Conventional central heating system with a water cylinder and three
port valve in the airing cuboard.

Recently, the radiator in the bathroom has been getting warm when
switched to "hot water only". It didn't do this before.

My thoughts are that the three port valve is sticking. Other than this
maybe the heat exchanger in the cylinder has failed. Any other
suggestions as to the cause?

How to diagnose whether 3 port or cylinder?

sponix

s--p--o--n--i--x wrote:
Recently, the radiator in the bathroom has been getting warm when
switched to "hot water only". It didn't do this before.

The bathroom radiator is often connected to the pipework serving the
hot water storage cylinder, so it would get hot when switched to 'hot
water only'. You'd have to trace the pipes to confirm this.

The theory is that you may want heating in the bathroom when the rest
of the heating system is off and the pipes are more convenient. This
wouldn't explain why it wasn't getting hot previously.

Recently, the radiator in the bathroom has been getting warm when
switched to "hot water only". It didn't do this before.

Are you sure it wasn't supposed to work like this before? It is common for
the bathroom radiator to be uniquely plumbed to come on in the situation you
describe. Perhaps little fingers have been playing with its TRV/handwheel,
so its only just come on?

Do other radiators also get warm?

Christian.

Aidan wrote:

s--p--o--n--i--x wrote:

Recently, the radiator in the bathroom has been getting warm when
switched to "hot water only". It didn't do this before.


The bathroom radiator is often connected to the pipework serving the
hot water storage cylinder, so it would get hot when switched to 'hot
water only'. You'd have to trace the pipes to confirm this.

The theory is that you may want heating in the bathroom when the rest
of the heating system is off and the pipes are more convenient. This
wouldn't explain why it wasn't getting hot previously.

All the ones on our estate are like that.
Its quite easy to spot because there is a pipe feeding the bathroom rad
Teed off the inlet to the 3-way valve

If its not connected like that then the 3-way valve is maybe not
shutting the CH side off properly. Although that should allow other rads
to get hot too.
If the coil in the cylinder was leaking this would cause the CH header
tank to overflow when the water was heated.

On Mon, 18 Jul 2005 17:44:34 +0100, "Christian McArdle"
wrote:

Recently, the radiator in the bathroom has been getting warm when
switched to "hot water only". It didn't do this before.

Are you sure it wasn't supposed to work like this before?

I'm told that it never did..

It is common for
the bathroom radiator to be uniquely plumbed to come on in the situation you
describe. Perhaps little fingers have been playing with its TRV/handwheel,
so its only just come on?

No TRVs on the sysem, only normal valves.

It turns out that one radiator was changed by a plumber recently, so I
suppose that he may have re-balanced the system which in turn could
cause this effect. I'm inclined to leave it and see what happens, in
the abscence of any other problems.

sponix

On Mon, 18 Jul 2005 18:00:38 +0100, OldBill
wrote:


If its not connected like that then the 3-way valve is maybe not
shutting the CH side off properly. Although that should allow other rads
to get hot too.

Even if the pump is not running?

s--p--o--n--i--x wrote:

Even if the pump is not running?

Yes, gravity circulation can cause the upstairs radiators to get hot.
Typically, the rads will get warm with the pump off, but will get very
hot as soon as the pump comes on. It depends on the vertical heights,
the pipe sizes, number of fittings, etc..