central heating not comming on

[tommyo]

i have a potterton boiler. thermostat on the boiler, thermostat in the lounge and a thermostat on the water tank. in airing cupboard with the tank there is a box. one pipe going in which then branches into two, DHW and CH. on the box there is a light for both DHW and CH and a manual override switch. When the boiler comes on, either timed or on, the boiler lights up and the 2 lights for DHW and CH on the boiler electric control unit, come on. the hot water heats up but the radiators dont get warm unless you hold the manual override switch.( in the tank, the DHW light is on but not the CH light, unless you hold the manual override switch, then they swap over). Its as if it is defaulting to heat the water rather than the central heating. have i set one of the thermostats too high/low. Please advise, Any reasons or solutions would be much appreciated.

Tom

[gasman]

The boiler Stat set to max. The Cylinder stat set to 60* and the room stat set between 18-21*

[tommyo]

there is a switch near the boiler with a light on it. would that be a pump of some sort. the heating worked fine last year and i dont hear any noise or notice any difference when the switch is on. there is also a switch in the airing cupboard. just above a box wich has wires leading to what looks like differnt pumps or valves. does this switch need to be on. again, i've not noticed anything when its turned on. The heating was working on tues without these switches being on.

[gasman]

Both switches should be left on unless you are going away for a few days etc... If you're Stats are set as above and it still does not work then check the programmer/timer is set to correct time and is on auto. If it still is not working then either the programmer/timer or the motorised valve in the cylinder cupboard is faulty and needs replacing with out testing them i cannot say which is faulty.

[tommyo]

unusual that it worked before without these switches being on. thanks for your help. i will check tonight and post the results.

[tommyo]

what are these 2 switches ( for reference )

[gucciman]

i'm confused by your description of the fault but the usual cause of no heating on a traditional boiler and tanks system when the waters working fine is the syncron motor failing in the diverter valve, this can be proved by manually locking the little lever on the valve into the manual position and seeing if the boiler fires up ( i wasn't sure if this is the overide you were talking about)