Ground Source Heat Pumps

Xander_Sim

Evening Lovesgshp,
I'm fully UFH, a friend of mine has a combo with both high output rads and fan assist dimplex units on trial over the winter which he is fairly chuffed with so far.
We have similar overall running costs up to now.

I am also trialling something new this winter.
I have closed a couple loops upstairs on my north facing bedrooms and am trialling a couple small dimplex electric panel heaters to get a comparative cost.
I expect it will be small beer but if I can cut a bit of cost without compromising on heat I will.
It'll be a worthwhile learning exercise anyway.

Cheers
Xander

lovesgshp

You can cut off up to 30% of the heating system if you need to, and are not using the rooms.

Patrol

I don't know as much as other contributors here so the below is more thoughts than anything else.

If I understand your graph correctly your compressor is running all day and cycling overnight. Turning your rads down sees the compressor cycling on 30 mins then off 30 mins. Overnight cycling is probably a result of a timer setting to reduce heating temperature.

I'm not sure turning the UFH down/off will help if set in screed as it should be a heat store for the entire house and should be more effective than the radiators? I'd focus short term on reducing radiator flow where not essential. Question: Does the house gradually warm up through the day and then cool overnight, if so you might want to remove the overnight temperature reduction so half the day isn't spent regaining it.

Longer term the suggestion of a buffer tank sounds sensible (last winter your DHW cylinder was fulfilling this role). I'm considering doing this depending how everything functions this winter.

Patrol

& thinking about it a bit more.

Return temperature is taking 3-4 hours each morning to increase to a consistent level but then can't reach the target level? 3 degree drop overnight might not save much but put a large demand on early morning requirements alongside DHW demand.

Did you increase the additional heat to 3/3, if so might be worth reducing that back, e.g. if you have single phase electric supply.

Are your radiators suitable for GSHP lower temperatures. Was the original design intended to have the GSHP on constantly during peak demand. Is it working as designed for a system with a large number of radiators (if that's the case, a buffer tank might have been a good idea from the start). Maybe call the supplier and talk it through with them as they may have design notes that give you additional insight.

If you know the expected heat demand (e.g. from EPC) and can see current use is significantly beyond that, you could have unexpected heat losses. Thermal imaging could reveal that, e.g. "obvious" like an unblocked chimney or something with defective workmanship.

beardymarrow

Patrol wrote: »

& thinking about it a bit more.

Return temperature is taking 3-4 hours each morning to increase to a consistent level but then can't reach the target level? 3 degree drop overnight might not save much but put a large demand on early morning requirements alongside DHW demand.

Did you increase the additional heat to 3/3, if so might be worth reducing that back, e.g. if you have single phase electric supply.

Are your radiators suitable for GSHP lower temperatures. Was the original design intended to have the GSHP on constantly during peak demand. Is it working as designed for a system with a large number of radiators (if that's the case, a buffer tank might have been a good idea from the start). Maybe call the supplier and talk it through with them as they may have design notes that give you additional insight.

If you know the expected heat demand (e.g. from EPC) and can see current use is significantly beyond that, you could have unexpected heat losses. Thermal imaging could reveal that, e.g. "obvious" like an unblocked chimney or something with defective workmanship.

Thanks Patrol,
Yes, that's exactly what's happening. I put the 3deg night drop in to prevent the GSHP running 24Hrs a day, which it would have without it. I left the Add heat at 2/3rds.
The house was built with GSHP in mind, so the rads are all appropriately over-sized.
Demand from the EPC for heat is 19,500 kWH for space and 2,450 for water. That's for the whole year, plus I guess it's the real kwH required, not the kWH consumed as the GSHP has the COP to multiple by, so difficult to compare against actuals.

I have managed to improve things a bit by removing the UFH and upping the curve as lovesgshp suggested, but obviously that's a fault finding technique not a long term option.
This morning I have left the UFH off and been switching off each of the 3 isolatable areas one by one and so far it looks like one of the 3 areas is having a much bigger impact than the others. So, once I'm 100% sure of that, I'll leave that area isolated, reintroduce the UFH and set the curve back down. Then I can work to narrow it down further to see if it's generally that area that's losing heat or one of the rads is somehow losing heat too quickly.

Will report back ASAP with a new graph :-)

beardymarrow

Definitely seems like one of my 3 rad areas is having more impact than the others :-

http://oi59.tinypic.com/a27xq1.jpg
When Area 2 is isolated the temp drop is much slower and the temp rise on warm up much quicker. So, I've isolated that area, re-enabled the UFH (was starting to get a bit chilly in that area), and set the curve back to 4, so it's appropriate for both rads and UFH. Will now monitor to check it's better. I know it'll take a while to settle now I've got the UFH on, so will leave it overnight. I've also disabled the -3degC curve adjustment overnight.

If all OK, then I can further narrow down where the heat is being lost.

Cardew

As I have said on more than one occasion, the posts above demonstrate one of the biggest flaws of heat pumps; namely the degree of technical expertise required of the end user to enable the system to operate properly - or even detect a fault.


How do manufacturers/installers expect people used to gas/oil CH to cope? My wife 'ain't thick'(as her MA might demonstrate) but she would have neither the knowledge or inclination to operate such a system.

lovesgshp

Can I just make a few comments with reference to some earlier posts?
1) A combined system with rads, should always have a buffer tank, as should a rad only circuit. The buffer tank is set to a higher temperature with a mixer valve to prevent the constant cycling from UFH to rads.
In this case with Beardy, there is no buffer, so the pump is operating @ UHF settings (level 4). The rads will therefore never get above the temperature return set and will just make the pump work more, as it is trying to reach different temperature settings.
2) Patrol. The DHW tank has nothing to do with the heating circuit, unless it is a heat store type of set-up.
If Beardy is happy to operate rads @ 35C, then obviously that is his choice. I do not recommend it.
Cardew I agree with what you are saying. On design/ installation, then everything should be set up correctly, so there should only be minor adjustments. The systems are not that difficult to manage. I have one female client who can work it better than her husband!!

Patrol

Re point 2, having a 3 way valve malfunction meant it was sharing. Agree it shouldn't in a correctly functioning system, sorry for the confusion.

beardymarrow

lovesgshp wrote: »

Can I just make a few comments with reference to some earlier posts?
1) A combined system with rads, should always have a buffer tank, as should a rad only circuit. The buffer tank is set to a higher temperature with a mixer valve to prevent the constant cycling from UFH to rads.
In this case with Beardy, there is no buffer, so the pump is operating @ UHF settings (level 4). The rads will therefore never get above the temperature return set and will just make the pump work more, as it is trying to reach different temperature settings.
2) Patrol. The DHW tank has nothing to do with the heating circuit, unless it is a heat store type of set-up.
If Beardy is happy to operate rads @ 35C, then obviously that is his choice. I do not recommend it.

Thanks lovesgshp,
Can you explain a little bit about how the buffer tank would work?

And, also how does the mixer valve work. I think I understand that the mixer valve is controlled by the GSHP, and has a different curve from the main one (with an additional temperature sensor, GT4). Does that mean that the GSHP will come on when the UFH drops below that curve, get that back up to temp, and then 10mins later (or whatever) come back on again and service the rads (at a higher temp).

I do completely trust you on this, but I'd like to know what I'm talking about before I get a quote for it.

Have you any idea what the sort of cost of installing a mixer valve would be. I guess that has to be supplied (and fitted?) by ICE (or another IVT supplier).
What about the cost of that plus the buffer tank? How big a one do I need to fit? I'm assuming the buffer tank is a much bigger job, so that may have to wait.

Sorry for the bombardment, and thanks in advance
Beardy