One radiator is on......but all thermostats off??

[Vanilla]

I have a weird problem with one radiator on a landing.

I have put all of there thermostats into defrost mode (ALL). However this one radiator still comes on at random times.

What could be telling it to do so when they are all either off or in holiday mode?

 

[doopydug]

Usually, the radiator at the highest point in the house cant be switched off s it allows the heat and air pockets to rise to the easiest bleed point?

 

[Orionaut]

Usually, the radiator at the highest point in the house cant be switched off s it allows the heat and air pockets to rise to the easiest bleed point?

Where is your boiler? Do you have a frost stat?

Firstly, as above, with a TRV system, one radiatior has to be always open (Usually bathroom towel rail, but depends on configuration of radiators and who installed the CH system) so that if the pump comes on, the water always has somewhere to go.

Secondly, If you have a frost stat and/or a boiler in an out building with a frost stat to protect it (Mine for example is in a lean to out building so has a frost stat because the outbuilding is not heated other than by the boiler)

Then the boiler will come on at random times, irrespective of the timer settings or even if you have switched the heating "Off" altogether, if it gets cold enough for the frost stat to kick in.

It has been sub zero in parts of the UK in recent nights (Even in S Wales I woke this morning to find thick ice on the car windscreen) Originally my frost stat was a bit over enthusiastic and cutting in about 55f which meant that the heating came on randomly during the night (Which was irritating cos it made the house too hot) but I have set it back now so it is no longer a problem ,

(I have only recently moved into house so not used to its systems yet)

 

[Vanilla]

Where is your boiler? Do you have a frost stat?

Firstly, as above, with a TRV system, one radiatior has to be always open (Usually bathroom towel rail, but depends on configuration of radiators and who installed the CH system) so that if the pump comes on, the water always has somewhere to go.

Secondly, If you have a frost stat and/or a boiler in an out building with a frost stat to protect it (Mine for example is in a lean to out building so has a frost stat because the outbuilding is not heated other than by the boiler)

Then the boiler will come on at random times, irrespective of the timer settings or even if you have switched the heating "Off" altogether, if it gets cold enough for the frost stat to kick in.

It has been sub zero in parts of the UK in recent nights (Even in S Wales I woke this morning to find thick ice on the car windscreen) Originally my frost stat was a bit over enthusiastic and cutting in about 55f which meant that the heating came on randomly during the night (Which was irritating cos it made the house too hot) but I have set it back now so it is no longer a problem ,

(I have only recently moved into house so not used to its systems yet)

To give points on both of your comments:

-- House has four floors
-- Boiler at the very top of the house
-- Rad in question is on the first floor
-- Not sure what a frost stat is but every room in the house has it's own thermostat. All are set to holiday / defrost only
-- At the moment i've turned that rad off at the plug but not sure if that's a bad idea?
-- London so it's been very nice, even at night

 

[bremen1874]

off at the plug

Plug???

 

[Abyss]

I have a weird problem with one radiator on a landing.

I have put all of there thermostats into defrost mode (ALL). However this one radiator still comes on at random times.

What could be telling it to do so when they are all either off or in holiday mode?

May be an obvious question but are you confusing the TRVs on the radiators and the thermostat?

The thermostat will decide whether to turn the heating on and pump hot water to the radiator (i.e. the random times you describe).
The TRVs on the radiator will then restrict water going through radiators.

It sounds to me like one of your valves is sticking or the TRV isn't working. As a starting point unscrew the TRV and check that the pin underneath it moves. If that works fine try swapping the TRV between 2 rooms, if this swaps which radiator gets hot it's the TRV.

 

[doopydug]

-- At the moment i've turned that rad off at the plug but not sure if that's a bad idea?

The RAD has a plug - is it electric?

 

[Vanilla]

Plug???

The twisty thing at the side closed it off.

Valve!

 

[Vanilla]

May be an obvious question but are you confusing the TRVs on the radiators and the thermostat?

The thermostat will decide whether to turn the heating on and pump hot water to the radiator (i.e. the random times you describe).
The TRVs on the radiator will then restrict water going through radiators.

It sounds to me like one of your valves is sticking or the TRV isn't working. As a starting point unscrew the TRV and check that the pin underneath it moves. If that works fine try swapping the TRV between 2 rooms, if this swaps which radiator gets hot it's the TRV.

Nope - the thermostats are all on the wall. Each controls one room. I've had previous issues with zones where different thermostats will controls random radiators but that's a problem for another day.

With all the thermostats in defrost this one rad is still kicking in at random times. I'll try what you suggested

Thanks!

 

[Dangerous Dave]

Do you have a hot water cylinder ? Could be reverse circulation happens when the return from the cylinder isn’t the last before the boiler.

A common issue in houses where cylinders have been moved or retrofitted. It normally only affects one or two radiators near the cylinder.

To confirm check what pipe on the radiator heats up with the heating on and when it’s warming up with the heating off the return pipe will heat up first.

 

[b0rn2sk8]

If each room has its own thermostat then you have a multi zone setup which isn’t typical.

Have you checked that the zone valve which covers the radiator in question isn’t stuck open?

 

[Simon42]

Firstly, as above, with a TRV system, one radiatior has to be always open (Usually bathroom towel rail, but depends on configuration of radiators and who installed the CH system) so that if the pump comes on, the water always has somewhere to go.

Not if you have an automatic bypass valve.