Discuss ASHP or MAINS GAS? in the Plumbing Jobs | The Job-board area at PlumbersForums.net

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I'm running rads on all mine at 50c, most don't need changing has insulation has been upgraded through years (my own house needed them all done) find all systems have run amazingly well, against oil payback without any grants is working out around 3-4 years, most places we go an oil boiler, new tank and cylinder will come in at 5-7k, heat pump fitted for 8-10k normally isn't a huge amount extra, with rhpp £1300 grant some come in very similar to oil install if tank and cylinder needed changing. Then customers are quids in, some are just taking the **** with install prices etc, seen costs of £12k just for a 9kw, no cylinder, rads etc, just unit, pumps, pipe bit of wiring etc.
 
@Eaton, thanks for that

I could be wrong, the way we see it is the problem with running rads at 50° comes with the SpF figures for the RHPP / RHI - firstly the heat emmitter design needs signing off and even at 50° they need to be 2.4 times bigger than normally required for that room / space. We find that in 95% of cases radiators are wrongly placed and wrongly sized (too small or too large) so unless you do a radiator refit, then the system wont be MCS compliant so wont qualify for RHPP/ RHI If now add in the costs of replacing a bunch of radiators and you see why biomass adds up (no rads to replace!)

Unless I've missed something?
 
@Eaton, thanks for that

I could be wrong, the way we see it is the problem with running rads at 50° comes with the SpF figures for the RHPP / RHI - firstly the heat emmitter design needs signing off and even at 50° they need to be 2.4 times bigger than normally required for that room / space. We find that in 95% of cases radiators are wrongly placed and wrongly sized (too small or too large) so unless you do a radiator refit, then the system wont be MCS compliant so wont qualify for RHPP/ RHI If now add in the costs of replacing a bunch of radiators and you see why biomass adds up (no rads to replace!)

Unless I've missed something?

On my heat loss calc it tells me the watts needed per room and then average rad size giving a % of +or- of the current rad eg
room size is
current rad size is
watts
current rad size ie 10%+
then you play around with rad sizes to get what you want ie +%

there is never an issue with over sizing! I've oversized mine to run at 45c and set heat pump to run weather comp curve to suit. Mcs only want you to prove rad size to suit that particular room, for eg my towel rail is supposedly 30% undersized yet room hits 21c at minus 4! Personally not had an issue but it depends on your heat loss calc I suppose. Got a 2 bed house to start Monday, 16kw, 210l unvented full heating system (storage heaters out) new fuse board total price £9.5k inc vat, some say that's cheap but I'm making very good money on that but I do buy at cheaper price than most
 
16kw! 2 bed castle!?

its good to hear positive feedback about heat pumps after so many numpty solar p.v companies started bashing them in wrong!
 
Mines 118m2 1975, cavity insulated, loft insulated and double glazing about 20 years old, units using about 65% capacity! was on borderline of a 9kw but would like to add a utility, bedroom/ensuite ext in few years so went with 16 for future proofing.
 
Yes I installed a bran new 15 Kw Dream ASHP in Sept 2012. It`s working brilliant my whole house has been so cosy, a 4 bed semi & attic conversion, with a 6 Mtr UHF conservatory and heated Koi Pond.
Well worth the capital outlay of £1,500 plumbed into my flow & return, I have the system wired to operate via an optimizer/stat. I set that to maximise the COP factor so that the ASHP does not ice over, (it costs to melt ice) when this happens the COP factor is not very good, as on all ASHP`s. That is why I use my Dream as a Hybrid when the dew point is likely cause less efficient use. The Hybrid use has enabled me to only use 20% of the gas I used on many previous years, that's now 80% of my heat coming from a more eco source, AIR. The Leccy use has not risen by very much ( I don`t think all my LED lamps have saved that much) so my outlay payback should be on track in about 4 years. The ASHP is controlled by my optimisation / stat wired so that when it`s inhibited, the Gas boiler will take over if frosty. Although the ASHP output temp is set lower, that has proved to be acceptable as I have some oversized rads & UFH thermal store, when it`s colder the gas boiler (at a higher temp) overcomes the greater heat losses. The "shoulder" months are when the COP values really pay off at 3, 4, or nearly 5 times the input Kw, so even allowing for high leccy prices over gas there is quite a good saving. Some have Mitsubishi, Toshiba or ( mine ) a Sanyo with the more efficient defrost system of a 4 way valve instead of elements to melt the winter ice. As you can tell I have had a mainly electrical career for well over fifty years so I have a relay for all zone digistats to be "ON" via the heat source in use. Many of the quotes that I had were horrendous £14 K to over £20 K for a system that is little better (if at all ) for under £2K as a pensioner I am well happy for such an efficient system. Hope you have found these comments helpful. I have No connection other than a very satisfied pensioner with a system that works well.
 
On my heat loss calc it tells me the watts needed per room and then average rad size giving a % of +or- of the current rad eg
room size is
current rad size is
watts
current rad size ie 10%+
then you play around with rad sizes to get what you want ie +%

there is never an issue with over sizing! I've oversized mine to run at 45c and set heat pump to run weather comp curve to suit. Mcs only want you to prove rad size to suit that particular room, for eg my towel rail is supposedly 30% undersized yet room hits 21c at minus 4!

That won't be a towel rail then, it'll be a radiator.
 
That's not a room it's a shower cubicle :)
 
That's what he said :
= 4 Sqm
Now 4m x 4m that's possibly a room = 16m2 albeit still a small one for our typical customers :)
 
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