Heat pump thread

Do we already have one of these? Sorry if I’ve missed it.

I did one of these online quote forms and have got a quote from a vendor, minus installation, and it looks like he’s given me options on the invoice rather than an actual quote – but not sure what they actually are. I’ve got things like this:

https://www.cityplumbing.co.uk/p/samsung-ehs-r32-monobloc-heat-pump-5-kw-ae050rxydegeu/p/467506#fo_c=2832&fo_k=86b9f668fb4e03fd35f1e04c8c11c375&fo_s=gplauk

But then also something that looks like this:

https://www.daikin.co.uk/en_gb/products/product.html/EHVH-UD6V.html

Not sure if I need both those things or are they just different choices? I assumed there was an indoor and an outdoor component to these things, is that what I am looking at?

Also he’s added a HW cylinder to the list – I already have one of those, do I need a different one?

Ok so it looks like a normal HW cylinder doesn’t have enough coil area to heat enough hot water – that’s fair.

If there’s a £7.5k grant available, then that looks like it would cover most of the cost of these items?

I was told that you realistically need 15mm pipework and preferably 22mm pipework to make it work efficiently, so If you don’t have that you’re looking at £4k-£9k for a replumb too.  

You might also want to do the rads too, so another £3-4K 

I was told that you realistically need 15mm pipework and preferably 22mm pipework to make it work efficiently,

Yes I understood this but more recently have heard conflicting advice. We have microbore but online (and one quote) told me its possible to do it using 10mm piping.

Yeah I know all about that. Just asking about the cost of the pumps specifically.

Our air source heat pump has two units, one outdoor and one indoor. The Samsung looks like the outdoor and the Dakine the indoor. These systems operate at a lower temperature to a normal heating system, so probably need a different HW cyliner to allow for this.

A couple of things that never seem to be mentioned:
1). Because of the lower temperature heat pumps work best with underfloor heating, or radiators have to be up-sized to suit.
2). They work better with a well insulated building.

Any heating works better in a well insulated building, a heat pump should work in any building providing you can fit a large enough emitter. Microbore may work but is unlikely and I would advise to remove it. The only size heat pump we would consider using 22mm pipework is the small 3.5kW. 5&7 are usually 28, 10&12 in 35mm. Design is critical, and I would chose the manufacturer carefully. The same goes for the installer. Check to see if they do maintenance as most seem to fit and run away. Also some that do service aren’t as thorough as they could be. We are inundated with maintenance work as there are so few that do it and unfortunately the industry is riddled with poor installers. 

Got the iStore 270l – from memory it was around 3k  for the unit and fitting (That’s Aus Dollery-doos) and was installed when we got our solar fitted. IIRC in total we paid under 10k (again, aus dollars).

It’s outside (people have them indoors???) and we’ve had it all for a about 18 months. Seems to provide around 35-40kWh and the app shows it’s solar is working from around 0430 until around 1630 but we’re only in October, Dec/Jan/Feb will be 30c+

The housing association my partner works for is retrofitting an entire estate. They seem to expect a big increase in electricity usage as the cabling and substations have been replace or added to.

I need to do something about our gas boiler but am sitting on my hands seeing what happens on this estate.

Worst case it will increase the energy bills of tenants of social housing.

i did a slight amount of research into this… old school house 1960s radiators etc

basically assumed that id need to upgrade the plumbing and rads

however, i also read that octopus are bringing a new heat pump to the market with the intention that it works seemlsessly with existing plumbing

Is that quote based on any heat loss calculations specific to your property or is it the old school approach of just chucking 8n the largest unit you can?

You could get away with it on boilers with cheap gas but it makes heat pumps less efficient.

There are heat pumps around now that will work but they will be expensive to run. The key is getting the flow temp as low as possible.
Octopus are forgetting that the building regs have been re-written to account for low temp heating systems. They are marketing something that in my opinion will be detrimental to the heat pump industry. Remember they sell electricity too!

Has anyone seen any good online sites that go into the detail of heat pumps.  We have 20mm pipework at the moment and the water in the pipes isn’t particularly hot so I think we are not in bad shape but I really want to understand a bit more before going looking for suppliers.

Is that quote based on any heat loss calculations specific to your property or is it the old school approach of just chucking 8n the largest unit you can?

The estimate was 4.6kW which is way more than enough to warm the house, based on my experience with a 9/12kW boiler. Perhaps not enough to do both HW and heating at the same time though. But there are 5 and 8kW units listed.

Has anyone seen any good online sites that go into the detail of heat pumps.

heatgeek.com

heatgeek.com

Brilliant, thanks

 They work better with a well insulated building.

When I see & hear this my standard retort is “every heating/cooling system works better in a well insulated building”.

Obviously, but the issue is that heat pumps can’t put out as much heat as a gas boiler, and they also lose more efficiency when run at higher temps; this means that the financial penalty for poor insulation is much bigger than with gas.

We got a quote for the Octopus system last year.  We have a mix of 8mm and 10mm microbore.  Octopus said this would have to be replumbed and best to do it with 28mm pipe.  The cost of the ASHP, 270l UV cylinder and a loft fill tank was £7900 AFTER the £5k grant.  The replumb was £7k with a mix of 15 and 28mm pipework.  

So even with the grant at £7500 today, we’d still need £8k plus insulation, plus rads/UF heating, so minimum of £15k AND it would cost more to run.  

Dumb question – if we want to see how a heat pump would work with our house as is, could we just turn down the boilers CH temp to whatever a heat pump would generate and then see if the place stays warm enough?

Dumb question – if we want to see how a heat pump would work with our house as is, could we just turn down the boilers CH temp to whatever a heat pump would generate and then see if the place stays warm enough?

yep – that is my understanding.

In the recent cold snap, our house couldnt hit the desired temperature (21c) with the boiler flow set to 60c, the temperature of the house just sat at 20.5 for 3 hours, until I increased the flow temp to 65c, then it hit 21c pretty quickly.

so I dont think our house is suitable for a heat pump without a lot of money being spent

Heat pumps can produce 60C I think, at least some – but the efficiency (Coefficient of Performance or CoP) goes down. Given that right now electricity is about 4x the price of gas, you need a CoP of 4 or more.

Models will vary of course. There’s a Samsung domestic one listed on some seller that shows the following for different flow temps:

@35°C 4.27
@40°C 3.98
@45°C 3.69
@50°C 3.40
@55°C 3.11

But it doesn’t say what outside temps that refers to.

EDIT those numbers are SCOP or seasonal COP which seems to be an average over the whole heating season..?

I just set our boiler to 40C and asked it to raise the temps, it put 1.5C on in about 2hrs, from 17.5C to 19C. But it’s 15C outside.

yep – that is my understanding.

In the recent cold snap, our house couldnt hit the desired temperature (21c) with the boiler flow set to 60c, the temperature of the house just sat at 20.5 for 3 hours, until I increased the flow temp to 65c, then it hit 21c pretty quickly.

That’s interesting. I had my flow temp on the boiler set to 50-55c last winter and it was ok, but then we prefer a cooler house heated to not more than 20c. Minimum loft insulation and no cavity wall insulation.

Assuming I topped up the loft insulation, would that suggest I could run a heat pump for our needs?

I wonder whether the answer lies in the table posted by molgrips, but I’m not quite sure how to read that.

I wonder whether the answer lies in the table posted by molgrips, but I’m not quite sure how to read that.

Well your house needs a certain amount of power entering it to offset the power leaving it i.e. heat loss.

Your boiler might supply a certain amount of power, say it runs for 3hrs at say 60C on any given day in total at 6kW, then you’ve used 18kWh of gas which would cost you something like £1.35. Given that electricity is 27p/kWh you would still have to run it for 3hrs at 60C, but to still be paying £1.35 you’d have to have a COP of 3.6 – which that model above wouldn’t manage. So at 60C you’d lose money with a heat pump.

But you can run it for longer at a lower power, say 6hrs at 40C, and output the same amount of heat BUT if the COP would be nearly 4 as per the table, you’d save money.

Thanks. So going by the data you posted for the Samsung domestic model:

@35°C 4.27
@40°C 3.98
@45°C 3.69
@50°C 3.40
@55°C 3.11

I’d need my house to be fine running at a boiler flow temp of 40c to be in with a shout of switching to a heat pump. If it isn’t then loft insulation and radiator upgrades first?

If it isn’t then loft insulation and radiator upgrades first?

loft insulation is worth doing regardless – if you have little to none already – its so cheap and easy to do, it’ll reduce your heating costs regardless of the heating mechanism.

In my head, it would only be worth going to a heat pump if also going for solar panels and batteries to offset the increased electricity consumption hoping you can fill the batteries during the day and empty them during the hours of darkness primarily through the heating, but it is one hell of an outlay!

I’d need my house to be fine running at a boiler flow temp of 40c to be in with a shout of switching to a heat pump. If it isn’t then loft insulation and radiator upgrades first?

As @molgrips mentioned earlier you really need to know at what external temperature those cop figures were taken. The lower the external temperature the lower the cop value, from memory they drop substantially once you get below zero. Heat pump running costs are at their most expensive when you need it most.

In my head, it would only be worth going to a heat pump if also going for solar panels and batteries to offset the increased electricity consumption hoping you can fill the batteries during the day and empty them during the hours of darkness primarily through the heating, but it is one hell of an outlay!

Yeah, forget that idea unless you’ve a couple of acres of panels with battery storage to suit. Generation for me through November-January over the last 5 years has been less then 100kWh per month, the worst being 53kWh for December last year, barely 2 days worth of heating if temperatures drop below zero.

Hmm.. well yes, I think so (I wrote a long post as I thought about it but came back to the same conclusion). The hotter the rads are the more heat enters your house. You may be able to run a heat pump for much longer at a lower and more efficient temp.

But it also depends on how you set your heating. If you want to run at 40C then it’s likely to be a bad idea to turn it off all night because say you cool down to 13C overnight, you’ll never get back up to 20C when running the boiler that low. But, if you let your house get down to say 18C over night instead, you might be able to run at 40C because it has less work to do. And, 20C after it’s been on all night at 18C feels a lot warmer than 20C after it’s been 13C overnight, so you could put your day temps to 18C (as I have) and let it drop to 16C overnight. Wether or not this works out cheaper is something you have to try out.

But regardless, definitely add as much loft insulation as you can fit, there is no scenario in which this is a bad thing. It’s cheap and will pay for itself in a single winter.

Also rads are cheap, and can be upgraded really easily if you have plastic pipes. I’ve replaced our 600mm single panel with 700mm doubles – around twice the heat output, and there’s enough slack in the plastic behind the walls so I just have to turn the valves off, drain the rad through the drain port, stick new mountings up and refill. And wipe up the inevitable black gunge spillage.

If you have dry lined walls, make a test hole with a screwdriver gently first, as the heating pipes coil up behind the wall and you can puncture them with the drill… not that I’d know of course…

ASHP NIBE system.

Some real world numbers, house is currently 22c with an outside temperature of 7c. Supply temperate is currently 31c with return temp at 18c. Used about 4.5kwh of electricity last 24 hours. House has very high level of insulation, under floor downstairs and oversized radiators.

If you have gas you could try and set the supply temperate lower and see if you freeze or house stays warm. You’ll need to do this over at least 48 hours to get a reliable result. The key is to keep that supply temp as low as possible to avoid need for supplementary heat via the immersion as that gets costly very quickly.

In my head, it would only be worth going to a heat pump if also going for solar panels and batteries to offset the increased electricity consumption

I’m hoping to break even, but I’m lining this up because our boiler will eventually fail and I don’t want to buy another gas boiler. If we can get a heat pump we can heat our home with 50% renewables, we can run lower and slower which is definitely more comfortable, it’s probably going to be quieter, and we can get an induction hob and have our gas disconnected which will save £20/mo on standing charge.

On top of that, we have an EV, which means we get really cheap electricity overnight, where we can heat our water for peanuts and we can keep the house warm overnight really cheaply. It would be worth running all night at 7.5p/kWh so that the heating has less to do in the daytime.

Oh yeah and running low and slow only works for heating – you can’t get 60C hot water if your gas or heat pump flow is only 40C…

Supply temperate is currently 31c with return temp at 18c.

You must have big rads – and/or a slow pump, or an intelligent one. In my experiment it was 45/31.

I want to get a heat pump but I have 22mm primaries and 10mm to rads. The last radiator on the run does get warm still with a low flow temp – setting 2 on the Worcester Bosch which is apparently around 43C . I’m not sure if the number displayed on the little lcd screen on the boiler is the flow temp and I couldn’t find anything in the basic instructions suggesting what it is.   I’m not sure if this proves I could run a heat pump relatively ok in terms of efficiency or if I’d be paying through the nose for it. Ideally, I’d get switched over to a heatpump and cylinder and then worry about the pipe work later as I’ve had a lot of the ceilings etc re-boarded a couple of years ago and I don’t want to rip it down as well as hack walls up to get new pipe work in as that was also all back to blockwork and re-boarded too. If only I had changed to at least 15mm when the new rads went in!

We’ve got oversized radiators  already in most rooms. 3 of the 4 bedroom rads ideally would be a little bigger as they are 600*800 K2s , those rooms don’t suffer but then we’ve not had a really cold snap (sub zero) yet with the lower flow temp.

I’ve made the house as airtight as possible and I really put the effort in. Only rooms not gutted and completely back to block work is the kitchen which I will do whenever that needs to be changed (new kitchen was done in 2014 so not planning on that for a while). House dropped to 17c after 4 days of the cold weather around the weekend before last week’s storm without any heating on, that was swiftly sorted as it was too cold. MVHR has been useful to a point but it won’t make up for the poor 75mm insulation in the walls and 50mm under the ground floor which is also beam and block so cold air rushing through underneath.

You can get a cheap thermometer with thermocouples from Amazon, that’s what I got to test my temps with. Also handy for balancing rads.

I’ve got solar panels with a battery. Just had an electric heat only boiler installed( uses same rads) with an air source water heater installed in the garage. My thinking is that the boiler will only run for half the year when needed, so offsetting the extra cost compared to gas. The water heater plugs into a normal electric socket and runs independently. Just had an induction hob installed and gas meter is getting removed next month saving on standing charge.

Another Nibe owner here (new build but certainly not passivhaus). COP graphs suggest 2.8 at zero degrees outside and 45C flow temperature. COP of 2.0 at -10C and 1.5 at -20C. Our actual energy use over the last 2 years suggests those numbers aren’t unrealistic (was down to -12C last winter). Never thought I’d say this but wouldn’t go back to gas and a combi.

Bit sick of reading garbage like this:

https://www.bbc.co.uk/news/uk-england-67059247

Who would ever guess that a heat pump isn’t viable for his house built in 1450 with leaded single glazed windows…..

You must have big rads – and/or a slow pump, or an intelligent one. In my experiment it was 45/31.

Combo of big rads but very high level of insulation.

Hot water set to start pump at 40c and 50c for stop. We are lucky to have good pressure with unvented hot at 3 bar so don’t need to run the hot water so high. Does a 65c legionella cycle every 14 days.

LOL at letting the house get down to 18 overnight. That’s what our thermostat is set to!

Well my thermostat is set to 17.5 so ner ner ner.

Another NIBE owner here – 2 year old new build Isle of Mull – thanks to the Gulf Stream we rarely see temperatures below zero. House is 110m sq, well insulated, airtight but not to Passivhaus standards, we have UFH downstairs on an insulated concrete slab with a couple of radiators upstairs (they rarely come on). There is no mains gas here. I managed to sneak in at the end of RHI and got £4200 back on the £10k it cost to install. System has been troublefree and doesn’t really need any maintenance only to check expansion tank twice a year.

To answer the original question, no, they are not the same. The Samsung is an air source heat pump, that unit is sited outside, and supplies the heated primary water to the HW cylinder and central heating.

The Daikin is a split unit. I’ve not got time to look it up at the moment (Daikin do a lot of different, similar looking units), but you have a similar unit as the Samsung outside, then the tall cabinet inside.The samsung has all the refrigerant in the outside unit, with just 2 water pipes heading into the house. The Daikin will have some thinner refrigerant lines going to the indoor unit. It is slightly more efficient doing it that way, but needs an extra qualification (F-Gas) and more expensive kit, to fit it, it’s basically an air con unit, but rather than pumping air around, the indoor unit transfers the energy into water. You cannot get the £7.5k grant for the air to air heaters, only the air to water heaters.

Split units are a lot more expensive (though rumour has it that Daikin are giving some large installers massive reductions), takes up more room, and I cannot see the need for it in a building that needs 5kW of heat. It does have one advantage, in that it can be used for cooling. It can probably only cool, not chill like an aircon unit. Another advantage is that the outside unit can be sited much further away from the building than the Samsung, which can probably be up to 10 metres away, off the top of my head, the split Daikin unit can be 30 or 40 metres away. It has an integrated tank/cylinder in the cabinet.

For the Samsung, you may need a new water cylinder/tank. It will most likely need to be pressurised (there are non-pressurised ones available, but why wouldnt you want pressurised hot water?), the size of it may need to be changed, and, most importantly, the coil inside the cylinder needs to have a minimum volume. Gas boiler cylinders do not, generally, have enough coil volume to allow the HP to heat the water in a short enough time. HP cylinders have a larger coil, and thus larger surface area to get the heat into the cold water to heat it.

Yes, I know a lot about HP’s!