Heat Pumps - post here.

You shouldn't really set it to run exclusively on off-peak. You should boost it at night and then set it back a degree or two by day but not turn it off entirely by day.

Depends on the HP. Presumably there is a setting where you can set the water temp but ultimately it will have to run longer by either heating the water to a higher temp or boosting it when it goes low.

The hot water and the UFH are separate systems. Your UFH is, as you said, at a much lower temp but it isn't pulling water out of your hot water tank. You simply need to run the HP for longer if you are running out of hot water but you should be able to do that just for the hot water.

Overall what is the verdict- is it worth moving to night rate electricity and running an air to water heat pump at night mostly? I was reading that for my Diakin 14kw unit that it consumes 30% more electricity if its 7/ 8c colder at night, plus in order to get through the day I'd have to heat it to a higher temperature at night.

i.e. My house in general loses 1c overnight, sometimes 2c. As such to keep the living space at a nice 20c in the evenings Im presuming I will need to heat it up to 21c or 22c by 8am. So using it at night means as well as the heat pump working harder as its colder out, it would need to stay on that bit longer to heat it over my desired evening temperature.

Using the HP to heat water at night might work, but my unit is set to come on depending on water use - i.e. if I wash my hands the pump won't come on, but after anybody has a shower it kicks into life, which I was told was the most efficent use for it. Most showers here are evening but long before mid-night.

In my case I have very limited other use for electricity at night - we could stick the washing machine on, but not the dishwasher, we dont use a dryer, and obviously the other big consumption items like the ovens are only on during the day. I dont have an EV either so Im thinking its a real gamble moving to night rate and switching the HP to run at night - am I right or is there a saving to be had?

I’ve been doing this for 3 years, works pretty well. May take a little modification as weeks get colder but the general jist Is - I have minimum thresholds set on the app by night eg if it gets below 20 degrees it will be running for at least 5 hours over night. And if by let’s say 5am it’s still on the colder side it stays heating for another few hours but by 8am it’s off for underfloor heating no matter what.

And to be fair the house is always toasty. Never below 20’. And if there any bit of sun that’s 21/22’

I have a Mitsubishi eco Dan and the app is a godsend. I insisted on it during installation and you have a full view of what’s going on. Run reports on daily, weekly, monthly consumption or anything you can think of really.

now that day time rate is 40c+ I think it’s a must. I have an ev also so night rate for me makes total sense.

average consumption for hot water and underfloor is 2700kwh. About 500 of that is water. A2 house 2800sqft

This is what I'm thinking. I have an existing combi and for the heat pump to be cheaper to run it would have to have something like a minimum SCOP of 4, plus all the extra cost of new rads/underfloor, heat pump and a new hot water tank.

Until the grid is using less gas to generate electricity(so either gas increases in price or elec reduces), it's not an attractive proposition.

Hi , what brand / model of pump is it .. the settings vary by pump, I have a Thermia ATAC pump and I can set the temperature of the water v outside temprature. I have the same issue where the weather is damp and cold you need more heat.. I can alter the curve by 2 degrees higher or lower at a specific outside temprature

I dunno what others do but from mid may to mid sept I turn off the UFH part of my system completely. I only leave on the DHW part.

Domestic hot water

I should probably have mentioned I have radiators, not UFH. So far, running the heating all night downstairs seems to be working for me.

Between the kitchen, dining and living area we replaced 28 spotlights which voided into the attic space. It was right cold air coming down through these and a pig of a job filling the holes, sanding, filling, sanding.... I have 5 in the bathroom to finish and that will be the end of them.

For the living and dining areas I made two oak long strip lights and then for the kitchen I used a surface mounted track with dimmable adjustable spots.

I am only in my house one year and I have a A2W heat pump as well and I am still learning, and for last winter I didn't have much data but now I am logging my Heat Pump circuit, so I know when it comes on or not.

You are right about the thermal mass though, for the last year I have just used the room stats to call for heat. Every room has a stat and to be honest what I am finding is the heating only really comes on at night anyway when the outside temp drops to really low so I don't really worry about setting for the night tariff it naturally does it anyway.

My house will hold 19-20 deg in most rooms without any heating (A1 BER) But one day last week one of the rooms was at 19deg and one of my young fellas was doing his homework and my missus decided to set the temp to 21.5 degs for the poor little fella... and I didn't know, and the room was set for 21.5 deg for overnight. It was only the next day when I went into the room and realized Jeese this is hot and saw the stat set and set it back to 19.

But what really surprised was that room held 21 degs for 2 days without any heat been called for. I could still feel the floor warm 2-3 days later...this has changed my whole though process on underfloor/heat pump heating. I tried this method for a couple of rooms over the next few days and it also worked. So there is merit in it.

We are having really mild weather the last few weeks/months, so my house has not been calling for heat at all so I have not had repeated this, but we are looking as a bit of a cold spell over the next few days and I might try it again.

The last line:

LS: enabled brings it to 60 or so periodically

We have an A2 house, airtightness almost passive. Our heating requirements usually stop in mid March never needed any in April or May. temp set at 21c.

Do you know what your blower door test was for airtightness?

Airtightness in my house was 2 or a just a bit over, but I think its actually a bit better than that as one sliding door the seals wasn't correct and it had a small draft but that has been fixed and other door.

Regarding heating stopping in March to be honest again, I think that was more to do with it been unseasonably warm in March this year. My house will hold 18-20 deg most of year without any heating. On cold windy nights it will call for it alright but as all the advice if you set your room temps too high you will call for heat. I don't have any room that is set above 20 deg and bedrooms are 19-18 deg. I know if I set a room to 21deg my heating will be on a lot. If I leave it at 19-20, it should not come on that much, apart from the very cold windy nights. If I feel a room is a bit chilly in an evening I will just up the temp to 21 deg and turn it back down to 20 when going to bed. But that will only be in the living room.

I do have a room stats in every room and hallway but again I just leave it alone and if it needs heat it will call for it. The graph below is a graph of some temp sensors I have around the house and as you can see, they are between 18-20. One of the lads has his room set to 18deg so that's why is a bit lower than the rest.

This is only my second winter in the house, so I am still learning how best to manage it but the number one rule as I can see is not to set the room temps to high...

Yeah, that was my problem also so I set up Home Assistant Home Assistant (home-assistant.io) on a Raspberry PI4 to log a number of key circuits in the house, Heat Pump, Zappi car charger, Utility room, Solar PV and the main ESB incomer and the kitchen Island with dishwater etc.

I can see when things cut in or out and how much they are consuming, if you want to start managing these things you need to start measuring, As the saying goes. I would recommend Home Assistant it can do lots more than energy.

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