Falcon II Boiler CH stopping

[Darren Verd]

I have a Falcon II boiler been in the property for years. Its been working fine no problems at all until today. I removed a radiator last week to paint a room, wife calls me at work the day after to say not CH working. I asked her to check the pressure, which had dropped. She filled topped up the pressure and all working OK. I come home from work to find the pressure off the gauge as the fill loop was still open.
I let some water out of the system and all working ok.
How water works fine, boiler lights up water comes through
CH reset boiler, heating fires up, runs for 2 minutes then shuts down, sounds like pressure is building up in expansion chamber.

If I leave the boiler alone and on it will keep doing this.

The pressure gauge is showing 3 bar, if I let water out of the system to bring it down to 2 bar the boiler starts and then stops immediately with the light flashing to show low pressure in system.

Also the pump is red hot, cant touch it to see if its running.

ant advise on determining if the pressure gauge has gone or if the pump is US

 

[Jay32Heating]

Hi Darren. it does sound like the expansion vessel is faulty... maybe burst and full of water or flat and needs repressurised. if you run the hot water and the pressure stays the same and then run the heating and the pressure gauge rises it's the expansion vessel. but from experience of your boiler... the pump might be more likely the problem here as the hot water doesn't rely on the pump to circulate and heat up as it goes through the main heat exchanger. so when running the heating with a faulty pump would cut the boiler out within a minute or two due to overheating from lack of circulation. hope this helps

 

[Darren Verd]

I have stripped off the pump, its full of hard black gunge, I don't expect previous owner had any inhibitor in the system, Ive been running a cleaner through it for a month but I expect it needs a bit more than that. Pump impeller does not rotate freely when turned by hand so I expect its jammed. I also tried to start the pump by turning it with a screw driver, I could feels some resistance but didnt start. Will start with a new pump head and see if that works.

 

[Jay32Heating]

Good place to start as it sounds like a pump issue. worth checking the pressure in the expansion vessel also. with no pressure in the system the vessel should be charged at 1bar and when you depress the shrader valve pin no water should spurt out.

 

[Darren Verd]

happy ending...
Called local plumber, New pump fitted, New pressure gauge, DWH flow switch and a service and the Falcon II lives on
Thanks for the responses