So your flow and return are 34 and 32 outside is 4C if you go to 4C on your WC curve what should the temperature be?  If that is 33 or 34 the heat pump is working correctly.

if the house isn’t getting up to temperature then that flow temp is too low for the house assuming the ufh is working correctly.  

Do you know what the heat loss for the house is?

@gary OK - so I changed the lower temp to 4 and comes back as 36 (picture attached).  I increased the flow temp to 45 degrees (from 40) this morning - do you think I should leave it for a day and then possibly increase tomorrow?

   I am assuming that the ufh is working OK - not sure how to check that - I could get an engineer to visit.  As for the heat loss - it is a new build part of the house - at one end of the living room that struggles to get warm - there is a flight of stairs going to the rest of the house - this part of house is heated with gas boiler rads and in cold weather is normally warmer than downstairs!!!  I do understand that there this could be a cause of heatloss - but not sure to what degree.  Thank you for your continued help with this - I appreciate it.

So it’s about right   How long do you run it for?  Eg mine came on at 12pm today it’s been running for 6 hours at 33C and the temp downstairs has increased by 0.3C. At these flow temps and single digit outside temps it will only maintain the temp in the house.  Just trying to work out your expectations of the heat pump its needs to be on constantly maybe setback 1C overnight when it’s this cold outside.  They are slow to react especially with ufh.

@gary Interestingly the living area got up to 17 degrees this evening.  I think I just need to increase the flow - I'll see how it goes tomorrow - I could have it come on earlier - think it is at 06:00 currently - maybe 40 degrees for my system was too low.  Thanks again.

@sarah on the front menu when your in WC mode you should see +\- symbols these adjust your set curve up and down.  Rather than adjusting your curve you could just move it it to +3 which would move it up 3C from where it is currently and see what effect that has.

If you have thermostats in the rooms controlling the ufh turn them up to 30C so they don’t turn anything off and leave it for a day and see where it stabilises at.  If it’s too warm turn it down a degree or too cold turn it up another degree.

good luck 

Posted by: @sarah

↑

@gary Interestingly the living area got up to 17 degrees this evening.  I think I just need to increase the flow - I'll see how it goes tomorrow - I could have it come on earlier - think it is at 06:00 currently - maybe 40 degrees for my system was too low.  Thanks again.

To add to what Gary has already explained, the WC curve needs to be adjusted to match the heat loss of your home. This can take a little time to achieve, since the weather is not always obliging, by supply a warm day and then a cold day, so that each end of the curve can be optimised.

Going from the cold end to the warm end of the ambient air temperature range, you will see that the WC curve consists of a horizontal line, somewhere between 30C and 60C, then a downward slope to a further horizontal line in the range 25C to 35C. The most important part of the curve is the slope in the middle, which needs to match, as closely as possible, the heat loss of your home.

Like most people, you probably have no idea what is the actual heat loss of your home, but you should be able to make an educated guess. If it is large and poorly insulated, then the heat loss will be high, if it is small and well insulated, then the heat loss will be low, most others will be somewhere between these two extremes.

To correctly set and optimise the WC curve it will be necessary to have the heat pump running constantly, since switching the heat pump on and off will distort the Indoor Air Temperature (IAT) values, which are monitored when setting the curve.

Dependent upon the type of heat emitters, and your assessment of the probable heat loss, set some initial WC curve values. In your case probably something like a Leaving Water Temperature (LWT) of 45C @ Outside Air Temperature (OAT) of -5C at the cold end, and a LWT of 25C @ OAT of 20C at the warm end.

Before starting any adjustments it would be useful to ensure that the WC offset is actually set to zero.

Then allow the system to stabilise, which could take quite a number of hours. Once the IAT has stabilised, check if the actual value is above or below the desired temperature. If the actual IAT is above the desired IAT, then the WC setting is too high and will need to be lowered. If the actual OAT is toward the lower end of the curve, then make the adjustment at this end, maybe lower the original 45C to say 44C.

Obviously, make adjustments to the warmer end of the curve when the OAT is warmer and vice versa.

The important thing is don't try to rush the process, always allow plenty of time for the temperatures to stabilise before making any further adjustments. Only adjust one parameter value at a time, otherwise you may not be certain which parameter change has caused the temperature change.

@derek-m Hi - when you say set the WC offset to zero - do you mean on the control panel - it is currently +0 - I'm right in saying that if my WC is 45 and -5 then +0 is 45 (flow rate)?  I set this to 45 yesterday - the floor did get up to 17 - today only 16 still (starting from 06:00 in the morning) - outside interestingly is +9 !

Posted by: @sarah

↑

@derek-m Hi - when you say set the WC offset to zero - do you mean on the control panel - it is currently +0 - I'm right in saying that if my WC is 45 and -5 then +0 is 45 (flow rate)?  I set this to 45 yesterday - the floor did get up to 17 - today only 16 still (starting from 06:00 in the morning) - outside interestingly is +9 !

Hi Sarah, the WC offset is as the word describes, an offset, moves the whole curve up or down by the value entered. So the the WC curve is set at 45C @ -5C and 25C @ 20C, then changing the offset from +0 to +1, will have the same affect as changing the curve settings to 46C @ -5C and 26C @ 20C. It saves having to go into the curve settings and make adjustments each time you may need to make a temporary change to the desired IAT.

The reason I suggested setting the offset to zero, is so that you would have the full range of adjustment, normally from +5C to -5C, should it ever be needed.

If you are switching the heating off overnight, then it may struggle to get back up to temperature when running during the daytime, particularly when OAT is low.

Heat pumps do not have the same capability as gas or oil boilers, in that they cannot produce an excess of thermal energy quickly, and if asked to do so may have to work very hard, with a subsequent detrimental effect upon overall efficiency and energy usage.

The bus word with heat pumps is 'Low and Slow', which means run the heat pump in a slow steady manner, keeping the LWT as low as possible, such that it meets the heating demand. Doing so should hopefully operate the heat pump in the most efficient manner and keep energy usage to a minimum.

@derek-m yes I understand.  I don't actually switch it off - the temp room controllers will call for heat depending on the set temp - so I may just leave it at 18 in the offending room that never gets up to temp for 24 hours and see what happens.  Thank you.

@sarah Hi this is because the flow temp for that room is too low, that’s why I suggested moving the curve up to +3 and see where it stabilises

@sarah I just want to check on one thing. reading back, you say you have 3 controllers? that would suggest your system has been setup to work on 3 zones, is that correct? this makes life a little more complicated to debug from afar.

one fact of physics: A heat pump can't generate heat at 3 different flow temperatures, only one. Is it obvious which of the 3 controllers is actually "in charge" of the flow temperature that your heat pump runs at ? 

then, you want all zones to be running all the time or as close to that as you can get. Is that the case?  this is the only way to get best efficiency from the HP.

with continous running, each room / zone needs to be tuned so that it has the right output level for comfort, by matching flow rate, emitter size and flow temperature to heat loss. it seems that in your problem zone/room you must have a problem with one or more than one of those.

try to set all controllers to a target temp  above the current temp. if you do this,  are you then able to monitor which zones / rooms are getting water flow? I can see something that could be flow meters in one of your pictures. If one room / zone stays constantly too cool, that could imply that its getting little / no flow.