GAH Electric Boiler Controller 10 fuse holders burning out

[martinxxxxxx]

Has anyone had any experiance of the pcb on this equipment charring near the fuse clips. The fuse protects a heating element which draws 14.3A. But as far as I can tell the fuseclips are only rated for 10A, the manufacturer understandbly denies any design fault or liability and I quote "This problem only happens in areas of the country where there is low voltage as this causes increased current on the fuseholders".

Untitled

• martinxxxxxx
• 11 Dec 2010
• 1

Untitled

• martinxxxxxx
• 11 Dec 2010
• 1

Opinions welcome

Martin

 

[Adam_151]

Is the heater a simple resistive load? or is there more to it than that? If its simply resitive then the current drawn will decrease rather than increase with lower supply volatages

Also might be worth checking your mains volatage at several times of day, equipment designed for the uk market should function with voltages in the range 230v +10%/-6% (might be +/- 10% now)

If the maufacturer won't gove you any joy, are you able to fit a heavier duty fuse holder in there

how much room is there in the casing? assuming the client is pressing you for a solution and the device is outside of its standard warrenty period....


Its not made in china is it? some of the stuff that comes out there is possivly shocking!

 

[holmslaw]

..

 

[martinxxxxxx]

Yes I was a bit shocked to have ohms law explained to me incorrectly too. I went on to ask him what the current would be if the element is 16ohms if the supply voltage dropped to 200V. He went silent and talked about the fact that the problem had mainly occured around the olympic village.

 

[bernardgreen]

Wearing my PCB designers hat....

Those clips are possibly totally un-suitable for a 10 amp fuse in a critical application.

I would never use them for anything above 5 amps. And some clients will not accept them for more than 2 amps.

There are similar fuse clips but made using berylium copper as the material to ensure they remain "springy" and still able to grip a new fuse after being over heated by a slowly blowing fuse. These are seldom used on commercial equipment as they are more expensive.

http://uk.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=7032798

The printed circuit design and manufacture is almost always put out to sub-contract companies with cost minimisation a major consideration and this compromises the standard of components and assembly.

For fuses above 10 amps I would use a moulded fuse holder and, where possible, mount it remote from the PCB. For one client I did replace PCB mounted fuses with front panel mounted fuses after a burnt fuse holder destroyed a PCB.

"This problem only happens in areas of the country where there is low voltage as this causes increased current on the fuseholders".

An indication of the the manufacturer's lack of technical knowledge. ( unless of course the heaters automatically change their resistance to maintain a constant wattage irespective of applied voltage ).

 

[Adam_151]

Their could be any number of reasons why resports are centered in any one paricular area:

Higher than permitted supply volatage is the obvious one. But other causes could be a batch of fusecarriers with pariculaly weak springs which ended up in a batch of products which went to a major wholesaling chain in that area, word of mouth, if one spark attends a problem with one and repairs it, he may consider it a one off, if he gets chatting to others down the wholesalers and another has had the same issue, then others there will recall the conversation if they ever end up at a similar fault and more likely to complain.

What was the role of the person you were talking to? I assume some kind of help desk person?

 

[TicklyT]

If it's running a resistive load, the (over)load may be less with a lower voltage, but it will continue for longer, so the amount of energy dissipated through that fuse holder should be about the same for each working cycle.

 

[martinxxxxxx]

The customer has obtained a replacement board from a distributor for a whooping £350 plus Vat.

I think, as Bernard indicates, that the fuse-holders may be being used in a situation which is outside of their design parameters. If that were to be true then one would expect them to be notorious in their unreliability. Hence my posting.

The latest boards made by the company no longer have the fuses for each of the heating elements. Which could be a clue to previous performance of the product.

Maybe I should ask to have this thread to the plumbing forum?

Martin

 

[bernardgreen]

Martin

I have put a comment on your home page.

Bernard