Ferroli 100FF Boiler

[trap0001]

Boiler won't start - relays all chatter like there's AC going through them - scoping relay coils reveals there is! 24V supply OK. Apparently this is a common Ferroli main pcb problem (which is actually manf by Honeywell).

Anybody have any clues what this could be or perhaps a schematic for the main board. A repl PCB is nearly £200 which considering what is on the board (handful of op amps and 4 relays , no intelligence at all) is actually nothing short of licensed theft!

 

[lagunaglen]

If your unsure of fault and cant get hold of literature then call technical , if your competent to do so, if not get someone who is?
Usually pay less than that for ferolli pcb though, but we have accounts and spend lots !

 

[tonybhoy]

Price of a gas valve ign module for a Maxima which is also made by Honeywell is about £185 inc vat (trade).

 

[Agile]

Its a little at variance saying the relays are chattering and you have 24 v across the operating coils!

Was the 24v DC ?

How else could the relays chatter unless the 24v supply was being interrupted or was raw DC ?

Did you look at the ripple on the supply rail to see if the main smoothing capacitor is failing?

Tony

 

[trap0001]

Its a little at variance saying the relays are chattering and you have 24 v across the operating coils!

Was the 24v DC ?

How else could the relays chatter unless the 24v supply was being interrupted or was raw DC ?

Did you look at the ripple on the supply rail to see if the main smoothing capacitor is failing?

Tony

The +24V supply across the main res cap is clean. There is AC going getting to the relay coils. But there is an AC tap being fed into the main circuits so it is difficult without a schematic to establish where the bad AC is coming from.

 

[Agile]

Sometimes the relays are fed from ac with a series diode and use a capacitor across the coil so the coil inductance and the capacitor create a smoothed DC. That diode can go short circuit and the capacitor rapidly fails within seconds. Easy to trace that fault with a scope though.

Most though use the 24 VDC rail and are switched by a transistor with a reverse diode across the relay coil.

Are you using a floating battery operated hand held scope?

Boiler PCBs can use some odd circuit techniques like leaving the fan live and switching the neutral connection.

Tony