why are my upstairs radiators always warm?

[giw]

I have oil central heating and the four upstairs rads are always warm even if the heating has not been on. I sometimes hear the central heating 'running' for a short period even when it is switched off' (even if no hot water is being used)I thought it was just circulating warm water that it had in the system but it was not put on this morning and at 5pm the upstairs rads are still very warm.

I was wondering if it is faulty and is switiching itself on and using oil. The downstairs rads are always cold unless the heating is on.

Does anyone know the answer?

Thanks

[Ron Lowe]

Probably the boiler is running to satisfy Hot Water demand ( the cylinder may be cooling naturally, tripping a stat, and running the boiler. ) Then gravity circulation is heating the upstairs rads. Depending on system layout, this could be a consequence of design, or a failure.

We'd need to know the exact layout ( what zone valves are installed and where, where the pump is in relation to the zone valves, where the cylinder is in relation to all of these. In otherwords, the complete layout schematic. ) to be more precise. Also, what kind of control system is in use.. What timer / controller / thermostats are in place.

Without detail, it's impossible to be more specific.

[Roger Mills]

Do you have separate upstairs and downstairs heating zones, each controlled by a motorised valve? If so, it sounds as if the upstairs valve is sticking open and bringing the boiler and pump on even when there is no demand from programmer and room stat.

If there *isn't* a separate zone, you could have gravity (convection) circulation - but that would only apply when the boiler was on for another purpose, such as heating the hot water.