Radiators ...

[Arfa Daily]

One of the rads in my lounge has developed a leak. It's a single panel type, seam topped and with a wavy bit of metal at the back. It measures approx 75 cms across the panel vertically, and 158 cms across the top water gallery. What 'official' size is this for obtaining a replacement - or is it even directly replaceable still ? About 25 years old. There seems to be a distressingly large range of rads around those sizes, but I would like to get a 'ringer' if possible because I would really like it to just be 'drop-in' due to current time constraints for DIY. Would there be any advantage to replacing it with a double panel rad if someone has one ? Are the fittings still the same sizes now ? I'd hate to get one and find that the original couplings were some obscure imperial size, now replaced by some equally obscure metric size.

Any advice and general thoughts on the job, most gratefully received ...

Arfa

[Lobster]

On 31 Oct 2014, "Arfa Daily" grunted:

I'd have thought the fittings would be the same then as now. Doesn't sound like a standard current size to me but best to google and see what you can find. You can buy extension pipes etc like this:

which may help.

Bear in mind though that modern radiators will be much more efficient than what you've currently got, so if you were to fit an identically dimensioned radiator nowm, chances are it would be over-specced for the room (though that's not as bad as being under-specced, obviously.

A double-panelled radiator is approx twice as powerful as a the equivalently dimensioned single rad, so that won't be the answer to your problem.

The 'correct' way to do it is to use one of the on-line calculators to determine how many BTUs you need for the room, and buy the appropriately dimensioned radiator for that. Once you have the correct BTU output needed, you'll find there are lots of differently dimensioned radiators with more or less the same heat output that you can choose from. Screwfix is a good starting point (try their drill-down menus for height, width, output etc.

But you may have to bite the bullet and do a bit of pipework!

[RobertL]

OTOH if you have a condensing boiler you want to run it with the return temperature as low as possible, so the radiators need to be bigger than they used to be.

Robert

[Roger Mills]

Radiator sizes used to be Imperial (although yours doesn't sound like anything in particular!) but are now metric - so you're very unlikely to get a new one which is exactly the same size. The good news is that the plumbing fittings are the same - so a new one will have the same 1/2" BSP female threads as the old one into which to screw the tails for the valves.

Radiators seem to come in 100mm (10cm) steps for both width and height.

700mm is a fairly common height (but less common than 600mm) - but that would be a couple of inches shorter than the existing one. Width-wise, you'd be looking at 1500mm or 1600mm. As others have said, you can get extra-long valve tails to compensate for the radiator being a bit narrower, but an extra 40mm per side is quite a lot. If there's a bit of flexibility to spread the feeder pipes, you might get away with a 1600mm rad with standard valves and tails.

In all events, the brackets are likely to be different - so you'll have to do some careful measuring to determine where to fix the brackets to the wall in order to get the water connections in the right place.

Most single panel rads have fins on the back these days, which increases their heat output size for size by about 50% (as long as you balance the flows to suit!). Unless the current rad is seriously under-sized, I wouldn't go for a double. They don't look very pretty and will almost certainly have their plumbing connections a bit further out from the wall - so you may have to adjust the pipe-work. [That may not matter if you're having to adjust it for a different size of radiator, anyway].

[John Rumm]

Sounds like an unusual size... 700x1600 would be easy enough to get though.

If you have difficulty getting the room warm enough, then yes.

The rad normally just has 1/2" BSP sockets, and the actual coupling come with the valve. So you can remove the tails from the old rad and install them in the new - then it will march the valves perfectly (if they reach!)

Be prepared to have to move at least one tail.

[Andy Burns]

Myson still do Imperial sizes

27x61" = 690x1556mm sounds the closest, but not close enough to simply drop in, so you might as well fit a metric replacement if you've got to adjust the pipework ...

[RJH]

Wouldn't that be 'effective' rather than 'efficient' for given dimensions?

When looking for radiators I see they're often labelled 'super efficient' but I don't see how, energy-wise. They may provide more heat for a certain size, but I can't see how they provide more heat per kW/hr.

It's going to be belting out a lot of heat to achieve a low return, isn't it? So a system that cycles frequently and hot rather than steady and warm?

[RJH]

If it's mounted on a stud partition wall, brace yourself for a world of pain if the bracket positions of any replacement don't match the studs.

[polygonum]

I know this isn't you being perverse, 'tis widespread, but why do we still use BTUs? And calories?

[Chris French]

Same reason people still use inches, feet, oz etc.

[Dave Plowman (News)]

If it's only 25 years old (1990 ish) would it be imperial? Plumbing fittings went metric long before that.

[Dave Plowman (News)]

Is this the valve to tail fitting? Normally a taper, so a washer wouldn't help. By all means use some PTFE if it makes you happy - but it shouldn't really be needed.

If it's the tail into the rad, I'd certainly use PTFE.

[Dave Plowman (News)]

Normally a taper, then? Although perhaps not on all valves.

[alan_m]

On my 20 year old radiator I had to use a reducing adapter to match the new valve I needed to fit. The tail on your older valves may be a larger diameter than the (threaded) hole in the new radiator that it needs to fit into.

[Roger Mills]

Most valves these days seem to use compression joints to connect both to the tail and to the external pipework - but 25 years ago the valve to tail connections were mostly taper.

If yours are taper, clean up both bits of the taper - male and female - with wire wool, and put a smear of LS-X on the mating parts when you re-assemble it.

[Dave Plowman (News)]

I'm really surprised at that if it's a normal domestic rad. Mine are more like 40 years old and use exactly the same tails as today's ones. I fitted all new thermostatic valves recently, and since they were a different make had to change the tails too.

[Andrew Gabriel]

One aspect of an "efficient" radiator would be one that has low heat capacity. This means you are not wasting energy heating up, say, a giant lump of cast iron and loads of water before you start getting heat out into the room, and similarly, it doesn't take ages to cool down and stops heating the room when the room has reached the set point without overshooting.

I replaced some radiators in my brother's place a few years ago, and it was quite noticable that the new ones cool down very quickly when the heating goes off, but the old ones, being thicker steel and larger water channels, take much longer to cool down.

No, just needs to be larger. I did that with the central heating system I installed. It actually performed better than I had intended, and can keep the house at normal room temperature when running at 45/40C flow/return, with no boiler cycling. That means the boiler is running just about as efficiently as it can, and wasted flue gas heat is only 50C.

[Roger Mills]

Me too, if it's only 20 years old. It was more common to have larger threads (3/4" or 1" BSP) 40 years or so ago because maybe not all systems were pumped in those days. When I moved in to this house nearly

40 years ago, a couple of the radiators had 3/4" BSP (I think) threads with reducing bushes in them to enable normal 1/2" BSP tails to be used.

[Dave Plowman (News)]

Pumped was the norm in the '70s. Microbore was also in vogue then. You'd have to go back a decade or more before that for gravity circulation to be common.