Flow & return Temps

[tworivers]

I am i right in thinking that a ASHP should maintain a set temperature.

 

I.e If  set to 45 the heating temp should reach 45 in all outside temps conditions and its only the COP that changes?

 

Or does the heating temp change with the outside temperature?

 

My ASHP is set to 40-45 flow and return. Rated to -3 degrees. But in the colder weather around 0 degrees i only seem to be getting an average F&R of 33 degrees. Is this normal?

 

Thanks

 

 

[ProDave]

You can set the temperature to change with outside temperature, it is called weather compensation, but that generally makes the water temerature higher as it gets colder outside.

 

What you are describing sounds like as the heating load increases, the ASHP is not able to keep up and maintain the set temperature.

[tworivers]

Thank you for your reply, that as helped me out greatly.

I had a heat pump installed in Sept 2019 but it as never performed the way i was told it would.

I have been trying to monitor heatloss  and flow and return temps to try and get to the bottom of what is going on. I am being told ( by the installer ) that the flow and return temps are cooler than expected because the heatloss from the house is greater than allowed for in the survey, rather than the heat pump not being up to the job.

 

His calculations are: heat loss 10433.89 (watts) and a running cost including immersion of 8225kw PA. First Year actual 13450kw.Is there a way of measuring the actual heat loss of the property? 

 

As far as i can work out either the heatloss is greater than estimated or the pump isnt working correctly. If anyone as any ideas of how i could determine what the problem is it would be greatly appreciated.

calculations.pdf

[Benjseb]

A few things to consider

 

if the heat loss calculation is incorrect, the heat pump provided would most likely be too small to cope with the actual heat loss that’s occurring. 
 

In that case then yes the heat loss is incorrect, but also, yes the Heatpump is struggling because of this. 
 

Also some heat pumps only output their stated kW down to certain external temps. If the installer isn’t aware he might not have accounted for this. 
 

Whether it’s the heat loss that’s incorrect or the heat loss is correct and the pump can’t handle  it, the installer needs to come back and sort it. 

[tworivers]

Thanks for your reply.

The installer as washed his hands of it.

I have complained to NAPIT who say  In dispute circumstances, NAPIT is not sufficiently independent to judge between the parties and because I am covered under MCS it been referred to RECC who have been dealing with my case for the last 6 months. RECC gave the following :

 

I note from the pre-installation survey and the points made by the installer, that the performance of the system is related to the following points;

·        Insulation – the insulation in the property was not consistent with the original information that was put into the pre-installation survey

·        The renovation of the property was not to the standard originally suggested by yourself.

 

I am in complete disagreement with what the installer is claiming. So I am left feeling completely alone with my situation and the so call bodies who are there to supposedly protect the consumer don't seem to be able to do a great deal to solve the situation. 

 

So I am trying to prove that the house is as I  stated in the 10min conversation i had with the installer at the survey stage. I would like to be able to measure the actual heat loss to compare to his estimated heat loss. Or is it an issue with heat pump.

 

Any help or information is massively appreciated. 

·       

[ProDave]

One way to measure heat loss is use and independant, measurable source of heat for a period.

 

e.g when the fabric of our build was completed, long before the house was habitable I wanted to see if the insulation etc came close to what was predicted.  So for a whole month, I had a single electric convector heater turned on in the centre of the ground floor of the house running at a known power level and with it's thermostat turned up to max so it would run continually.  I logged the internal and external temperature dailiy so had a measure of the temperature difference between inside and out and throughout the test period the temperature difference almost exactly matched the predicted temperature difference for that amount of heat power into the house.

 

I can see the installers POV as well as yours.  You told him this is the insulation values that you will install.  So he calculated the heat loss based on that.  The heat loss now appears to be a different figure, of course he is going to blame you.  He did not fit the insulation did he?

 

Perhaps a lesson for others is don't size the heat pump on exactly the predicted heat loss, size it a bit bigger to allow for the heat loss being greater than you think.

 

The bottom line is, regardless of flow and return temperatures, is the house getting hot enough?

[tworivers]

Thanks again for the reply.I am learning a lot.

 

I didn't give the Installer any insulation values. I had already insulated the house a few years before deciding on having a ASHP installed. I had less than a 10 min conversation with him regarding the insulation. He asked how I had don't it and what had been used. I told him exactly how it had been done what had been used. I cant see how he can blame me if what i have told him is the truth. I paid him £200 for the survey and answered all his questions honestly.

 

The house isn't quiet reaching the temps quoted by the installer of 21 but it is just about ( when it 0 out side) reaching 19. Its only failed to reach temp in 2 room when the temp hit -3. I am happy with the house at 19. but its costing way more than i was led to believe.

[J1mbo]

How does the installers calcs compare to the EPC?