Car forums lol

Off work with a bad case of leprosy and found this "circuit breaker " on a car forum.

I wonder...

looks legit

really!? 

I thought it looked like a contactum DP isolator???

As a functional isolator, to be used 'off load' (and not knowing what the load is, though suspect Barry Boys style car hifi) I have seen far worse.

However, if it was mine, I would have a terminal mounted megafuse and a hell of a lot more downstream overload protection myself...

But isn't that AC rated,?

and not DC,,,,,

steptoe said:

But isn't that AC rated,?

and not DC,,,,,

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Wouldn't matter at that low a voltage. 

Rob. said:

Wouldn't matter at that low a voltage. 

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It's the amps I'd be concerned about, not the voltage,

Volts jolt

Current kills

But, i don't know tbh, I've always used DC switches on DC

Rob. said:

Wouldn't matter at that low a voltage. 

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In what sense?

I'd imagine still not an issue unless regularly switched on-load.

he's probably using it as an MCB. well it does say 100A on it, in the same was some people think a 40a 30mA RCD will trip at 40a...

steptoe said:

It's the amps I'd be concerned about, not the voltage,

Volts jolt

Current kills

But, i don't know tbh, I've always used DC switches on DC

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Lurch said:

In what sense?

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The current carrying capacity is exactly the same AC or DC. 

The reason items of equipment come with a DC rating is due to the nature of DC. It likes to produce an arc when broken under load. So DC rated equipment usually has larger contact separation or forms of arc quenching. From those batteries at 12V possibly 24V DC the seperation in the contacts will be more than good enough to extinguish the arc. 

Andy™ said:

he's probably using it as an MCB. well it does say 100A on it, in the same was some people think a 40a 30mA RCD will trip at 40a...

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Oh probably, a bit like (years ago admittedly) the plumber who was doing my alarm customers rewire that fitted a 100ma RCD because 'the trade counter had an offer on, and that's got to be better than a 30, hasn't it?'.

I don't know why, but it reminds me (if you've ever seen one, you'll know what I mean) of those fish frying ranges that had a Wylex board fitted at the factory as a distribution block!

25A for the elements, 16A for an aux socket, 6A for the light, etc... As it was a factory fitted item to a fixed appliance, we were never quite sure how to document them on an inspection.

Rob. said:

The current carrying capacity is exactly the same AC or DC. 

The reason items of equipment come with a DC rating is due to the nature of DC. It likes to produce an arc when broken under load. So DC rated equipment usually has larger contact separation or forms of arc quenching. From those batteries at 12V possibly 24V DC the seperation in the contacts will be more than good enough to extinguish the arc. 

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Rob, I'm sure you're a very intelligent bloke,

But, have you seen the size of an arc an even small DC welder can hold at <48v (that's what mine puts out), it's certainly iro 4or5mm , if not more.

steptoe said:

Rob, I'm sure you're a very intelligent bloke,

But, have you seen the size of an arc an even small DC welder can hold at <48v (that's what mine puts out), it's certainly iro 4or5mm , if not more.

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Don't get me wrong I know this. 

Just having used MCB's for years in control circuits, (Yes I understand the current is a lot lower) after speaking with technical from most major MCB manufacturers, they all informed me that at 24V DC the MCB's were fine to be used on DC.

Certainly when I owned a narrowboat, I went through 2 quality, remotely switched contactors in ten years (made for low voltage, high current marine use in New Zealand not China) which I can only assume were due to arcing, despite the fact they would only ever have been separated at low-load, i.e when the boat was fully stopped, engine off, equipment off and about to be left for a week or so.

datadiffusion said:

As it was a factory fitted item to a fixed appliance, we were never quite sure how to document them on an inspection.

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if its part of the appliance then its not covered by 7671 so your I&T ends at its supply

Andy™ said:

if its part of the appliance then its not covered by 7671 so your I&T ends at its supply

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I, personally, always thought that - we had 4 smaller chippies on the books all with all-electric ranges - the same model.

Various inspectors had differing views, the owner of the firm was never 100% convinced by me, you can never bloody win though can you.

Anyway, long part of history, although to my amusement one of the shops is unchanged down to a screw since I last did any

work there nearly 17 years ago. I used to often drive past there, funny enough until I got rid of aforementioned narrowboat above,

but probably will do again when my other half moves back to her old employer!