Weather compensation and air source heat pumps
Posted by: @abernyte
I am afraid that I have never peered too deeply into the settings to find exactly how the curve is configured. The installer spent some time on this part of the commissioning and acknowledging that the house is a leaky and exposed timber frame he wanted to match the "normal" heat loss with the input as low as possible and I do not seem to get much cycling at all with long uninterrupted runs unless defrost is called for. It was further tweaked by a couple of local (Perth) Mitsubishi service agents when it got it's first service from them at year three. They squeezed out every last drop of efficiency and got the normal flow temps down even further so it rarely goes over 35C. Big radiators and a big heatpump and a heavy dose of glycol to boot. They only do heat pump servicing and repairs with Mitsubishi and Daikin, no installation work, and are worth every penny!
Where are you based? I would love to find a company such as you have found to service and tweak my installation in the E Midlands area.
Currently, my service is carried out by the installer who isn't very close to my location, isn't exactly cheap and charges a hefty mileage fee on top. I'm sure my set up can be improved.
Retrofitted 11.2kw Mitsubishi Ecodan to new radiators commissioned November 2021.
I am a bit away from you in the hills of eastern Perthshire. I reluctantly switched the servicing away from the very knowledgeable installer when he became seriously ill and took out the Mitsubishi contract to avoid potentially sitting looking at a dead heat pump mid-winter wondering who to trust to repair it. It has worked out well, if a touch pricey, for complete piece of mind.
Posted by: @morgan
If anybody can recommend in the Derby, E Midlands area I'd be obliged.
Hi, you might try Daniel at
He recently serviced a friend’s Mitsubishi ASHP in Dronfield and seemed good. He ‘charges £170 plus VAT for the service and this will be a one off payment for the year and covers unlimited call out and maintenance required if the system stops working.
You wouldn’t have to deal with any call centre and I can be out next day to you.’
He used to work for my installer, but left as he didn’t agree with their customer care, which was a recommendation in itself as I couldn’t agree with him more!
Hi - I found this great forum and changed some of my setting in the early part of the year. I set the compensation curve (through the engineer mode on my Mitsubishi Ecodan controller) to 40 and -3 - however when I look at the compensation curve NOT via the engineer mode - it says 40 and -30 - I cannot seem to change this or do I just ignore? Also Having my system set at 40 doesn't seem to get one of my rooms with UFH up to temp and although the temp in that room is set to 18 it NEVER gets to that - this is since I changed to compensation mode back in March - I've only really noticed it in the recent code weather - last week - the temp never got above 15 - any ideas? Many thanks.
The problem may be due to the flow being too low to the UFH loops in that particular room. Can you provide a photo of the UFH manifold?
@sarah can you also post a picture of your WC curve.
When the heat pump is running under the engineer mode go to running information and input code 540 this will tell you the flow rate of the heat pump in litres per min.
If you have the Mel cloud app pictures of the hourly flow and return temp would also be useful
As Derek has eluded to it will either be the heat pump not getting the water to temp or the flow in the UFH being too low or not on for long enough is it running 24/7 or do you set back at night? Do you know how deep the UFH is set in the concrete? Is the UFH zoned and controlled by different thermostats in each room?
I have also (last night) changed the comp curve to 45 (from 40) - it's not too warm outside today - so I will see if that makes a difference. I've never been able to get this right in the 8 years I've had it - it either uses so much electricity when running that we are at the stage where we have to decide if we can afford to run it or when I make changes it doesn't heat up the area. I really want to like the ASHP but I never have.
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