Rad sizes/BTUs

[Alison556]

Sorry if this sounds an ignorant question (but I'll ask it anyway!!).

If you have a radiator of, say, 800mm wide by 500mm tall and it's a double radiator, would the output of any radiator that size be the same? (Does that make sense?).

One of my bedroom's NEVER heats up no matter how long or how high the heating is on for. I've been trying to work out if it's the right size for the room, but I got a bit confused with the outputs.

The room is 3.5m x 3.5m with a ceiling height of 2.6m. There are two outside walls - one north facing, one west facing. The west facing wall has a window which is 66" high by 39" wide. The radiator is 800mm x 500mm.

Does it sound like the radiator is big enough for the room?

 

[Richard C]

Modern radiators are more efficient than old radiators but, generally, radiators the same size made by different manufacturers will give roughly the same output as they will be made to the same BS. You don’t say if your rad single or double panel. A new, double panel radiator that size is rated around 4000 BTU & your room size will need roughly 3700 BTU so if your rad is double panel, it should be OK. This is a generalisation & the age of the house, insulation, double glazing or even draughts will make a big difference to the heat requirements. You say the bedroom never heats up but does the radiator actually get hot? If not, you have a flow problem rather than an heat output problem.

 

[Alison556]

The one thing I forgot!! It's a double radiator.

It does get hot but not as hot as the other radiators in the house - them you can hardly touch they're so hot, but that one isn't like that.

It's a new (ish) system, having just been fitted two years ago come February but to be honest, it's been nothing but bother - the old double radiators and hot water tank seemed much more efficient than these new rads and combi boiler.

Oh, and the radiator is under the window (as they all are). I'm a ground floor flat, so roof insulation doesn't come into it. There are HUGE foundations under the house (been given estimates of anything between 10 and 15 feet deep). There is no under floor insulation, but that's something I'm going to look into. I don't think I've got cavity walls, so I can't insulate them (it's single skin brick then just the plaster with an air gap between). The house was built in 1919. The other rooms heat up fine - just this one bedroom doesn't.

 

[Richard C]

A double radiator should give adequate heat output for that size room, if the radiator isn’t getting as hot as the others, you have a flow problem. First thing to check is the rad. valves; assuming you haven’t got TRV’s, one end will be an isolator valve fitted with a knob which opens & closes the valve; this should always wide open. At the other end or the rad is a lock shield valve which will (should!) have a knob that doesn’t appear to do anything but spin freely; it maybe partially closed & is used to balance the flow through the CH system; remove the knob from the other end of the rad & open the valve by a further ¼ turn. If it’s already wide open, you have a system problem; it could be silt, a blockage or that the pipe work hasn’t been properly designed for size/route; either way you are going to have to get some professional help, fitting a bigger radiator wont cure the problem.

 

[bengasman]

If it was converted from open vent, chances are with what you are describing that the system was either not cleaned properly or not balanced properly.
FAQs will help you on the way

 

[Alison556]

Sorry, I don't know what open vent is. I think everything was replaced though - pipes as well as rads and boiler.

I know, in theory, how to balance the system but I don't think I've got the confidence to do it in practice, so I'll need to find a plumber to come and do it for me.

I'm sure it was Stevie Wonder that fitted this system.........

 

[Alison556]

I know what I forgot to ask - if I do pluck up the courage to try and balance the system myself.

Now I know that the rads should be balanced in the order they come on the system............

But how do you know or find out what order they come in?

I have an idea of what would make sense for the order - but that's not to say that they do come in that order.........

 

[Richard C]

Try what I suggested first; there is a chance that it will work if that rad has just been shut down a little too far. If it’s already wide open or opening it further upsets the balance somewhere else in the system, put it back where it was. If you’re feeling really adventurous, you could try closing down the rads before it ¼ turn (one at a time) to see if that helps, starting with the one nearest the boiler. Balancing the system properly is obviously a little more involved but if it gets you out of trouble, what the hell! If you can t resolve it put everything back where it was & then call in the plumber.

 

[Alison556]

Thanks, will try that - only difference to your instructions is that there is a TRV on the radiator - is there anything different I need to do for the TRV?

 

[Richard C]

Thanks, will try that - only difference to your instructions is that there is a TRV on the radiator - is there anything different I need to do for the TRV?

Yes definately; if you’ve got a TRV on the rad it could be seized & restricting the flow so that’s the first thing to check!

 

[Alison556]

Is that where I just take off the knob with the numbers on it and give the pin a gentle whack to see if it releases (not very technical, I know)?

We have had bother with the TRVs in every room. The main bedroom the radiator wouldn't switch off at all cos the pin was stuck and all the other radiators, if you turn it down to 4, the radiators go off and won't come back on again unless you turn the TRV up to full, or turn the heating off, wait a while, then turn it back on again. Does this sound like carp quality TRVs?

 

[Richard C]

I think you know more than your letting on

 

[Alison556]

Are you winding me up?

There's a difference in knowing something in theory but having the confidence to put it in practice!

I'm frightened to undo anything in case I cause a leak - did that with the bloomin cistern! It was dripping, took the lid off, saw this little spout/tap thing that was dripping away, went to give it a twist and a push on (like that would work - it's like kicking the tyres on a car to see how hard they are!!), somehow managed to pull it off and the next thing, had Niagra falls in the bathroom, with me screaming for a screwdriver to turn off the isolator valve!!

 

[Richard C]

Are you winding me up?

There's a difference in knowing something in theory but having the confidence to put it in practice!

No but having checked out some of your previous posts, I am unsure if you are?

Anyway, you’ve got the right idea; remove the TRV head & push (don’t whack) the pin firmly down a few times & make sure it moves through the full length of travel; around 3mm. If you satisfied the pin is moving freely, leave the TRV head off the valve & run the system; if the rad now heats up, you know the valve itself is OK. Put the TRV head back on, open it to max & see what happens; if the rad does not get to full temp, the thermostat in the head is faulty.

 

[Alison556]

Honest, I'm not taking the mick. I probably do know more than I think but I just don't have the confidence in what knowledge I do have - I always have this wee niggle that I'm wrong.

I'll get stuck into the TRV when the heatings off - dunno when that'll be though - it's bloomin freezing here. I'll also look at that other valve (return valve?). I would imagine that this radiator is second last on the system (with my logical thinking), so that valve should be pretty much wide open?