Vertical or horizontal radiator in living room?

Ken2000

I'm getting radiators installed in the house but am struggling with where (and what) to put in the living room. Currently, there's a storage heater under the window. If I were to place a radiator there, it would be a short but wide (2m) radiator but would mean then not having full-height curtains (the current ones came with the house and need replacing). The other options are to install 2 smaller radiators in different areas of the room or to install a vertical radiator elsewhere, but I'm keen to keep the room reasonably flexible for the future. 

Gerry1

Presumably it has a storage heater because there's no gas.  If so, it''ll a BIG mistake to get rid of it: your electricity bills will be cripplingly expensive, especially if you stay on Economy 7 !

Talldave

The positive of the under the window position is that it doesn’t  block any furniture,  although my other half would strongly disagree due to the curtains issue!

Ken2000

Gerry1 said:

Presumably it has a storage heater because there's no gas.  If so, it''ll a BIG mistake to get rid of it: your electricity bills will be cripplingly expensive, especially if you stay on Economy 7 !

I'm getting an air source heat pump (and switching from THTC to a single meter), which from what I can gather will reduce my bills and give me more consistent heat.

Robin9

I agree with your wife re radiators under the window and the problems with curtains - but not convinced by the air source on a capital and running cost basis.

Gerry1

THTC to ASHP?  Admittedly I don't have experience of either, but that seems to be from the frying pan to the fire, or the devil and the deep blue sea !

There seem to be two big potential issues (and perhaps noise as well):-

• ASHPs seems to be very inflexible.  Fine if you'll always be at home all day (ditto for any future purchaser of the property), but a nightmare if you expect to come home from work, switch it on and be cosy within half an hour.  You'll also need big radiators to cope with the low flow temperatures.
  

• It may be expensive to run.  You may not get the efficiency you expect, particularly in cold weather, and if you have to leave it running all day when you aren't there you'll be wasting a lot of energy.

Have you read the ASHP thread?  Might be worth upgrading the storage heater size(s) so that you can use E7 and get competitive quotations from umpteen suppliers, and using clever well insulated storage heaters such as Dimplex Quantum.

Mouldymeat3

Have you considered underfloor? It is possible to get an overlay wet system.

Mouldymeat3

As Gerry1 says, air-source has its limitations. We have air-source because it was a condition of our planning and the bungalow was designed with that in mind with masses of insulation. It cannot be treated as a boiler. Read the back pages of any brochures, this is where you will find the real info. Further north, hybrid systems are needed to cope with low ambient temperatures.

Gerry1

Mouldymeat3 said:

Have you considered underfloor? It is possible to get an overlay wet system.

Probably the worst of all worlds !  There won't be enough storage capacity to use E7 rates, so again it's a case of lots of heat wasted in the daytime if you're not there.  Slow to heat up when you get home, and daytime electricity will be cripplingly expensive.

Talldave

Ken2000 said:

Gerry1 said:

Presumably it has a storage heater because there's no gas.  If so, it''ll a BIG mistake to get rid of it: your electricity bills will be cripplingly expensive, especially if you stay on Economy 7 !

I'm getting an air source heat pump (and switching from THTC to a single meter), which from what I can gather will reduce my bills and give me more consistent heat.

You'll need large radiators with ASHP as they'll run much cooler than with GCH.  It's like having underfloor heating but on the walls!

matelodave

We installed a wet overlay u/f heating system together with our air source heat pump in 2010. It does work and IMO is pretty economical to run (our total leccy bill is still just under £900 a year) BUT as others have said, it needs to be designed, installed, configured and operated correctly. Do not think that an ASHP can simply replace a boiler or be operated like a boiler. It can't and it'll cost you a fortune to run if you try.

Most people who have a problem usually have an undersized HP, undersized radiators and then end up having to use the back-up/boost heater to try to get the place warm. Radiators or heat emitters have to be sized to suit low flow temperatures

We are at home all day, so the HP runs almost continuously with a flow temperature of around 35degrees (its weather compensated and varies between 30-40 degrees depending on the outside temperature). The u/f heating is controlled by programmable thermostats in each room which set back from the daytime & evening temperatures, however the minimum temperature is set to 17 degrees. and the normal day/evening temps are about 20 degrees depending on which rooms are in use - the response time is very slow but as we've had the system for ten years we've got the controls optimised to suit.

It takes about 36 hours to reheat the house if the system is shut down so when we go away the programmable stats turn it back on at least a day before we return.

Most radiator outputs are specified for a "deltaT" of 50 degrees, which means that the rad flow is at about 70 degrees and the room is at 20 degrees. Lower flow temperatures require the radiator sizing to be increased to compensate, so you need to check very carefully that you are going to get the required heat output with a lower delta T (possibly as low as 20 degrees). Look at low temperature rads which are designed for low flow or low surface temperatures.

Having a quick shuft at some of the specs the heat output is roughly halved when the delta T is reduced from 50 degrees to 30 degrees and will be even less for 20 degrees. Bear in mind that the COP of a heatpump is usually spec'd at 7/35 (ie 7 degrees outside and 35 degrees flow) so increasing the flow temp (or reducing the outside temp) will decrease the COP and thus increase the running costs.

ASHP will usually only manage flow temps up to 50-55 degrees before the back-up heater kicks in (COP=1) You need to avoid using the backup heater in all but the most severe weather or to occasionally sterilise the hot water tank.