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Merlin Gerin Masterpact STR58U

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millswf

Electrical
May 2, 2013
2
Unfortunately I found this website 3 years to late. In 2010 I had a problem with a 1200 amp unit intermittently tripping. It had an STR28D trip unit. This was part of a emergency transfer system gear normal breaker. Square D had tested the breaker in place and said it was fine. I had run chart recordings on the circuit for over a week and nothing was abnormal. The problem got so bad I had to turn on the generator and run on the emergency breaker until I could do an overnight outage to replace. It too started tripping. Square D and my contractor were involved in replacing the normal breaker (unfortunately it was a bolt in breaker so it took over 10 hours to change out). Total bill for replacement with a spare breaker that I had was over $11,000, plus the bill for recording meter testing and for testing the original breaker off site. I sent out the breaker for testing and everything came back fine.

Just 4 weeks ago I had a 1600 amp breaker in the gear start doing the same thing. It to had the STR28D trip unit. Square D finally admitted there are problems with that trip unit and that unit is obsolete. They recommended replacing the trip unit with an STR58U and that their tech had to do it. It only took 30 minutes and cost over $4500.

I have 5 more breakers with the STR28U trip units in them and requested a quote for replaceing all 5 ($24,000).

After going through this experience, I am looking into buying the trip units from a third party and having my contractor do the replacement (trust me, it's not rocket science to replace).

So buyer beware. After reading these forums, I discovered Schneider/Square D knew about this problem prior to 2000. The gear I have was installed in 2001 just prior to my coming to this company. I consider their practice of installing devices know to be defective and further not admitting it 10 years later when the problems started is less than ethical. Save yourself the agravation and your company the money and make sure you are not getting ripped off.
 
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Those trips unit are horrible, there are replacement units available from a few different manufactures, we replace a lot of those in our breaker shop and you are right, they are pretty easy to replace since they are direct replacement and use existing CT's and wiring harness.
 
Zogzog thanks for your response. Right now I have three 1200 amp units, one 1600 amp unit, and one 2500 amp unit to replace. What are your recommendations of where to buy them and did you try to get Schneider to compensate you for yours?
 
I am a breaker shop, so I wouldn't be the guy Schneider would compensate. I doubt they would anyways. I have these replacement units available for a lot less than you would think.
 
We have had several clients retrofit the AC Pro trip unit from Utility Relay in a variety of 480 V circuit breakers. I've never heard a complaint about them.
 
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