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Merlin Gerin NS250 contactor not working

Merlin Gerin NS250 contactor not working

Merlin Gerin NS250 contactor not working

(OP)
Hi, I have a merlin gerin compact NS250N breaker dealing with the power changeover between generators and shore power on my boat. When I change manually by pressing the buttons on the front of the breaker there is no problem. When I try to do it automatically the contacts try to close and i get a buzzing for a few seconds which then stops and the contacts stay open. I have replaced the main breaker and the front end control but it still does it. Is it a problem with the breaker or am I looking in the wrong place? Hope someone can help me

RE: Merlin Gerin NS250 contactor not working

Sounds like a bad close coil or module, these are cheap breakers, and you may be better off to reaplce the breaker than to repair. I might have some of those breakers and coils around here somewhere.  

RE: Merlin Gerin NS250 contactor not working

Soumds like the close amd open commands are om at the same time
 

RE: Merlin Gerin NS250 contactor not working

Is the toggle of the breaker correctly engaged with the motorised actuator? Does the buzzing sound like a small motor and gearbox working hard? I'd pull the actuator and verify operation while it is not attached to the breaker. The motor actuator uses motor power to open and spring to close, presumably to allow it to be used in synchronising applications. While the breaker and actuator are separated check the breaker mechanism if you can do it safely - from what I remember the original front cover has to be removed to fit the motorised actuator, so doing this check 'live' is not a sensible option.
  

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If we learn from our mistakes I'm getting a great education!
 

RE: Merlin Gerin NS250 contactor not working

(OP)
Many thanks for your replies, it turned out that the alarm system was telling the breaker to open. Good call RODMCM

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