A little different 2

[joeyww12000]

Ok I posted a thread yesterday or the day before about bonding and grounding a service. I didnt explain the whole system properly. Still a 600a service. We have an outside utility transformer with service coming undergroung to a 600a disconnect, out to a transfer switch for a generator, neutral is not switched, into building to a MDP with a 600a main breaker, with a couple other breakers to feed other equipment. Right now the 600a disconnect outside has the grounded conductor bonded to the can by a bonding screw and also has a grounding conductor out to a groundrod. Also from the service disconnect outside is ran feeders to mdp where neutral and egc are bonded together inside the mdp. How can the MDP can not have objectionable fault current on it when a fault occurs on one of the panels being fed from the MDP?

 

[joeyww12000]

Actually there will be neutral current on the EGC, right?

 

[steelersman]

Actually there will be neutral current on the EGC, right?

I think that there can be since you are creating parallel paths.

The last time I did a service simailar to this the MDP was the service disconnecting means. Another words the wires came straight from the transformer pedestal at the street into the MDP which had I think 6 breakers.

 

[joeyww12000]

correct, we have a disconnect outside the building with service hitting it before coming into the building to the MDP. The MDP even has neutral and egc connections bonded together, but nothing bonding the can of the MDP, Im just a little confused on this one. Electricity is electricity though, if the MDP was a panel I would seperate the grounded conductor and grounding conductor.

 

[Pierre C Belarge]

Ok I posted a thread yesterday or the day before about bonding and grounding a service. I didnt explain the whole system properly. Still a 600a service. We have an outside utility transformer with service coming undergroung to a 600a disconnect, out to a transfer switch for a generator, neutral is not switched, into building to a MDP with a 600a main breaker, with a couple other breakers to feed other equipment. Right now the 600a disconnect outside has the grounded conductor bonded to the can by a bonding screw and also has a grounding conductor out to a groundrod. Also from the service disconnect outside is ran feeders to mdp where neutral and egc are bonded together inside the mdp. How can the MDP can not have objectionable fault current on it when a fault occurs on one of the panels being fed from the MDP?

As per
250.24(A)(5) Load-Side Grounding Connections.

As you posted, this is not permitted. I tell people it leads to either of 3 things: shock, fire, death.

 

[don_resqcapt19]

As you posted, this is not permitted. I tell people it leads to either of 3 things: shock, fire, death.

While I agree that it is a code violation and may be a hazard in some cases, why, if it is such a serious hazard, does the NEC require some parallel paths on the line side of the service disconnect?

 

[Pierre C Belarge]

While I agree that it is a code violation and may be a hazard in some cases, why, if it is such a serious hazard, does the NEC require some parallel paths on the line side of the service disconnect?[/quote]


Don
It bewilders me why this is so. I cannot answer that question other than to say myself....Why?

We both do understand and know that it can lead to a dangerous situation.