Bond or not Bond:

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plowe

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I have a 100 amp 208 3 phase 4 wire (3 hot, 1 common) circuit running from the main service panel out to the production floor running a 100 amp 208 3 phase bus duct. The bus duct then runs a 60 amp panel used to operate equipment. I discovered in this 60A panel the ground and the common are bonded together with a bonding bar. The equipment grounds are all essentially connected to the common conductor in the panel. To my knowledge this 60 amp panel is considered a sub panel and sub panels are not to have the grounded conductor and ground bonded together. Is this correct? My plan is to ground the bus tap to the bus using a #10 wire, then run a ground from the tap to the sub panel, Disconnect the bond from the ground bar and common bar, then add a bonding screw from the grounding bar to the panel case. Will this be sufficient ground considering the conduit and building structure are all metal??
 
plowe said:
I have a 100 amp 208 3 phase 4 wire (3 hot, 1 common) circuit running from the main service panel out to the production floor running a 100 amp 208 3 phase bus duct. The bus duct then runs a 60 amp panel used to operate equipment. I discovered in this 60A panel the ground and the common are bonded together with a bonding bar. The equipment grounds are all essentially connected to the common conductor in the panel. To my knowledge this 60 amp panel is considered a sub panel and sub panels are not to have the grounded conductor and ground bonded together. Is this correct?
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Correct, you are not permitted to reconnect the grounded and equipment grounding conductors after the main or system bonding jumpers.


My plan is to ground the bus tap to the bus using a #10 wire, then run a ground from the tap to the sub panel, Disconnect the bond from the ground bar and common bar, then add a bonding screw from the grounding bar to the panel case. Will this be sufficient ground considering the conduit and building structure are all metal??
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First off how is the bus duct grounded and bonded?

Is the conduit supplying the bus duct the EGC for the duct?

Also #10 copper equipment grounding conductor would be sufficient to ground and bond the 60 amp panel in accordance with Table 250.122

Chris
 
The buss duct is grounded through the conduit to the main service panel and the hangers from the steel I beams of the building.
 
The steel I Beams would not be considered as a grounding means for the buss duct, but the conduit would.
Is the 60 amp panel protected by a 60 amp buss plug ?
 
plowe said:
I have a 100 amp 208 3 phase 4 wire (3 hot, 1 common) circuit running from the main service panel out to the production floor running a 100 amp 208 3 phase bus duct...
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The grounded conductor should not bond at the destination either, you need to provide an equipment ground with this 100A feeder circuit.
 
augie47 said:
The steel I Beams would not be considered as a grounding means for the buss duct, but the conduit would.
Is the 60 amp panel protected by a 60 amp buss plug ?
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Augie,
What are you referring to as a buss plug, a 60A fuse where the buss feeds the panel? :confused:
 
yep OP stated 60a panel was being feed from a 100a buss... did not say what the feeder was protected by
 
didn't notice... I would have said " y'all "
I questioned it as the size of the equipment ground to the subpanel, if a conductor was used, would be base on the OCP at the buss.
 
plowe said:
...My plan is to ground the bus tap to the bus using a #10 wire, ...
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Typically, busway plug-in units ("bus plugs") are self-bonding.

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If it somehow does not make an adequate ground-fault connection to the bus duct, your bonding jumper will have to be at least #8 copper because of the "feeder" rating.
 
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