Boiler throwing trip - suppressor?

[chris-s]

The last couple of days, our boiler has been throwing the trip. It's an 'older' boiler, a Stelrad Ideal W. Being older it's easy to diagnose and fix I hope!

I've traced the problem to the boiler, and on opening the small 'control' box found the thermostat control, a suppressor and the electrical connections to the solenoid valve, simple!

When power is applied, the valve opens briefly and there is an arc between the two solenoid connections which throw the trip.

So, whats the most likely cause of this? Although the supressor looks visually ok could it be the cause?

Cheers

Chris

 

[gas4you]

I would suspect the gas valve/solenoid.

You need to check the resistance across the terminals with the wires disconnected, using a multimeter.

 

[Agile]

I would be looking at the arc !!!

Tony

 

[chris-s]

Thanks for the replies guys.

I got a reading of 3.5K across the terminals, is that good or bad?

Would a faulty suppressor cause this kind of arc? I know inductive currents can be quite high, but it suprises me that a faulty supressor would be having this kind of effect.

Chris

 

[ChrisR]

3k5 is probably ok.

A solenoid coil creates a high voltage when it's switched off, which can cause a spark, and the supporessor is there to absorb the energy. If the suppr is missing you don't usually get a spark, but you do get interference with radios etc.
SO where exactly is the spark?
If it's live to earth, that would blow an earth leakage type trip.

 

[chris-s]

If you are familiar with a 'Honeywell' gas valve similar to this...

...there are two spade terminals on the valve assembly to which the thermostat/mains is connected, the arc is between these two terminals. The connectors are mounted on a plastic base, slightly recessed, and at the closest point are separated by a gap of about 1mm.

I'm sure if the terminals were more insulated, then there would be no arc, but there is obviously something amiss here somewhere.

So, if the suppressor is just really for noise suppression, then guess there must be an electrical fault with the solenoid.

It is definitely not a short to earth, you can see the arc points on both contacts plus the earth trip isn't being thrown, just the fuse.

Chris

 

[chris-s]

SOLVED!!!

I got some decent time and light on the situation and found a water leak that was dripping ever so slowly from up inside somewhere onto the valve assembly and then seeping down over the connections and BANG! Funny thing is it only dripped when it was running.

Got a temporary fix in place to just divert the drips until I get chance to strip the cover off for a proper look.

Thanks for all your assistance, a great forum and no doubt I shall be back again in the future.

Chris