Discuss Supply to 3 phase DB tripped in the Commercial Electrical Advice area at ElectriciansForums.net

Midwest

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As above, place I work at as maintenance, had supply tripped off at the weekend. Not some stuff I’m fully conversant with, so just seeking views here.

3 phase DB supplying power and lighting for rooms, using RCBO’s. Panel has this as main switch;

766C3B3F-062E-48C3-B982-A4C53837E689.jpeg

The supply panel is this;
BC0C312C-48C5-4B7B-AAF2-829D5F97894C.jpeg

From what I can glean from the schematics, the supply panel breaker is 100A, and from the Eaton breaker it’s In is 250A, which seems unusual, two in series?

The supply panel tripped. No apparent reason. No one plugging in large loads, and no RCBO’s tripped. Breaker reinstated, and fine since.

Never experienced supply tripping like this. Cause for any concern, apart from me being there :).
 

davesparks

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Th emost likely reason for the 250A mccb incomer on the DB is misordering, misunderstanding or the specifier just generally not paying attention to what they are doing. (unless it has an earth leakage relay or remote tripping device connected then it may be there for good reason)
 

Pete999

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Th emost likely reason for the 250A mccb incomer on the DB is misordering, misunderstanding or the specifier just generally not paying attention to what they are doing. (unless it has an earth leakage relay or remote tripping device connected then it may be there for good reason)
Someone pushed the trip button? in error or mischief?
 
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Andy78

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Overload would be my first thought, however I don't know the place or pattern of use over the weekend.
I can imagine a 200A DB with 250A incomer being overloaded past 100A though as additions filter in over the years.

I have also had it in the past where MCCBs trip when re-energised after a powercut due to the downstream devices all being on and the startup spike being too high. Any instances of that in your area this weekend ?
 

Pete999

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As above, place I work at as maintenance, had supply tripped off at the weekend. Not some stuff I’m fully conversant with, so just seeking views here.

3 phase DB supplying power and lighting for rooms, using RCBO’s. Panel has this as main switch;

View attachment 51266

The supply panel is this;
View attachment 51267

From what I can glean from the schematics, the supply panel breaker is 100A, and from the Eaton breaker it’s In is 250A, which seems unusual, two in series?

The supply panel tripped. No apparent reason. No one plugging in large loads, and no RCBO’s tripped. Breaker reinstated, and fine since.

Never experienced supply tripping like this. Cause for any concern, apart from me being there :).
Is there any under voltage monitoring that could have caused the trip?
 
OP
M

Midwest

Electrician's Arms
Messages
11,675
Location
Oxfordshire
Th emost likely reason for the 250A mccb incomer on the DB is misordering, misunderstanding or the specifier just generally not paying attention to what they are doing. (unless it has an earth leakage relay or remote tripping device connected then it may be there for good reason)
Not sure on your last bit, but don’t think so. Nothing mentioned on the schematics.
 
OP
M

Midwest

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11,675
Location
Oxfordshire
Overload would be my first thought, however I don't know the place or pattern of use over the weekend.
I can imagine a 200A DB with 250A incomer being overloaded past 100A though as additions filter in over the years.

I have also had it in the past where MCCBs trip when re-energised after a powercut due to the downstream devices all being on and the startup spike being too high. Any instances of that in your area this weekend ?
It’s just bedrooms & corridors. One of the team had a call out, reporting loss of power etc. DB was all on, then found the supply panel tripped. Powered back on, all ok.

Did have a network power failure early Thursday morning.
 
OP
M

Midwest

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Oxfordshire
Is there any under voltage monitoring that could have caused the trip?
Again not sure on that, but it’s a large place, nothing else gone off. Strange one. Somebody mentioned loose connections, but think we’d have more probs since Saturday?
 

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