changing breaker style in a UL listed piece of equipment

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bobsherwood

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Dallas TX
In the past couple of weeks I have had two breaker failures. 125 amp 3 phase in a VFD. A 400 amp 3 phase in an emergency generator. These are not off the shelf breakers and cost an arm and a leg. 125 A-$1300 400 A $2800. If I use an off the shelf breaker to replace these, do I blow the UL listing for the equipment. I am thinking probably. I've spent the money and bought exact replacements but, in the future, I'd like to use a regular molded case breaker. Any help here?
 
In the VFD, C phase was a loose connection (by VFD company) and burnt/trip and just would not reset. Emergency generator was being load tested and it tripped at 75% load and would not reset. Not resetting means ... when I turn the breaker to off position, that's fine but, when I push to on, it's like a dead short and goes to tripped position. No power on the breaker. I will have them re built. I'll let you know what the problem in the breaker was. VFD was 2 years old.. Gen 6 years old and has had regular load tests and the breaker was exercised.
 
bobsherwood said:
In the VFD, C phase was a loose connection (by VFD company) and burnt/trip and just would not reset. Emergency generator was being load tested and it tripped at 75% load and would not reset. Not resetting means ... when I turn the breaker to off position, that's fine but, when I push to on, it's like a dead short and goes to tripped position. No power on the breaker. I will have them re built. I'll let you know what the problem in the breaker was. VFD was 2 years old.. Gen 6 years old and has had regular load tests and the breaker was exercised.
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A loose connection by the VFD manufacturer sounds like a warranty issue to me. But $1300 for a replacement? Were the contacts made of gold? You got hosed... Even if it had an electronic trip, $1300 for a breaker that small is a hosing if you ask me.

The generator breaker sounds as if you have an Under Voltage Release (UVR) in it, somewhat common for generator breakers. They do it that way specifically so that you CAN'T close the breaker until AFTER the generator is at full output already. That may also explain the early trip: the voltage dropped and the UVR tripped the breaker rather than damage the generator. So what you typically have is a voltage sensor of some sort on the generator output and if it sees the proper voltage, it feeds 24VDC to the UVR in the breaker, allowing you to close it. If the genset can't handle the load and the voltage drops, the sensor sees that and opens up the breaker. The voltage drop could happen for some other reason by the way, the point is that there may be nothing wrong with the breaker.
 
bobsherwood said:
In the past couple of weeks I have had two breaker failures. 125 amp 3 phase in a VFD. A 400 amp 3 phase in an emergency generator. These are not off the shelf breakers and cost an arm and a leg. 125 A-$1300 400 A $2800. If I use an off the shelf breaker to replace these, do I blow the UL listing for the equipment. I am thinking probably. I've spent the money and bought exact replacements but, in the future, I'd like to use a regular molded case breaker. Any help here?
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I am with Jraef, sounds like you got "hosed". What is the breaker type? Let me see what I have.
 
I took the day off today. As for the breakers, I went to two of my loyal suppliers, $1400 from one.. the other found it for $1300. The gen breaker has no low voltage wires on it... line and load only?? I'll take some pictures Monday and post them. I will be having them rebuilt! As for warranty.... it took almost 5 years for the loose connection to show it's self. Thanks for the replies!
 
bobsherwood said:
I took the day off today. As for the breakers, I went to two of my loyal suppliers, $1400 from one.. the other found it for $1300. The gen breaker has no low voltage wires on it... line and load only?? I'll take some pictures Monday and post them. I will be having them rebuilt! As for warranty.... it took almost 5 years for the loose connection to show it's self. Thanks for the replies!
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You still got hosed, what was the cat# of the breaker? For most style breakers there is no difference in price between a 125A and a 400A, or very little difference.Maybe this is a special breaker, I could be wrong, lets see.
 
The 400 amp is a Merlin Gerin NSJ400N. Merlin Gerin is Sq D... The 125 amp is a Cutler Hammer Cat No. EGE3125FFG. Have fun! I don't have time to take pictures but by appearance... nothing at all special.. just molded case breakers.. thanks!
 
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