Ferolli Modena 80 problems after changing thermsistors

[Zack1uk]

Hi

I have just changed the thermsistors on my boiler due as I was constantly having to reset it in order to keep the CH on.

However, although the boiler now fires up, it runs for about 30s then makes an incredible clanking / popping noise seemingly from the pump / pipes at the bottom of the boiler. At this time the pressure rises to about 3 bar, but is very eratic (actually fluctuating between 2.5 and 3 bar). It then shuts down and goes into standby, requiring a reset to get it going.

I have bled all the radiators and released teeh valve on the top of the pump, but it still does it.

I thought at one point that I had sorted it as it ran fine for about 3 mins. I then turned the HW tap on, ran some hot water. Within seconds of turning it off the noises started again and the boiler went into standby (with the red ignition light on in the middle of the panel)

I'm not sure if its relevant but I noticed that when I drained the CH system down, I only got half a bowl of water.

I'm guessing that there must be an airlock somewhere, but I can't figure out where for the life of me.

Any hints, tips or fully fledged solutions are greatly appreciated.

Thanks.

 

[Bonesy60]

Might seam like a stupid question but did you close the isolating valves on the flow or return pipe under the boiler and if you did did you open them up fully.

 

[bengasman]

first thing i thought, it sounds like the heat is not dissipated and the water in the boiler is literally boiling.
same thing would happen if the pump does not run