Feeble woman about central heating

I have so many things that need doing yesterday in my new house and I had hoped to avoid doing anything to the central heating this year, but I don't think its going to work out like that.I have never owned a central heating system before so its a bit of a black box.
The system is 20+ years old and will be replaced in the next year or so. It is oil fired and has microbore piping.
There are devices on each radiator which control the temperature to that radiator. How do thay do that? There is a pipe leading to the device, then to the radiator and then another pipe leading from the radiator onwards, so it can't be by flow control or the next radiator down the line would be controlled too.
One of these devices doesn't work, so one radiator is at full blast the whole time and thats in the guest bedroom so wasteful. Presumably I need to replace the device? What is it called and does replacing it mean draining down the whole system? Is that worth doing at all considering that the weather is going to get warmer and the heating will be turned off in a month or two.
Anna -- ~~ Anna Kettle, Suffolk, England |""""| ~ Lime plasterwork, plaster conservation / ^^ \ // Freehand modelling and pargeting |____| www.kettlenet.co.uk 07976 649862
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Hello Anna
On Tue, 10 Feb 2004 08:06:16 +0000, Anna Kettle wrote:

They are mechanical thermostats - often filled with liquid, which when it expands, will push down on a valve and close off the water feed.

The radiators are usually connected in parallel across the water feed, so each can take what it wants without affecting (well not much) the other radiators.
As you have microbore, each radiator's pair of pipes usually go back to a pair of water distribution blocks which are on the hot and cold sides of the boiler respectively.

It sounds pretty definate that it has failed.

A thermostatic radiator valve. A popular maker is Drayton.

It used to. But it's possible these days to freeze the pipes both sides of the radiator with either an electrical freezer for plumbing, or for short intervals one can use a special freezer spray but don't run out in the middle of the job(!). Bear in mind that the radiator itself will have to be emptied - but that's not as bad as the whole system.

If you can wait (there's no risk by the sounds of it) then wait until the new boiler is fitted and fix it then.
But if you're fed up with it, a plumber shouldn't make a big deal of it.

Hope that helps.
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It is by flow control. Your assumption about the radiator tail leading directly to the next radiator is false. With microbore, the feed and return to each radiator will either go all the way back to a manifold near the boiler, or will connect to much larger feed and return pipes that snake around the house. Any water that circulates through the system will only go through one radiator before returning to the boiler.

It is a TRV. Replacing it might not require draining the system. Most makes of TRV have replacable heads, which simply screw on to the valve body. If you can find the make, and the heads are still available, you're laughing. Otherwise, draining down the system to replace the whole shebang is probably the way to go, particularly as you won't know the state of the system, so a flush and refill with inhibitor might be beneficial anyway.
Christian.
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On Tue, 10 Feb 2004 09:29:19 +0000, Christian McArdle wrote:

Ooh - good point - I'd forgotton that option!
Tim
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Tim S wrote:

And also - many TRVs come with a plain plastic cap that you can replace the TRV with. If you can find one (plumbers merchant may be able to do you one if you have none knocking about) yo can take the TRV head off and replace with the cap and then use that like a manual valve - the more you screw it down the cooler the radiator will get - screw it tight down and the rediator is turned off altogether.
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John.

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In an earlier contribution to this discussion,

Also, each radiator will hopefully have a lockshield valve at the opposite end to the TRV. As a short term measure, you could partially close the lockshield (it will require a small spanner or pair of pliers to turn the shaft) to restrict the flow through the radiator which is currently too hot.
--
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Set Square wrote:

But count how many turns (write them down as you do it if you have a memory like mine, too) you close it off by. That way you will be able to open it by the same number once you have the TRV sorted, and restore the radiator to proper working, without the need to try to rebalance the whole system.
Of course, I could be talking total nonsense here, and it might be that TRV systems have their lockshields fully open. I don't have TRV's but I know having them and fully open lockshields wouldn't work in my house - it would lead to the far end of the house (which is also the colder end) taking a lot longer to heat up than the near end (which is usually the warmer end).
Velvet
Velvet
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In an earlier contribution to this discussion,

You are perfectly right in principle - to count turns when shutting lockshields, even if TRVs are fitted.
I didn't mention this because I assumed - rightly or wrongly - that the system had never been balanced, and that this was one of the reasons why this particular radiator was red hot.
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Aargh! :-) Overwelmed with information but I asked for that I suppose. Lots of good advice and the one that I like best is

Anna -- ~~ Anna Kettle, Suffolk, England |""""| ~ Lime plasterwork, plaster conservation / ^^ \ // Freehand modelling and pargeting |____| www.kettlenet.co.uk 07976 649862
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Some might suggest that, but I wouldn't. Unless you have a well-insulated house and a massively over-spec'd boiler and rads, some rooms will heat up at ten times the speed of others. I have been around my house tinkering with the lockshield valves on all 14 (TRV-fitted) rads. One is wide open, a couple of others about half-open and most of the rest are open at most 1 turn (there is one so-and-so that is just cracked but still gets plenty of flow). Prior to this, the room with the now wide-open rad used to only start to seriously warm up after an hour. Quite possibly the pipework to that radiator could be improved, but that would be a big job.
--
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John Laird wrote:

Ah, nice to know my gut instinct on that was right, then.
Velvet
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For a quick and dirty fix, just crank down the "lockshield" valve at the other end as much as it takes. It will probably have a plastic cap over it, push-on or secured by a screw, under that will be a valve stem with flats on it that should turn with a spanner / mole, or pliers if you are lucky. It's just a tap.
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