Central heating systems...

[iCraig]

Any of you guys know stuff about them?

Now and again the rad in my room gets very hot (as though it's on full) but it's turned off. The "dial thing" at the top is set to "Off"

After a few hours it cools back down, but why is it doing that? My room is hot enough in the summer months, I can't be doing with the bloody radiator coming on in the night. :(

[Zico]

An educated guess... is the valve from the tank to the radiators stuck open perhaps?

[iCraig]

Possibly, but it's intermittent.

[Zico]

If the valve is on the way out then it may stick between diverting hot water to the radiators or taps.

I'm no plumber by the way, just going on what has happened to our tank/valve here a few years ago.

[iCraig]

I won't be trying to sort it myself based on info on here, don't worry. It's just so I can get a rough idea what's going on before I call a plumber. :)

[TinkerBell]

I have had a valve stick, it sometimes wanted to divert all the hot water to the radiators when it was wanted for the shower. So it could be that.

[Mark]

Is the heating (in general) meant to be on at the time the rad gets hot? If not, then I concur with a stuck divert valve. If the heating is on then it sounds like the valve on the radiator itself. Depending on your system, you might have another valve the other end of the radiator.

PS - some radiators can't be turned off to prevent a situation where the boiler fires up but all the radiators are off. They're usually located in the bathroom though.

[Jonny69]

I've been sat here during the day when the heating was supposed to be off and the boiler comes on for a few seconds and sends some hot water round the heating system for seemingly no reason. I don't know why it does it. Settings all seem ok andit's definitely 'off' so I can't explain it.

Is it an old style tap on the rad or the newer type thermostat thing? On the old style central heating systems you had taps that controlled the amount that went through each rad in series and it was a balancing act, newer ones seem to have a thermostat valve on each rad which, if playing up, could make the system do some funny things.

Thinking about it, if the heating is switched on then it's got hot water in the system and it's pumping it round the pipes. The individual radiators have thermostats and are techinically off, but if one is playing up and thinks it's off when it's actually wide open then the rad will get hot.

Make sense? No, thought not, it's because I've been in the pub :(

[Mark]

I've been sat here during the day when the heating was supposed to be off and the boiler comes on for a few seconds and sends some hot water round the heating system for seemingly no reason. I don't know why it does it. Settings all seem ok andit's definitely 'off' so I can't explain it.
You sure it's hot water? Mine pumps cold water round the system for a few seconds every few days. Don't know why, but it does. Could be something to do with the main thermostat on mine (it's wireless).

[lostkat]

What sort of boiler do you have? Combi/conventional etc.? How old is the system?