Air to air heat pump?

matt_drummer

How is the COP calculated?

Where does the heat generated data come from?

My A2W heat pump uses a MID certified heat meter that measures flow rate along with flow and return temperatures.

I have lots of experience with A2A including modern units and there is no way to establish the COP in anything I have ever seen.

Newbie_John

@matt_drummer , the app can estimate it quite well - it knows the temperature indoor, outdoor, the electricity consumption, internal flows and speeds..

Then estimated thermal output / electricity consumption and I get:

Nov: 4.5

Dec: 4.6

Jan: 3.9

Feb: 4.4

March: 4.6

April: 4.97

This is the heat output chart corresponding to the electricity usage:

Newbie_John

or here some comparison between app estimates and metered values - looks quite accurate during months with longer runs:

https://community.openenergymonitor.org/t/daikin-altherma-electricity-used-and-heat-values-accuracy/27242

matt_drummer

https://forums.moneysavingexpert.com/discussion/comment/81970147#Comment_81970147

Thanks for the link to a thread where I contributed to the discussion!

We were talking about A2W there, it has no relevance to A2A.

As a Daikin owner I use the Onecta app.

I don't use it to establish how my heat pump is performing though.

The app uses flow rate and water temperatures to establish heat production.

I don't know how anybody can establish the heat produced by an A2A heat pump, it's pure guesswork.

Martyn1981

Inspired me to look at what my 'smart' A2A unit can do, which isn't much it seems. But clocked up 186kWh in Jan, the highest month. Assuming the other unit (not smart), is similar, then ~400kWh for the month. I have some oil rads, and a heated towel rad in bathroom, that run overnight on cheap rate, so maybe an extra 5kWh per day, so around 550kWh input for heating in the 'worst' month. Quite surprised at that, better COP than I had expected.

Newbie_John

https://forums.moneysavingexpert.com/discussion/comment/81970190#Comment_81970190

If it was a pure guesswork they wouldn't put this functionality into the app. I understand thats nowhere as accurate as A2W, but it follows all the trends I would expect - lower COP in Jan than April, lower COP when it has to work harder etc. Combining indoor and outdoor temperature, knowing compressor and fan speeds and using data from lab tested equipment - you can do a pretty good guess imo.

Kind of posted it here more for a reference if anyone is debating to get one.

Martyn1981

Yes, hopefully a good 'guesstimate', that supports hopes / suggestions.

TroubledTarts

I suspect your cop could be right following cost tariff cheap rates and utilizing the 1-4pm cheap zone when even this winter we had some decent afternoon temps.

You have the evidence of the savings so even if it said copy of 3.3 it wouldn't make much difference as it's obviously doing the job you intended it for.

I haven't read fully or checked what other threads but what make and model and system did you get and rough home size etc.

We already have a heat pump but are considering a two room split system primarily for summer air conditioning but also the start of winter say October and then April like this morning when 0oC hit and rather than fire up the ASHP just take the edge off with A2A

Newbie_John

@TroubledTarts our house is SE London, 40m^2 per floor with downstairs fully open plan. Just one Daikin unit 3.5kW, Stylish type inside. It's mostly for heating and as it raises it heats the upstairs, through either ceiling or open corridor door. Main reason we went with A2A was lack of radiators - so costs of A2W even with grant were too big.

Size wise Id say it was just enough, there were maybe 5 days this year with day temperature below 0 where upstairs needed additional support. All other days perfectly fine.

ispookie666

https://forums.moneysavingexpert.com/discussion/comment/81970032#Comment_81970032

I use the heating KW from melcould and electricty consumed by the Mistubishi from my home assistant. It has averaged 3.5 over the winter months. It has been our primary heat source with oil as back up. We have just about got rid of our oil heating and put in a A2W Vaillant Arotherm + 10 Kw and switched off the Mitsi.

We all hated the feel of warm air being blasted and the house cooling down quickly.