My Heat pump Story -Davec

Rob666

smallblueplanet How quickly do temperatures change where you live?

Not very quickly. What it boils down to is I want to be warm for an hour or so in the morning when I get up and comfortable from 5PM to 11Pm. The house does not get too chilly overnight even on very cold days and the gas CH is external temperature compensated to make sure I’m warm at the set times in the morning and evening. In short I only need heating for 8 hours out of 24. Running a heat pump 24/7 just doesn’t make sense to me.

smallblueplanet

Rob666 Running a heat pump 24/7 just doesn’t make sense to me.

It doesn’t literally have to run 24/7. But it’s okay your mind is made up. Maybe when you need a new boiler.

DavecUK

Rob666 Running a heat pump 24/7 just doesn’t make sense to me.

There’s a few good reasons:

Running 24//7 (in the winter months, not in summer) allows a lower flow temperature and higher efficiency, it’s cheaper to run
Cycling the compressor is what shortens it’s life, the heat pumps last longer if they are not on/off/on off like a gas boiler
Night time can use a setback for a lower temperature
They don’t work like a gas boiler, they take a lot longer to put heat in, they will input the same amount of heat, just low and slow and much more efficient. A gas boiler blasts heat in, then the place cools down, heat pumps won’t warm a place that fast
I’m home all day and rather than 3 hours in the morning and 3 hours in the evening of gas boiler and a max of 19C with periods in between dropping to 14C, I can have the house at a constant 20C during the day for a similar cost at full price cap tariff, or Ovo heat pump tariff for around 40% cheaper than mains gas,

Every 5% change in flow temp is a 10% change in efficiency, so they set the heat pump for a max flow temp of 50 for heating, I will be reducing that to around 40C if I can, and getting 20% more efficiency with less or no cycling. I’m looking to get a cop of around 4:1, so for every kW of electricity I get 4kW of heat output or more. With DHW, I will be using 50C

Heating the Hot water cylinder is best done during the warmest part of the day

HarveyMushman

Yep fully agree, induction all the way for us. A friend of mine who fancies himself as a bit of a chef just had his kitchen redone and giving me the tour he says ‘oh we had to have gas hobs, you know, you just need the precise control’… I’m thinking, ‘have you ever used an induction hob?!’…

Also these days most pans other than copper work fine on them. And yes, a doddle to clean, I do not miss disassembling and scrubbing the gas hob.

Also ours has a ‘boost’ setting which means very quick water for the V60 in the morning!

Cuprajake

We have our heating set to 17c and then boost if we need to

This sees us pay about £2200ish a year

This month we used £105 electric and £35 in gas

dfk41

Cuprajake We have our heating set to 17c and then boost if we need to

We set ours to 21c from 7.00 till midnight and 17c overnight. It is important to me to have instant heat as my wifes needs dictate that. I also have a flueless gas fire that works superbly meaning the main room where we spend the day has all 3 radiators switched off permanently.

dfk41

DavecUK What happens if you are not an engineer? Everything you talk about is a paper calculation looking at efficiency whereas the vast majority of people could no give a monkeys chuff about efficiency! They want heat delivered when they want it!

I understand your theories Dave but after a cold winter, I will be interested to see how it pans out. I did ask @smallblueplanet earlier in this thread this question:

dfk41 if you want to shift a room from 18 to 20 when it is minus 2 outside, how many weeks does it take to adjust (and this is presuming it actually can)? There is nothing more economical than not having to use a heater. You are talking about efficiency as in getting the best from the system.

Can you answer it? You get your calculations slightly wrong and due to a cold snap the house is not warm enough……what happens next?

smallblueplanet

dfk41 Can you answer it? You get your calculations slightly wrong and due to a cold snap the house is not warm enough……what happens next?

I don’t do such precise calculations. But for anyone interested in how ashp are then:

We had the ashp put in last November - in the coldest week there was!!! Anyway it was on and off as they adjusted things and actually from a standing start it warmed up from c13C to warmish pretty quickly an hour or so - this is on poor memory. Yes for economy it is better to run a heat pump ‘low and slow’ with large emitters but it isn’t unable to heat up quickly it’s just not as efficient. It is also more efficient to run if you have some reasonable insulation, we have a 1950s semi with double glazing, loft insulation and cavity wall cavities (I don’t believe in cavity wall insulation).

Anyway we ran it over winter and the house was at mostly constant temps of 21C during the day and 19C at night. Although it was slightly different as the radiators are sized to provide heat to bring a room to a set (by regs) temperature. So the upstairs rads were sized and balanced for the temps to be around 19C and the downstairs were similarly for 21C.

We replaced an old oil boiler with the ashp and I guestimate that the costs over winter were pretty similar, over summer will probably be same. It can be a bit tricky to get it set up, but doesn’t have to be.

It is run by a wall mounted screen or a phone app. The app is great for changing settings when away from the house. I’m very glad we had it fitted and as long as people who want to have one installed understand that they operate differently to oil or gar boilers then they are the mutts nuts.

DavecUK

dfk41 Can you answer it? You get your calculations slightly wrong and due to a cold snap the house is not warm enough……what happens next?

There is an external as well as an internal thermometer, the first for weather compensation (the situation you describe) and the second to monitor and maintain the internal temperature by modulating heat pump output up or down and increasing or decreasing flow temperature. It’s something I won’t have to worry about or deal with on a daily basis.

As for shifting a room temp up by 2C, it doesn’t take very long, certainly not weeks, but probably a few hours….unless you want to do it more quickly at a loss of efficiency. I believe there is a “boost” type setting on the controller.

smallblueplanet

dfk41 Can you answer it? You get your calculations slightly wrong and due to a cold snap the house is not warm enough……what happens next?

We run ours in the same way that any other boiler tends to, via wall mounted thermostat ie in Daikins case a Madoka. Some people run their ashp via lwt, but we use the internal thermostat like a ‘normal’ heating system and the heat pumps software modulates to correct the weather curve. Oh and as per @DavecUK hopes we were installed to run at 50C at (edit) -2.2C but actually changed the weather curve to be more like 40C at (edit) -2.2C.

But basically lots of people just allow the software to run the heat pump and use the wall mounted thermostat to monitor actual temperature.

dfk41

smallblueplanet but it isn’t unable to heat up quickly it’s just not as efficient.

When I was working, I used to tell clients hung up on investing solely into ISA’s, ‘do not let the tax tail wag the investment dog’.

For anyone wondering, I am digesting and enjoying this thread. You can only learn by asking questions.

HarveyMushman

This may be a very stupid question and I already feel foolish asking but do these systems do cooling also?

With the way our weather seems to be going I’m getting more interested in cooling than heating. Our house admittedly does a great job of keeping heat in during the colder months but frustratingly an equally great job of keeping heat in during warmer months.

I’m guessing the clue is in the name but perhaps there are systems that do both.

smallblueplanet

HarveyMushman

There are systems that do both, I think our Daikin model could but the conditions of the govt BUS grant don’t allow for it, so ours is heat only. Edit: no idea how that works tbh.

dfk41

I also have air con fitted. That allows for both heating and cooling. We do not use the cooling side that often but when we do it is invaluable. We only have a bungalow with 4 units fitted. When it is cooler we often have the hall unit on most of the day and it blows air into the lounge from the hall. The big unit in the open plan lounge diner can be oppressively hot (yes I know you can set the desired output) so just the trickle the hall produces is enough.

The installation being a bungalow was a doddle but I can imagine it being a PITA for a house with 2 or more floors. That said, you can elect for say a unit in just your lounge or the room you spend the most time in, then it would be a doddle

HarveyMushman

dfk41

How long have you had it installed and have you had any problems with the system?

I’m certainly considering it as the past couple of Summers have become almost unbearably hot indoors despite the efforts of the ‘windows open at night, blinds closed during the day’ approach.

I work from home quite often now since Covid and spending all day in a sweltering home office with the blinds closed while it’s 36 degrees outside isn’t much fun so some sort of home-wide AC would be ideal even if it’s only in use for a couple of months each year.

dfk41

HarveyMushman How long have you had it installed and have you had any problems with the system?

It was installed in May 2023. The chap recommended Mitsubishi equipment. We had 3 quotes and they varied wildly. Initially the idea was one unit in one room and the first firm back wanted £2750. The chap who did the actual installation quoted £1350. This led us to re-think and we ended up with a 10kw unit outside feeding 4 indoor units. The largest is a 5kw, then a 3.5, then a 2 then a 1.5. They work via remote control or from an app. The first firm to quote said we had to sign an annual service contract. The installer said absolute nonsense, no maintenance needed! I suppose if the unit had been under a tree it may have been relevant. You do end up with a big lump of an outdoor unit though.

HarveyMushman

Brilliant, thanks.

We’ve considered portable temporary units but given the good ones all need to be vented through a window or similar it would make sense to have a more permanent solution.

DavecUK

HarveyMushman Brilliant, thanks.

We’ve considered portable temporary units but given the good ones all need to be vented through a window or similar it would make sense to have a more permanent solution.

I have had an aircon unit fitted in the loft room for 13 years now…It’s an inverter system and can be used to heat or cool. It’s a pretty large loft room and it gets oppressive on warm summer nights. So shut the door, unit on and in 15m without using the “powerful setting” for quick cool down, it’s nice and cool. Litrerally maintains it for approx 200/300W usage per hour.

I can of course run Dex on my Samsung and work up there if the office gets too hot. They require minimal maintenance, just clear any leaves and crap and clean the case each year. The one thing I may do next year is put new insulation of the flow and return pipes as it eventually deteriorates.

AlbertR

HarveyMushman We’ve considered portable temporary units but given the good ones all need to be vented through a window or similar it would make sense to have a more permanent solution.

I would strongly advise against using a portable air conditioning system. The poor performance of these devices is only surpassed by the immense electricity costs…

From the beginning of the 1980s, I had a permanently installed split system for about 10 years to cool my office, a flat I have rented for my IT business. This was mainly necessary because there I was working with department computers, but also the summer temperatures in Binningen (Switzerland), often were quite high. The installation of the AC was absolutely no big deal.

Living in an area where you do not need AC is obviously prefererable. This is one of the reasons we picked for our retirement a location at an elevation of 900m. After all, air conditioning contributes to global warming.

HarveyMushman

DavecUK

This sounds really great, many thanks for the info. Very reassuring you’ve had it a good while and minimal maintenance. We typically need to clear the gutters each year anyway so not a big deal to keep an AC system clean also.

I think a one or two room solution for just the upstairs might actually work quite well for us.

DavecUK

AlbertR I would strongly advise against using a portable air conditioning system. The poor performance of these devices is only surpassed by the immense electricity costs…

I used to have one vented through a window, they are absolutely useless.

Performance is poor
very noisy
use lots of electricity
They work by sending warm air outside….which drops the pressure in the room and warm air comes back in…making them completely ineffective for room cooling

The best you will get is spot cooling, which you could achieve far more cheaply with a fan. Too cool a room cheaply and effectively you need a “split system”. I have a Fujitsu unit in my loft (which can get incredibly hot sometimes.

Shut the door, turn on the unit, it’s cool within 15 minutes and uses around 200W to keep the room cool. Once I am ready to go to sleep I usually turn it off, unless it’s a particularly warm night. The trick is to not set them to make the room cold, like American aircon or some hotels, I set mine to around 21C….then they don’t cycle much and use very little power.

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