I bought a Heat Pump

markin

Im sure all heat pumps have an back up electric defrost? if it reversed to defrost and it wasn't enough heat to do it you would soon be without any heat.

Probably no way or reason to disable that.

akwexavante

My ashp does not have an integral electric heater. My hot water cylinder does and it's used specifically and exclusively to finish off the disinfection cycle only. 

I've have been told that if the weather gets seriously cold - 15 or worse the heat pump will stop heating the house and look after itself. Having a multifuel stove resolves this unlikely problem. It's not impossible and it has gone down to - 15 in the area where I live, I think it was in 2010 but only for a few days.

I'll be firing up the stove long before it gets down to - 10 anyway. 

Reed_Richards

My heat pump, too, really does not have an integral electric heater.  If it needs heat it takes it from the warm/hot water in the buffer tank.   

ispookie666

The compressor runs at higher speed (Mitsubishi) and power draw goes up to 1600W both the indoor and outdoor fan stops working. Otherwise it ticks over at 500-600W/hr for an reasonably sized living room

Reed_Richards

My average consumption for December was 36.8 kWh per day, or an average power of about 1.5 kW.  Given the cold spell we had in December that really doesn't seem to bad to heat an entire bungalow and provide its (near instant) hot water.  But it's the worst monthly figure since the first two months of operation when I had not got to grips with Weather Compensation.    

Mstty

Our December average for heat and hot water was 20.8 kWh per day. (£6.08 a day on our tariff) 0.87 kWh per hour.

Weather compensation curve with all thermostats downstairs set to 25oC so it's all down to the curve. Consistent 20-22oC throughout December. Upstairs set to 20oC max and rarely came on.

Left like this 24/7 no setbacks overnight as this was a test to see how efficient the system could be.

Very happy with the results and a very happy warm Mrs mstty.

Although we ended up using 45kwh more than last December we were decidedly warmer and December 2021 was 4oC on average warmer than December 2022 for our village.

Reed_Richards

Well done @Mstty . 

It's difficult to make comparisons between different dwellings.  Perhaps we should normalise by dividing by the heat pump rated output, 12 kW in my case?  So my 1.5 kW December average is 1/8th of the maximum rated output of my heat pump.         

shinytop

Reed_Richards said:

My average consumption for December was 36.8 kWh per day, or an average power of about 1.5 kW.  Given the cold spell we had in December that really doesn't seem to bad to heat an entire bungalow and provide its (near instant) hot water.  But it's the worst monthly figure since the first two months of operation when I had not got to grips with Weather Compensation.    

31.2kWh per day average for heating and HW here in rural East Midlands.   All WC curve here too, and 20-22 deg throughout 4 bed bungalow.  December COP was a smidge over 3, which given the cold snap, I'm pleased enough with.

BTW my lowest 24hr COP was 2.4 on 14th December when average temp was -2.  Best was 4.5 on the 19th when average temp was 12. 

Mstty

Reed_Richards said:

Well done @Mstty . 

It's difficult to make comparisons between different dwellings.  Perhaps we should normalise by dividing by the heat pump rated output, 12 kW in my case?  So my 1.5 kW December average is 1/8th of the maximum rated output of my heat pump.         

That's probably not a bad way of recalculating to negate factors such as built in with a new build to retrofit and other things like house type and age.

So ours is a 8.5 kW Mitsubishi Ecodan so our .87 kW represents roughly 1/10th.

matelodave

Just to chuck in my fourpennyworth

Our overall consumption for December was 1149kwh = 37kwh/day. As our summer consumption works out at around 10kwh/day we can assume that heating has averaged at 27kwh/day. We do have an Efergy monitor on the power supply to the heatpump so can get a reasonable estimate of the consumption (depending on the reliability of the wifi and Efergy's servers which do seem to be a bit variable)

However our worst day was Tuesday 13th December when we chewed through a total of 69kwh. The Efergy monitor suggested 44.96kwh for the heatpump (both heating and hot water)

Ours is an 11kw Daikin. Although it's fitted with a 6kw back-up heater in the hydrobox and a 3kw heater in the hot water tank, neither are switched on (we can isolate them). Defrosting is carried out by reversing the flow for a few minutes which doesn't seem to have much effect on the power consumption or even the floor temperature - in fact the compressor seems to shut down during defrost periods.