nearly 5 years

 

[theeggman]

Pete,
Which turbine did you go for and how much (ballpark)?

We have 4KW of solar and keep thinking about adding a windmill. We looked into it when we had chickens but there was no FIT then and it didn't make economic sense.

 

[MikeT]

Just checked the installation cert the pump is rated at 17kw hence the much longer pipe runs. I was contemplating a wind turbine, have lost interest after the company Wingcrop went to the wall, may look at it again. I have also thought of solar panels, but they would spoil the look of the place especially as the barn is single story and has a traditional Norfolk pantile roof.

 

[theeggman]

The turbine we were looking at was Iskra which turned into Evance which I think is the one that went t**s up most recently, Proven were around but they went belly up as well.

We installed the solar in Feb 2011 and it's 66% paid back and that's NOT allowing for the free electricity we use and therefore don't buy. EDF pay us approx. £1900 per year and we pay them approx.£550.

 

[DanBee]

The honey house and visitor areas here are heated with a GSHP and underfloor heating in the concrete screed. I got my system back in 2010 from NuHeat as they are about 5 miles away; not a great customer experience but technically the system has been very good. The GSHP is a twin pump Nibe 30KW unit.

The biggest learning curve was the lag time for raising or lowering the temperature of the concrete slab floor. I recall some tweaking of the flow rates on each zone at the manifolds to get this right during commissioning. Simple dial thermostats (either on or off) in each room/zone.

The system was extended for the tea shop / seminar room / honey shop when that was added in 2013. All south facing, large windows, four zones. This time we had better thermostats specified - Polypipe 'Digital 2 channel time clock' (PB2CTC). It seems a lot easier to keep these rooms at the right temperature than the other rooms in the building, particularly on sunny days, compared to those south facing rooms with dial thermostats. (However the major other south facing room is the extracting/bottling room so I tend to keep that quite warm anyway.)

These digital thermostats can be programmed for a heating programme across the week, and are supposed to 'learn' the heat requirements - i.e. if you set it for 18 deg C at 8am, the thermostat learns when to open the loop to reach 18 deg C by 8am... apparently! Also you set a baseline temperature for when the thermostat programme says 'off' so that the system ticks-over at a low temperature, so doesn't let the slab cool completely overnight or over long 'off' periods.

It's on my long to-do list to check compatibility and upgrade to these digital thermostats for the other zones. A quick Google shows them at £40 each inc. postage, which should be easy to recoup given the potential savings from heating some rooms/zones 10-12 hours a day rather than 24 hours at the moment.