Air Source Heat Pumps

Cardew

shortperson wrote: »

I know that an ASHP will cost more to buy and install, but are we completely bonkers to consider it rather than a new gas condensing boiler?

In a word - Yes!

Even if you were lucky enough to get a system that gave an overall COP of 3.0 it still would be a bad idea.

The problem with your plan to get Solar PV to run the ASHP is that PV produces precious little output when you need heating i.e. winter!

zeupater

Hi shortperson

I agree with Cardew's observations.

Regarding the pv, there is the possibility of running a small air-to-air heat pump which could provide some heat in Spring & Autumn to take the chill off as well as operating in cooling mode in high Summer, but that's probably all you would reasonably be able to run from a standard sub 4kWp pv system.

HTH
Z

TiredGeek

shortperson wrote: »

and we are on mains gas.

I know that an ASHP will cost more to buy and install, but are we completely bonkers to consider it rather than a new gas condensing boiler?

Probably.

If you have access to mains gas then it's most likely the cheapest to run.
It's also a far cheaper system to install.

Also, as you have mains gas you won't qualify for the RHI should it ever actually come in, so the ASHP won't be subsidised in any way, therefore if it is actually a bit cheaper to run an ASHP system it'll take years and years to break even with a good gas boiler, and if gas turned out cheaper you'd never see a return.....

I can't believe I'm saying this, but put the money you save by not buying an ASHP in the building society and the interest will more than cover any higher running costs a gas boiler may have (though it may be cheaper to run gas anyway).

(Cardew has just fallen off his chair )

Harryo

I also agree with the previous three posts re heat pumps. Plus I would add that overall maintenance costs will be higher, whether or not you enter into a service agreement. Also heat pumps are not true renewable energy systems. They use grid electricity which results in far more carbon emissions than natural gas. So therefore a heat pump will be doing more harm to the environment, if you believe this is an issue.

Solar thermal is just not cost effective, particularly with mains gas as being an option. Compared to a gas fired boiler you would most likely be talking about 50 years plus simple payback, by which time the ST system would have needed replacement anyway. Also if you do not use much hot water them of course the payback becomes longer.

UFH will be fine with a gas fired boiler, although far more expensive than radiators. If laid on top of the timber floors then obviously the floor levels will be raised, which will have certain implications. If laid under the flooring then possibly the inverted hat type tray system would be a good option. That would also enable you to incorporate thermal insulation readily. The whole floor would need to come up and be re-laid with the later. This needs to be done by a craftsman.

Gas condensing boilers have become more reliable over the past five to ten years. The life expectancy is only about twelve years though and they can cost a fortune to repair though when they go wrong. I would say this is still your best option. A full parts and labour service plan is worth considering. If you do not know of a good and reliable installer, I would strongly recommend you go for a CIPHE Registered Plumber. You can find some close to you via their website.

[Deleted User]

Even though my COP was hovering around 4.1 yesterday mains gas is the better option but for off the gas grid ASHPs make a lot of sense.

nande2000

jeepjunkie wrote: »

Even though my COP was hovering around 4.1 yesterday mains gas is the better option but for off the gas grid ASHPs make a lot of sense.

Ill second that. Makes no sense having a heat pump if you are on the mains gas grid.

Cardew

TiredGeek wrote: »

(Cardew has just fallen off his chair )

I wouldn't have done so if 'TiredGeek Mk1' (who spent £14,000 on a system that just didn't work) had posted as above.

'TiredGeek Mk2' is more forgiving;)

shortperson

Thanks to all of your for your opinions and information - it has reinforced what I was thinking!!

shortperson

Harryo wrote: »

UFH will be fine with a gas fired boiler, although far more expensive than radiators. If laid on top of the timber floors then obviously the floor levels will be raised, which will have certain implications. If laid under the flooring then possibly the inverted hat type tray system would be a good option. That would also enable you to incorporate thermal insulation readily. The whole floor would need to come up and be re-laid with the later. This needs to be done by a craftsman.

Thanks Harryo - when you say UFH will be more expensive than radiators, do you mean in the cost of buying and getting it installed, rather than to run the system? I think we will need to take the floors up anyway to insulate underneath them so laying the UFH system underneath wouldn't be a problem.

lovesgshp

@ Shortperson.
I agree with the comments above, that if you are on mains gas, then stay with it, especially with a ASHP, as they cannot operate as effectively as a GSHP at very low temps.