Odd load spikes over 3000W - advice please

Hello to all the knowledgeable folk on this forum.

We have been experiencing some strange load spikes for the last few days. Please have a look at the two images. 11th May is a typical day. Spikes can be explained by dishwasher, washing machine, shower and cooking. But if you look at 15th May there are some regular spikes of over 3000W every hour or so which I can't explain. We were out at work all day, no washing machine, no heating (ASHP).

Any idea what is causing this? Is it actual consumption of something somewhere? Or is it the system misreading something? The change has come since an Octopus visit on 12th May. We are looking to get an EV charger installed and as part of their checks they turned off the power briefly to check our main house fuse. It has been since that moment that we've been getting the spikes.

I don't know where to start to solve this. Thanks in advance

Ange I don't know where to start to solve this.

Water heating? I assume you use ashp for that. Is it configured to keep topping up the hot water? Could there be a hot water leak?

You could try turning off individual circuits at the consumer unit, to try to pin down which device might be doing it.

Ange

If you turn on the “battery charge” toggle on that graph, is it co-incident with battery charging? I’ve noticed since the 2020 update (D315 and D316) that I am seeing spikes of 858w multiple times a day where one inverter appears to be “topping” up the pair of batteries on that inverter and producing spikes like your graph. Not as high as yours though.

Ange

DD i turned the water heating off last night thinking that might be playing up but the spikes continued.

DD So I've just checked the hot water again and realise I didn't turn it off fully. But now I notice that the temperature is reading 60 degrees, when it's set to heat to 50 degrees. So maybe it's constantly running it's legionella cycle for some reason. I wonder how I can fix that? I hope it's not a call out job?

[unknown] depends on your ASHP how you configure the anti-legionella cycle and the hot water.

I have turned my anti-legionella cycle off completely as we turn the water over in the tank often enough for it not to be a high risk (see article on heat geek website). The hot water I have changed to heat only once a day from 12-4pm so it heats on solar now and the heat in the tank is enough for showers and a bath for the rest of the day. If we were taking multiple baths then I would need to have the hot water on longer.

[unknown] I have a Daikin HP. The default configuration was to top the water temperature up throughout the day (to "eco" level) whenever it dropped by about 10 degrees. But I turned that off since I only want to heat overnight when power is cheap. Daikin also has a "boost" mode which also runs the immersion heater. I assume that would also cycle as the water reached temperature then cooled.

My installation has a switch to turn off the immersion heater. (But interestingly I don't seem to be able to turn it on independently of the HP, which means should the HP fail for some reason, I don't have a backup for heating water. Installer didn't have an answer to that one.)

Ange I'd also suggest checking how your ashp heats the hot water. For my LG I found it did most of the heating by using the heat pump, but did the last bit with the immersion heater. I changed the settings to heat pump only. Might take a bit longer to heat the water but much more efficient

Just to let you know I got to the bottom of this. I called our ASHP installer and they said it can happen when there is a power outage. Our immersion had reset itself to a permanent 60 degrees. I just had to drop it down to 15 degrees and then it has a programme to boost to 60 once a week. Then the ASHP continues working at its setting of 50 degrees. It's all still a learning curve here.

[unknown] why doesn't the heating pump do that rather than the immersion?

Ange why doesn't the heating pump do that rather than the immersion?

probably @geoffreycoan has a low temp heat pump and he wants his water heated above what the pump can do?

dragos.balaban Certainly we like our hot water about 65oC which means less efficient heat pump heating or a short top up with the immersion heater.

A flow of 75oC works fine for heating a tank to 65oC but is right at the top end of many heat pumps leading to long periods trying to put that last bit in the tank. The immersion heater does it in less than 5 minutes. Just use the timers correctly (or some automation).

dragos.balaban probably @geoffreycoan has a low temp heat pump and he wants his water heated above what the pump can do?

That's a good point, I don't think my heat pump will get up to 65 degrees, I was only thinking about the efficiency of heat pump vs immersion.
My hot water is set to 46 degrees which is within the heat pump range so I only use the HP. The default settings for the heat pump are to use the immersion, probably for the top end boost

geoffreycoan got ours on 50c heating in the IOG cheap period but it only ran for about 1 hour last night for example peaking at 4kw briefly. We haven’t run out of dhw yet and the cop is 4.3 overall but above 5 this month. Still got the heating on (about 13c today and 6 tonight and a nice northerly) but it is hardly actually running currently 25.1c flow temperature.