Cooker hood circuit board keeps frying

[sven]

Hi, I am looking for a bit of advice on what may be causing the cooker hood circuit board to stop working.
In four weeks it has blown twice, at £50 delivered a go. The hood is a Designair FGHD60ss,sealed ducting to outside, it is connected via moulded 13amp plug to socket in stainless steel chimney area(not exposed to moisture) connected to fan isolation switch, then to kitchen ring main. The ring main is protected by a 63a RCD. I believe that it is caused by the switching of the 45A cooker switch which is on an unprotected circuit. It seems to have blown the circuit board next time I tried to use the hood. Question is, is there something that could/should be inline to the cooker hood/45A cooker switch. I don't want to spend another £50 for it just to go pop again. But I am also considering bypassing the circuit board and just using the fan isolation switch to turn it on and off, basically just having a single speed fan. It may just be the the cooker hood is of a poor design/reputation.
Any ideas would be helpful. sven

 

[Marvo]

There's lots of possibilities, could be steam or condensation getting to the PCB or it could be something that's controlled by the pcb that's got a fault and is in turn damaging the PCB output. Do the two damaged PCB's show any signs of burning/moisture/flash damage? Could even be blocked vents or something else that's causing overheating.

 

[Octopus]

Hi, I am looking for a bit of advice on what may be causing the cooker hood circuit board to stop working.
In four weeks it has blown twice, at £50 delivered a go. The hood is a Designair FGHD60ss,sealed ducting to outside, it is connected via moulded 13amp plug to socket in stainless steel chimney area(not exposed to moisture) connected to fan isolation switch, then to kitchen ring main. The ring main is protected by a 63a RCD. I believe that it is caused by the switching of the 45A cooker switch which is on an unprotected circuit. It seems to have blown the circuit board next time I tried to use the hood. Question is, is there something that could/should be inline to the cooker hood/45A cooker switch. I don't want to spend another £50 for it just to go pop again. But I am also considering bypassing the circuit board and just using the fan isolation switch to turn it on and off, basically just having a single speed fan. It may just be the the cooker hood is of a poor design/reputation.
Any ideas would be helpful. sven

Dam return key isn't working. As you sure about this. Sounds like you need to get a competent spark round.

 

[sven]

There's lots of possibilities, could be steam or condensation getting to the PCB or it could be something that's controlled by the pcb that's got a fault and is in turn damaging the PCB output. Do the two damaged PCB's show any signs of burning/moisture/flash damage? Could even be blocked vents or something else that's causing overheating.

Thanks for replying Marvo


No Damage apparent, it is the button board. no marks whatsoever on it, I was assuming it maybe some kind of electrical spike in operating the 45A cooker switch that did it. I don't normally turn it off, but both times the hood has failed I have used the 45A switch. I was hoping it would be a case of inserting a suppression inline somewhere.
I think I might have to bypass the board and go for single speed, turbo stylie.
Gut says its not anything that controlled by the board ( and I have a big gut )

 

[sven]

Dam return key isn't working. As you sure about this. Sounds like you need to get a competent spark round.

I will make sure it is safe before I do it, as far as I can see the button board operates the lights and fan speed. may add a rheostat but definitely a transformer, switched on by the fan isolator. I cannot afford to just keep bunging new button boards into the hood.
Just posted for ideas, it must just be I've two faulty boards but they were working.

 

[Marvo]

You can test the transformer on the board and you can dismount the 4x relays and test them. All these components are replaceable with off-the-shelf items from RS Components or Farnell. There's some SMD's on the back that are also testable if you have some electronics knowledge. Maybe if it's outside of your skillset you have a friend who could help you.

You could add some surge arrestors into the appliance or at the isolator or even the CU but this might be better done by someone with experience. The best thing to focus on is finding the root cause. If the isolator shows signs of excessive arcing when it operates then replace it. It would also be worth running the usual barrage of live and dead tests on the circuit.

 

[DPG]

Going to be a nightmare testing that surface mount IC on the back - and this is probably the most susceptible to spike-induced damage item on the PCB. Daz

 

[benji]

ringmain protected by 63a rcd ???

 

[DPG]

ringmain protected by 63a rcd ???

Good spot. Must be a typo surely? Daz

 

[telectrix]

probably a 63A, 30mA RCD.

 

[DPG]

Wonder why it needs 4 relays ?? Daz

 

[Silly Sausage]

Wonder why it needs 4 relays ?? Daz

For switching 4 speeds?

 

[telectrix]

or 3 speeds and 1 light.

 

[DPG]

Antiquated and clumsy method of speed control these days that. The IC would be better off driving a triac - component cost would be much cheaper then, and life of product would be longer. Daz

 

[pjcomp]

What fuse is in the 13A plug? Hoods usually only need a 3A or 5A - if it's a 13A and it's not blowing it might not explain the cause of the problem but a lower-rated fuse might at least protect your board.

PJ