Thanks again Tim, and Alan.
Having been monitoring DHW tank temperatures for nearly a week, I’ve realised that it’s at legionella optimal growth temperatures of between 42 and 32 for days at a time.
I’m trying to monitor energy consumption of the DHW cycles, via heatpumpmonitor.org, but seeing some weird graphs which people in the OEM forum are suggesting is air in the system interfering with heat meter readings, and also not great for the system long term.
When that’s settled down a bit, I’ll check DHW running costs as best I can and then look at different DHW cycles to optimise cost v hygiene.