Ground Source Heat Pumps

Moshie

Thanks for the info everyone, I guess the best thing forus to do would be to speak to a supplier and see what they have to say on it. Ihave not spoken to anyone yet, I came on this forum to read up on the GSHPsystems so that I ask the right questions etc and feel that I have enough questionsto fire in their direction.

Other than GSHP’s our only other options are:

-Solidfuel
-Oilheating
-ElectricStorage heaters

Out of the above oil heating and electrical storageheaters are not really cost effective in the long term as electricity & oilare only going to get more expensive. The solid fuel option could be used inconjunction to the GSHP I suppose (in Shetland we cut our own Peat to burn sothe cost is almost non-existent) but clearing out the ash tends to be dirtyetc.

I will update my findings and decision if anyone is interested.

Thanks

lovesgshp

Hi Jeepjunkie.

Having read completely through that link that you supplied, I thought that it would be worthwhile making more comments, due to some of the answers that were given to the poster of the problem and from the pictures posted.
1) The IVT/WBosch units have a expansion tank supplied as part of the package for the ground loop setup. This is to compensate for expansion/contraction of the coolant. If the OP had a system leak as is verified, this would lead to a vacuum and collapse of the tank.
2) The ground collectors appear to be too shallow and very poorly designed, as you would not normally use screw type connections, but thermally welded joints for unexposed situations.
3) From the OP: " From what I can find a 14kw system requires around 170-240 meters of DN20 or DN32 pipe buried at least 1m below ground. There is a trade off on depth: deeper = more geo thermal but less heat from the sun on the ground.
14 kw requires circa 2 x 125 mtr trenches each carrying 2out/in flows @ 30cm spacing, therefore 500mtrs each heat/return flow. We normally excavate at least 1.2 mtrs.

They suggest a backfill with sand to minimise voids and wet soil against the pipes, and insulating the return flow. Ideally backfill should be a flowable sand/cement/ash mix but I think that ius rare in the UK."
The sand bed is normal practice in a soil that may have flint etc.Wet soil is good. Return flow insulation is also a norm as the spacing of the ground loops become closer as they reach the collectors, which can mean they reduce the inlet flow temp in cold weather.

To be quite honest, the whole installation looked unprofessional and I hope the guy does now have it working ok. It also showed that some of the replies to the problem were coming from people that did not have a clue of what they were talking about.

Sorry for the long ramble!!

[Deleted User]

Geotherm wrote: »

Hi Jeepjunkie.

Having read completely through that link that you supplied, I thought that it would be worthwhile making more comments, due to some of the answers that were given to the poster of the problem and from the pictures posted.
1) The IVT/WBosch units have a expansion tank supplied as part of the package for the ground loop setup. This is to compensate for expansion/contraction of the coolant. If the OP had a system leak as is verified, this would lead to a vacuum and collapse of the tank.
2) The ground collectors appear to be too shallow and very poorly designed, as you would not normally use screw type connections, but thermally welded joints for unexposed situations.
3) From the OP: " From what I can find a 14kw system requires around 170-240 meters of DN20 or DN32 pipe buried at least 1m below ground. There is a trade off on depth: deeper = more geo thermal but less heat from the sun on the ground.
14 kw requires circa 2 x 125 mtr trenches each carrying 2out/in flows @ 30cm spacing, therefore 500mtrs each heat/return flow. We normally excavate at least 1.2 mtrs.

They suggest a backfill with sand to minimise voids and wet soil against the pipes, and insulating the return flow. Ideally backfill should be a flowable sand/cement/ash mix but I think that ius rare in the UK."
The sand bed is normal practice in a soil that may have flint etc.Wet soil is good. Return flow insulation is also a norm as the spacing of the ground loops become closer as they reach the collectors, which can mean they reduce the inlet flow temp in cold weather.

To be quite honest, the whole installation looked unprofessional and I hope the guy does now have it working ok. It also showed that some of the replies to the problem were coming from people that did not have a clue of what they were talking about.

Sorry for the long ramble!!

Brirfly, I guess the reason I posted it was... Just like an ASHP I tend to investigate all that can wrong with these systems i.e. how not to do it so when you go through the process of getting your own done you have a better idea what ask, expect etc. Cheers

528mike

one point being missed is the ground acts like a battery at some point its going to go flat ie (cold or frozen!) unless you have a very large ground collector, what i have done on my gshp is put a recharging system in my system?
this consists of 100m of 25mm of pe pipe below the rooftiles to work like a solar panel this pipe has a s plan valve and a pump and stats in circuit, it pumps low level heat back into the ground loop, i say low level as the mdpe pipe doesnt like high level heat?? 20c at the most
i have seen this working when the heat pumps working so the little bit of heat seeping out though the roof and the winter sun on the roof it was most likly acting like another ground loop to the heat pump
dont know as yet to how well its going to work but going on the last few weeks its being shoving a lot of heat down into the ground

lovesgshp

528mike wrote: »

one point being missed is the ground acts like a battery at some point its going to go flat ie (cold or frozen!) unless you have a very large ground collector, what i have done on my gshp is put a recharging system in my system?
this consists of 100m of 25mm of pe pipe below the rooftiles to work like a solar panel this pipe has a s plan valve and a pump and stats in circuit, it pumps low level heat back into the ground loop, i say low level as the mdpe pipe doesnt like high level heat?? 20c at the most
i have seen this working when the heat pumps working so the little bit of heat seeping out though the roof and the winter sun on the roof it was most likly acting like another ground loop to the heat pump
dont know as yet to how well its going to work but going on the last few weeks its being shoving a lot of heat down into the ground

Hi Mike.
The point you are making, has not been missed at all. If you read all the posts, then recharging by alternative methods has been discussed and it is suggested for compact collector systems and boreholes.
In a correctly designed ground loop/pump system, then there should be no need for extra input, unless you feel the need to spend more for minimal return.
Would be interesting to know a few more details e.g input/output temps from loops (winter), loop lengths, pump/house size.

lovesgshp

I was asked on a Italian forum for the running costs of the heating/DHW, with a GSHP so thought this may be interesting to those in the UK who are possibly considering installing a unit.
Please note that our electricity costs are far higher than yours!!

Just worked out the heat pump (160 ltr tank) DHW running hours for the last 12 months (13/6/2011 - 18/06/2012). Running hours DHW = 366 x 2.2kw = 805kwh. Have multiplied that by 0.25 cents per hour, so cost came out just over 200 Euro. Recharge time from 46C to 53C approx 5 mins.

Total operating hours over the same period, were 1830. The split DHW/Heating 20/80%. So 1464hrs x 2.2kw = 3220.8 kwh is the 24/7 heating cost. If you base that @ 25 cents per Kwh, then it works out just over 805 Euro to heat the house for the year.

thejebbulator

Hello all, I read the thread with interest.

I have a problem, a big one! Please forgive the bullet points but hopefully this will keep things simple:

New build house, obviously well insulated Block and lime render. Completed 15 months ago.

6,100 square feet.

2X 7kw IVT GSHP's Installed. 400m straight run (not coiled) ground loops.

Underfloor heating loops on ground floor, rads upstairs.

Usage is 30,500 units since 15 Nov 2011. Average of 114 units per day.

Rooms downstairs have stats set to 18 degrees and are satisfactory temperature. Except one carpeted room that rarely reaches required temperature. I am struggling to get the floors warmer than that.

Rooms upstairs are generally always 17 or below. Too cold for my wife!

I'm told time and again by the supplier that the Heatpumps are fine and my circuit is not balanced correctly. Yet I'm not convinced.

We have decided we need an independent expert heating engineer to come in and do a full report, this may well lead to legal action.

Here is the official spec from the supplier:

SPEC:
Ground Source Heating System comprising design, supply, commissioning and warranty. Project Type is defined as RETRO (Domestic)
Floor Area to be heated is 511m2 [I notice this is incorrect! It should be 574m] using Measurements (no plans seen) provided by client. Maximum heating demand is assumed at 20.2 kW
Heat Pump
IVT Greenline HT+ E7 Ground Source Heat Pump (Single Phase)
Rego 600 Computer Controller and Weather-Indoor temperature compensation sensors
Please refer to Unit Specifications to ensure electrical & space requirements can be met.
Water Storage Cylinder
IVT DVB300 300 litre (mains pressure) hot water cylinder
Ground Loop (per Heat Pump)
2 trenches 50m long, 1m wide by 1m deep are required.
Total of 400m of pipe work to be supplied as 2 x 200m coils, with connectors. Each trench to recieve 200m of pipework in 200mm sand bed. Trenches must have a minimum separation of 2m.
Ground works and sand works to be sub-contracted by customer.

Many thanks for looking.

lovesgshp

thejebbulator wrote: »

Hello all, I read the thread with interest.

I have a problem, a big one! Please forgive the bullet points but hopefully this will keep things simple:

New build house, obviously well insulated Block and lime render. Completed 15 months ago.

6,100 square feet.

2X 7kw IVT GSHP's Installed. 400m straight run (not coiled) ground loops.
Looks well undersized

Underfloor heating loops on ground floor, rads upstairs.

Usage is 30,500 units since 15 Nov 2011. Average of 114 units per day.

Rooms downstairs have stats set to 18 degrees and are satisfactory temperature. Except one carpeted room that rarely reaches required temperature. I am struggling to get the floors warmer than that.
Carpet may be insulating it too much.

Rooms upstairs are generally always 17 or below. Too cold for my wife!
Buffer tank temp should be high enough to allow circa 50C to the rads.

I'm told time and again by the supplier that the Heatpumps are fine and my circuit is not balanced correctly. Yet I'm not convinced.

We have decided we need an independent expert heating engineer to come in and do a full report, this may well lead to legal action.

Here is the official spec from the supplier:

SPEC:
Ground Source Heating System comprising design, supply, commissioning and warranty. Project Type is defined as RETRO (Domestic)
Floor Area to be heated is 511m2 [I notice this is incorrect! It should be 574m] using Measurements (no plans seen) provided by client. Maximum heating demand is assumed at 20.2 kW
Wonder why they only gave you 14kw output, max undersize would be 10%.
Heat Pump
IVT Greenline HT+ E7 Ground Source Heat Pump (Single Phase)
Rego 600 Computer Controller and Weather-Indoor temperature compensation sensors
What sensor influence on the indoor unit?
Please refer to Unit Specifications to ensure electrical & space requirements can be met.
Water Storage Cylinder
IVT DVB300 300 litre (mains pressure) hot water cylinder
Ground Loop (per Heat Pump)
2 trenches 50m long, 1m wide by 1m deep are required.
Our usual spec is 1.2 mtrs wide x min of 1.2 deep
Total of 400m of pipe work to be supplied as 2 x 200m coils, with connectors. Each trench to recieve 200m of pipework in 200mm sand bed. Trenches must have a minimum separation of 2m.
Again this is close, we specify minimum of 3 metres apart
Ground works and sand works to be sub-contracted by customer.

Many thanks for looking.

My primary view is that the units you have are much too undersized for the house. The other point is the trench sizing and spacing.
Is the company a accredited GSHP designer?
Can you give me readings of the heat button should be between 1 - 10.
All readings from the menu 3.
What timer settings are you on?
Access customer 2 menu, readings from 7.1 - 7.4.
List any fault codes.

thejebbulator

Thanks so much

I'm not sure what you mean by sensor influence on indoor unit?

At install I remember an IVT sensor being installed on the upstairs landing, but this was removed at 2nd fix, I don't know why.

Heat is 5. However the heat slope on the step controller is at 6.

here are some readings from one heat pump:


MENU 3: GT1 - OFF 60.2 NOW 34.5

GT2 -27.2

Went into service mode to get the following:

Front screen date and time which is always wrong!


GT6 Compressor 78.6

timer in menu 6: DHW Peak timer reads 0h 0m 0s
Add. heat timer reads 0h 4m 26s counting down.

7.1 = 3192 Heat pump HOURS
7.2 = 100% RAD 0% DHW
7.3 ADD HEAT HOURS 1110


hope that helps? thank you again very much!

lovesgshp

thejebbulator wrote: »

Thanks so much

I'm not sure what you mean by sensor influence on indoor unit?
When you go into the heating settings in menu 1 on the K2 menu, scroll down to room sensor influence. That will tell you how much it is compensating against the outside air temp. If it has been removed then it should be zero

At install I remember an IVT sensor being installed on the upstairs landing, but this was removed at 2nd fix, I don't know why.
see above

Heat is 5. However the heat slope on the step controller is at 6.
Looks too low for a combined UFH/Rad circuit, that is just over the underfloor max of 4. Try a change to 7

here are some readings from one heat pump:


MENU 3: GT1 - OFF 60.2 NOW 34.5
Should be nowhere near that variance

GT2 -27.2
Minus 27.2 outside air temp!!!

Went into service mode to get the following:

Front screen date and time which is always wrong!
Just reset in the K2 or service menu


GT6 Compressor 78.6
ok

timer in menu 6: DHW Peak timer reads 0h 0m 0s
Add. heat timer reads 0h 4m 26s counting down.
This means the electrical immersion is going to start in under 5 mins.

7.1 = 3192 Heat pump HOURS
Extremely high for just over 1 year running
7.2 = 100% RAD 0% DHW
Second pump controlling hot water only?
7.3 ADD HEAT HOURS 1110
That is ridiculous


hope that helps? thank you again very much!

You appear to have a major setup problem. I reread your initial post, where the installer ASSUMED the requirements. There should have been a full heating survey carried out, not just a assumption.
Can you give the second pump readings as well