Newbie: utterly confused with my Mitsubishi Zubadan air source heat pump running on 55C set flow temperature

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Air Source Heat Pumps (ASHPs)

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Sandman1600

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Topic starter 16/10/2025 10:09 am

@davidnolan22 Hi..! We've only just turned on the heating again following the summer but it's not overly concerning right now. It's cycling a little but we're getting COPs of between 3.5 and 4. I'll keep my eye on it as the weather gets colder.

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dgclimatecontrol

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16/10/2025 10:23 am

Posted by: @sandman1600

↑

Hello! I’m new here and looking for a bit of advice. I’ve been waking at 4 in the morning stressing about our energy usage, googling until my eyes cross and this eventually led me here.

We’ve just moved from a Grant oil boiler to a Mitsubishi Zubadan ASHP. We have Polypipe underfloor heating throughout the whole house. The only radiator is a towel rail in the bathroom.

With the old boiler we’d have a setback temperature 2 or 3 degrees lower than the desired temp and just have the rooms heating when we wanted them to be warm. The manifold temp was set to 50 upstairs and 53 downstairs (concrete pad and takes longer to heat).

I understand that the recommended setting for ASHP is just to have them on continually so we’ve now just set a target temperature for each room with a 0.5 degree setback.

However, since the HP was installed we’ve seen electric consumption pretty much quadruple and I’m worried we’re not setting something correctly. This week has been cold so maybe this is causing extra pressure.

The installers set the flow temp to 55 degrees. I immediately lowered this to 50 as I understood that an air pump needs to be lower to benefit from the efficiency. I’m now thinking it’s just running a lot of the time and electricity usage is therefore rocketing.

Is it better to set it to a 55 degree flow temperature and let it heat up rooms a little quicker and not be heating as continually. Or is it better to be running more at a lower temperature?

Does that make sense? If there’s any other information I can supply, I’d happily do this.

It'll bring on electric back up heaters if at 55C as they'll work quicker in the winter. Not sure about old ME units but Daikin had a 6 or 9kW back up! often working to start the system off then being taken over by the HP. You need it setting to 40C max and leave it on, if bills high or not warm enough its the installation.

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Sandman1600

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