New boiler - Air source heat pump vs mains gas - future proofing

Bathsheba309

Reed_Richards said:

Best of luck with that timing @Bathsheba309. 

Have you had the heat loss survey done yet and sorted out all the radiator sizes you will need?  You've gone up from your initial planned 14 kW heat pump to a 17 kW one and to me, with approximately 9 kW worth of radiators, that seems a lot.

We have, the 14kw figure was just based on the salesperson's estimate. The radiator output adds up to slightly less than 17kw. We are having to have quite a few replaced, but I have managed to reuse some of the bigger ones that we have currently. Overall the RHI payments will be 3k short of recouping the cost and a new gas boiler would have cost us a couple of thousand anyway. We also think that the pressure to reduce CO2 emissions is going to accelerate very quickly now - and at the moment there's a decent sized carrot and no stick, but for how much longer?

Bathsheba309

Cardew said:

People are free to install any heating system, for green or financial motives. Albeit Bathsheba309 has focussed on the financial aspects.

My objection was this statement:

'We have decided to go with an ASHP There are a lot of 'experts' out there, who don't have any experience of ASHPs, prophesising doom and gloom about costs / cold houses etc.'

Having made his decision to install an ASHP he seeks to justify it with a sarcastic comment about 'experts' and the implication that unless you have had experience of an ASHP comments on costs and cold houses are invalid.

Where else would the comments about high costs and poor performance come from but those with unsatisfactory experience of heat pumps and the independant trials of retrofitted systems. That is not to say many are happy with their heat pump. 

People who research Heat pumps and decide  that they are unsuitable, do not claim to be 'experts and their opinions should not be sneered at because this poster has decided to buy.

I haven't been on here for a bit so I missed all this! If the people who posted previously saying they decided not to have an ASHP thought I was sneering at them (or even referring to them for that matter) I apologise to them completely.

I put a few posts on social media asking if any of my contacts had direct experience of them and got back lots of responses like 'My mate Dave, who fits gas boilers, says you're bonkers for even thinking about it because he reckons they don't work properly. He says you need to wait for hydrogen.' it was these type of comments I was meaning, certainly not anything I've seen posted on this forum!

Reed_Richards

Bathsheba309 said:
The radiator output adds up to slightly less than 17kw. 

You'll need some headroom for when the heat pump is heating the hot water and when it is defrosting itself in cold weather.  At those times it isn't supplying any heat to the radiators.    

Bathsheba309

Just wanted to update this and thank people for their input (so thank you for your input ) . We had the heat pump installed and thankfully we were in plenty of time to get the RHI. The cost of the whole installation including radiators was £4200 more than the RHI payments and a new gas boiler would have cost around 2700, so it has cost us around 1500 net (but really not even that, as it also includes new radiators throughout that are far more efficient that the ancient ones we had before). During the winter months we were paying around 250 a month for gas plus around 100 for electric. We've had the heat pump for 2 months now and our total electric bill has gone up to around 240 a month (we're on a fixed tariff so unaffected by price increases as of yet). That's an extra 140 a month in electric compared with the 250 we were paying for gas, so, in conclusion it's looking like a very good buy!

Reed_Richards

Well done.  Your heating bill will go up when your fixed tariff ends but then your gas bill would have gone up also.

Hudsonbutler

In no way am I critical of ashp, but what happens at the end of serviceable use and have to be replaced.? What do they do with the refrigerant gas? Which we all know is not green.

matelodave

They collect it, just like they should do with fridges and freezers and it then gets recycled.

AFAIK stuff like R22 which is actually ozone depleting was discontinued around seven years ago and replaced with other types, which  dont deplete the ozone layer. R22 must be reclaimed and stored when the equipment is decommissioned although I don't know what they can do with it.

Manufacturers are changing the stuff they use in refrigeration systems but in the end I don't think that any are totally benign

I'll accept that heatpumps will use refrigerants but probably not much in comparison with the billions of refrigerators, freezer, automobile aircons and any other sort of aircon (domestic or industrial), many of which are still filled with R22

Have a look at what's in your fridge, freezer or car air-con

What does the GWP value mean?

GWP stands for “global warming potential”, which is the potential for a substance to contribute to climate change. The GWP value of a refrigerant defines its global warming potential relative to CO₂ (also known as CO₂ equivalent). The value describes the global warming effect over a certain period of time, which for refrigerants is usually 100 years.

The higher the GWP value, the more harmful the corresponding substance is to the climate. A specific example: The CO₂ equivalent of R-134a, a commonly used refrigerant, is 1,430 viewed over a 100-year period. This means that one kilogram of R-134a contributes 1,430 times as much to the greenhouse effect as one kilogram of CO₂ within 100 years after release. The release of 1 kg of R-134a is therefore equivalent to the release of 1,430 kg of CO₂.

The most common fluorinated refrigerants and their GWP:

R-134a = GWP 1,430

R-404a = GWP 3,922

R-407c = GWP 1,774

R-407f = GWP 1,825

R-449a = GWP 1,282

R-410a = GWP 2,088

R-422d = GWP 2,729

R-32 = GWP 675

R-1234yf = GWP 4

For context, here are some alternatives to F-gases and their GWPs (natural refrigerants)

R-744 (CO₂) = GWP 1

R-717 (ammonia) = GWP 0

R-290 (propane) = GWP 3

R-600a (isobutane) = GWP 3

QrizB

matelodave said:

Manufacturers are changing the stuff they use in refrigeration systems but in the end I don't think that any are totally benign
I'll accept that heatpumps will use refrigerants but probably not much in comparison with the billions of refrigerators, freezer, automobile aircons and any other sort of aircon (domestic or industrial), many of which are still filled with R22

Motor vehicles switched from R-12 to R-134a around 25 years ago. There will be very few of those left with any refrigerant in their systems (since they're not hermetically sealed, ie. they all leak). Similarly, domestic fridges and freezers in the EU have been mainly R-600a for a decade or more.

Let's look at an example Mitsubishi Ecodan heat pump. It contains 2.2kg of R-32 with a GWP equivalent to 1.49 tonnes of CO2. If we assume a ten-year life, delivering 10000kWh/yr of heat, that's 14.9g of CO2 GWP per kWh. Compared to more than 200g/kWh from burning natural gas and it seems to me that even if the refrigerant isn't captured & recycled you're still better off with the heat pump.

matelodave

Perhaps I should have said, may be filled with R22

My 12 year old Daikin is filled with 3kg of R410a which although is ozone friendly has quite a high GWP potential of around 6.25tonnes of C02 which I guess is quite a lot compared with a more modern appliance.  However as you say, at around 10,000kwh for 12 years is about 52g/kwh.

Again a lot less than burning gas and I'd hope to get quite a few more years out of it which would improve it's energy/gpw ratio even more