Ground Source Heat Pumps

beardymarrow

lstevensuk said:

Just playing around with my IVT heat pump trying to learn a bit more about the different settings (any good resources on this?). I came across setting 8.1 - Additional Heat - Setting additional heat timer. This is set to 120mins - what does it actually do and can I turn it down?

Hi,
The manual is a really great resource for what the settings do - Here's a copy - https://u.pcloud.link/publink/show?code=XZCjGYXZPcHhhW7eRNR8qHTFFgu8fSh3Y86X

8.1 is "Add. heat timer The function gives you the possibility to set the time that should elapse before the additional heat starts if the heat pump cannot produce sufficient heat on its own. On delivery the heat pump is set to one hour."

Mine is set to 1Hr. 2Hrs as you have would be more efficient then mine as it's going to keep trying the compressor on its own for longer before resorting to switching the immersion heater on as well, but it could mean the house temperature fluctuates a bit more as a downside to that, in really cold weather. If you're happy with temperature stability in the house when it's really cold, then I'd leave it be. It'll only increase electricity consumption to lower it :-)

lstevensuk

Thanks @beardymarrow that makes sense now.

I was more after some beginner tutorials on the heat curve settings - has anyone done anything on YouTube. Can only find basic this is how you set it type things - not the why and what you should be looking for.

lstevensuk

@beardymarrow what does the fine tune menu option do? Mines set to + .5 but unsure what it’s actually doing? Thanks

beardymarrow

So, basically the curve (which is a bad name, it's really a slope) defines how hot the heat pump wants to get the radiators for a given outside temperature. The colder it gets outside, the hotter the heat pump gets the radiators.
The slope determines how much hotter it gets for each degree it gets colder outside. The higher the slope the more heat the pump will give you per degree outside below 20deg.

If it's too cold inside when the temp outside is below 5deg, then you increase the slope (only do this by say 0.2 each time and leave it a day or two to settle). If it's too hot, you decrease the slope.

Fine tune can tune that by increasing or decreasing the target radiator temp across the board (regardless of the outside temp), so if it's not hot enough inside when the temperature is warmish outside (above 5deg), but it's OK, then you can increase the fine-tune a bit.
If it's too hot inside when the temp outside is warmish, but it's OK the rest of the time outside you can decrease the fine-tune.

Hope that helps.

lstevensuk

beardymarrow said:

So, basically the curve (which is a bad name, it's really a slope) defines how hot the heat pump wants to get the radiators for a given outside temperature. The colder it gets outside, the hotter the heat pump gets the radiators.
The slope determines how much hotter it gets for each degree it gets colder outside. The higher the slope the more heat the pump will give you per degree outside below 20deg.

If it's too cold inside when the temp outside is below 5deg, then you increase the slope (only do this by say 0.2 each time and leave it a day or two to settle). If it's too hot, you decrease the slope.

Fine tune can tune that by increasing or decreasing the target radiator temp across the board (regardless of the outside temp), so if it's not hot enough inside when the temperature is warmish outside (above 5deg), but it's OK, then you can increase the fine-tune a bit.
If it's too hot inside when the temp outside is warmish, but it's OK the rest of the time outside you can decrease the fine-tune.

Hope that helps.

Thanks as ever! That makes some sense now. I might actually reduce it a bit then as it certainly doesn't feel cold inside. Although my UFH never seems to be able to go hot enough in comparison - a tricky balancing act!

beardymarrow

lstevensuk said:

Thanks as ever! That makes some sense now. I might actually reduce it a bit then as it certainly doesn't feel cold inside. Although my UFH never seems to be able to go hot enough in comparison - a tricky balancing act!

Maybe just open the UFH mix valve up a little bit more? That will put a little bit more of the heat into the UFH, and a bit less into the rads, and might balance itself out a bit better? Could still turn the slope down as well if you wanted. Only do it a little bit (0.1 or 0.2) at a time and leave it a day or two for the temperature to settle.

Strummer22

lstevensuk said:

beardymarrow said:

So, basically the curve (which is a bad name, it's really a slope) defines how hot the heat pump wants to get the radiators for a given outside temperature. The colder it gets outside, the hotter the heat pump gets the radiators.
The slope determines how much hotter it gets for each degree it gets colder outside. The higher the slope the more heat the pump will give you per degree outside below 20deg.

If it's too cold inside when the temp outside is below 5deg, then you increase the slope (only do this by say 0.2 each time and leave it a day or two to settle). If it's too hot, you decrease the slope.

Fine tune can tune that by increasing or decreasing the target radiator temp across the board (regardless of the outside temp), so if it's not hot enough inside when the temperature is warmish outside (above 5deg), but it's OK, then you can increase the fine-tune a bit.
If it's too hot inside when the temp outside is warmish, but it's OK the rest of the time outside you can decrease the fine-tune.

Hope that helps.

Thanks as ever! That makes some sense now. I might actually reduce it a bit then as it certainly doesn't feel cold inside. Although my UFH never seems to be able to go hot enough in comparison - a tricky balancing act!

I wonder if it's not quite as simple as adjusting it until it's the 'right' temperature inside. Your thermostat should take care of that. The lower the weather compensation curve is set, the cooler the radiators/UFH and the longer the heating will need to be on to reach the thermostat temp. If your heating is on constantly and your house does not reach the thermostat temp, then the compensation curve is definitely too low and should be increased.

Because heat pumps are most efficient at low flow temperature, the weather compensation curve should be set to the lowest level that will still heat the house (even if that takes hours, assuming you're okay with that) as that will use the least electricity. 

DazzlerDazza

I've never seen any detailed guide on how to set the curve and fine parameters accurately. Everything I've seen, even the official IVT guide, simply discusses it in quite general terms referring to whether it is "cold" or not (below -5°C) as the driver for whether to change curve or fine. When you also take into account the fact that you can add breaks and additional points in the curve, it makes it - in my view - quite a complex subject.

I found it tricky when my IVT Greenline HT+ E11 was first installed 11 years ago, taking me a couple of months of trial and error to find an appropriate combination of curve and fine settings. I eventually ended up with a curve setting of 5.7 and a fine setting of 2.5. I had to increase the fine because I found it wasn't warm enough when the outdoor temperature was close to zero, so the whole curve needed lifting a bit. Heat at very low temperatures was never a problem.

I would be interested to know what process professionals go through when determining the optimal settings, finding the right balance between acceptable heat and as high a COP as possible.

beardymarrow

Strummer22 said:

I wonder if it's not quite as simple as adjusting it until it's the 'right' temperature inside. Your thermostat should take care of that. The lower the weather compensation curve is set, the cooler the radiators/UFH and the longer the heating will need to be on to reach the thermostat temp. If your heating is on constantly and your house does not reach the thermostat temp, then the compensation curve is definitely too low and should be increased.

Because heat pumps are most efficient at low flow temperature, the weather compensation curve should be set to the lowest level that will still heat the house (even if that takes hours, assuming you're okay with that) as that will use the least electricity. 

Hello. I think it is that simple (in concept). The thermostat is really in my opinion for tweaking the internal temp, for example if you have a secondary heat source (fire place) or it's a very sunny, but cold day. The pump should be able to usually keep the house temperature stable based on the external temp. The thermostat works by increasing the required rad return when the internal temp drops, it doesn't switch the GSHP on and off as a normal gas boiler one would.

If the curve is set lower than ideal, then :-
The GSHP will cycle as it will easily be able to hit the required rad return temp, remember the IVT pump is on or off, not variable like some newer GSHPs.
The internal temperature in the house will gradually drop over a few hours as not enough heat is being input for stability
The pump will then increase its rad return target in response and work harder to get to that.
The internal temperature in the house will gradually rise as more heat is being input
The GSHP will drop its target rad return
Everything will eventually stabilise, but this will take hours, if not a day, by which time the external temp will have changed and the whole thing starts again.

This will repeat as external temperatures increase and decrease.

In my opinion, the curve should be set to be correct, and then internal thermostat then tweaks it, otherwise you end up with rad returns too low and too high alternately, rather than a more stable average temperature.

I have seen this myself. If I set my curve too low or too high, the internal temp fluctuates and gets compensated for by the internal thermostat. When it's correct, it's usually stable.

beardymarrow

DazzlerDazza said:

I've never seen any detailed guide on how to set the curve and fine parameters accurately. Everything I've seen, even the official IVT guide, simply discusses it in quite general terms referring to whether it is "cold" or not (below -5°C) as the driver for whether to change curve or fine. When you also take into account the fact that you can add breaks and additional points in the curve, it makes it - in my view - quite a complex subject.

I found it tricky when my IVT Greenline HT+ E11 was first installed 11 years ago, taking me a couple of months of trial and error to find an appropriate combination of curve and fine settings. I eventually ended up with a curve setting of 5.7 and a fine setting of 2.5. I had to increase the fine because I found it wasn't warm enough when the outdoor temperature was close to zero, so the whole curve needed lifting a bit. Heat at very low temperatures was never a problem.

I would be interested to know what process professionals go through when determining the optimal settings, finding the right balance between acceptable heat and as high a COP as possible.

It definitely is trial and error, and that's a pain. Cynically, my suspicion is that installers will set it to a level that means the occupants aren't going to call them back out because the house is too cold, and not worry too much about the COP, as that won't impact the installer.

Mine was all an absolute mess when we moved in. The 3-way valve was knackered and the house was absolutely boiling, which the previous occupant had tried to overcome by massively lowering the curve (which obviously didn't work), so I effectively had to set it to factory defaults and go from scratch.

From scratch :-
Set the internal temp influence to zero, otherwise this muddies the waters.
Get the slope right
Fine tune with the fine adjust
Add in internal temp influence

If too cold below 5deg, increase slope (0.2-0.6 at a time)
If too hot below 5deg, decrease slope
If too cold above 5deg, increase fine (0.5-1.0 at a time)
If too hot above 5deg, decrease fine

As you say, you can also tweak the individual points in the curve, but I've never found a need to.

Each time you make a change leave it a day or two as GSHPs produce a much lower amount of heat than a normal boiler, so changes take time to impact.

One thing, you said you had to increase the fine because it wasn't warm enough at close to zero? It should have been the slope that was increased to achieve that, and then possibly the fine reducing a bit if that caused the temp to be too hot at warmer external temps?