Testing MCBs

[SJD]

Much though I don't like it, once in a while I use a second hand MCB - for one that has long since gone obsolete and new ones are unavailable. What about testing used MCBs before reusing them, does anyone actually do this?

I just tested a 5A MCB at a couple of values of loading, it seemed to more or less follow the curve in the BGB - for example, at 12.5A, it reliably trips after approx. 25s. I'm thinking this is all I can practically do.

NB: For a much larger rated MCB, even this would get tricky, I don't have readily available loads.

 

[LeeH]

Don't go there, it's well out of a sparks remit.

The machine will probably be the same price as a Porsche.

 

[SJD]

Don't go there, it's well out of a sparks remit.

The machine will probably be the same price as a Porsche.

Umm what machine, can you elaborate?
I'm testing using a spare CU on the bench, some loads (e.g. kettles & toasters) and a stopwatch!

 

[LeeH]

Just thinking about this out loud, I'm sure someone will correct me if I'm wrong.


Say a D40 60898 requires testing for instantaneous disconnection. That's x20 In? 800A?

Not to be done in ones shed.

 

[SPARTYKUS]

LeeH is right its expensive. Can't remember its name but the learn-ed chap who enlightened me may well post.

 

[Marvo]

For smaller MCB's like 1A - 10A you could just apply an appropriate load and test the curve of the thermal operation, for larger values you'd need to invest in a current injection unit. Problem is though you won't be able to test the disconnection times of the mag operation under fault conditions.

I'd say it wouldn't be acceptable to use second hand MCB's at all to be honest.

 

[SPARTYKUS]

Current injection unit!!!

 

[SJD]

I'm really only interested in domestic MCBs, so mostly type B, but even then I know I don't have the current to test at 5x rating for the higher values like 40A or 32A. The post was more to ask is anyone actually doing any testing at all in these circumstances, and if so, what.

 

[SJD]

For smaller MCB's like 1A - 10A you could just apply an appropriate load and test the curve of the thermal operation, for larger values you'd need to invest in a current injection unit. Problem is though you won't be able to test the disconnection times of the mag operation under fault conditions.

I'd say it wouldn't be acceptable to use second hand MCB's at all to be honest.

I really don't like to use second hand MCBs (it is rare that I do), and I certainly don't like the thought of using one without at least some testing.

You can find a huge number for sale on the likes of eBay. Some sellers describe them as removed from a working board, occasionally a seller will say they are tested but whether that is actually the case or not is difficult to verify. There must be people out there buying and using these, or they wouldn't be the market there is for them.

 

[Silly Sausage]

And how would you measure the trip time with any reasonable amount of accuracy?!
1: assume they'll operate as specced
2: don't buy 2nd hand gear that you don't know its history

 

[Geordie Spark]

How much do you pay for brand-new MCBs anyway?

 

[uksparks]

I have used a second hand breaker once to feed a sub board for a shower, the board was too old and had to go down the used route, only option, I'd prefere not to, but sometimes you have to.

 

[Marvo]

....... occasionally a seller will say they are tested but whether that is actually the case or not is difficult to verify.

I don't see that helping you if there's ever a comeback because one of them failed to operate when it mattered. If they'd been tested to any relevant standard they'd come with a certificate.

 

[Geordie Spark]

It sounds a bit like buying a box of matches with a label on telling you that every match has been individually tested.

 

[Silly Sausage]

Like those 2nd hand johnnies...

 

[Geordie Spark]

Like those 2nd hand johnnies...

We all bow down to your obvious superior knowledge on that subject :38:

For sale. Only used once by one careful owner .............

 

[Silly Sausage]

We all bow down to your obvious superior knowledge on that subject :38:

Well, with three kids, I'm beginning to think they're not entirely reliable.

 

[Engineer54]

You would need a primary injection set or a decent MCCB/Breaker tester to fully test a MCB with any accuracy, and as someone has already pointed out, they DON'T come cheap!!

Have a look in ''Test Meter'' product range, you'll probably find one or two lurking around in there.
We use the Megger PCITS 3000-2 (comes in 2 sections) to test our ACB/GCB's's and current relays etc, and that cost around £10K 6 or so years ago. We made up our own current test leads, or you'll be paying something like £1.5K per lead (£3k for both)!! Expensive business what, but you will get 5% discount from our sponsor!! lol!!

So best policy is, if you suspect a malfunctioning MCB, replace it with a new one for the cost of a few quid, you know it makes sense!!.... lol!!

 

[Former Sponsor TM]

You would need a primary injection set or a decent MCCB/Breaker tester to fully test a MCB with any accuracy, and as someone has already pointed out, they DON'T come cheap!!

Have a look in ''Test Meter'' product range, you'll probably find one or two lurking around in there.
We use the Megger PCITS 3000-2 (comes in 2 sections) to test our ACB/GCB's's and current relays etc, and that cost around £10K 6 or so years ago. We made up our own current test leads, or you'll be paying something like £1.5K per lead (£3k for both)!! Expensive business what, but you will get 5% discount from our sponsor!! lol!!

So best policy is, if you suspect a malfunctioning MCB, replace it with a new one for the cost of a few quid, you know it makes sense!!.... lol!!

Every little helps!!

 

[ipf]

You would need a primary injection set or a decent MCCB/Breaker tester to fully test a MCB with any accuracy, and as someone has already pointed out, they DON'T come cheap!!

Have a look in ''Test Meter'' product range, you'll probably find one or two lurking around in there.
We use the Megger PCITS 3000-2 (comes in 2 sections) to test our ACB/GCB's's and current relays etc, and that cost around £10K 6 or so years ago. We made up our own current test leads, or you'll be paying something like £1.5K per lead (£3k for both)!! Expensive business what, but you will get 5% discount from our sponsor!! lol!!

So best policy is, if you suspect a malfunctioning MCB, replace it with a new one for the cost of a few quid, you know it makes sense!!.... lol!!

Clunk clik every trip