n00b Questions on Air to Water Heat Pump

fireglo2020 · 24-12-2020 12:30AM #1

1. I bought a new place and it comes fitted with a Air to Water Heat Pump for heating and hot water (no gas, immersion etc). The house is well insulated and top rated (BER A1 I believe)
2. From my basic understanding - it works like a reverse fridge. You always leave it on and it provides heat all day round (the same way you leave on a fridge and it provides cold all day round)
3. Being a child of immersion/gas boilers - I can't "mentally" getting around turning it on/off all the time or even not switching it off when I go out.
4. Developer has told me not to do this as it will end up costing me more. Premise being that it takes more energy to get water from 0 - 20 degrees than it does from 30 - 40 etc.

I haven't gotten an electricity bill yet and won't for a few weeks.

I am wondering if anyone has any advice on best way to use it so I don't end up with huge energy bills please.

Any advice greatly appreciated.

TheChizler · 24-12-2020 12:39AM

It's not necessarily the case that it would cost more to be turning off and on, it possibly costs more to maintain a higher temperature as more heat will be lost through the walls of the house all the time than bringing it up from cold when you need it. It makes sense to leave it on cause heat pumps work relatively slowly, so you'd be ages waiting for the house to heat. Turn it off if you're away for a day or something like that. It shouldn't cost a huge amount to leave it on once the house is warm cause you likely have very good insulation.

fireglo2020 · 24-12-2020 12:43AM

Thanks so if I understand correctly.

1. If I am going to be at home alot leave it on at 19 - 20 degrees all day
2. If I am going to be away turn it off or down
3. 1 above would cost me the same as if I had gas heating and turning it on/off every evening

It still feels weird to leave it on all day lol but that's childhood immersion trauma for ya!

TheChizler · 24-12-2020 10:09AM

1 and 2 pretty much yes, you'll get a sense of how quick the house is to heat over time. I have gas in a pretty badly insulated house but I find I don't need the heating on before dark, a lower temperature, say 18.5°C, for most of the evening, and only need closer to 20 late at night when we've stopped moving around. You'll find out what you find comfortable quick enough.

3 couldn't tell you what it will cost.

I have a friend who just moved into a house with a heat pump who just has it set to 23° day and night and the place is like an oven, I'd say that will stop once they get their first electricity bill.

Calahonda52 · 24-12-2020 11:38AM

The piece that is missing from this thread so far is the use of the night rate billing, which is critical to the economical use of HP with UFH.

The theory is to heat the slab as much as possible on the night rate, not over heating, just let it run to the normal temp and then the slab will give heat out during the peak power hours.

What our European colleagues do is have a buffer tank for heating at night but this has never caught on here except when spec'ed at design stage

The other variable is the width of the dead band in the stats, ie: how far above and below your target temp will your HP cut out and cut in respectively

Biker1 · 24-12-2020 11:41AM

I would be surprised if it has a BER of A1 even if it falls under the 2019 regs. You should have been provided with the BER cert with your purchase documents.

FluffPiece · 24-12-2020 12:24PM

I'm in the same boat as the OP.

In a new build, dormer bungalow, rated A3 and has a heat pump but I have no clue about it nor did anyone I asked that was involved.

It's a Hitachi Yutaki-S and there's 3 rads upstairs with 6 downstairs. I had to bleed the air out of the rads downstairs at first but they seem to heat quite quickly ( and probably expensively ). There's a manual dial thermostat for each floor that I have on 20.

Currently, I think I'm using it inefficiently as in I come home about 5 or 6 in the evening and switch it on for the rads to heat up on circuit 1 set to 40 and the house heats up fairly quickly and I knock it off after about an hour or 2 and the heat stays warm enough til bedtime.

I switch the DHW function on in the morning and have enough hot water for a shower very quickly.

I assume I'm using it incorrectly and it's costing a small fortune although the first bill is roughly the same as what I would have paid for elec & gas in previous house. All my life thus far it's been gas or oil for heating with the open fire if needed.

So it seems the circuit 1 ranges from 20 - 50. Should I have it on 20 - 22 and leave it on for longer to use it more efficiently? The same question for the hot water really. Looking like I might have an option to work from home so it would be a good time to get it set up correctly now.

Bill Ponderosa · 24-12-2020 01:44PM

I've air to water heating also, set it to 21 in the morning and then 22 degrees at night but off from 8pm to 8am. I'd find 20 degrees cold in a house as I like to wear t-shirt and shorts. All works off the electricity on a good rate from energia. I level pay 70 euro per month and that gets me through the year. Great system imo.

fireglo2020 · 24-12-2020 01:51PM

Yeah I think the timer option is the way to go.

Kieran

TheChizler · 24-12-2020 02:13PM

FluffPiece wrote: »

It's a Hitachi Yutaki-S and there's 3 rads upstairs with 6 downstairs. I had to bleed the air out of the rads downstairs at first but they seem to heat quite quickly ( and probably expensively ). There's a manual dial thermostat for each floor that I have on 20.

Currently, I think I'm using it inefficiently as in I come home about 5 or 6 in the evening and switch it on for the rads to heat up on circuit 1 set to 40 and the house heats up fairly quickly and I knock it off after about an hour or 2 and the heat stays warm enough til bedtime.

Rads would be a different kettle of fish to the underfloor, which was what I had in mind when replying. Since you've no mass of concrete in the floor to heat up first it'll be relatively quick to heat. The most thermally efficient time to do the most heating might be an hour or two earlier during the day when it's warmest outside, you'd have to do the sums to see if night rate would be better overall.

n00b Questions on Air to Water Heat Pump

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