How much gets replaced / how disruptive is it when fitting a heat pump?

matelodave

Even with a super-duper tariff an electric boiler will always use 3-4 times more electricity for the same amount of heat than a heat pump and will therefore cost 3-4 times more than a heat pump to run. 

Even storage heaters which use significantly more leccy than a heat pump (for the same amount of heat) have the advantage of storing the heat at off peak times, so they can be nearly as cost effective. An electric boiler can't do that unless you have a ginormous thermal store.

FreeBear

Exiled_Tyke said:

Olinda99 said:

it will be disruptive and dusty - three or four workmen in your house for five days drilling banging soldering lots of pipes and tools everywhere

May be different experiences for different people?  We worked at home while ours was installed and it wasn't too disruptive or dusty.  That said it's pretty clear the op will need all the pipework replacing so that will be a big job. 

It really depends on the size & length of the microbore pipework. If they have 12mm copper, it may be sufficient depending on the size of the radiators. If it is 8mm plastic pipe, then some/all of it may need to be replaced.

One test that @AyJaydee could do is turn the flow temperature down on the boiler. If the house will heat up at a reasonable rate at 45-50°C when it is freezing outside, there may not be any need to replace radiators & pipework - I experimented with 35-45°C flow temperatures during December. The internal temperature would increase by about 0.5°C per hour in most rooms with an outdoor temperature of -3°C.

matelodave

FreeBear said:

Exiled_Tyke said:

Olinda99 said:

it will be disruptive and dusty - three or four workmen in your house for five days drilling banging soldering lots of pipes and tools everywhere

May be different experiences for different people?  We worked at home while ours was installed and it wasn't too disruptive or dusty.  That said it's pretty clear the op will need all the pipework replacing so that will be a big job. 

It really depends on the size & length of the microbore pipework. If they have 12mm copper, it may be sufficient depending on the size of the radiators. If it is 8mm plastic pipe, then some/all of it may need to be replaced.

One test that @AyJaydee could do is turn the flow temperature down on the boiler. If the house will heat up at a reasonable rate at 45-50°C when it is freezing outside, there may not be any need to replace radiators & pipework - I experimented with 35-45°C flow temperatures during December. The internal temperature would increase by about 0.5°C per hour in most rooms with an outdoor temperature of -3°C.

The speed at which the room temps increase is really dependent on how you want to heat your place. A quick blast in the mornings before going to work and in the evening when you get home will require a different set up to a long slow gentle cook (or in our case - simmer)

We've managed to keep our place at a nice comfy 20-21 degrees at -5 with a flow temp around 30-35 but that's because it runs nearly continuously (we are at home all day) rather than having on/off cycles. However if we let the place get cold it can take a day or so to get back up to temp.

Alnat1

Had an Octopus install in January which took 4 days and cost £2700. The first thing the team did on arrival was cover all the floors with plastic in the areas they needed to work and on the stairs. 8 radiators were changed but they made very little mess, just a bit of drilling to fix new brackets to the walls and they tidied up as they went along.

We had 10mm microbore and this was fine for all but one radiator in the living room which needed to be re-piped as it was over 1kW output. Luckily this was on the wall that has the integral garage behind it. The gas boiler was in the garage and once it was removed the plumber extended the in/out pipes through to the living room radiator. This kept the dust from drilling the wall in the garage. The other radiators that were changed were a similar size to the old ones, just chunkier, so no redecorating necessary.

Our house is lovely and warm 24/7 and we certainly have had some really cold weather in Jan and Feb. Happy with the energy cost and a decent COP of around 3.7 with only a few tweaks. Octopus surveyors always plan to 50C leaving water temperature but I've been able to lower the curve to 40C at -4C. 

NedS

Every retrofit is going to be different, depending on the calculated heat loss, size of existing radiators and the existing pipework.

We decided to go for a complete re-plumb and replaced the existing microbore with 22mm copper primaries dropping to 15mm copper into the radiators. A lot of the new pipework has been fitted above skirting boards. Some of it we have left on show (for an industrial type look) and in other places we have covered with snap on trunking covers which snaps onto the pipe clips. Personally I'd rather have a bit of piping on show and know the job has been done properly than worry about it all being hidden from view. We had all new radiators too, with each radiator correctly sized to the heat loss of the room. Maximising our radiator sizes has allowed us to run 32-35C flow temperatures this winter which has kept the SCOP high and the running costs low. I wouldn't want to be running 45-50C flow temps on a standard rate tariff. The savings on our bills will more than offset the cost of a decorator painting a few walls / skirting boards around a new radiator. It's a heating system that you are going to live with for the next 30-40 years, so my view is do it right, even if that means a little disruption. IMHO just bolting an ASHP onto a non-optimal heating system (microbore pipework, small radiators) is always going to lead to a compromised system at best.

AyJaydee

Thank you for that, something for the 'back burner' (No pun intended)