mcb tests

[devlin maguire]

Is it possible,practicable,advisable to test MCB's it seems that these little items are left out when it comes to T+I, and faith alone seems to be the order of the day, admirable but a poor substitute for stratigy, we place such absolute reliance on them being manufactured to such high standards, is there a test, can we overload them to within the rated trip curent, any thoughts??
Mac

 

[DurhamSparky]

no way to test other to short L&N out and cause an overload! other than that buy from reputable source and your normally ok!!

 

[pevvers]

It is possible, but the piece of equipment you need to do it is rather large and expensive! I don't reckon you'd be able to carry it round in your tool bag....

Here's my find from a quick search of Google for current injection kits!

Or have a look here: -

SMC-12 Automatic MCB circuit breaker test system

 

[devlin maguire]

Hi Guys I was thinking about some installations that have had the same mcb's for some years, I thought about it when I checked a RCD which stayed in during test and the test button would not kill it either. I know there is more to wrong in a rcd, still the thought remained,
Mac

 

[pevvers]

Well your answer is above, but I'm reckoning there's a damn big toriodal transformer in there, so not something you would want to lug about all the time,

Of course, you can test 6A type 1 3871s and some 6A B type 60898s with a high current loop tester, but they only need 24-30A to trip in 0.1 of a second. Any thing bigger and you're looking for something that can inject a current of at least 40 amps, which is the low end of the scale when you think that a D32 would need 640A to trip instantaneously....

But the equipment above will do it! Dunno what the P&P from India for a hulking great mass of ferrite is gonna be though,

---------

But in answer to the OP.

Is it possible

Yes

practicable

Hell no.

advisable

If you're that worried, then just replace the MCB's, as it'll be cheaper than getting the gear to test.

 

[Sintra]

I have seen a device used for this purpose but can't google it.
Basically if i can remember correctly it was a variable resistor with settings from 12 ohms down to 1 ohm.
This was placed across mcb and the resistance was decreased until the mcb operated.
Will keep trying to google for it.

 

[pevvers]

If this potentiometer was put across the MCB then it would cause nothing more than to divert current across it, as there is no potential across the MCB.

I could understand it if it was put between the load side of the MCB and either the earth bar or neutral bar, but I can't think of any small sized potentiometer/variable resistor that would be able to handle the currents needed to test MCBs up to instantaneous trip.

A picture of a pot that can handle only 4kW is pictured below, so around 18 amps. Pretty darn big, and way too small a current rating to test the majority of MCBs/fuses properly.

 

[Jason Smith]

On this subject, was called out to a fault, loss of lights etc. I disconnected the circuit from the board, lent them my extension leads and my loft lighting lights. I then went back to the party and promised to return in the morning. When I got there, they said the shower had stopped working. In front of my eyes, the ring main went down. Nothing tripping, just stopped working. Then the shower light started to flick on and off. Clearly the fault was at the board somewhere. Testing revealed 5 faulty MCBS. Duly changed and now all is well. What are the odds of 5 of them going down in a 12 hour period?
The only history is the customer had caused a fault by putting a screw through a wire, properly repaired. They had a large family gathering and every appliance had been on in the house for two days, cooking, cleaning etc, so just before the fault there had been an adnormally heavy load.
There was a bit of discolouration at the main neutral terminal, but seen much worse. any ideas ?

 

[mcb-expert]

I'm using a portable appliance tester for MCB with satisfactory results. Also our sales team uses several of those for demonstration to dealers & wire-men.
I found it over-all nifty for all ratings of Miniature Circuit Breaker.



It is available from SCR ELEKTRONIKS

 

[Brightspark2]

Looks like it's been taken out of docs deLoreon...

Whats the price tag?...

 

[Golden_Boy]

I once saw a "lash up" using an old arc welder to test MCB's . The current being measures with a clamp meter while the wheel on the welder was turned untill the breaker "broke".