Ground Source Heat Pumps

beardymarrow

JHen1 said:

So just reread you post and it looks like the second picture is the GT11 sensor.

Hi, I'd be surprised if it was, but I'll be honest I've only got practical experience of my E series. From the manual though, it should be inside the unit. Take a look at Page 42 and that will show where the cold side pipes enter the unit. The two in the back right corner are the cold side pipes. GT10 will be inside the unit on the In (Pipe 5 on the drawing) and GT11 on the Out (Pipe 6).

beardymarrow

JHen1 said:

Ok, from your last post I think this is it, the sensor in my last picture is also shown here  

Yep, that's the cold side filter in (the silver thing just to the left of the two red knobs). That is the GT10 sensor as it's on the In side (same side as the filter). That's strange, as the manual shows it inside the unit (see Page 53) factory fitted. The installer must have moved it for some reason. It's therefore possible they moved the GT11 to outside the unit, too. Probably makes your job of checking them and/or swapping them over easier though :-)

JHen1

So I checked last night and the alarm had gone off, but the readings were GT10 2.7 and GT11 138.3 and this morning, alarm still off and readings GT10 1.8 and GT11 130.0

JHen1

JHen1 said:

So I checked last night and the alarm had gone off, but the readings were GT10 2.7 and GT11 138.3 and this morning, alarm still off and readings GT10 1.8 and GT11 130.0

I also took the front cover off and tried to trace the GT11 cable. It appears to go to a pipe and the bottom, back right of the cab. Unfortunately this not that easy to access for me as my cab is located in a cupboard with no access to the right of the cab.

beardymarrow

JHen1 said:

So I checked last night and the alarm had gone off, but the readings were GT10 2.7 and GT11 138.3 and this morning, alarm still off and readings GT10 1.8 and GT11 130.0

Great, that's got to be a sensor issue then, not a "real" one. The sensor will show really high temperatures if the resistance across it is really low (like if the two wires touch each other, or one of them touches something else metal).
In order of likelihood for where the problem is :-
1. Most likely. The insulation on the two wires to the sensor have worn through vibration and rubbing and they are touching. Find the problem, cut the wire and then reconnect it with a little chocolate block. It doesn't matter which way around the wires go.
2. Next most likely. Sensor itself is faulty. Replace with new.
3. Least likely. The sensing circuitry on the main board is faulty.
If you can swap the GT10 and GT11 connectors over where they connect to the circuit board, and the problem moves to GT10, but GT11 is fine, then you know the circuit board is good and No 3 can be ruled out.
Unfortunately there's no way to fix this without checking the whole wire from the control unit to the sensor and if that's all good, replacing the sensor. I realise that's easier said than done with a C as you've got the hot water cyclinder taking up loads of space. Maybe you can undo and remove the right hand panel just enough to get in there?

JHen1

beardymarrow - much appreciated 👍

JHen1

So I finally replaced the GT11 sensor. I was not able to access the side or the rear of the unit so I have run the cable up the unit (following the other cables) and have attached this cable externally to the unit onto the pipe. I can only someone had the same problem with the GT10(?) cable this is also externally connected (as per my previous photo)

After doing so I had initial readings of GT10 6.1 and GT11 4.0, but now these are GT10 2.7 and GT11 -1.5 - Is that ok ?

beardymarrow

Awesome, well done. Looks like you've fixed it. You should aim for between 2 and 4 degrees difference between gt10 and gt11 (gt11 will always be cooler). I'm running at -3.8 and -0.1 right now (so 3.7 delta). You're a little over that at 4.2 which is slightly more than ideal, but personally I'd call that all good given the cold outside temps at the moment.
Good job. 
Also thanks for feeding back. Often don't hear back from people so I assume the advice given helps, but it's good to confirm so I know for future. 

poohbear59

The cottage we let for holidays has a gshp. There has been no one in since 12th December. I read the electricity meter yesterday and 24 days had cost me £129. I have set the room temp at 16C: we have had some very cold weather recently. The only power use has been some led lights on the front of the cottage and the heat pump. 
Can you please help me to learn how to make power savings please? Is there another setting I can use so the heat pump isn't on so often? 
Thank you.

matelodave

We need lots more info on your set-up and setting before anyone could come to any conclusions or make any suggestions.

What make and model of heat pump, what sort of emitters (Radiators, underfloor, fan coil units). Does it also heat hot water, if so is it still set, for how long and to what temperature.

What is the flow temperature,  is weather compensation active. Has it got a boost or immersion heater. Is it activated.  What sort of temperature & timer controls has the cottage got apart from the controller on the heatpump. How big is the place. How well is it insulated

What was you electricity consumption over that period in kwh as that's more informative than just how much it all cost especially if you are on an expensive tariff. What tariff are you on (price per kwh and s/c)