Ground Source Heat Pumps

captainhindsight_2

Patrol wrote: »

I did enquire but as my installation was completed before 2009 was told it was not valid. i'm fairly sure the £1500 I got back was part of the scheme before that.

Ahhh yes, top of my head anything installed before 15th April 2009 will not qualify for legacy RHI.

beardymarrow

Hi,
I've run into a new problem with my GSHP now that the weather has turned cold. It just won't get the Rad Return up to the required temp so the Compressor is running basically all day with the Rad Return stuck at approx 36.5degC. I can get it to go up to about 38 if I switch all the radiators with stats off, but clearly that's not a particularly warm solution :-)

I've checked the rad filter inside the GSHP and the collector filter on top and all good. DHW is produced no problem.

Here is a graph showing the various parameters that I think are interesting (ignore after 12noon, as I was switching it off to clean filters etc. then) :-

http://i59.tinypic.com/35881fd.jpg
As you'll see the add heat doesn't even kick in to sort the problem out all the time.

Any ideas?

Beardy

Xander_Sim

beardymarrow wrote: »

Hi,
I've had the add. heat running on my IVT E11 a little bit over the last couple of weeks (big DHW usage so set the extra hot water on, and then went away for a few days so set holiday mode), so the GSHP has been working hard to bring back up to temp.

Anyway, my cassette is set to 2/3rd (so 6kw) max. Should I set it to 3/3 (9kw) so that on the rare occasions when it's needed, then it does the job more quickly. Surely 6kw for 1Hr is the same as 9kw for 40mins in terms of consumption and the amount that it'll heat the water by? Or am I missing something.

Thanks guys

Beardy

Beardy, I see you are hoping to get some help on a couple points.
I've been reading through your previous posts and gained a bit more info on your system.
All I can do is offer my experience, others here no doubt have a deeper understanding.
We both have the same IVT E11.
I tried the variety of additional heat options and combined this with cost vs. kWh I found that it always seems to be cheaper to have the heat pump running on compressor for much, much longer before adding additional heat. Then I also found it cheaper to run her on the lowest additional heat setting for longer rather than higher for shorter if you get my meaning.
It was simple trial and error for me in this case.

Xander_Sim

Hi Beardy,
I love this gizmo you have for monitoring your heat pump, absolutely great to see how the unit deals with the demand.

I have two comments which I really hope helps a bit buecause this is a difficult one...
Firstly, I can't see why the heatpump would not achieve 38 unless it was a setting issue so some background thinking is required. Focussing on the use during the night against what happens during the day. What causes the heatpump to start up then shift into standby every hour? Is it the return temperature sensor or room thermostat/s? This could be down to your thermostats their influence or curve settings. Or;
Secondly, could it be; it may be simplistic but do you have enough pressure in the system and does your water circulation pumps run all the time, because they should be even when the compressor is off.
I can't understand why your temperature drops so quickly after the unit goes into standby - surely for a underfloor or large domestic hot water system this should take some time. Do you know why?
My unit comes on infrequently does its work on compressor then is off for a significant number of hours other than when you use some hot water.

I really hope this is of help to you!
Xander

lovesgshp

Hi Beardy.
A few thoughts.
I remember that you carried out a factory reset in a earlier post, but cannot remember if you have a buffer tank. Could you confirm?
If you have the tank, then please confirm the heat curve readings down to minus 20C. Also the setting from 1-10 on the unit.
As it is a combined UFH/Rad system, there should be a mixing valve for the temperature requirements. Check that is switching properly between the 2 circuits, as at the moment it looks like UHF only.
Check the heating circulating pump for air, as possible after your 3 way valve change.

beardymarrow

Xander_Sim wrote: »

Hi Beardy,
I love this gizmo you have for monitoring your heat pump, absolutely great to see how the unit deals with the demand.

I have two comments which I really hope helps a bit buecause this is a difficult one...
Firstly, I can't see why the heatpump would not achieve 38 unless it was a setting issue so some background thinking is required. Focussing on the use during the night against what happens during the day. What causes the heatpump to start up then shift into standby every hour? Is it the return temperature sensor or room thermostat/s? This could be down to your thermostats their influence or curve settings. Or;
Secondly, could it be; it may be simplistic but do you have enough pressure in the system and does your water circulation pumps run all the time, because they should be even when the compressor is off.
I can't understand why your temperature drops so quickly after the unit goes into standby - surely for a underfloor or large domestic hot water system this should take some time. Do you know why?
My unit comes on infrequently does its work on compressor then is off for a significant number of hours other than when you use some hot water.

I really hope this is of help to you!
Xander

Hi Xander,
Thanks for the replies. Over night, what causes the heat pump to start-up and then go off is the return temp. I have that set 3degC lower at night. So the return temp drops (quite quickly as you can see), the pump comes on, brings red return back up to the setting and goes back off.

I topped the pressure up yesterday to 1.5Bar. It had only dropped to about 1.3 since last checking a few months ago.

The point about the temp dropping really quickly is incredibly useful. I hadn't thought that unusual, but now you point it out, that makes sense. Clearly if it's losing a lot of temp, then the GSHP can't get it up to temp as it's constantly fighting the loss, plus of course it has to come on more frequently.

I have UFH and Rads. There are 3 zones coming off the GSHP. One is for the UFH that is further split by a manifold into 4 zones (2 for the kitchen, garden room, and utility room). The other 2 zones are the downstairs rads and then the upstairs rads.

The house is 3 story with the UFH and rads ground floor and rads 1st and 2nd floor. One the 2nd floor there is a manifold and pump, as far as I can tell the ground and 1st floor rads are normal distribution straight off the external CH pump.

Water circulation pump is constantly on, yes.

I'm at a complete loss as to why it's losing temp so quickly. The house is fairly big (5 bed detached, 302m2), but it's only 2 years old with very thick cavity insulation, composite wall ties, loft is full of insulation (literally) etc.. 78/100 on the EPC with zero recommendations to improve that.

How do I narrow it down?

beardymarrow

lovesgshp wrote: »

Hi Beardy.
A few thoughts.
I remember that you carried out a factory reset in a earlier post, but cannot remember if you have a buffer tank. Could you confirm?
If you have the tank, then please confirm the heat curve readings down to minus 20C. Also the setting from 1-10 on the unit.
As it is a combined UFH/Rad system, there should be a mixing valve for the temperature requirements. Check that is switching properly between the 2 circuits, as at the moment it looks like UHF only.
Check the heating circulating pump for air, as possible after your 3 way valve change.

Hi Lovesgshp,
There is no buffer tank, no. I can't see any mixing valve either. There's a main CH pump, a seperate pump for the UFH and a seperate pump for the 2nd floor rads. I think the split between UFH and rads is done by the different speeds that the 2 pumps are running at, but I could be wrong.

Room temp is now set to 17.8. Was at 19 but I've been gradually lowering it over the last couple of days to try to prevent the GSHP being constantly on. I've also lowered the curve from 4 to 3.7, again for the same reason. It has helped, in that the GSHP can get the rad return up to temp now (29.7 on 34.7 off), but of course as soon as it switches off it plummets and then comes back on again.

Will go and check the heating circulation pump for air. Can you remind me how to do that? Do you mean the one inside the GSHP or the external ones?

lovesgshp

Beardy.
You just need to unscrew the centre on each pump to check for air.
I need the heat curve settings . At the moment, you are set purely for UFH and not rads. Anything under floor is at max 4, so this looks like the main problem.

beardymarrow

lovesgshp wrote: »

Beardy.
You just need to unscrew the centre on each pump to check for air.
I need the heat curve settings . At the moment, you are set purely for UFH and not rads. Anything under floor is at max 4, so this looks like the main problem.

Thanks. Done that. Water immediately started coming out.

The heat curve is just set at 3.7, and is a straight line (no adjustments made to it).
20 - 20
15 - 23
10 - 26
5 - 28.9
0 - 31.9
-5 - 34.8
-10 - 37.8
-15 - 40.7
-20 - 43.7

Should I isolate the UFH or all the rads and see what happens? I actually have 4 zones (one for the UFH) not 3 as I previously stated. So I could switch off the 3 non UFH ones (or vica-versa)?

lovesgshp

OK the pumps seem to be clear of air, so that is eliminated.
Your problem, from how I see it at the moment is the heat curve is far too low for the radiators. The pump is only trying to supply 31.9C @ 0C outside. This is why it is probably operating so much, as the rads are losing the heat faster than the UFH.
Are the rooms with the UFH at a reasonable temperature? If so, shut down the UHF system and turn the curve up to 5. The pump should run to the new flow temp. May take a while to settle for running time, but the rads should increase temperature.