Stinsy wrote: ↑Mon Jul 17, 2023 11:35 am
sharpener wrote: ↑Sun Jul 16, 2023 5:05 pm
How are you going to ensure enough heat transfer to the DHW? Ongoing discussion
here. Perhaps you will bite the bullet and put in a new tank? Personally I regard that as a waste but have not found an installer who will fit a new HP without one, or agree to a recirculating pump or heat exchanger instead.
Re the OP we always put the programmer to OFF when we are away in the summer, wouldn't rely on the thermostat. Have checked the gas meter on several occasions, result is absolutely nil consumption. Vokera Minute 12kW, manual says the anti-blocking cycle runs the pump only, not fan or burner (don't see the point, fan not likely to sitck as it is not sitting in claggy water).
1) The plan for DHW not quite finalised. Thinking originally was for a 180L “solar” DHW tank with a small coil at the very bottom the heating circuit would run through that coil then into the radiator circuit. The immersion would bring the DHW to 45℃ On cheap-rate and solar electric. The more I think about it the additional cost/complexity doesn’t warrant it and I might go for a cheap “Ecconomy7” tank and resistive heat only.
The problem you have with “installers” is that the grant can only be paid for installs that meet a particular set of one-size-fits-all design requirements.
Yes, difficult. Our HW tank is almost entirely heated by the PV, full tank uses about 9kWh/day. So if it were heated by the HP instead at say CoP = 3 then there would be 6kWh @ 45p worth = £2.70/day available for HP to do space heating (so 18kWh delivered). Occupied full-time that would be say £500/year
so maybe capex of £2k5 to achieve it would be worthwhile.
Or heat the tank at night with HP running off E7, 3kWh @ 15p but this saves a futher £3kW @ daytime rate so now £3.60/day, even better. Hope I have not double counted anything, these sums are quite complicated to do in one's head.
But for sure not having to replace the tank would make the capex a lot lower.
Today's game is responding to all the points planners have raised as to why my application fails validation. Unfortunately the Vaillant 12kW is 0.1 cu metre over the limit but if I DIY I will need PP anyway, did you have any problems with that aspect of yr project?
Stinsy wrote: ↑Mon Jul 17, 2023 11:35 am
2) I know someone who went~to Australia for a few weeks last winter. He returned to a house with every pipe burst. He’d turned the boiler off at the FCU!
I edited to add "in summer" for that very reason. In winter it costs us £2/day at frost protect temps, cheap for peace of mind.
In shower / bath water not hot enough.
