Am replacing my rad valves with TRVs.
I was going to mount them vertically, the same as the existing valves...however, before I do so is there any benefit (Either operational or efficiency) to mounting them horizontally?
sponix
They are supposed to work more effectively in a horizontal position, as air currents flow more freely past the sensor. However, I think they look naff mounted that way, and (having kids) look all too tempting to stand on.
I have one rad with the TRV that way round (installers put it at the wrong end and didn't notice until after the system was filled), and it is always at a noticeable lower setting for the same room temp, so there is something in that argument. But I find all the vertically-mounted ones behave perfectly acceptably.
One last question..
The new TRVs come with olives, compression nuts and a stub of pipe that is threaded at one end.
The radiators are 35 years old and I don't think the old 'stubs' will come out. Obviously removing the old olive I may damage the stub and have to renew the stub.
If I re-use the old nut/olives/stub is it likely to leak? Is there an easy way to remove the old stub of pipe?
sponix
Heat and stilsons
Regards Jeff
On Tue, 27 Sep 2005 10:30:54 GMT, snipped-for-privacy@email.com (s--p--o--n--i--x) scrawled:
Shouldn't be any adverse affects from reusing the tails, they should all be the same size. Just make sure you seal them properly when you're reassembling.
The "stubs" are known as radiator tails. It's unlikely you will damage one in the act of removing an olive, as the olive is much softer (the tail is a lump of steel). Some tails are presented to the valve as a length of 15mm (or 1/2", same size) pipe, and the join is made with a compression fitting and an olive. If your existing tails look like this, and your valves have
15mm compression fittings on both ends, then you can use the old tails. However, some valves and tails have a mating surface which looks like part of a sphere. These must match, and will have been supplied together. If your existing pipework has these, then you will need to replace the tails. It should be easy to tell - the tightening nut is much larger than a normal 15mm compression one.It's not usually that difficult to get tails out - I have had more trouble getting a decent seal putting new ones in (they have a tapered thread). A large hex wrench from the plumbing section of your local diy shed is the usual tool - it should exactly match the new tails. It may or may not match the old tails, or they might have internal splines which mesh with slots in the wrench. I've sometimes had to jam a large screwdriver in alongside the hex tool if the tail hole is too large. Put new ones in with PTFE tape, and do them up *tight*.
I would get a move on though - the first real cold snap will always coincide with a heating system disaster ime.
A comment I read here, which appears to make sense is that the TRV can be placed in the return instead of the flow (if it's a biderectional one, and I think they mostly are) on account of the return is 10 deg cooler, with a bit of luck, and the lockshield goes in the flow; I'm giving it a whirl, though I think, TBH, you just set the thingy to feel right, and it'll be ok regardless
mike
It had crossed my mind that they might be like that..
Do all tails have the same thread? As the rads are early 70s I'm worried that there may have been an imperial-metric changeover at some point in time.
Shhhh! Don't tempt fate!
sponix
You need a big allen key to get them out (or rather get them in, if need be you can apply stillsons to extract them).
The threads will all be 1/2" BSP (British Standard Pipe) - which actually has an OD of 0.825" (21mm) because it's the thread which would be on the
*outside* of an iron pipe with a nominal 1/2" bore.Pipe threads have stayed the same over the past few decades even though copper pipe sizes have gone metric.
The only thing to watch out for is that some old radiators have 3/4" BSP (just over 1" in real money) threads - so they will have been fitted with internally/externally threaded bushes to enable them to use 1/2" valves. If your rads have got these, try not to disturb the bushes - hold the hex of the bush with a wrench whilst you unscrew the valve tail from it.
I never realised rads could be so much fun!
Thanks everyone who responded
sponix
I suppose if it is placed in the return then the TRV will be less affected by the heat of the water flowing through it?
sponix
Yes, that was the reason given here, not long ago, but I can't find it - it's prolly deeply buried by now. The same sort of reasoning as mounting them horizontally.
I doubt if it makes a ha'porth of difference, but once someone's suggested a thing like that, I just *have to do it.
(Its a BOF thing)
mike
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sponix
LOL :-))
mike
The 'stub' doesn't usually have a removable olive - it's part of the pipe.
But they're usually chrome plated, and if there's evidence of PTFE tape should come out ok.
There's a hex inside it which an allen key fits.
What does that look like, a large fist imprint?
But he's probably got two 'combi's'
An olive on the valve end of the tail.
sponix
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