ASHP flow temperatures in winter

[Orion331]

Hi,

 

I've recently had an ASHP installed (Mitsubishi Ecodan Monobloc 8.5kw) and have found since it's install in July there have been no issues with it. However, since November where temperatures outside have dropped below double digits, I am unable to get a single part of the house up to 21 degrees even when the flow temperature is set to 55 degrees for 24 hours.

 

I have contacted the installer and explained this but they are advising me that I need to run the heat pump at max during the colder months. I don't feel this is correct and that the issue may be that the radiators in my house aren't correct sizing, even though they inform me they "should be okay if the flow temperature is at least 55 degrees. 

 

This is costing me lots of money in energy bills when we were sold this as a cheaper alternative to heating our home.

 

Any advice would be great!

[Orion331]

It's a detached 4 bedroom house, new build (Feb 2022) and insulted very well above building regs. The original heating was an oil boiler.

 

The company that designed the original heating system with the oil boiler are telling me the radiator output isn't good enough for the house where as the ASHP installer are telling me it's fine as long as your flow temps are 50+ degrees.

[jack]

@Orion331, I've closed this one off in favour of your other post, which got a reply first. Ideally, we don't want the same question being answered across different threads, as it can make them hard to follow.