gas boiler not firing; immersion->boiling water in cold t

[tinsel]

I recently moved into a new (by that I actually mean old Victorian) house with both a 10-yr old gas boiler (Potterton Suprima) and a regular immersion heater. A couple of days ago I tested the central heating (which initially worked fine) but now the boiler is refusing to fire (red flashing light even after pressing reset button) leaving me with no hot water and no heating. I then decided to use the immersion heater, which I left on for a couple of hours before stepping into the shower this morning... well, as soon as I switched on the shower, I heard this loud thumping noise coming from the attic above. I went up to have a look, and the pipes were shaking violently, with boiling water running into the cold tank. I immediately went downstairs and switched off the power to the immersion heater, and ran the shower until the water ran cold, so as to drain all the hot water out of the cold tank.

How likely is it that these problems are related? Or am I just incredibly unlucky? Could the problems be caused by air in the system from not bleeding the radiators before testing them? I am assuming that the problem with the boiling water flowing into the cold tank has to do with a faulty thermostat in the immersion heater, but could this alone stop the gas boiler from firing? (The gas boiler won't fire, even 15 hrs after the immersion heater has been switched off)

Appreciate any advice you might have. And yes, I am planning to call out an expert, but I would like to have some idea of what might be causing the problem(s) before he/she comes out. Thanks all!

 

[Slugbabydotcom]

I just skimmed through your post as it sounds like the now famous suprima PCB part number 5111603.
Just do a search . Theres loads about it on here.
Last I heard was that Potterton were replacing these free of charge after they got a good dressing down on BBCs 'Watchdog'

 

[tinsel]

Thanks. I have already read reports about the potterton boilers, and called them up (299 pounds to fix as more than 10 yrs old) but surely that wouldn't explain why there is boiling water feeding into the cold tank in the attic when we use the immersion heater (with the gas boiler switched off)? Can it really be a coincidence that the gas boiler and the immersion heater packed up on the same day?

 

[Slugbabydotcom]

The thermostat in your immersion heater is either wrongly set or more likely knackered. It is likely that this was the case long before you had the boiler problem and they are not related.
New ones are cheap and have a reset button in case they fail.
Just make sure you get the right size stat for the job.