Turning our heat pump off over summer and a general moan

[RogerH]

Hi All, this is my first post. We have a 6kw ecodan installed to radiators in dec 2021. We have hot water taken care of with a mixergy tank and solar PV and octopus go so not connected to heat pump. Therefore we have no need for it over summer. It looks like the pump uses about 20 kWh of energy over each of the summer months. I only noticed when I was looking back at the ‘consumed’ monthly figures in the ftc. In summer there are consumed figures but nothing ‘delivered’ . Our total kwh consumed by pump for 2022 was 1560 kwh so quite a bit of that, about 120 kWh was from it ‘doing its own thing’ in the summer. Can I safely turn it completely off in summer? 
Also I have been taking daily readings from ftc recently (of delivered and consumed energy), how accurate do people think these figures are for the purposes of determining COP? ( Also the Mitsubishi app is hopeless). If the consumed kwh for summer have not delivered anything then they have to be deducted from the total delivered figure to get an accurate COP. Also if I want to really get on top of our COP is it worth doing something like open energy monitoring? By the way our COP for 2022 was 2.4 so I am working on ways to improve it., also the installer has gone bankrupt!
BTW we have been through all the NAPIT complaints procedure to no avail. They think the pump was installed properly. 

In general, the installer was hopeless and now non existent , MELCloud hopeless, NAPIT hopeless. But we did get RHI and we don’t use much energy because we have done a deep retrofit (37 kwh per m2 for space heating), not because the pump is working efficiently. 
And relax.

 

 

 

 

 

[SteamyTea]

Welcome

 

Have a read of this:

 

Quite a bit in it.

 

kWh not kwh

[JamesPa]

20kWh per month is only 27W.  That's almost nothing (and consistent with the spec).  I bet your baseload is 10 times this.

[SteamyTea]

1 minute ago, JamesPa said:

20kWh per month is only 27W

Seems to be about normal for a controller.

 

Would annoy me having a controller that used that much power.

[ProDave]

19 minutes ago, SteamyTea said:

Seems to be about normal for a controller.

 

Would annoy me having a controller that used that much power.

My LG heat pump controller seems to take all summer to consume 1kWh doing nothing.

[RogerH]

Thanks people, will check out the tread you suggested ST.

20w is 20w . We turn off our MVHR in summer and it only uses 9w. 
so is it safe to turn it off?

[JamesPa]

20 minutes ago, SteamyTea said:

Seems to be about normal for a controller.

 

Would annoy me having a controller that used that much power.

Fair enough if you have gone to strong efforts to reduce your baseload.    Your router, computer and other sundry items will consume 10-30W doing nothing.  Your fridge probably averages a lot more, freezer ditto.

 

But if 25W concerns you (which it should, every little helps the planet) then just turn it off!

 

I'm not saying that 25W should be ignored, just that for most it will be a small proportion of the baseload so perhaps not the most important thing to worry about.

[JamesPa]

4 minutes ago, RogerH said:

Thanks people, will check out the tread you suggested ST.

20w is 20w . We turn off our MVHR in summer and it only uses 9w. 
so is it safe to turn it off?

I admire you for turning off a 9W load, most, sadly, wouldnt. 

 

Unless the ashp is heating the dhw then it can be turned off.  It might need a few hours to start up again (but probably won't).  

 

Edited January 18, 2023 by JamesPa

[SteamyTea]

4 minutes ago, RogerH said:

so is it safe to turn it off?

Probably, just may take a while to start up, the crankcase may need reheating.

May be worth seeing if you can put it on a weekly cycle.

If you have UFH, you may want to run that in the summer to distribute any/some room heat around the house.  This can help lower overall temperatures.

 

Purely out of interest, why do you not heat your DHW with it?

Edited January 18, 2023 by SteamyTea

[SteamyTea]

11 minutes ago, ProDave said:

My LG heat pump controller seems to take all summer to consume 1kWh doing nothing.

My Raspberry Pis I use for monitoring seem to use so little that they don't register.

 

A Micro Contoller needs about 0.25W, or about 2 kWh a year.  Still a quid.

[PhilT]

52 minutes ago, RogerH said:

 ( Also the Mitsubishi app is hopeless)

What's the issue with the MELcloud app?

[RogerH]

Thanks again.

Steamy tea, the DHW is from PV solar diverter (eddi), octopus go overnight , and a mixergy tank (very efficient). PhilT, the mel cloud app is utterly inaccurate when I ask for an energy report. It is saying delivered energy is about half of what the ftc says and has the COP graph wildly wrong. 
 

So either turn if off in summer or put it on a weekly cycle ? ST, does that mean switch it on for a few hours once a week over summer?

As far as base load goes, we don’t mess with the fridge, router, car charger, hot water but all else that plugs into sockets is switched off when not in use using smart plugs.

I have quickly gone through the other thread on standby of ecodan and it seems that about 25w is what it uses (but not in the heating season). 20 kWh per summer month may not be too far off as a guess. I strongly agree that installers should be upfront with this sort of thing.

[JohnMo]

Put it on Colling duty, run it off your solar. 

 

Heat your hot water 4 times as quick as an immersion, as you get a CoP of 4 ish in the summer, immersion CoP of one.  So even on a poor sun day you should get a bigger chunk of your hot water at zero cost.

[SteamyTea]

5 minutes ago, RogerH said:

o either turn if off in summer or put it on a weekly cycle ? ST, does that mean switch it on for a few hours once a week over summer?

Yes, mainly to ensure than it works, could be fortnightly.  That way, if any problems, you get prior notice.  Really only needs to be on for an hour.

 

If you heated your DHW with the ASHP, you would use less energy.

 

Turning everything off when not needed is a good move.  I have reduced my parasite loads, some hours I draw no power at all.

[RogerH]

Thanks again. Will give some thought to using the heat pump for DHW . We used 382 kWh of grid energy for hot water in 2022. Most is heated by solar. So presumably we could reduce that to about 130 kWh if we connected the heat pump. I will give it some thought, the tank is ‘heat pump ready’. Financially it is cheap because we only use octopus Go (overnight) at 7.5p kWh.

[SteamyTea]

2 minutes ago, RogerH said:

7.5p kWh.

Could reduce that to an effective 2.5p/kWh

[JamesPa]

24 minutes ago, RogerH said:

We used 382 kWh of grid energy for hot water in 2022. Most is heated by solar. So presumably we could reduce that to about 130 kWh if we connected the heat pump. I will give it some thought, the tank is ‘heat pump ready’.

Im interested in your thoughts/findings on this one.  Solar diverters rely on modulating the immersion element down to match the instantaneously available excess solar power.  With a resistive heating element that easy to do, not so with an ASHP.  I cant quite see how to use an ASHP efficiently to mop up excess PV generation with currently available technology.

 

Of course if export and import charges were more closely matched, then all would be sorted.  Simply turn on the ASHP to heat the water, and whatever energy deficit/surplus you have gets netted off and the energy would be used as efficiently as possible (and therefore global warming minimised). 

Sadly that would require that energy suppliers pay nearly the same for export as they charge for import, and there is no business or regulatory incentive to do that.

 

Obviously this logic applies only in the sunny months, in winter (other than on very bright days) solar is most likely to be inbsufficient to heat the water and in that case ASHP surely makes sense.

Edited January 18, 2023 by JamesPa

[SteamyTea]

1 minute ago, JamesPa said:

I cant quite see how to use an ASHP efficiently to mop up excess PV generation with currently available technology.

It becomes a statistical exercise.

The idea is to run the heavy load at the times when PV generation are most likely to be high i.e. hour and a half either side of local noon, or depending on your PV orientation, whatever time you get maximum generation.  Then the heavy load will probably use all the generation and import less.

This is part of the reason that oversizing PV is not always the most economical thing to do.

[JamesPa]

4 minutes ago, SteamyTea said:

It becomes a statistical exercise.

The idea is to run the heavy load at the times when PV generation are most likely to be high i.e. hour and a half either side of local noon, or depending on your PV orientation, whatever time you get maximum generation.  Then the heavy load will probably use all the generation and import less.

This is part of the reason that oversizing PV is not always the most economical thing to do.

Fair comment.  I might try running the stats based on PVGIS when I have some spare time, unless someone else already has the spreadsheet!

Edited January 18, 2023 by JamesPa

[SteamyTea]

2 minutes ago, JamesPa said:

I might try running the stats based on PVGIS when I have some spare time, unless someone else already has the spreadsheet

Put a bit of randomised multipliers into it, plus or minus 5%.

[PhilT]

1 hour ago, RogerH said:

PhilT, the mel cloud app is utterly inaccurate when I ask for an energy report. It is saying delivered energy is about half of what the ftc says and has the COP graph wildly wrong. 

That is odd. My FTC and MELcloud data are totally in sync and the estimated COP figures look reasonable. I know they were having some server problems recently (now fixed). Have you spoken to Mitsubishi tech? They have been quite helpful. I must admit I use MELcloud a lot and I find it really good.

[Marvin]

2 hours ago, RogerH said:

Thanks people, will check out the tread you suggested ST.

20w is 20w . We turn off our MVHR in summer and it only uses 9w. 
so is it safe to turn it off?

We don't turn the MVHR off because we would have moisture issues in the ensuite, however, this year we aim to run the MVHR solely from PV, all year.

[Marvin]

1 hour ago, JohnMo said:

Heat your hot water 4 times as quick as an immersion, as you get a CoP of 4 ish in the summer, immersion CoP of one.  So even on a poor sun day you should get a bigger chunk of your hot water at zero cost.

IMHO this is a bit of muddled logic.

 

Our diverter only diverts excess energy from our PV.  Excess PV is all the bits which are not used and would otherwise go to the grid.

 

Our diverter can channel 200 Watts for hours to the immersion heating up the water. It can also channel 3kW for 30 seconds. Neither of these energy profiles would produce more heat in the hot water tank using our ASHP.

 

Our ASHP will not run on less than about 700Watts, but the diverter would stop these bits of energy from going to the grid and use them heating the water.

 

During the winter months we have often heated the hot water on little more than the odd cloud break or the spare energy in between the ASHP cycling.

 

I would recommend checking out a solar diverter to anyone who has PV and a hot water tank with an immersion.  

 

 

 

[SteamyTea]

2 minutes ago, Marvin said:

Our ASHP will not run on less than about 700Watts, but the diverter would stop these bits of energy from going to the grid and use them heating the water.

Not trying to run a heat pump purely off the PV, it reduces the grid imports.

Actually don't need an diverter for that as any PV generation will go to the nearest load anyway.

[Marvin]

5 minutes ago, SteamyTea said:

Not trying to run a heat pump purely off the PV, it reduces the grid imports.

Actually don't need an diverter for that as any PV generation will go to the nearest load anyway.

You miss the point. Quite surprising for you SteamyTea. Perhaps it me.

Edited January 18, 2023 by Marvin