Posted by: @jamespa

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You are absolutely correct that the capacity table MUST be consulted.

Yes, here's mine. From the service manual parts numbers (compressor etc), the 12-14-16kW models are identical, and all are actually "much more than 16kW at 7/35°C heat pump" with a software limit to the official power on the label (in my case 16kW).

Since the three models are the same, in the same conditions (air, water, power) the COP is the same and defrost is also the same. The more powerful models just allow more watts at worse COP, which may be useful. Minimum power is the same. The heat exchangers are the same, so a bigger label won't magically pull more watts from the air at the same deltaT or cause less frost to form...

Sometimes below this table you get a tiny footprint *includes defrosting or *does not include defrosting, but that's at a specific temp/humidity, not necessarily yours.

Personally, since I have about 500 tons of stone walls and slabs with exterior insulation, I oversized it by about 2x, so it runs at high COP during the day when air temperature is higher, COP is higher, and electricity from PV is free. 

@davec did you get anywhere with the installer?

@johnd yes, the original installer is going to remove the Peak ASHP and cylinder and fit a Grant cylinder for us.

Just waiting on timescales from them once they’ve sourced the correct cylinder we’ve asked for, to work with the new Grant 12kw ASHP that Ribble Valley Heating are currently booked in to install mid May.

We haven’t had an exact figure back from them on how much we’ll get back but it covers the cost of the new replacement cylinder and should be a reasonable amount to go against the new Grant ASHP.

They will then deal with Peak directly to recover their costs as best as they can.

@johnd our Peak system is no more. 

The installer came in today and removed the Peak cylinder and fitted the new Grant cylinder in its place. With the external unit being removed tomorrow. 

Ribble valley are coming in on the 7th May to fit the Grant ASHP. So we're just using the immersion heater for the hot water until then.

I setup the Grant controller with the cylinder and it is so much easier to use. 

Have you organised anything with your Peak system and installer or are you persevering with your 16kw unit?

As a final update on this thread from me; Ribble Valley completed the Grant 12KW ASHP installation on Friday, and now I can see and appreciate the efficient, quiet and warm aspects of an ASHP!

The house feels warm throughout and the temperature is maintained, what a wonderful thing working weather compensation is.

The main and immediate difference to note is the volume level of the external unit, even though the new ASHP is a dual fan unit the Grant is whisper silent in comparison to the Peak.

Happy we made the leap to get it replaced as the Peak unit would have been a disappointment for years to come and it made recommending ASHPs to anyone difficult.

But with the Grant installed I can confidently say we will be recommending ASHPs to anyone who asks, extremely happy with it.