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NIBE ASHP not doing so well - help needed

 
Air Source Heat Pumps (ASHPs)
Last Post by Derek M 3 years ago
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 JohnS
(@johns)
Active Member Member
Joined: 3 years ago
Posts: 6
Topic starter 19/01/2023 8:19 pm   [#763]

Hello - I’m John and we had a NIBE ASHP installed last summer in our mid-sized early Edwardian house. Nothing about the installation and first six months has gone well - engineer fell out with the builders and had disagreements with the architect. Upshot is that we were freezing before Christmas - installer eventually put in a mixer and pump (?) to raise temperature in radiators. After Christmas we realised we are using a huge amount of electricity - our energy provider estimates 25,000 kWh / year. Really scary. Paid for another company to come in and have a look - they changed some settings - that was it. Original installer is unreliable and unresponsive (says the builders owe him money). My wife and I are not sure where to start - although we realise parts of the house are poorly insulated. We would really welcome any thoughts and advice. Thanks, John



   
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 Graham S
(@graham-s)
New Member Member
Joined: 4 years ago
Posts: 4
23/01/2023 12:32 am  

Hi John,

Sorry to hear about your problems. I'm not sure what advice I can give you other than some feedback from both a NIBE ASHP and a NIBE GSHP. The ASHP was installed last year in a new build village hall, which is, of course, well insulated to meet current building regs. It feeds underfloor heating throughout the hall and ancillary rooms. Although it's not cheap to run it's been working pretty effectively - maintaining c. 18C - 21C throughout the winter, even the two sub-zero spells we've now had, with flow temperatures averaging around 35C. During the last cold spell in December we were using up to 100kWh per day. Whilst not directly comparable with a house, this demonstrates that, with high levels of insulation, ASHP's can work pretty effectively, though certainly aren't cheap to run.

The GSHP was installed in an old cottage with 500cm thick stone walls that I've been renovating. We did what we could by way of insulation - 150mm Geocell (foamed glass) under a 100mm limecrete floor slab with underfloor heating (oversized radiators upstairs), 6cm of lime/hemp insulated plaster, new double glazing throughout, 250mm sheeps wool in the loft. Again the heat pump has managed to cope with the cold spells but I've had to run it at much higher average flow temperatures averaging around 45C. During the cold spell in December we were using about 50kWh/day

As I'm sure you will already be aware heat pumps work most effectively (and economically) at lower flow temperatures - and need to be left on 24/7 just doing there thing in the background. The conclusions I've drawn are that they work most effectively in a new build that's been designed for a heat pump: high levels of insulation - floor, roof and walls, double glazing - with underfloor heating. When retrofitted in an old house like yours and mine you really need to focus on (1) the insulation and (2) the suitability of the heat emitters - do you have underfloor or just rads? Are the rads oversized to operate at lower temperatures? Is all the distribution pipe work new and well insulated? If the installers just fitted the ASHP to feed your old radiators then it's almost certainly not going to deliver the kind of warmth you want at a price you can afford - but I would perhaps also argue that if they did this then the design of your system is poor - and maybe this is something you should take up with them if you weren't informed?

Finally some thoughts on trying to optimise the system you have: as I said above you want to minimise the flow temp (to minimise the cost) but consistent with getting sufficient heat out of it to give you comfortable room temps. Leave it on all day but use your room thermostats to wind it down a little when you don't need it - e.g. if you're out of the house during the day, or at night when you're asleep. But not too much - if your target is say 18C then perhaps wind it down to 16C. If you let it go colder then it'll use more electricity to get it back up to your target temp. (Unless you have Economy 7, in which case you could try winding it UP at night and down during the day and use it a bit like an old night storage heater - but this will only work if you've got underfloor heating and good insulation.

Hope this is of some help,

Graham

 

 



   
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 Brendon Uys
(@heacol)
Prominent Member Contributor
Joined: 5 years ago
Posts: 415
23/01/2023 1:31 am  

Posted by: @johns
↑

Hello - I’m John and we had a NIBE ASHP installed last summer in our mid-sized early Edwardian house. Nothing about the installation and first six months has gone well - engineer fell out with the builders and had disagreements with the architect. Upshot is that we were freezing before Christmas - installer eventually put in a mixer and pump (?) to raise temperature in radiators. After Christmas we realised we are using a huge amount of electricity - our energy provider estimates 25,000 kWh / year. Really scary. Paid for another company to come in and have a look - they changed some settings - that was it. Original installer is unreliable and unresponsive (says the builders owe him money). My wife and I are not sure where to start - although we realise parts of the house are poorly insulated. We would really welcome any thoughts and advice. Thanks, John

Complain to Nibe, they can be very good depending on the area. If you still have problems, PM me.

 



   
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 Derek M
(@derek-m)
Illustrious Member Member
Joined: 5 years ago
Posts: 4425
23/01/2023 1:51 am  

Posted by: @johns
↑

Hello - I’m John and we had a NIBE ASHP installed last summer in our mid-sized early Edwardian house. Nothing about the installation and first six months has gone well - engineer fell out with the builders and had disagreements with the architect. Upshot is that we were freezing before Christmas - installer eventually put in a mixer and pump (?) to raise temperature in radiators. After Christmas we realised we are using a huge amount of electricity - our energy provider estimates 25,000 kWh / year. Really scary. Paid for another company to come in and have a look - they changed some settings - that was it. Original installer is unreliable and unresponsive (says the builders owe him money). My wife and I are not sure where to start - although we realise parts of the house are poorly insulated. We would really welcome any thoughts and advice. Thanks, John

What is the size of your heat pump?

Do you have any heat loss calculations for your home?

What is the floor area?

What heat emitters do you have?

Do you have a buffer tank or low loss header installed?

Is your system operating in fixed water flow temperature or weather compensation mode?

 



   
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