iboost+ seems a little odd, when I think it is switching on, but could be OK!

I looked at my software and noted a high load. The 3313 watt load seems around 3000 watt too high, but before I could check the immersion heater load had dropped. This does not seem long enough to be the immersion heater. Second spike wife was out, so nothing she has done, the first peak seems to follow the solar production, so that would seem to tie in with iboost+ but I can't think of anything other than the iboost+ that could use 3 kW, but the time seems too short.

It may be that a thermostat will do this, and nothing wrong, but I would have expected a thermostat to stay energised for longer. But until yesterday, this year there has not been enough solar for it to use a full 3 kW, so not noticed those spikes. But can't think of anything else which uses 3 kW. Monday and Wednesday both high solar, and it seems similar both days, so is once every 2.5 hours about normal for an immersion heater to cut in?

ericmark said:

It may be that a thermostat will do this, and nothing wrong, but I would have expected a thermostat to stay energised for longer. But until yesterday, this year there has not been enough solar for it to use a full 3 kW, so not noticed those spikes. But can't think of anything else which uses 3 kW. Monday and Wednesday both high solar, and it seems similar both days, so is once every 2.5 hours about normal for an immersion heater to cut in?

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I'm not sure whether this is relevant, but even in the case of my extremely-well-insulated immersion-heated DHW cylinder, after the initial period of getting the water up-to-temp, the thermostat switches the immersion on very briefly far more frequently than "once every 2.5 hours" (roughly 'once or twice per hour'), usually just for a minute or three, as can be seen in this fairly typical graph of one night ...

Thank you. Seems mine doing as one might expect then.

ericmark said:

Thank you. Seems mine doing as one might expect then.

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You're welcome. Yes, it does seem that such is the case.

With a 'normal' (rather than my 'excessive'!) amount of insulation, I presume that the 'top-up' bursts of heating would probably be more frequent than what one sees in my graph.

I suppose with electric resistive heating it does not matter if the slewing range of temperature is 0.1ºC, 1ºC, or 10ºC. With something which needs to warm up first, be it gas, or oil or a heat pump, then we want a large slewing range. My beer brewing thermostat can be adjusted in the range of 1-30ºC.

I noted when using oil, it was costing more, likely due to heating the boiler and pipework up. I had it set for once a day at ½ hour per day, but it would only run for 20 minutes, and before it had cooled enough for a second firing the ½ hour had run out.

I had heard so many times oil and gas were cheaper, I simply accepted it as fact, same with the solar, I had heard how it was cheaper to heat DHW with solar, and I had not studied the tariffs, and since I pay 6.5p/kWh off-peak, and solar export paid at 12p/kWh better to just use off-peak. But now I have an iboost+ not really worth changing it. My luck if I did, the tariffs would change.