Soldato
A 12kw heat pump seems massive. We have a 130m2 bungalow that has no issues on a 5kw HP. The bungalow is pretty old too at 65 years. COP is about 4.4.
Heat Pumps: anyone have one/thought about it?
- Thread starter fish
- Start date
Associate
- Joined
- 21 Jun 2004
- Posts
- 1,670
I am considering going to a heat pump. The house is 225m2, but there is a seperate annexe extension as part of that is only used occasionally. Current boiler is 17 and struggles to warm the house up. We need to replace radiators anyway (lots of original single rad no fins - though all are at length) and likely put some triple radiators in to the extension. Our cold tank is the original and the hot water tank is 160L, so not particularly large for family of 4.
Need to add extra loft insulation and cavity wall insulation which should hopefully help for next year. Given the extensive change needed it does make me wonder whether it is sensible to change. We have a gas hob and won’t want to change so can’t avoid using gas. Cable supply to cooker wasn’t sufficient for the oven and induction hob.
Do you need to have unvented cylinders with heat pump? We have good pressure, but the flow is only 14L/minute. Which I didn’t think was enough. Can you use TRV valves with heat pumps? It would be looking to limit the bedroom temps and the extension when not in use, no control the system it self.
Many thanks
Need to add extra loft insulation and cavity wall insulation which should hopefully help for next year. Given the extensive change needed it does make me wonder whether it is sensible to change. We have a gas hob and won’t want to change so can’t avoid using gas. Cable supply to cooker wasn’t sufficient for the oven and induction hob.
Do you need to have unvented cylinders with heat pump? We have good pressure, but the flow is only 14L/minute. Which I didn’t think was enough. Can you use TRV valves with heat pumps? It would be looking to limit the bedroom temps and the extension when not in use, no control the system it self.
Many thanks
Yes - IMO. Particularly as you need to update the system anyway.
If your existing rads don’t even have fins, you probably wouldn’t even need doubles, let alone triples. A lot of mine went from type 11 to type 21 (single with fins to double but only one with fins).
You can get another feed added to your kitchen in time, there is no rush to bin gas completely. If you do go heat pump, I expect the £90/year standing charge just for a gas hob will be a motivator to do induction in time!
As for insulation, do the loft and do it now. I’m not sure why anyone delays this, particularly given energy prices, it’s cheap and easy to DIY.
As for cavity, IMO, this is optional. Installing cavity wall insulation is not risk free and if you go ahead, make sure you find someone who knows exactly what they are doing when it comes to a retrofit.
Yes, they’ll be un-vented. 14l/min is probably ok, you may be able to increase it if you have a restrictive main valve or don’t have a 22mm cold feed to the cylinder location.
They’ll bin off your cold header tank and convert everything to mains pressure. Get a big hot water tank, at least 200L, ideally 250L.
You can use TRVs, that’s not a problem and they are installed on all rads as part of the installation process anyway. You’ll take a small hit to efficiency but if the annex is genuinely an annex, the heat bleed from the main house into the annex will be minimal so less of an issue.
Bedrooms are designed with smaller radiators so they naturally don’t get as warm as living spaces which means you can run the TRVs fully open most of the time everywhere else.
Associate
- Joined
- 21 Jun 2004
- Posts
- 1,670
Great thank you.
Our current shower flow rate is probably more like 2-3L/minute, so even 10 would be luxury.
Additional insulation has been delayed by time limit on my part. I’ve added extractor fans (previously none in shower and bathroom vented to loft space. Need to add down lights to bedroom before and raise the board height. Hopefully will be sorted when I take some leave in February.
Soldato
No TRVs on our install. All radiators were upgraded and new pre-insulated pipes were run from the manifold to each. The rads have been sized based on the specific heat loss calcs for the rooms they are in. It is just the bathroom that is separate, with electric UFH and towel rails. Ours is a bungalow with a big open kitchen diner so in practice the heat flows quite evenly, therefore room specific TRVs adds little, better that the whole house holds a steady comfortable temp. We also have a 200l unvented cylinder.
Associate
Got heat survey on Wednesday hopefully to work out rads/pump. Excited but wife’s dreading the work.
Best of luck. Mine didn't even bother quoting as despite 4m gap the noise was too much for neighbors
Soldato
A few pics of my loft install.
Last edited:
That looks like a really neat job.
Do you happen to know the dimensions (just approx) of the board all that gear in the loft is sitting on? And height? Trying to work out what size cupboard I'd need to fit all of that in.
Most installs ask for 1m x 1m but it can be done smaller if needed. Things like horizontal and slimline tanks are available.
Mines split between the airing cupboard and loft, tank is in the airing cupboard, the volumiser/buffer is in the loft.
Mines split between the airing cupboard and loft, tank is in the airing cupboard, the volumiser/buffer is in the loft.
I didn't think putting the tank in the loft would be recommended? Our loft is effectively always at outside air temperature thanks to the insulation doing its job and keeping the heat in the house - so a hot water tank sat at nearly 0ºC ambient temperature seems a little... inefficient?
Soldato
- Joined
- 19 Jan 2006
- Posts
- 4,633
For £175 per month I'm getting all my hot water, all my heating, all my electric which includes "fuelling" my car - this is without any solar generation at this point. Pretty damn pleased all in with the switch to ASHP / electricity.
I wouldn’t say ‘recommend’ but if you’ve got nowhere to put it inside, it’s by no means problematic.
Yes it will have higher standing losses than inside and you’ll spend a little more money heating it but it’s all relative.
Hot water is a small proportion of most people’s energy use in reality. Modern tanks also have very low standing losses anyway so you are starting from a low base and you can always add more insulation if you really want.
The tank certainly isn’t 0C all the time, the space in the loft is a bit warmer than the outside temperature likewise it’s generally not that cold, even in winter. Don’t forget, for 3-4 months of the year, loft temperatures are normally higher than the inside ambient temperature.
Yep fair enough. Like most in this thread, we're at least interested in the possibility of a heat pump, but with three "drawbacks" as we see it: just the amount of work to re-plumb the house away from our combi; the (potential) loss of our only storage cupboard in the whole house (curse of new builds); and the loss of the gas hob which we vastly prefer to induction hobs (and which itself might incur some electrical rewiring to support).
EDIT: Looking on the Octopus site, they reckon they'd be able to do a heat pump install for £500 - I assume at this price it has a higher likelihood of being a cowboy install? (And yes, I realise it'll be subject to survey etc).
Last edited:
Octopus are not cowboy installers. The price would actually be £8000 when you factor in the grant.
Associate
- Joined
- 6 Apr 2010
- Posts
- 38
Yeh they suck
I guess one of the things throwing a spanner into the works is the relaxing of the rules next year which will allow the install of air-to-air systems which also provide cooling. This gives us the option of doing a split system for most rooms in the house, but having to retrofit electric underfloor heating into the bathrooms which will be a touch too small to have wall units in.
Soldato
I think it is 1.2 x 1.2, essentially a half sheet of ply. As above, you could go for a slimline tank which would save a bit of space.That looks like a really neat job.
Do you happen to know the dimensions (just approx) of the board all that gear in the loft is sitting on? And height? Trying to work out what size cupboard I'd need to fit all of that in.