PCB Fire!!!

[frontshop]

Hi Everybody

Can anyone help, for nearly a year now I have been trying to find out why my dishwasher set on fire! I have narrowed it down to the relay HF3FD fitted on the Flextronics PCB that I feel is underrated for the potential failures during the dishwasher operation. If anyone out there can shed further light on this matter please help me, you can view my findings and pictures here:

dishwasherfire.blogspot.co.uk

Advanced thanks for any help

 

[jnnewton]

What is the output of the relay switching? If you know the load, it should be fairly easy to determine if it's underrated. From the looks of the one picture i saw on that blog that doesn't seem to render properly in firefox, It seems there is a blue capacitor, possibly an AC film cap? It looks like it might have blown out the bottom. What is the cap, and what is the voltage / current applied to it? Ripple current on that cap could be an issue.

 

[Dr_Doggy]

also suspecting relay, could perhaps moisture inside, mechanical wear/failure, be the cause, i agree it goes back to the relay since you can see the flame starts there, and relays are notorious for sparks arcs, and inductive kicks.\\
i cannot tell furshure but are those 2 puncture holes on top of relay?


... another suspect would be whatever is in the bottom corner of the board since it looks like most of the flame hit there, from here it looks like it almost burned through, also the big black thing next to the big blue thing(the relay i presume), looks as if the flame was traveling up along the outside of the bottom, thus meaning the point of ignition was exterior to the relay, relay is probably rated ok though(not that i checked, i just trust)

pulling this up, i have a feeling its yours
**broken link removed**

judging by alignment with flare i'm now more to say that it was a fault on the main prongs which caused arc then ignition, and fuel: surface looks clean so i doubt grease/oil or dirt buildup, however the plastic could have burned as fuel if it was heated enough, which suggests you had current surge, which indicates somehow a short circuit, and not likely a bad relay.
more likely the prongs or the plug was the failure... maybe a heat buildup in atmosphere to decrease resistance(?)



.....btw im not a pro at anything, this is just my guess

 

[electroyas]

Fire when too much heat due to many reasons

If there was a fire it may becuase of over heating of some circuit element beyond operating condition. Then it could lead to break down of that element and cause some short circuit. If no proper fuse for the circuit then it it could lead to many damages and disasters.

 

[dr pepper]

If the fault was on the board then I'd be suspecting spark suppression components around the relay as mentioned, however the fault might not be on the board, you could be looking at effect rather than cause, there could be a short in one of the pumps or heater, or also quite likely a wiring loom has rubbed through and shorted to ground, this happened to my washing machine last september and it too blew a hole in the board, and yes it was also a hotpoint.

 

[frontshop]

Hello Everyone

Thank you for your replies. The reason I thought it was the relay was due to the same relay been present in various Bosch dishwashers that have also failed in the same way around the same relay but on a different PCB.

I also know that Hongfa made another relay that on their site says it was to replace the HF3FD. This was the HF3FA which they started manufacturing in 2009 the changes were to the Dielectric strength which was increased to 2.5KVA also the HF3FA no longer uses AgNi and only has AgSnO2 present on the contacts which I believe has a higher melting point.

dishwasherfire.blogspot.co.uk

 

[frontshop]

Hi Dr Pepper, Thanks for your reply. Just out of interest what model washing machine was it?

 

[kinarfi]

I have never been a real fan of spade connectors, if put on wrong, the loosen and make a poor connection which generate a little heat which causes a few more mΩ which creates more heat which causes corrosion and more mΩ and more heat and eventually a melt down or fire. I've seen it more times than I care to have seen. It's also possible that the solder joint on the under side of the board got damaged during assembly.

 

[dr pepper]

It was a WD81 I think, WD something anyway, I got it in 2002 and it lasted till 2012 so no complaints on longevity.

The water pump from it does a good job of watering my plants in the greenhouse.

 

[frontshop]

I agree totally with you kinarfi the fact that such spade connectors are present on such a small flimsy PCB in my view is asking for trouble

DISHWASHERFIRE.BLOGSPOT.CO.UK

 

[frontshop]

Thanks for the reply Dr Pepper

I have just added to my Google map at DISHWASHERFIRE.BLOGSPOT.CO.UK
I am amazed that there has been 45 dishwasher fires that the Fire Service have had to attend so far this year. I'm sure that there are more that I am unaware of. It's a frightening fact that they all seem to be failing over the last couple of years, also I appeared on the ITV Tonight programme on the 4th of July (a great date for the US of A) It is unbelievable that currently in the UK there are 2 million products that have been recalled and out of that 2 million only 1 million have been located!!!