No Central heating ignition but fan is running

matty_hunt

Hi. My son has just told me he has had no heating in his flat for two weeks. Ive investigated as much as I can but Im stumped. Its a Worcester 24i gas combi. The hot water works fine but when heating is switched on, the fan starts up and runs for a few minutes but there is no ignition. Ive bled the rads and toped up the pressure. What could be causing it not to fire even though the fan is running for the CH but all ok for water?
I assume the room stat works as the boiler fan starts, suggesting stat has signaled to boiler to turn on. Edit: Fan also runs when CH switched on at boiler but stat set at zero.
The ignition system and gas supply is ok as it fires up for hot water demand.
I cant hear or feel the pump doing anything but dont know if it should at this stage, ie before ignition. Has check it is not jammed and spins freely.
Cut out valve has not tripped.

Many thanks

macman

Divertor valve sticking in the DHW mode?

matty_hunt

Thanks. That would have been my first thought too but this combi doesnt appear to have a diverter valve! Looks like separate HW and CH pipes run into the top of the heat exchange. The flow and return of each, HW on the left side, CH on the right.

JohnB47

matty_hunt said:

Hi. My son has just told me he has had no heating in his flat for two weeks. Ive investigated as much as I can but Im stumped. Its a Worcester 24i gas combi. The hot water works fine but when heating is switched on, the fan starts up and runs for a few minutes but there is no ignition. Ive bled the rads and toped up the pressure. What could be causing it not to fire even though the fan is running for the CH but all ok for water?
I assume the room stat works as the boiler fan starts, suggesting stat has signaled to boiler to turn on. Edit: Fan also runs when CH switched on at boiler but stat set at zero.
The ignition system and gas supply is ok as it fires up for hot water demand.
I cant hear or feel the pump doing anything but dont know if it should at this stage, ie before ignition. Has check it is not jammed and spins freely.
Cut out valve has not tripped.

Many thanks

I did a search for that problem with that boiler and found a suggestion to reset it:

"People also ask:

Why is my Worcester boiler not firing up?

How do I reset my Worcester boiler 24i?

The appliance can be reset by pressing the fault indicator button and holding in for 5 seconds when the appliance has cooled."

matty_hunt

Thanks John for taking the time to look that up. Unfortunately this Worcester 24i, which Ive since discovered is a 24i RSF doesnt have a fault indicator button. There is a reset button on the top of the unit that pops up, but that has not tripped.
Today I took the large screw out of the front of the pump whilst the thermostat was calling for heat. The fan started up but the pump did not spin. I assume the pump probably should be running before ignition.

JohnB47

matty_hunt said:

Thanks John for taking the time to look that up. Unfortunately this Worcester 24i, which Ive since discovered is a 24i RSF doesnt have a fault indicator button. There is a reset button on the top of the unit that pops up, but that has not tripped.
Today I took the large screw out of the front of the pump whilst the thermostat was calling for heat. The fan started up but the pump did not spin. I assume the pump probably should be running before ignition.

No problem. Well I'm no expert but I too would expect the pump to be running before the boiler fires up. 

plumb1_2

It would need checking if the pump is getting a power supply. If inside the boiler you need a gri 

ThisIsWeird

matty_hunt said:

Today I took the large screw out of the front of the pump whilst the thermostat was calling for heat. The fan started up but the pump did not spin. I assume the pump probably should be running before ignition.

Possibly. I don't know. 

It could be that the flue fan always starts up first, for obvious reasons, but the pump might not do so until told by the diverter valve. But, I don't know.

If the pump isn't spinning, and since you have already accessed the bleed screw at its end, then the only thing I'd suggest is to look for a slot in the end of the exposed pump shaft, and (with boiler off) try turning it with a screwdriver to see if the pump is seized. 

Other than that, it's GasSafe time, I'd suggest.

macman

I'm still puzzling out how you build a combi without a diverter valve, so what do I know?

JohnB47

macman said:

I'm still puzzling out how you build a combi without a diverter valve, so what do I know?

I was curious about this too so I did some searching.

Sure enough, it is common for combis to have diverter valves. And it is common for them to become stuck, or faulty, so that you get get water and no CH or vice versa.

OP - have another look at the boiler and do some searching about things you can do to confirm that it's a diverter valve problem and what you could do to solve it.

Might still need an expert though.

akira181

Considering it seems like a mechanical fault with the boiler and you've checked the basics, you should be getting a GasSafe registered engineer to diagnose/repair and not be poking around further yourself with information from the internet. If not for legal reasons then for obvious safety reasons (not to mention it's your sons flat and not yours so if anything were to go wrong when you're not there, could your son identify and make safe potential issues without you?)

There aren't many GasSafe engineers that can diagnose a boiler without physically seeing it and even fewer that will give advice on how to fix it to a DIYer