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 The company have contacted me to say that the heat exchanger is obsolete / no longer available and have quoted to replace the boiler.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.

 

[Timmy D]

I’ve had it happen on a Vaillant. Zero water on the pcb. Powered down and back on and poof, dead board. Typically happens when there’s been a leak in the boiler and inside the boiler is humid.

I have also then used a hair dryer to heat the board for maybe 20 secs and the boiler then turned on.

 

[Bev GG]

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.

To clarify the engineer claimed that heating the relays with a hairdryer would often make a dead PCB work again, not re-soldering the joints'
When you say often, could you elaborate with how many years you have been working on boilers and how many times that you have observed PCB failure at power up. Thanks.

 

[Bev GG]

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.

Thanks for the reply. Out of interest how many years have you been working on boilers and never had a PCB blow when turned off and back on? As for heating the relays, yes it does sound daft, any suggestion as to why you believe that it might work?

 

[ShaunCorbs]

I’ve had loads had one gloworm hxi and vaillant eco this week due to power networks upgraded shutdowns also had a few Worcester fan pcb blow this year when we had the cold spell

3 months ago I had an old Worcester Cdi turned it off to do a diverter valve replacement turned on and wouldn’t work due to being off for 2 hours

 

[Deleted member 120897]

Thanks for the reply. Out of interest how many years have you been working on boilers and never had a PCB blow when turned off and back on? As for heating the relays, yes it does sound daft, any suggestion as to why you believe that it might work?

I’ve been working on boilers for about 5 years now and only had the pcb fuses blow, not the actual pcb, but our housing stock although quite vast has the same type of boiler. I think I might have had one actually blow, but that was due to a wiring fault, not turning off and on again. It’s what I’ve read/heard about, not done personally. I have used a hairdryer on a boiler once, but it was to dry the wiring harness following a leak.

 

[Scott_D]

Yes, I have had a worcester fan pcb and Vaillant Pcb go

 

[Ric2013]

I am relatively inexperienced but it happened to me on a Glow-Worm heat-only boiler. Turned it off to convert system to Y-plan. Fired system back up; all radiators getting hot; lagging a pipe; re-fixing a floorboard; then cough and splutter and it died. Luckily it was a mate's house, and when the RGI came and said it was just an old, shoddy, boiler that just didn't want to be switched off, my friend said it was all fair enough and got it replaced as it was also leaking.