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Topic Title: Removal of Merlin Gerin MCB
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Created On: 04 September 2013 06:39 PM
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 04 September 2013 06:39 PM
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kitleach

Posts: 44
Joined: 19 August 2009

Hi,

Has anybody ever had trouble replacing Merlin Gerin circuit breakers (Type: Multi 9 - C45N - BS 3871) from 3 phase DBs?

I tried to replace one yesterday, but found it impossible to remove from the board.

If you've had a problem with them, how did you end up getting it out? I ended up giving up after struggling for the best part of an hour & half!

Regards.
 04 September 2013 06:53 PM
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Fm

Posts: 585
Joined: 24 August 2011

Dont suppose there is a clip that needs a flat driver to release from the din rail hidden by the load conductors?
 04 September 2013 07:01 PM
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perspicacious

Posts: 7032
Joined: 18 April 2006

"Has anybody ever had trouble replacing Merlin Gerin circuit breakers (Type: Multi 9 - C45N - BS 3871) from 3 phase DBs?
I tried to replace one yesterday, but found it impossible to remove from the board.
If you've had a problem with them, how did you end up getting it out? I ended up giving up after struggling for the best part of an hour & half!"


Which generation is the MG DB?

1) The type that has a detachable Y shaped link that connects bus bar to CB.
2) The type that has a fixed link.

Regards

BOD
 04 September 2013 07:05 PM
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kitleach

Posts: 44
Joined: 19 August 2009

Thanks for replying.

Yes there is a plastic clip holding the breaker on to the din rail, but having pulled that out & undone the screw which holds it to the bus bar, I had no joy whatsoever.

I've never had a problem replacing breakers before, so wondered if there was something else you had to do with the M.G. ones?

Obviously, if it was a single phase domestic style board I could just remove the entire bus-bar if I was having trouble, but, with it being a 3P DB, I don't have that luxury.

I even tried removing the breaker at the top left (L1) in the hope I could slide it off the DIN rail & have a look at what was causing the problem, but I had no joy getting that off either.
 04 September 2013 07:09 PM
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kitleach

Posts: 44
Joined: 19 August 2009

Which generation is the MG DB?

1) The type that has a detachable Y shaped link that connects bus bar to CB.
2) The type that has a fixed link.

Regards

BOD


I am not sure. How do I find out? I have only ever seen the type where the MCB just screws on to a bit of bus bar that pokes out from the centre of the DB at each position in the DB.

Thank you for taking the time to help.
 04 September 2013 08:00 PM
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perspicacious

Posts: 7032
Joined: 18 April 2006

"I am not sure. How do I find out? I have only ever seen the type where the MCB just screws on to a bit of bus bar that pokes out from the centre of the DB at each position in the DB."

Apart from the obvious screw on the bus bar spine to secure the Y link? These are not present on the later type of pre-fitted.......

Ideally look at an unused way as very often they were left without the Y link fitted and kinder electricians left the bag of them in the DB.

You mention C45N and to me that is the older type of CB that I know were in use in 1985 along with the Y links as I fitted them in that era. As to when the pre-fitted ones came into being, I can't recall.

I do have new bags of the Y links that I've salvaged over the years if anyone needs any.

To remove the CB from the Y link type, you need to slacken the bus bar spine screw quite a bit but obviously only when the complete DB is isolated as it will be slack enough to fall out when you release the CB.

Regards

BOD
 04 September 2013 08:24 PM
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kitleach

Posts: 44
Joined: 19 August 2009

Thanks for that, I shall look for it when I return.

Regards,
 05 September 2013 12:54 AM
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alancapon

Posts: 5700
Joined: 27 December 2005

Originally posted by: perspicacious
. . . To remove the CB from the Y link type, you need to slacken the bus bar spine screw quite a bit but obviously only when the complete DB is isolated as it will be slack enough to fall out when you release the CB. . .

If you are unlucky, you can lose the "Y-Links" into the busbar housing, where they slide along the bar. When you turn the main switch back on, they can then spin round and create an impressive phase-to-phase fault!

Regards,

Alan.
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