Hygena cooker hood circuit board

[Petemate]

Please see my post and replies under “Appliance Spare Parts Enquiries & Help”

Now the progress:-

Well, sorted it all now. Removed complete assembly, took it into the workshop and stripped out the electrics. Snipped the pink wire from the circuit board. Soldered a new wire to the microswitch output ( the tag with the blue wire on) fed this wire through the sleeving after pulling the pink one out. These wires then were extended out with the input wiring. Put it all together again, and wired in a fused supply socket with a 3 amp fuse in, next to the on/off supply socket in the cupboard above the hood, after refitting the hood assembly. Result? Fan still works, governed by the microswitch as before. Light comes on every time the hood is extended, and not affected by the seperate switch (who cares!) Now if a pesky bulb decides to commit filament suicide, only a 3 amp fuse to replace. Chuffed with the result.
I still can’t work out why the manufacturers feed the lights through a circuit board which is fed from a 13 amp fuse. It is a wonder that when the bulbs fail by way of an internal short, wiring doesn’t catch fire. Fair enough, the circuit board strip burns out but to my way of thinking it is a poor design which could easily be solved by having a low current fuse somewhere in the assembly. If I ever move I will be checking any future-owned hood for this set-up, and if necessary at least fit an in-line 3 amp fuse in the light feed.
FWIW
Pete

[kwatt]

Re: Hygena cooker hood circuit board

Hi Pete,

They do it because it has to be so to meet the safety standards and so everything is on the one circuit. Now you have two and, if the microswitch fails, which they do, you’ll have the lights on all the time and no way to switch them off without isolating the hood. Which really isn’t so clever on an appliance that’s getting wacked with steam almost constantly.

In short, it’s a bodge job IMO and, whilst it may well work practically for you, it’s highly inadvisable to alter the specification and we can’t condone it in any way.

You also have to consider the next few hundred people that read this and don’t have the skill, may fry themselves or the wiring colours are different or they could even be colourblind. Think how good you’d feel about your “fix” if someone got injured trying this, started a fire or even got killed.

It also will invalidate any warranty and, if I come across something like that in the field I walk away. I’m not risking my life with some mad modification and I sure ain’t going to risk a customers either.

K.

[Petemate]

Re: Hygena cooker hood circuit board

Hi Kwatt
Thanks for your reply. I fully realise that you are giving advice in good faith. However, I still cannot understand why a circuit is designed so that in the event of an internal bulb failure a strip of circuit board blows out. How can this be possibly considered a safe standard? In the case of the microswitch failing, I do not see that a hazard as my light circuit is now protected with a 3 amp fuse. We often leave the lights of the hood on during evenings as this gives a nice lighting for the kitchen area. With regards to warranty, our unit is now well over ten years old (probably why we cannot obtain the correct PCB)
With regard to others reading my post, I would expect that most of the users of this forum have a good knowledge of electrics and those who have not will seek professional advice. However, let me state for the record that I posted my solution mainly to highlight my opinion of the inadvisability of a light circuit being fed by a 13 amp fuse thus putting the PCB in jeopardy. I stand by this opinion.
Pete

[kwatt]

Re: Hygena cooker hood circuit board

Hi Pete,

I often advise people that assumption is the mother of all mistakes.

Perhaps not worded in quite the same manner, but same result.

To assume blindly that all visitors are competent to re-route and rewire an internal circuit is, at best, a fantasy I’m afraid. People will try stuff like this to save £25 on a PCB and, potentially, risk life and limb to save a mere £25. Personally I rate a life at more than that.

Those lights BTW are NOT designed to be used as mood lighting, they are designed for short-term use only. That’s why the PCB’s burn out in the first place more often than not as they are left on for hours on end and, if you do that, the holder will burn which is another possible fir risk. Either that or the plastic covers melt and, if it’s glass, the heat is transferred to the glass which subsequently melts the plastic holders for the glass.

I’ve been doing this for a few years and seen more than a few hoods in my time. 😉

K.

[Petemate]

Re: Hygena cooker hood circuit board

Hi K
Point taken regarding the lights not designed to be used for long periods. If I could obtain a new PCB, I would still wire in a 3 amp fuse. If you consider what I have done, I cannot agree that I have created two circuits – merely extended an existing one. There is still only one power input to the hood unit. I have just taken the feed to the lights from the switched side of the microswitch, thus divorcing the PCB light control. Upon your advice, we will now turn off the power supply on nightly retirement and not leave the lights on for long periods. Regarding the microswitch, I have had one of these to bits years ago and, correct me if I am wrong, but with the mechanical lever design I can’t see how one could fail in a way that would make the connection.
Our PCB failed when we pulled the hood out to switch the lights on. One of the bulbs had internally shorted. Now this may well have been the result of leaving the lights on for long periods, but the point I’m trying to make here is that I would not be willing to replace the PCB each time a bulb decided to blow the board when a simple 3 amp fuse is quicker and cheaper to replace.
I hope you understand my position and if you consider it necessary I am more than willing to delete my posts.
Pete

[kwatt]

Re: Hygena cooker hood circuit board

Hi Pete,

Microswitches do fail closed, the contacts effectively weld themselves shut, usually as a result of a short for whatever reason which is normally hard to fathom. It could be condensation, could just be arcing, but it does happen, often. I suspect this is why that the light power is normally routed through the PCB as then you have a triple safety, the PCB, the mains fuse and the microswitch. What you’ve done is to effectively do away with the PCB as a safety device as well as the main fuse to AC and rely on the switch which is dodgy IMO and a jury rigged fuse.

In the end that little switch is carrying 240VAC, I certainly wouldn’t trust it not to short. As an additional safety, fine, but as a primary… no.

I understand your position fine, well at least from my point of view anyway. That is, that you’d rather have faith in the single point of failure than the cost of a PCB.

Of course you also have the 3A fuse, but that won’t guard against heat or any other failure in the hood as it’s out of circuit, for example someone inadvertently leaving the lights on and going to bed.

I’m not saying that it would happen or that I agree with the safety that’s there, but I can see how it could become an issue.

If there was a fire or whatever and this was identified (there’s several fire officers that frequent the site that can answer this) then your house insurance would be worthless as well, you modified something that doesn’t comply with regulations so, you’re on your own as your insurer will disown you. But, trust me, those guys are VERY good at tracking down the source of an incident and they are legally bound to report their findings.

K.

[Petemate]

Re: Hygena cooker hood circuit board

Cheers K. All points noted. I still think that a 3 amp fuse is a better safeguard than a strip of PC material which made a HUGE bang when it blew, whereas a 3 amp fuse will blow in a “contained” manner. The small lamps in our houses all have 3 amp fuses don’t they? So why rely on a strip of PCB as a safety device? Also to say that the 13 amp fuse is one of the safety devices I cannot agree. A friend some years ago had a small table lamp bulb short and blow its fuse. The fuse in the plug was a 13 amp one. It went off with a horrendous bang and illustrated that 13 amp is not suitable. The burnt mess at the back of our PCB also illustrates that it was also not a good item to regard as a safeguard.
All the above IMHO of sourse.
Regards
Pete

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