No Central heating ignition but fan is running

ThisIsWeird

ThisIsWeird said:

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.

Sorry - read your first post, Matty - you have checked the pump is free to rotate.

That leaves the diverter valve as the most likely candidate - almost certainly it has one (only Intergas boilers manage without?). I suspect - but suspect only - that the room stat does signal the boiler, the fan fires up and the diverter valve would move to the CH position if it could, closing a microswitch to then fire up the pump and flame. But pure guesswork.

As others have said, I really think you have reached the point of getting the pros in.

RonRamsgate

so its a worcester i rsf.
Have seen them before where the splined spindle has snapped behind the temperature control knob (knob also has a positive off setting). Although the knob will rotate in the facia It will not be in contact where it needs to be in the pcb. Effectively in an OFF position.
Could gently with pliers pull the knob straight out of the facia and compare it to https://www.adlink.co.uk/worcester-24-cdi-28-cdi-rsf-26-cdi-xtra-boiler-control-knob-87161410440
The pump on that boiler is for central heating only, even if its seized or otherwise goosed The boiler will still ignite under a positive demand for central heating but very soon the burner will shut down when the overheat stat kicks in.

Think a few diy fix's have already been mentioned, good luck thou.

Its been mentioned that they dont have a diverter valve which is true, they have a 4 connection bi thermal (see google)  heat exchanger. Hot water for the taps is produced like a fan assisted gas multipoint water heater 

FreeBear

macman said:

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

Intergas have two sets of coils in the heat exchanger (one for CH, the other for DHW). Whether that is a better design or not, I'll leave you to decide.

matty_hunt

Thank you to all who replied. The engineer was also surprised not find a diverter valve, but such is the design. He concluded that whilst there was power to the pump, he thinks the coils have broken down as the housing gets a little hot but the propeller, which is free, does not spin. Have yet to have a replacement fitted. 

bris

Pump doesn't run the it cant circulate the water, nothing to sent to the diverter valve. pumps at fault here.

Take the cover off the pump, that's the big silver round bit that looks like a screw.

A little water will come out but don't worry about it.

Then with the screwdriver give the pump a few turns and see if it starts, you can also try changing the pump speed, there is a small lever that lets you choose the speed try a different one.

If the pump doesnt start spinning then the pump needs replaced.

Dont focus on the diverter valve until the pump needs to work first before you need to worry about other problems.