As Winter will soon be here and I have had my Central heating off, I thought I better test out the system to see if it was ok and sods law I have a problem with one of my radiators on my central heating system the actual system works fine and is about 2 years old for some reason one rad gets really hot where the others do not. Each Rad has a Terrier II Thermostat on (as the regs state you must have these on all new installations) the themostat on the dodgy rad even if i turn it right down still gets really hot. could this be a faulty thermostat on this rad or could anything else be causing it, also if it is the thermostat how easy are they to replace as Screwfix do them and there bound to be cheaper than getting a plumber in to fit it.

your thoughts please

thanks

In an earlier contribution to this discussion,
Dazkb wrote:

As Winter will soon be here and I have had my Central heating off, I
thought I better test out the system to see if it was ok and sods law
I have a problem with one of my radiators on my central heating
system the actual system works fine and is about 2 years old for some
reason one rad gets really hot where the others do not. Each Rad has
a Terrier II Thermostat on (as the regs state you must have these on
all new installations) the themostat on the dodgy rad even if i turn
it right down still gets really hot. could this be a faulty
thermostat on this rad or could anything else be causing it, also if
it is the thermostat how easy are they to replace as Screwfix do them
and there bound to be cheaper than getting a plumber in to fit it.

your thoughts please

thanks

My first reaction was that your system has probably never been balanced
properly - and whilst that may still be true, the chances are that you've
*also* got a problem with a TRV (thermostatic radiator valve) - because the
rad shouldn't get hot if you turn it right down.

TRVs are in 2 parts - the wet part and the head. The head contains a wax
capsule which expands when it gets hot, and presses down on a pin protruding
from the top of the wet part - cutting off the flow. The head may be faulty.
If so, you should be able to replace it without disturbing the wet bit.

You should have been supplied with a manual head to fit in place of the
normal one when you want to close the valve positively - for example when
removing the rad to decorate. You can check whether the wet part is ok by
fitting this manual head and screwing it down. If all is well, the rad
*won't* then get hot.

Once you're sure that all the TRVs are ok, you may *then* need to balance
the system to make sure that it warms up evenly, and that some rads don't
get hot a lot sooner than others. If necessary, come back here for advice
when you're ready to do that.
--
Cheers,
Set Square
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Set Square wrote:
You should have been supplied with a manual head to fit in place of the
normal one when you want to close the valve positively - for example when
removing the rad to decorate. You can check whether the wet part is ok by
fitting this manual head and screwing it down. If all is well, the rad
*won't* then get hot.

As an addition to that, if you don't have the original decorating cap,
you could always (assuming you have the same type TRV on another
radiator) swap the TRV with another radiator. You should then see the
problem move to that radiator and will have established the problem!

In an earlier contribution to this discussion,
Richard Conway wrote:

Set Square wrote:
You should have been supplied with a manual head to fit in place of
the normal one when you want to close the valve positively - for
example when removing the rad to decorate. You can check whether the
wet part is ok by fitting this manual head and screwing it down. If
all is well, the rad *won't* then get hot.

As an addition to that, if you don't have the original decorating cap,
you could always (assuming you have the same type TRV on another
radiator) swap the TRV with another radiator. You should then see the
problem move to that radiator and will have established the problem!

Good idea - just swap the heads, of course - no need to disturb the
plumbing.
--
Cheers,
Set Square
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