ASHP having to work hard to deliver lots of hot water

[Timbones (Tim)]

@MyForest

I thought I’d share this example of a 14kW air source heat pump having to get on with providing four showers after a few weeks of being switched off. We have a 300L tank. It was 22 °C outside.

For comparison, and back on topic, here’s my 11.5 kW EcoDan heating up 250L from nearly cold (water out of the tap was barely warm). It took a little over 90 minutes to heat up to 53°C, delivering 10 kWh of heat with an average COP of 3.5. Outside was 19 - 20°C.

Note that I gradually increase the target temperature to keep the HP power draw to around 35%, so that it stays within the generated solar. I find that if let EcoDan do it’s own thing, it ramps up the compressor quite hard as it races to get the flow temperature up. I prefer it to be slow and steady, though I’ve not noticed that it makes any difference to the overall COP.