Air-source heat pumps - are they good/crap?
Discussion
MrHappy said:
Have your parents tried adjusting the temperature at the manifold? Ours was set at 45c. When the room temperature hit the wall thermostat target temp of 21c, the residual heat in the floor was giving us a temperature overshoot. I’ve gradually tweaked the manifold temp lower, now at 35c, and this gives us less of an overshoot and a more stable temperature. It’s trial and error as to what manifold temp will work best.
Yeah, it was set up by a pretty knowledgeable heating engineer - they run it set at a constant 20c room temp and the temperature stays pretty much bang on. The issue only arises in 2 scenarios - cold weather that suddenly warms up or cold weather with lots of sunshine. Tweaking the flow temp any lower just results in the temperature never reaching the set point.Anyway, way off topic!
r3g said:
mcbook said:
I also run my HW at 50 degrees and have no issues with washing greasy dishes. Not sure if you've ever tested it but 50 degree water is very hot and not comfortable to have your hands/body in.
Hmm, I have to beg to differ. 50 degrees is the top end of warm. Certainly quite comfortable to have your hands submerged in but it needs to be hotter to remove grease and baked on crud IME. Of course the dish washer argument is a fair one if you have that luxury. Anyway, moving on.. 
https://www.argos.co.uk/product/8907363
jonathan_roberts said:
We have one and its excellent. However, we have triple glazed windows, 25cm insulation jacket on the outside walls, plus underfloor heating. It uses around 4000kWh per year, most of which occur during winter. Outside temps are between -20 and +40. The system runs at 50 degrees for HW and depends on outside temp as to what temp it runs the floors. Once the structure is warm, the energy usage is very little.
ETA: I think it is excellent. I would probably not retro fit one without doing insulation, windows, and UFH.
Pretty much the same as mine. I also run the DHW at 50C and it's more than hot enough, and the installer warned against running it any hotter as I did ask in the interest of eking out a bit more 'shower temperature' water volume/ETA: I think it is excellent. I would probably not retro fit one without doing insulation, windows, and UFH.
hidetheelephants said:
Tanks need to at least cycle through 60 at some point to kill bacteria, otherwise it's a petri dish for legionnaires etc.
The tank occasionally and automatically cycles up to 75 degrees for this very reason (can't remember the exact frequency). That's independent of the regular temperature at which it's set. hidetheelephants said:
Tanks need to at least cycle through 60 at some point to kill bacteria, otherwise it's a petri dish for legionnaires etc.
Not totally true - 70 deg is the temp at which Legionella bacteria is killed instantly - 60 deg it's 100% kill in 30 mins Watch from 5.42 if you just want the facts around store temps
Storing water at lower than 60 deg temps can be perfectly safe for example if the turnover of the water is high - other reasons are equally valid
B'stard Child said:
Not totally true - 70 deg is the temp at which Legionella bacteria is killed instantly - 60 deg it's 100% kill in 30 mins
Used the generalist guidelines.20° or less – Legionella survives, but in a dormant state
20° to 45° – Legionella will grow rapidly
50° – Most Legionella bacteria will die within hours
60° – Most Legionella will die within minutes
70° – All Legionella bacteria will die instantly
Hence if you're running something like an immersion sustaining temperature for a couple.of hours in night or even a few times a week then you're fine.
Evanivitch said:
Used the generalist guidelines.
20° or less – Legionella survives, but in a dormant state
20° to 45° – Legionella will grow rapidly
50° – Most Legionella bacteria will die within hours
60° – Most Legionella will die within minutes
70° – All Legionella bacteria will die instantly
Hence if you're running something like an immersion sustaining temperature for a couple.of hours in night or even a few times a week then you're fine.
An immersion heater will mostly heat the top half of the tank, meaning there's a band in the middle which is Legionella Utopia.20° or less – Legionella survives, but in a dormant state
20° to 45° – Legionella will grow rapidly
50° – Most Legionella bacteria will die within hours
60° – Most Legionella will die within minutes
70° – All Legionella bacteria will die instantly
Hence if you're running something like an immersion sustaining temperature for a couple.of hours in night or even a few times a week then you're fine.
I'm sceptical whether thisis really an issue though, with chlorinated water and unvented tanks.
OutInTheShed said:
An immersion heater will mostly heat the top half of the tank, meaning there's a band in the middle which is Legionella Utopia.
I'm sceptical whether thisis really an issue though, with chlorinated water and unvented tanks.
Immersion heaters are not just top mounted in modern tanks...I'm sceptical whether thisis really an issue though, with chlorinated water and unvented tanks.
And yes, I agree unvented cylinders go some way to address this too.
OutInTheShed said:
I'm sceptical whether this is really an issue though, with chlorinated water and unvented tanks.
Frankly, worrying about legionalla at all is not far off being on a par with worrying that your umbrella isn't fitted with a lightning conductor. It's so rare for it to cause problems that it took us until 1977 to even realise the illness existed.
And yes, with chlorinated water and an unvented system, the risk becomes infinetesimally small.
Notsofastfrank said:
This is completely incorrect. We bought a new-build with ASHP (LG) 3 years ago. It works absolutely fine and the house is always warm in winter, regardless of how cold it gets (lowest overnight temperature this winter has been -6c). The house is 3000 square feet and we pay £110 pm with the assistance of 7kw of solar panels and a 5kwh battery, without the solar/battery the cost would be about £225 a month. Ours was not correctly installed when we moved in, we had a local specialist rectify this which the builder paid for. Since then it has broken down once due to a faulty board, which were all being replaced by the manufacturer. We were without the ASHP for 2 weeks, we were not prioritised as it was the summer and the solar provided hot water.
An ASHP does not heat up as fast as a gas boiler, but you soon get used to that. One thing you soon learn is not to let room temperature drop by more than 2c overnight when it is cold or it will take 7 to 8 hours to warm back up. Also if you ask the ASHP to work hard it becomes less efficient, and it is also less efficient in colder weather, however it continues to work fine in sub-zero temperatures.
Make sure the radiators are of sufficient output at 50c as that is the temperature your radiators will be, you can tell the system to heat the water to 55c but this will use a lot more electricity. Underfloor heating is great, no radiators on the wall and very comfortable.
The biggest negative to an ASHP is the ridiculously high cost of electricity, you even get charged VAT, whereas gas doesn’t, so much for the government’s green energy policy.
I would have no problem buying another house with ASHP, as long as it was correctly installed and the house was well insulated.
Reading this just makes me glad to spend £1000 a year on oil. An ASHP does not heat up as fast as a gas boiler, but you soon get used to that. One thing you soon learn is not to let room temperature drop by more than 2c overnight when it is cold or it will take 7 to 8 hours to warm back up. Also if you ask the ASHP to work hard it becomes less efficient, and it is also less efficient in colder weather, however it continues to work fine in sub-zero temperatures.
Make sure the radiators are of sufficient output at 50c as that is the temperature your radiators will be, you can tell the system to heat the water to 55c but this will use a lot more electricity. Underfloor heating is great, no radiators on the wall and very comfortable.
The biggest negative to an ASHP is the ridiculously high cost of electricity, you even get charged VAT, whereas gas doesn’t, so much for the government’s green energy policy.
I would have no problem buying another house with ASHP, as long as it was correctly installed and the house was well insulated.
Notsofastfrank said:
<snip>
The biggest negative to an ASHP is the ridiculously high cost of electricity, you even get charged VAT, whereas gas doesn’t, so much for the government’s green energy policy.
I would have no problem buying another house with ASHP, as long as it was correctly installed and the house was well insulated.
Since when has Gas been VAT freeThe biggest negative to an ASHP is the ridiculously high cost of electricity, you even get charged VAT, whereas gas doesn’t, so much for the government’s green energy policy.
I would have no problem buying another house with ASHP, as long as it was correctly installed and the house was well insulated.
I've been paying 5% vat on it for as long as I can remember!!!
Can I claim it back?
Our gas boiler is on its last legs so I'm getting quotes to replace it. However, given the way things are going it seems sensible to consider the ASHP route too.
I've been doing a load of reading this weekend and plan to get a few quotes this week to see how viable it is for us, but one thing I can't find a good answer to is how it affects the value of the house. I'd initially dismissed them on the basis that we'd probably move before ever seeing a ROI, but maybe that would be negated by the value added by having one installed?
Reading around suggests a bump in house price between 1-3% (which would probably cover the cost of installation) but I'm a tad sceptical of the sources.
Does anyone have any real world experience of what ASHP does to a house price, if anything?
I've been doing a load of reading this weekend and plan to get a few quotes this week to see how viable it is for us, but one thing I can't find a good answer to is how it affects the value of the house. I'd initially dismissed them on the basis that we'd probably move before ever seeing a ROI, but maybe that would be negated by the value added by having one installed?
Reading around suggests a bump in house price between 1-3% (which would probably cover the cost of installation) but I'm a tad sceptical of the sources.
Does anyone have any real world experience of what ASHP does to a house price, if anything?
durbster said:
Does anyone have any real world experience of what ASHP does to a house price, if anything?
My parents inlaws have been looking at houses recently, a few had ASHPs, had zero influence on appeal of the property. They did have concern about how loud one of the units was at one house they saw.If I was buying I would suggest unless the seller can demonstrate to me how air tight their house is ASHPs are a potential liability for me. At most it wouldn't influence any offer I put it, at worst, if I'm not convinced on the amount of insulation in the house, it'll decrease the value of the offer I put it, as I may have to spend £££££ getting better insulation in place.
The heating in our own build was on for the first time today, a warm house after 18 months of starting building works, am so glad we DIDN'T go for ASHP for heating given just how much work it's taken getting a traditional boiler setup installed/going.
Edited by gangzoom on Saturday 4th May 04:58
A quick look at utility bills will give you a pretty good idea how efficient a house. A lot of ASHP systems now have data logs so you can see how the system has been performing. The efficiency/effectiveness of an ASHP system is as much about flow rates, radiator size and how well the system has been set and and installed as it is about how air tight the house is.
Cheib said:
A quick look at utility bills will give you a pretty good idea how efficient a house. A lot of ASHP systems now have data logs so you can see how the system has been performing. The efficiency/effectiveness of an ASHP system is as much about flow rates, radiator size and how well the system has been set and and installed as it is about how air tight the house is.
Set up is a huge factor, I went to look at a mate’s daughter’s house last week, she’d had ASHP and solar installed foc under one of these grant schemes (in wales) , they were complaining about their electricity costs, there were a few issues, but the major one was the installer had just set the ASHP set point at 50 deg c and left, no setting weather compensation, no explaining how the system should work, a complete cowboy, taking government money and clearing off!Gassing Station | Homes, Gardens and DIY | Top of Page | What's New | My Stuff