Ecodan - are these COP figures correct?

dllive

Hi,

Ive been keeping logs of the Consumed/Deliverable figures for a few months. At the moment I have the heating turned off (obviously) and the DMH is set to 41 degrees.

This morning it shows for July 2022:

Consumed: 83kWh (15 DHW; 67 Heating); Delivered: 45kWh (45 DHW; 0 Heating)

DHW COP: 3

Heating COP: 0

Overall COP = 0.8

So does that mean that over the past 30 days the system has taken 67kWh to operate? It drags the overall COP down to just 0.8, so Id be better off having a traditional system?

Do the above figures look good? It will be interesting to see what is reflected when the heating goes back on.

Thanks

Reed_Richards

Some heat pumps seem to suffer from a very high "standby" or "vampire" load.  I have been reading a thread on another forum about this, search for "Ecodan standby power consumption" and you may find it.  My monobloc LG ASHP uses under 10 W in standby so your issue is not something every heat pump suffers from.  With Ecodans I think there was some indication that the two-stage types are more prone to this problem.

The problem you have is pretty dreadful if the figures are correct.  With a COP of 0.8 you would be better off cutting all power to your heat pump and using the immersion heater.       

Reed_Richards

Forum regular @shinytop has an Ecodan, I think, so should be in a good position to comment.

matelodave

Earlier heatpumps had a sump heater which keeps the refrigerant from separating the oil out - my Daikin has one and it uses around 120watts continuously. To get around it I shut the heatpump off in the summer except when I want hot water.

It's a bit of a pain but I can heat the tank to 45 degrees in less than an hour for about 1 to 1.5 kwh and at this time of the year I can get enough hot water for two days so I only have it on for an hour or so every other day.

Depending on the model  and age of your Ecodan it may have a sump heater.

dllive

Hmm. I have mine scheduled to heat the cylinder up to 41 degrees every 48 hours at 3pm. It usually takes about 30 minutes to heat the water back up to 41 degrees.

So really, my ASHP is only 'active' for about 30 minutes every 48 hours! ( similar to @matelodave@matelodave )

I will find the exact Ecodan model I have later, but I know its a recent one (about 4 years old). Theres definitely something consuming a lot of energy!

dllive

Ive juct checked and the model number is PUHZ-W112VAA.

matelodave

have a look at this - https://forum.buildhub.org.uk/topic/26840-ecodan-standby-power-consumption/?tab=comments. Dunno if it helps, but I guess you'll have to do a bit of investigation.

dllive

Thats an interesting thread. In this post he mentions the 3 examples of usage in standby mode https://forum.buildhub.org.uk/topic/26840-ecodan-standby-power-consumption/?do=findComment&comment=409086 . But the figures are in watts(?). How do these compare with the 67kWh mine is consuming over 30 days?

Reed_Richards

30 or 31 days in a month, so about 2.25 kWh per day on average.  24 hours in a day so a bit less than 0.1 kWh per hour = about 100 W on average.  That's about the same as a really efficient/small fridge.     

dllive

Thanks @Reed_Richards , I kind of understand that now. All these numbers and figures confuse me.

So in that post I linked to, he says:

=================

@joth is seeing reliable 5.5W average standby load (266 Wh consumed in 48 hours). I have high confidence in this figure, as 2 different CT clamp arrangements agree (one dedicated on the ASHP, and another pair measuring grid import and household "indoor" consumption)

@LA3222 is seeing 200W continuous standby draw. There was a comment that "To be honest I haven't scrutinised the system too much." and "Not sure how accurate the readings are that I'm getting", so I'm not sure of the confidence here.

@Kenway is seeing 300W standby. They appear confident in that number, however I'm a little suspicous of the line chart showing kWh plotted against hours (is that kWh per hour, or extrapolated to per day, or something else? kWh is a quantity of stuff so this should be a stacked bar chart to make mathematical sense, not a line chart)

=================

So my 100 W falls between those three.

The first figure says "...266 Wh consumed in 48 hours" . Whereas mine is using 4.5kWh in 48 hours.

Perhaps the fact is that my Ecodan takes the same energy as a small fridge to keep itself running, even when its only used for 30 minutes every 2 days. Doesnt seem very 'eco' to me. Unless perhaps - during the winter months - it offsets it by being really eco! Although, in 2 years Ive never managed a COP of more than 2.1.

Reed_Richards

I suspect that Mitsubishi engineers had a "blind spot" about how large their standby load is, or can be.  Because my heat pump was installed towards the end of the RHI scheme it was obliged to have its own electricity meter which monitors the power it draws.  That means I can be pretty sure about what mine is doing.  I'm also "Reed-Richards" on that other forum so you can read my comments.(nothing profound).