I have certainly noticed something similar. A few months ago, when we were running HVO, our heat pump was in standby mode and when I’d go into the utility room, I would notice that one of our mandated RHI metres (because we’re running bivalently) would occasionally flash its red light indicating that the heat pump was using electricity, but not generating heat.

I raised this with Global Energy Systems and they assured me that the pump was not working and consuming electricity.

Our heating has been off completely since late April so our consumption is down. The heat pump is doing HW and is in standby 24/7.

I noticed something odd a few weeks ago on our SolarEdge app. We get hourly spikes in consumption. I couldn’t put my finger on it. Then last week, I turned our heat pump off completely to see if it was responsible. It was. With the heat pump off (not in standby) the spikes vanished.

Can an ASHP be turned off for a protracted period without damage?

Posted by: @editor

I have certainly noticed something similar. A few months ago, when we were running HVO, our heat pump was in standby mode and when I’d go into the utility room, I would notice that one of our mandated RHI metres (because we’re running bivalently) would occasionally flash its red light indicating that the heat pump was using electricity, but not generating heat.

I raised this with Global Energy Systems and they assured me that the pump was not working and consuming electricity.

Our heating has been off completely since late April so our consumption is down. The heat pump is doing HW and is in standby 24/7.

I noticed something odd a few weeks ago on our SolarEdge app. We get hourly spikes in consumption. I couldn’t put my finger on it. Then last week, I turned our heat pump off completely to see if it was responsible. It was. With the heat pump off (not in standby) the spikes vanished.

@editor Mars,

see attached. This is how Mitsubishi explains how crankcase heating works.  It does manifest itself as spikes.  Not all compressors (and not even all Mitsubishi ones) do this. 

@ronin92 

I think yes within reason.  They will have a start up procedure before they start running properly.  Best ask your installer/manufacturerto be sure.

@kev-m, very interesting. At least that's confirmed my suspicions. It's a shame our ASHP doesn't have a timer to just turn it on to do HW in the summer. It would save the spikes and wasted energy.

Posted by: @ronin92

Can an ASHP be turned off for a protracted period without damage?

Yes, I believe it can. Do you mean off off, like totally off doing nothing? We have switched our heat pump off for weeks at a time in the summer when we've had loads of sun around at the solar PV heated our HW. But as Kev suggests, speak to your manufacturer because different compressors behave differently. 

I've wanted to answer this question for some time.

Recently I switched the timer for heating and hot water to off for a whole day. The power supply to the ASHP remained on.

We still used 15kWh over that 24 hour period. Not conclusive as daily demand varies depending on use of the washing machine and oven.

Last week when away I switched the ASHP off completely for 5 days. Daily usage over that period was 8kWh (6 day, 2 night).

So, I still don't know for sure what the  background usage of the ASHP is but that everything else takes 8kWh.

I'm now trying to work out where that background power goes. I have a plug in power meter so can check the appliances. The fridges and freezers take about 2kWh between them. We also have a waste treatment (Klargester) unit which is on constantly. That may account for most of the rest but it's still hard to see that appliances on standby make up the remainder. I'm still investigating.

During the current hot weather I'm keeping the ASHP switched off. We don't have much need for hot showers and can turn it on again after a few days when the water gets too cold.

Mike

@mike-patrick, how did your investigation go? Any significant findings worth sharing?

@editor I didn't discover anything further of significance.

The fridges, freezers and a few other minor appliances + the Klargetser seem to account for all the background usage. The minor appliances are the only ones that could be switched off but in reality they take so little power as to make no significant difference.

Mike