Boiler Is Firing Up But No Central Heating

[dave50]

My Worcester Bosch boiler provides hot water fine. When I put the central heating on, the water is not being pumped through the radiators. I remember on old systems you could take the plug out of the back of the (usually Grundfos) pump and turn it round manually with a screwdriver to release the debris that had settled inside while the heating wasnt being used during the summer. I was wondering if I have the same problem now but of course the pump is inside the boiler unit. Has anyone taken the cover off and tried this solution on one of these modern combi-boilers please?

[TWR]

Air in the system, is this the first time you have switched the CH On?

[frugalfred]

Do you have a radio thermostat? Check the battery.
Have you bled the system using that funny plastic key?
I wouldn't mess about inside the unit.Best left to the professionals.

[ummmm]

Turn all the radiators off, put the heating on and turn them back on one by one.

[dave50]

Its been off about 6 months and I have re-pressurised it and the radio thermostat works fine because it fires up when I turn the thermostat up but no water circulates. I will try your solution ummm, see what happens.

[Tuvok]

Bleed the radiators

[Khandro]

It could be that there is insufficient water in the system after standing all summer. do you have a dial to show that? Mine (Buderus) has to be attached to the mains every so often to top up the water.

[The Builder]

After a long period of inactivity through the summer, it's quite common for the diverter valve in the boiler to have stuck in the Hot Water position.

This valve diverts water to either HW or CH (central heating.) The usual remedy, if you can locate the valve, is to tap it with a small hammer to persuade it to go over to CH.

It's the first thing I would try.

[DTCwordfan]

what about the burner clicking out, The Builder, it's igniting ok but won't sustain itself, going to the red ignition light....thermostat perhaps?

[BRIGHT SPARK]

DT.....yours sounds like the thermostat/thermo couple or a main jet issue..assuming its gas.Has it got a reset button.
Daves could be ..diverter/circ pump/pipe stat/flow sensor/pcb.

[DTCwordfan]

it's oil.....the reset button, push, it ignites but won't hold....my suspicion the thermostat (which is aged)

[BRIGHT SPARK]

DT....if its oil it may be the thermostat/thermo couple.Some boilers have a magic eye to sense that the flame is operating.

[Togo]

Listen to builder, it is most likely the motorised diverter valve. After a period of inactivity ie hot water only and no need to operate, the first time the motor part is asked to turn the valve it pops off the spindle because the brass valve has stuck. Just remove the plastic motor part (it come off by just pushing a little release clip) and then pull it gently off the brass fitting. Then with a pair off plier just turn the spindle back and forth. Note it only does a quarter turn to cover all three options, water only, heat only, or both. When you have done this LEIVE THE BRASS VALVE SPINDLE IN THE SAME POSITION AS THE PLASTIC MOTORISED PART and refit the motor part making sure it is seated properly on the two guide nibs that are on the valve.

[DTCwordfan]

I suspect so, BS, no hot water on the one here....engineer booked but not available until 10/10 but will service both the heating and the Aga....

[DTCwordfan]

thanks though.....

[Dodger666]

Our Baxi Combi boiler runs the pump every now and again during the period when the heating is switched off. I don't know if they all do.

[jennyjoan]

I have had that problem twice this year - one (I simply had no oil left in my tank oooops) - the second I did need a boiler man to come out and "do something with it".