400A Main turns off by itself

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By design, does this particular 400a main trip all the way to the off position, rather than center, on either dead shorts or overloads?

Is it the same "multiple 120v/208v circuit breakers" that trip, when you do have breakers tripping before the main? Do those branch breakers usually/always trip before the main does?

Can you do a load calculation that brings you anywhere near 400a, on any phase?

Does the coffee shop own anything particularly weird, or non resistive, in the way of roasting, grinding, brewing equipment? Was it built over an ancient burial ground?

Am I really the first on this thread to suggest demonic possession? Does zbang have any specific background in countetintelligence or related stealthy arts? (Because his "see if secretly-unloaded branch breakers keep tripping" trick is worthy of John Le
Carré.)


 
Does zbang have any specific background in countetintelligence or related stealthy arts? (Because his "see if secretly-unloaded branch breakers keep tripping" trick is worthy of John Le [/COLOR]Carré.)
None I'll admit to, I'm just a sneaky b'st'rd :D. And I've dealt with similar things in other systems (like a dummy "Save" button in a program that always auto-saves or dummy surveillance cameras). Oh, and I used to do burglar alarms and access control.
 
HAHAHA!! I have not ruled out demonic possession!

It went down again yesterday.

I was called in. When I arrived, I was told and saw 3 - 120v cb's were in the tripped position (which happened first). Then the employees told me about 5 minutes after those tripped the 400A went down. Again, it went into the off position.

I reset the 3 tripped breakers then turned on the main. Everything came back up. I remained there for another hour or so, then as I watched it, the 400A main again simply turned off by itself. Absolutely no one else in the room with me.

I am led to believe there is a floating neutral somewhere. I spent the entire day Saturday isolating all grounds/neutrals (aside from main bonding jumper), I removed all feeders/branch and tested/meggered bussing on the panel, I then unplugged all equipment and tested/meggered all branch to the equipment. My tests showed no faults on my wiring at all.

I'm at the point of hiring a generator co. to power the building for a few days to rule out the utility co. If the problem still persists, I feel it is a piece of their equipment causing this disruption through some kind of electronic circuit boarded device. I am just about out of ideas....
 

iwire

Moderator
Staff member
Location
Massachusetts
Stop guessing, a recording power meter rents for about 500 a month.

Connect it on the load side of the 400 and see what it records.

It will record volts and amps on each conductor.
 

iwire

Moderator
Staff member
Location
Massachusetts
I have recorded volts/amps borrowing a meter from another company. It showed no spikes/surges or drops prior to power going out.
Well this is making less sense all the time.

If you have been recording you would know for sure if it was a utility issue or not.

I would not be telling a customer they need to rent and fuel a genset for a while to rule out the utility.
 

roger

Moderator
Staff member
Location
Fl
Occupation
Electrician
I have recorded volts/amps borrowing a meter from another company. It showed no spikes/surges or drops prior to power going out.
Have you locked the breaker in the closed position? This will not explain the tripping breakers but it stop the ghost from turning off the main.


Roger
 

mgookin

Senior Member
Location
Fort Myers, FL
Sounds like OP is saying:
Branch circuits were in the tripped position upon arrival following notification by staff.
400A main opened and moved to the off position (not tripped) while he was the only person in the room.

Can we get a part number on that main breaker?
 

GerryB

Senior Member
Sounds like OP is saying:
Branch circuits were in the tripped position upon arrival following notification by staff.
400A main opened and moved to the off position (not tripped) while he was the only person in the room.

Can we get a part number on that main breaker?
OP said SqD told him it couldn't happen, yet he says he has changed the 400 amp main 3 times? Does not make sense. Someone would pay for that?
 

Little Bill

Moderator
Staff member
Location
Tennessee NEC:2017
Occupation
Electrician
Sounds like OP is saying:
Branch circuits were in the tripped position upon arrival following notification by staff.
400A main opened and moved to the off position (not tripped) while he was the only person in the room.

Can we get a part number on that main breaker?
I believe OP said he changed the main breaker, maybe twice.

ETA: Went back & looked, looks like three times!

Upon calling Square D and them reassuring me it cannot happen, I've since changed that main breaker 3 times as each one did the same thing.
 

brian john

Senior Member
Location
Leesburg, VA
Guys please. There is no one physically turning the breaker off.

I have heard that before.

Look this stuff ain't magic and for a molded case circuit breaker to go to the OFF position from a overload or short is in my experience very, very, very rare and I have tested literally 1000's upon 1000's of circuit breakers (high current tested) and I have seen handles do some weird things but that I can remember to the OFF position I cannot remember any.

If you have done complete trouble shooting.

Meggered all feeders.
Visual inspection.
Fall of Potential under load.
Measured loads for a period of time including the supposedly tripping to off.

Have the CB tested by a testing firm or replace the CB.
 

kwired

Electron manager
Location
NE Nebraska
I have heard that before.

Look this stuff ain't magic and for a molded case circuit breaker to go to the OFF position from a overload or short is in my experience very, very, very rare and I have tested literally 1000's upon 1000's of circuit breakers (high current tested) and I have seen handles do some weird things but that I can remember to the OFF position I cannot remember any.

If you have done complete trouble shooting.

Meggered all feeders.
Visual inspection.
Fall of Potential under load.
Measured loads for a period of time including the supposedly tripping to off.

Have the CB tested by a testing firm or replace the CB.
He claims it has been replaced three times. Don't know exactly what he has but if a Square D panel pretty good chance it is same 400 amp main I have seen many times and probably the LA series unless there is high enough available fault current something else is required. I've never had this kind of trouble with that breaker, and wouldn't expect it to be a defect if it did it with three or four different breakers. And defect includes tripping to the off position instead of the trip position.

Something else has to be going on.
 

brian john

Senior Member
Location
Leesburg, VA
I should add I am not saying what he is saying is not possible but in my experience I have never seen a CB tripping to the OFF position. I was ask the other tester for input.

Can he post the full cat no. for the CB.
 

kwired

Electron manager
Location
NE Nebraska
RTL, does your main breaker have a manual trip operator? Many larger frame Square D mains I have come across do - usually a little recessed button you may need a small object to press it with to operate. Next time it is out try manually tripping it if it has this feature, to see if when it trips the handle moves to mid position or full off position. Also make sure there is no magnetic trip adjustment, if there is increase the setting it may be something draws too high of starting current and takes it out. Those usually are shipped at the lowest setting. Not sure what that has to do with the branch breakers you say are also tripping though.
 
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