UPDATED: Air Source Heat Pumps/Air Con - Full Info & Guide, is it cheaper to run than mains gas?

albyota

Delta T is the value of the temperature differential that the radiator will operate at. Follow the example to see how it is worked out.
Problem. Need to work out the delta T where the supply water temperature is 70°C, the return water temperature is 55°C, and the required room temperature is 20°C
Solution.

Add flow and return temperature
70 + 55 = 125
divide the result by 2
125/2 = 62.5
subtract the room temperature
62.5 - 20 = 42.5
Your Delta T is 42.5°C

paceinternet

And to follow that on for "peat".
The Stelrad document on page 4 is showing radiator outputs at 75/65/20.
As albyota demonstrates, this would be 70-20 which gives a delta t of 50.
When you look at the table on page 7 you will see at 50 deg C the factor is 1, confirming the table on page 4 is at delta t 50.

The example for peat of a 600 x 1000 single K1 radiator happens to be 1000 watts on page 4 (delta t 50).
But if the delta t was only 30, which could be 55/45/20, the factor is 0.515, so you would get 515 watts

toerag33

We appreciate all the information that has been so kindly posted by members. :beer: Currently we are trying to understand it all! It is a bit of an idiot's guide we are needing.

The hot water is a problem - it is important it is available at all times. Heating is less of a problem because the house is so well insulated it doesn't really get too cold. The boiler is usually only on at heating level 1, 1.5 or 2 twice a day and in the really cold weather we had recently I had it up to 3. Most of the radiators are at 3 or less with some turned off.

richardc1983

toerag33 wrote: »

We appreciate all the information that has been so kindly posted by members. :beer: Currently we are trying to understand it all! It is a bit of an idiot's guide we are needing.

The hot water is a problem - it is important it is available at all times. Heating is less of a problem because the house is so well insulated it doesn't really get too cold. The boiler is usually only on at heating level 1, 1.5 or 2 twice a day and in the really cold weather we had recently I had it up to 3. Most of the radiators are at 3 or less with some turned off.

All the air to water systems do not produce hot water on demand, instead during set times during the day the system heats up the tank of hot water, during this time heating to the radiators is not available. So if you use a lot of hot water you could set it to do more hot water cycles as you say the house doesnt get too cold due to insulation.

thills

albyota wrote: »

thills, sorry to here about your ASHP planning application refusal, :mad: I hope you manage to find a decent heating system that will suit your requirements.
Al

Thanks Al..
It is disappointing & frankly, ignorant. There were no objections from the other 5 in the block, the nearest adjoining property is 18M distant. To appeal would take to long.
So much for support of renewables.

Cardew

toerag33 wrote: »

We appreciate all the information that has been so kindly posted by members. :beer: Currently we are trying to understand it all! It is a bit of an idiot's guide we are needing.

The hot water is a problem - it is important it is available at all times. Heating is less of a problem because the house is so well insulated it doesn't really get too cold. The boiler is usually only on at heating level 1, 1.5 or 2 twice a day and in the really cold weather we had recently I had it up to 3. Most of the radiators are at 3 or less with some turned off.

As I understand it you have a biggish house with 15 radiators and a working combi gas boiler?

Also you have a requirement for constant hot water.

For all the merits of Heat Pumps, I think you would be ill advised to consider getting such a system.

You will need to get a Hot Water tank installed, in all probability you will need bigger/extra radiators and you are probably looking at a bill of several thousands of pounds for a system that is unlikely to lower your running costs, or if it does it will be marginal.

rhubarbe

If it's mains gas I would agree. Perhaps. But maybe it's an old combi. Maybe it qualifies for scrappage. It'll certainly qualify for the £900 grant. If a new ASHP is installed by an MCI accredited installer, and the ASHP is on the approved list too, then they'll qualify for the RHI Initiative Feed-in-Tariff, starting April 2011, which on its own will, in all likelihood, pay the entire running costs of the ASHP for 18 years.

I'm certainly intending that my new ASHP (when we get it) will cost me nothing to run with the RHI FIT.

I think it's worth at least doing the costings..

peat

One of the potential installers that I have contacted has stated that I would have to change the pipework to my radiators as I currently have 8mm microbore and the heat pump requires 15 mm. Does this apply to all ASHP systems?

albyota

peat wrote: »

One of the potential installers that I have contacted has stated that I would have to change the pipework to my radiators as I currently have 8mm microbore and the heat pump requires 15 mm. Does this apply to all ASHP systems?

The issues with microbore pipe is the fact that the manufacturers of any new boiler/heating system, be it, gas, oil, LPG, or air source heat pump will insist the heating system pipework and radiators are 'clean' i.e. properly powerflushed, or the warranty is void, this is because the heat exchangers in new boilers and ASHP's are smaller with either plate heat exchangers or small bore pipes and the smallest bit of crud or sediment can block the system.

However, if a microbore piped system is cleaned and has minimal 90 degree bends, and the water can flow unrestricted, then it would work like any normal system.

It is the systems circulating pump which sends the water round the pipes and rads, which, if set at the correct flow rate would be fine.

If by powerflushing a microbore system actually blocks up the pipes (mainly at the bends or the manifolds), then you would have to consider replacing the pipework. OR.... fitting a buffer tank so that the heat pump can dump all its heat in to the buffer tank and then the circulating pump can run at its own pace.

peat

Thanks for the reassurance one of the other potential installers mentioned the need for the system to be flushed. Also, I had proposed to link the ASHP to my thermal store anyway.
Cheers
Peat