I know they do. Even got some work to do on a 400A Wylex panel board next week. It's being retired!! Yay
Scary Find of The Week
- Thread starter Iggifer
- Start date
Not for years, they used the MK breakers with the dolly that sort of slides. They have a bit of flimsy vacuum formed plastic around the main switch which is a bit tacky and in both the ones I saw, didn't really fit properly either.
Mk sentry single pole mcbs about 3rd generation, fitted merlin gerin boards and were exactly same casing, till recently, i often see the mk single pole in 3 phase merlin boards.
I have seen 1st generation 3phase mk boards with rcd main switches, but never seen a 3 phase mk breaker and as you say seen no newer mk boards.
Yes I know the type, I have an MK one here, but no Merlins! Just the old 3871 type designed for those old boards that use those horrid little Y links. Thank goodness those boards are no longer made. I wanted to open them both to see what the difference is inside, if any. The MK ones are all rated 6KA, the Merlins are often all 10KA.
Did merlin ever make a 6kA breaker?
Yes, I have a 3 pole one here in my hand. It still has it's little Y links too.
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Are those links for plugging the breaker in to a square D busbar?
No!
They are for the older type of Merlin Gerin busbar... before they came up with the iso-bar sliders.
http://www.flameport.com/electric_museum/old_equipment/merlin_gerin_amg9_busbar_detail.jpg
I came across one of these DBs last year where the breakers were not sitting right... on further inspection it seemed tha instead of the forked terminals, ring crimps with a bit cut out were used!
Ahh interesting stuff. Never come across these before.
The design is supposed to be safe, having no exposed busbar fingers. But it is really rather an unsafe design if you need to add/remove MCBs with the main switch on.
I understand it has been known for the forked pieces to be 'lost' inside the busbar assembly on three phase boards, manage to sit in there for a few years and then later on (often when the main switch is operated) fall across two phases
If you then loosen one of the forks it swings down and shorts to the one below!
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