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 Kettle, Suffolk, England
|""""| ~ Lime plasterwork, plaster conservation
/ ^^ \ // Freehand modelling and pargeting
|____| www.kettlenet.co.uk 07976 649862
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
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.
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.
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.
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.
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
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
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.
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.
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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