BIASSI M90F 24S Pops PSU fuse intermittently

[Adrian244]

Hi all,

My Biassi combi boiler M90F 24S has developed a liking for 1.6Amp fuses on the main board.

It seems to pop the fuse about once a week and usually first thing in the morning when the heating comes on. Apart from the fuse prob everything seems to work fine otherwise. No undue noises etc.. slight hum from the windings on the transformer in the PSU but that could be normal.

As my system is unknown, new house and I'm in the middle of replacing a few rads I surmised it could be a sludge prob overloading the pump. So on the weekend I ran cleaner in the system for 8 hours then flushed it all through for ages before it came clean, then added inhibitor.

My CH waters now fresh and clean and this morning the fuse has pop'd again...

Before I start throwing money at it can anyone suggest something to try?
I'm still suspecting the pump?

I understand electronics so not afraid to get stuck in...

Cheers for any advise

 

[Agile]

Its almost certain to be the pump. Probably because water is leaking into it. But there are other more rare causes.

I would advise you power the pomp externally through a 3 A fuse and see what happens then.

A stalled pump takes little more current. A faulty pump might show a rsistance to chassis. The main winding might show a different resistance to normal but knowing exactly what its likely to be is a problem. Its typically about 180 ohms but thats not the exact figure and depends on the exact pump model fitted.

Tony

 

[Adrian244]

Thanks Tony for the reply.

I have noticed water dripping from the pump onto my worktops. I suspected this was leaking from the mounting flange due to pressure build up (my sludge theory)

But if water can leak into the pump windings then I guess that could be the water I'm seeing coming from plastic housing...

that's something I can look at later...

 

[Agile]

The water will probably be leaking from the front screw and running down the inside of the motor.

I expect you thought you were bleeding the pump and ended up spoiling it.

Tony