heating problem alpha 280e combi boiler

[Torryloon]

won't give a drawn out speel. Here's the short version. Alpha 280e combi boiler, renewed the inhibitor, repressurised the system and stupidly left the refill loop connected. Came home from work to find shut off valve had failed and water pouring out the back of the boiler and pressure gauge just touching the red zone. Did the usual cleaning up and sorted out pressure in boiler now i have no heating. Hot water from taps and shower are fine. For the central heating the boiler fires up as usual but extinguishes after 28 seconds pumps goes through it's cycle and boiler fires up again and goes out after 28 seconds. Both thermistors are brand new as is the DHW heat exchanger. Diverter valve has been refurbished with all new parts. Everything else appears to be working as it should. I am just wondering if the expansion vessel at the back has been damaged. Can't afford a new boiler at the moment. Any advice would be really helpful. As long as it has nothing to do with the gas i am confident enough to change out parts. Boiler is 19yrs old and only had two diaphrams perviuos to the new parts being fitted this year

 

[Gasguru]

You might want to check the gauze filter located in the front section of the return isolating valve.
Whilst you've dropped the pressure check the expansion vessel as per FAQs.
I assume you mean the pressure relief valve had opened (the red capped valve).
You will probably have to replace as it may continue to drip..cleaning isn't as straightforward as it seems (the opening pressure setting can easily be thrown out).

I would urge you to have the boiler properly serviced/checked. By this age there's every chance the flue has rotted out and the combustion could be unsafe.
It is also normal on these models for the combustion chamber cover spire clips to have corroded...another potential hazard if the chamber is no longer sealed.

 

[Torryloon]

Thxs for that. Already checked the filters all was okay (none blocked) With regards to the pressure release valve NO this had not opened. The water was pouring down the back of the boiler where the expansion vessel is located. Boiler was serviced 4 months ago and all was okay back then. Also just checked again. The flow pipe was cold, switched on heating again fired up and went out after 30 seconds but within that time flow pipe was that hot you could barely touch it. Possible it may be heating water to quick

 

[Torryloon]

Update on previous post. Just managed to get access to expansion vessel. Went to let a little air out and it is full of water. Looks like expansion vessel has failed