Altherma 3. The hot water tank is currently set to schedule only and comfort heat during the off-peak early hours period to 50c. This gives us enough hot water for the whole day.
On cold nights, say close to freezing or lower, the house will lose a good 0.5-1c while the tank heats (typically 60 minutes). The house then takes most of the day to recover, leaving it a bit on the cool side when we wake up. We don’t have a setback on the schedule btw.
I’m considering the idea of configuring space heating priority, setting equilibrium [5-01] at 4c or so and [5-03] at 6c, perhaps even lower for those values. From what I read, that should cause the resistive heaters to heat the tank on the really cold nights, leaving the compressor taking care of the space heating. On milder nights, I assume the compressor only would heat the tank.
Given this will all happen during the off-peak period, I’m not too worried about the cost increase. The COP isn’t huge anyway when its really cold out and it’s having to defrost at least once mid-way through the hot water heating cycle.
Is my understanding correct and has anyone else done anything similar?
I assume the long recovery of house temperature is due to running on pure weather compensation rather then hybred weather/load compensation.
If the recovery was fast, then I would be thinking of DWH at start of cheaprate so house temperature is fully recovered by end of cheap rate. (Maybe even heat house to 1c higher in last part of cheap rate.)
Is the DWH configured so the full power of heatpump is used for the full reheat?
The long recovery may also be because I forgot to remove the LWT mode scheduled -2c overnight setback which I’ve just noticed kicked in despite switching back to RT mode yesterday.
Yes, I had similar thoughts - I’m going to move the DHW schedule from 03:30-05:00 to 00:30-02:00 and see if that helps a) avoid the coldest part of the night and b) space heating recovery time.
Yes, it uses from 2kw to 4kw during comfort heating, ramping upwards over the heating period.
ive set up a automation so the tank element comes on if the outside temp is below 2 degrees C , and its triggered by the heat pump doing a hot water cycle in the early hours , so in reality the heat pump will do one cycle on the hotwater but below 2 degrees there is a high chance of a defrost cycle
i figure its better to heat the hot water at off peak@100% with a element rather than loose temp in the house which ends up causing the defrost cycles again
