Ground Source Heat Pumps

lovesgshp

Thanks for that info.
The temperature drop on start is quite normal, so nothing to worry about.
Try setting the DHW temp to 48C and time again when you get the chance. The 54.4C cutout seems high if the hysterisis is 4C.

A/B seems to be working. Good for the no air in cylinder..

Patrol

DHW now on 48C. Are we measuring the same thing, i.e. my twin cylinder is 300l + 160l so just want to check whether that would increase heating times or similar as one indirectly heats the other?

I've replaced the batteries on a smart-meter in my consumer unit to spot when the heat pump activates more easily. While doing this I noticed my electric use for 30 hours was 11 units. I've never had a sub 15 unit day since the house was built in 2007. It feels like the GSHP has never operated as it should.

& another question. In my original post I stated my GT1 setting, having looked at other values posted my "on" value looks very low. What are the implications of this?
Return Radiator GT1 on 8.0 now 32.8

lovesgshp

Patrol wrote: »

DHW now on 48C. Are we measuring the same thing, i.e. my twin cylinder is 300l + 160l so just want to check whether that would increase heating times or similar as one indirectly heats the other?
Yes, checking the same thing, as would like to see if there is any shorter operating time. There may well be no difference, but the range is slightly lower to cutoff.

I've replaced the batteries on a smart-meter in my consumer unit to spot when the heat pump activates more easily. While doing this I noticed my electric use for 30 hours was 11 units. I've never had a sub 15 unit day since the house was built in 2007. It feels like the GSHP has never operated as it should.

& another question. In my original post I stated my GT1 setting, having looked at other values posted my "on" value looks very low. What are the implications of this?
Return Radiator GT1 on 8.0 now 32.8

You beat me to that one!! I was looking at that reading last night as it was staying constant at 8C, but the return value has always been high. If you look in the manual p41, then you will see the GT1 sensor cable is supplied and what it looks like.
If you do not feel confident with the following steps, then suggest you get a electrician to check this one out, as believe that sensor may have gone faulty.
1) Switch off the pump completely.
2) On the terminal board, look for the GT1 connector (Manual P60) and follow the cable route of that to the actual sensor.. The sensor itself may be held on by aluminium tape.
3) Remove the connected sensor from the return pipe.
4) Switch the unit back on. You may have to wait until the unit does its full pre-start checks.
5) With GT1 on the menu, hold the sensor and see if the temperature starts to drop to body heat, or alternatively use one of those air cleaner sprays for computers to reduce it more rapidly.
6) If very little change then GT1 needs to be replaced.

7) If you use a electrician, then I can let you know the Ohmeter values a different temperatures, or if you have the full manual then the details are on P68.

Let me know how you get on. If you do not have the full manual, then PM me a email address and will send you it.

Patrol

Yes, checking the same thing
I meant are you expecting that tank combination to take 10 mins, do you have a similar setup or a different size? & are electrical supply and other factors relevant, I'm on single phase for example.

GT1 checked, it went up to 8/33C while held for a few minutes and was still going up so expect it would eventually get to body temperature. Is back in position and showing 8/22.3.

The installation guide suggests GT1 should be located 1-2 metres away from the pump and near a corner of the return heating supply. It was attached about 30cm above the pump on the vertical flow return heating supply with a 5mm cable tie instead of tape. I assume I need to rectify both these points to improve accuracy.

This evenings DHW at 48C, temperature outside 13.1C. 27 minutes seemed quicker than usual (earlier example without detailed timings won't be as accurate as I was approximating).
6.07: 45.9
6.10: 45.1
6.13: 46 / 62.3 / 49.1 / 43.6 / 10.6 / 7.8
6.17: 47 / 68.5 / 49.9 / 44.4 / 10.3 / 7.5
6.20: 48 / 72.6 / 51.4 / 46 / 9.9 / 7.2
6.23: 49 / 69.6 / 52.6 / 47.1 / 9.7 / 7.1
6.26: 50 / 74 / 53.6 / 47.9 / 9.5 / 6.9
6.29: 51 / 77.5 / 54.6 / 48.9 / 9.4 / 6.9
6:33: 52 / 80.3 / 55.8 / 50 / 9.3 / 6.8
6.34: 52.1, stop

Still no heating cycle.
Hours: 13954 (+2) / 900 (unchanged)
Final ground loop temperature is about 0.4C higher this time

lovesgshp

Patrol wrote: »

Yes, checking the same thing
I meant are you expecting that tank combination to take 10 mins, do you have a similar setup or a different size? & are electrical supply and other factors relevant, I'm on single phase for example.
Mine is a different size and on 3 phase. I am comparing your figures with a 14Kw output unit for heating times of the DHW tank of the same size, which takes between 10 - 15mins to recharge @ 50c. The recharge figures for your unit, are because of the smaller pump and we will have stay with that.

GT1 checked, it went up to 8/33C while held for a few minutes and was still going up so expect it would eventually get to body temperature. Is back in position and showing 8/22.3.
OK that is reading. What is room temperature GT5 showing and also is there any other heat source being used near to the GT5 sensor? If GT5 is showing high, then we need to go to the 0 setting or isolate it from the system as another test.

The installation guide suggests GT1 should be located 1-2 metres away from the pump and near a corner of the return heating supply. It was attached about 30cm above the pump on the vertical flow return heating supply with a 5mm cable tie instead of tape. I assume I need to rectify both these points to improve accuracy.
Aluminium tape will help, but not a problem at the moment, there are other things to resolve before the finer details.

This evenings DHW at 48C, temperature outside 13.1C. 27 minutes seemed quicker than usual (earlier example without detailed timings won't be as accurate as I was approximating).
6.07: 45.9
6.10: 45.1
6.13: 46 / 62.3 / 49.1 / 43.6 / 10.6 / 7.8
6.17: 47 / 68.5 / 49.9 / 44.4 / 10.3 / 7.5
6.20: 48 / 72.6 / 51.4 / 46 / 9.9 / 7.2
6.23: 49 / 69.6 / 52.6 / 47.1 / 9.7 / 7.1
6.26: 50 / 74 / 53.6 / 47.9 / 9.5 / 6.9
6.29: 51 / 77.5 / 54.6 / 48.9 / 9.4 / 6.9
6:33: 52 / 80.3 / 55.8 / 50 / 9.3 / 6.8
6.34: 52.1, stop

Still no heating cycle.
Hours: 13954 (+2) / 900 (unchanged)
Final ground loop temperature is about 0.4C higher this time

The +2 are just the DHW I would think. Have you set it on a timer, or is it still 24/7

Patrol

Thanks, understand about the recharge figures and GT1.

My main heating zone is showing 21C throughout. Either GT5 is reading high by 1.5-2C or my digital thermometer reads low (it doesn't show 10ths so can't narrow down further).

2 of 3 rooms with UFH thermostats set to 16C are also reading 21C, their doors are open. The third door is shut and is recording 19C. All 3 of these rooms have cooler tiles than those in the main zone.

So I think the UFH is circulating a small amount of heat but not sure where that heat is coming from. 3 way valve is one option, but the house design might be another.

GT5 is in a tiled central hallway approx 12m x 2m and no direct southern exposure. The UFH manifold is 2m from GT5, under the stairs and not noticably warm to the touch or heating that space today. Both of which it normally does under a heating cycle.

Heat sources;
- Woodburning stove. 6m and 1 door away. Not used for 2 months.
- Cooker. 5m away separated by a block wall. Door just past GT5.
- Possibly fridge/freezer; other side of the wall to GT5 in a sealed unit.
- Sun onto 20m south wall & through windows / doors onto tiled floors. Tiles may be warming the screed and UFH?

The house was built in 2007, while not an outstanding specification I did specify 150mm blockwork, 100mm underfloor insulation and tiled floors with screeded UFH. We then added multifoil roof insulation after the heating calcs because of concerns around the air pressure test through a tiled roof. That test result was quite a lot better than required and the house retains heat a lot better than my previous houses.

Our upstairs rooms were a bit of an afterthought. I compromised with radiators instead of UFH and not sure they are suitable for the water temperature (my mistake as I didn't check). My daughter has moved upstairs so I'm thinking about replacing them with more suitable ones if the rooms are too cold for her later this year.

The GSHP supplier calculated 6.4kw maximum demand if that is of any help. They initially suggested a smaller setup with integrated cylinder but when we discussed hot water requirements for a family of 4 + visitors they recommended the larger units instead.

I haven't set the timer, this is menu 4? For our use I was thinking about 10pm-5.30am with a reduction of 2C so ready for my weekday 5.45am routine. Believe I tried it 10-6 a few years ago before switching everything off at those times and never switched it on again.

lovesgshp

Thanks for the info.
GT1 on at 8C: This is a combination of factors that include the room temp sensor reading 21C against the setting of 18.8C. The sun coming in is also helping to keep the switch on to that lower figure.
Have just physically checked by a setting change on my unit. Room temp set at 18.5, influence 5, actual 19C. Changed to temp 15.5. At that point the switch on dropped to 7.5C.
You could try the test by increasing the room temp setting to say 1C above its current level and then check the GT1 on temp.
Yes, it is quite possible the sun is also keeping the ambient temp high.
With the radiators, then the installer/design engineer should have specified a buffer tank. As you haven't previously mentioned one, then I am presuming there is not one installed. Please correct me if I am wrong on that point.
As it is underfloor heating in the main areas, then if you are going to use the timers, then only reduce by 1.5C.
With the sizing of the pump, in my honest opinion, it is too small for a house of over 200m2. My reasoning for this is the high electrical heater input since install, as that should be minimal. A E9 or E11 would have been more suitable. Difference in cost would be more, but when you multiply the number of hours the electricity has input x 6Kw, then you would be saving more in the long run.
Yes, now move the GT1 sensor away to the correct location.

Patrol

Helps to know the size of your own house. I was approximating external measurement and was about 10m out downstairs. If I remove the external wall/cavity thickness it works out about 150m interior space and removing eaves space upstairs drops that to 35m.

No buffer tank so far as I am aware.

Room temp 22C has GT1 go from 8 to 14.9. 23C has 19.9. I've set it back to 18 for the time being.

When you say reduce timers by 1.5 do you mean menu 4.1 or the bedroom thermostats?

GT1 has been moved, showing 8/22.1.

lovesgshp

Patrol wrote: »

Helps to know the size of your own house. I was approximating external measurement and was about 10m out downstairs. If I remove the external wall/cavity thickness it works out about 150m interior space and removing eaves space upstairs drops that to 35m.
OK, apologise if I misread the property size. We calculate on heated floor area requirements, so that was reason for the comment. 180m2 for yours would look more like a E9 Here we have a heated floor area of 120m2, although the house is 240m2. The lower floor is not used at the moment.

No buffer tank so far as I am aware.
You should consider, having one installed before changing rads etc., as this may not have been considered in the original design specs. It will help with both the UFH and rad temps.

Room temp 22C has GT1 go from 8 to 14.9. 23C has 19.9. I've set it back to 18 for the time being.
Thats fine, it is working correctly.

When you say reduce timers by 1.5 do you mean menu 4.1 or the bedroom thermostats?
In 4.1. You only need to reduce the flow return temperature, so use 4.1 and 4.1.1

GT1 has been moved, showing 8/22.1.

OK, things are looking better. Suggest you look into the buffer tank for the rads. It will probably be far less expensive than changing them.

Patrol

More a case of me mis-stating it

4.1.1 reduced from -2 to -1.5.

This is how I understand a buffer tank would work.

Iincreased volume of water in the heating circuit, e.g. from 160l +ufh / rads to 160l + ufh / rads + buffer.

This would provide more consistent flow temperatures as e.g. x% extra water would contain y% extra heat and take longer to drop from peak heat to reheat point.

It would also help the GSHP as the heat cycles would be less frequent and longer duration, reducing the cycle startup overhead.

My GSHP is in a corner with the cylinder next to it so a buffer tank would have to sit the other side of the cylinder. I have a pump about 50cm from the GSHP heating supply pipe which I think might need to be moved to after the buffer tank so it draws from that rather than the GSHP. Then feed the buffer tank back to where the pump output goes.

I can get a quote for this work, presumably there is a sensible size of buffer tank to complement the GSHP, etc.
- UFH : 560 metres.
- Rads : 3 600mm x 480mm twins. 1 120mm x 480mm twin which I expect is not sufficient for the 5m x 5m room my daughter now occupies. Wasn't a problem when it was used as a junk room.

& I haven't mentioned the towel rails (sigh). 3 900mm x 480mm which I don't really want much more than lukewarm.

On the positive side, the heat pump has only used another 2 hours ground loop and my electric meter had a 15kw day which is usually only seen in the heat of summer.

Another question. Is there a recommended way to check each manifold flow / return temperature such as sticky thermometers so I can check that is set up correctly too.