Anybody had a PCB blow after turning a boiler off and back on again?

[Bev GG]

An engineer attended a boiler in my mothers house yesterday and he tried to convince me that turning off the boiler and turning it back on again was likely to blow the PCB. He also claimed that sometimes heating the relays on the PCB would make it work again. I spent 20 years as a field service engineer working on washing machines, dishwashers, tumble dryers and cookers and have never had a PCB blow after turning a machine off and back on again. I am also experienced with electronics and find it impossible to believe that heating up relays can make a PCB work again. In fact what the engineer was heating was the power module on the PCB, not a relay. By the way it is a Viessmann W100 WB1B system boiler.

 

[gmartine]

I doubt Viessmann would approve, how was his visit concluded?

 

[Bev GG]

I doubt Viessmann would approve, how was his visit concluded?

The engineer claimed that the heat exchanger was blocked and that the cause was the system being filled through a water softener. Viessmann technical say that their heat exchangers are stainless steel so would not be affected by softened water and in fact recommend filling the system with softened water in very hard water areas. The company have contacted me to say that the heat exchanger is obsolete / no longer available and have quoted to replace the boiler. Viessmann direct spare parts told me that the parts are available for this boiler.

 

[Chuck]

Depends what he meant by 'heating the relays'. The soldered joints associated with a relay can fracture after a long period of operation because they are vibrated every time the relay operates. If arcing hasn't caused too much damage 'reheating', i.e. desoldering, the joint may fix the problem or, at least, reset the clock before it happens again.

Boards often do seem to fail at power up but this is not cause and effect. A fault can develop while the board is running normally but only manifest itself when the board is cool and/or under startup, e.g. in-rush, conditions.

 

[Deleted member 120897]

Yes, I’ve not had it personally, but believe pcb’s can blow when power is turned off on and back on. Could have heated using a hairdryer, which may sound daft, but believe to work too, again, not something I’ve done personally.

 

[SimonG]

Yes, circuit boards can go when switched off and back on again. Haven't seen it on an oil boiler but was doing a bathroom when somebody came out to service the glow worm in the property. Turned it off, did what he needed to do, and then turned it back on and poof, pcb gone.

 

[gmartine]

Never seen it but PCB fuse would've protected it surely?

 

[SimonG]

Never seen it but PCB fuse would've protected it surely?

Not on the one when I was there. Bloke said it blew the board.
I know the older worcester oil boilers have the fast blow fuse as I carry a little packet of them in the van and always first port of call when no power.
Don't do gas so don't know about on board fuses.

 

[Deleted member 120897]

Never seen it but PCB fuse would've protected it surely?

I thought this, but have heard about it from other sources (another forum) and they mentioned earlier Glow worms, which might be the one @SimonG is on about, and they never mention pcb fuses, just a new board I think.

 

[EvilDrPorkChop]

Only like the PCBs in the Worcester Fans. Turn the power off and back on, and sometimes the fan is kanckered. You can heat them up with a hair dryer, and it will get them going sometimes - Rare though usually new fan.