Ground Fault Protection of Equipment

[dvcraven052256]

Been working on high-rise project for several months. I have attached a partial one line diagram. I don't know how I missed this but I believe the 2000/3p disconnect show on MSB-1 and 2 will require GF sensing. Is that correct?

Dan Craven

 

[infinity]

Is the GFPE protection mentioned elsewhere in the specifications?

 

[dvcraven052256]

Not that I am aware of.

Could site an example of what you might be referring to?

 

[electrofelon]

Wouldn't the 4000/3 require and be GFPE?

 

[dvcraven052256]

No that is 208/120 service.

 

[mauk]

What does Note 20 say?

 

[dvcraven052256]

Note 20 only says it a 100% rated breaker.

 

[jim dungar]

Been working on high-rise project for several months. I have attached a partial one line diagram. I don't know how I missed this but I believe the 2000/3p disconnect show on MSB-1 and 2 will require GF sensing. Is that correct?

Dan Craven

It is hard to coordinate a single level of GF with branch breakers as small as 70A. This results in faults on branch circuits taking out the whole service. My preference is to add GF on all feeders with adjustable trips

 

[infinity]

There should be GFPE protection. Why a 3000 amp switchboard and only a 2000 amp OCPD?

 

[Strathead]

Yes. Refer to the following code section.


"230.95 Ground-Fault Protection of Equipment. Ground-fault protection of equipment shall be provided for solidly grounded wye electric services of more than 150 volts to ground but not exceeding 1000 volts phase-to-phase for each service disconnect rated 1000 amperes or more. "

 

[Strathead]

No that is 208/120 service.

Not according to your one line. It is a 480/277 system.

 

[electrofelon]

Yes. Refer to the following code section.


"230.95 Ground-Fault Protection of Equipment. Ground-fault protection of equipment shall be provided for solidly grounded wye electric services of more than 150 volts to ground but not exceeding 1000 volts phase-to-phase for each service disconnect rated 1000 amperes or more. "

The disconnects in question are probably not service disconnects, but there are analogous requirements in articles 210 and 215.

 

[infinity]

The disconnects in question are probably not service disconnects, but there are analogous requirements in articles 210 and 215.

They appear to be service disconnects given the location of the utility metering and the fire pump connections.

 

[mauk]

Note 20 only says it a 100% rated breaker.

I believe GFPE and arc energy reduction would apply for each of the 2000A breakers.

Is there no metering for feeders to the transformers (T-BD1/2)?

 

[don_resqcapt19]

Not according to your one line. It is a 480/277 system.

But the 4000 amp breakers are on the secondary of transformers that have a 480 volt primary.

 

[dvcraven052256]

Just to be clear. The 2000amp breakers on MSB-1 & 2 feed a 480-120/208 transformer with bus duct risers for multi metered sections per floor.

 

[Strathead]

But the 4000 amp breakers are on the secondary of transformers that have a 480 volt primary

I don't understand the context of your statement. The OP was asking about the 2000A breakers not the 4000A

 

[Strathead]

Just to be clear. The 2000amp breakers on MSB-1 & 2 feed a 480-120/208 transformer with bus duct risers for multi metered sections per floor.

The 2000A breakers require GFP per the NEC. The code section is 230.95 in the 2020 NEC

 

[electrofelon]

Good

They appear to be service disconnects given the location of the utility metering and the fire pump connections.

Good point. So is this a situation where the utility has a 208 network distribution and is supplying the transformers to supply 480?

 

[infinity]

Good
Good point. So is this a situation where the utility has a 208 network distribution and is supplying the transformers to supply 480?

I believe it's the opposite. The service is 480Y/277.