Boiler problems

[Broadband For Niton]

I have an oil fired boiler which has started to behave a little strangely.

I won't seem to fire-up to heat the radiators but is quite happy to heat the water in the tank.

Any suggestions

Thanks

[Set Square]

Well the boiler obviously works - or it wouldn't heat the hot water. It doesn't *care* what it's heating - so your problem is unlikely to be with the boiler itself, but is somewhere in your control system.

If your system heats the hot water by gravity circulation, but has pumped circulation for the radiators, it sounds like the pump isn't working. This could be because the pump is faulty, or because it isn't being told to run by the programmer and/or room stat.

If your sytem is fully pumped, there will be a 3-port valve (or two 2-port valves) to direct the water from the boiler into the hot water or heating circuits, as required. These valves are an integral part of the control system, and switch the boiler and pump on when they have moved to the requisite position. If hot water is working but heating isn't, it could be caused by a faulty zone valve - particularly if it's a single 3-port valve, whose microswitches are prone to misbehave.

[Broadband For Niton]

Thanks for that, I have been playing around with the bits and bobs of the system and it would seem you are correct with the 3 Port Valve issue.

I can slide the lever across to manual and bingo the heating comes on. It just doesn't seem to function in the automatic mode. It also seems extremly difficult to slide the lever to manual, should this be the case?

I am going to source a new motor tomorrow and give that a go.

Thanks

[Set Square]

The motor drives the valve to the "Both" or "CH" position, through a high reduction gearbox, and the valve has a spring return to the "HW" position. When you move the valve with the manual lever, you have to overcome the spring *and* drive the motor round quite fast. It is easier if you do it fairly slowly.

If the actuator is faulty, it is easiest to replace the whole thing. Most of them unbolt from the valve itself without any need to drain the system. Make a careful note of where all 5 wires are connected in the junction box, so that you can connect the new one in exactly the same way.

If you're good at fiddly jobs and fine soldering, you may be able to repair the actuator rather than replacing it - you can buy the synchron motors and micro-switches separately - but if the cams get worn and fail to operate the microswitches correctly, there ain't a lot you can do.

Just a final thought - I assume that your programmer and room stat *are* calling for heat and are working correctly? It would be a pity to rip the actuator apart if the problem is elsewhere!