What size of air source heat pump to install? Would really appreciate any help

[Beelbeebub]

3 hours ago, sharpener said:

 

Not quite. The scenario might be we return from a winter break in the Canaries and find the house in darkness from a lengthy power cut. It has been a sunny day so there is enough charge in the battery system to run the HP for >2 hrs  though. Frost protection would mean we can heat the house, burst protection not. Fortunately we have a WBS, an oil-fired AGA and even oil lamps.

That's a fairly unique set of circumstances. 

 

Basically an extended power cut and temperatures in the "mushy glycol" zone.

 

I'd imagine, if you arrived back to an ongoing power cut you would want to conserve your battery power for things like Internet, phone charging, lights etc. and off using your precious power to run the heating pump and using your aga as the heat source. 

 

The only downside of glycol is the expense, which can be countered by not using giant buffers and the mess issue*. The efficency and viscosity in normal operating conditions seem to be very close to water. 

 

*as someone who regularly has to deal with small leaks from heating systems and small spills of water when fixing them, this is the biggest drawback for me. 

[sharpener]

1 hour ago, Beelbeebub said:

I'd imagine, if you arrived back to an ongoing power cut you would want to conserve your battery power for things like Internet, phone charging, lights etc. and off using your precious power to run the heating pump and using your aga as the heat source. 

 

Bit of an extreme scenario and haven't really thought about it in a lot of detail. But one priority would be hot water, the HP will be ~3x more efficient than the immersion heater so a full tank would use up about 1/3 of the battery.

 

Would have to use the microwave for cooking as the AGA takes overnight to reach operating temp. Once going it keeps the kitchen/dining room warm and also the bedroom above it, not something MCS calcs take into account.

 

One installer said he would insist on fitting rads in the kitchen "in case a future purchaser takes the AGA out". In which case, I said, he can put the rads in, I am not going to pay for them. Fortunately the people I am talking to currently are more pragmatic.

[Roger440]

14 hours ago, Beelbeebub said:

 

I do see the reluctance to using glycol in a system with a huge (say 100l) buffer or volumiser but we should be aiming to remove those anyway

 

Why is that? Removing the tank that is.