Calculated Load and PDB

[jap]

There is a 200 amp 1ph service on an old school building.
It consists of a 200 amp overhead riser, 200 amp meter base and a 20 circuit ITE 3r 200 amp main breaker panel mounted on the outside of the building which is full but the school is being used no more and the load on the panel is roughly 60 amps total.

An event took place at the location where the sound guy needed a termination point for a 2/0 cord to run his distribution box for the sound and lighting.
The main in this distribution box is a 150 amp main breaker but doubtful that it pulled that much.

The Electrician at last minute had installed a 3p power distribution block inside the existing panel between the incoming service conductors and the main breaker.
Then installed a 200 amp fused 3r disconnect next to the outdoor panel and extended the service conductors from the PDB to the line side of the 200 a fused disconnect so the sound guy could have a place to terminate the cable.

Is the PDB inside the 1st panel a violation of any sort ? or does this seem to exceed the allowable ampacity of the service conductors?


JAP>

 

[petersonra]

I don't think the PDB is a violation.

If I am understanding correctly what you are saying, previously the service had a 200A OCPD. Now it effectively has a 400A OCPD. That seems inappropriate at first glance.

 

[jap]

I don't think the PDB is a violation.

If I am understanding correctly what you are saying, previously the service had a 200A OCPD. Now it effectively has a 400A OCPD. That seems inappropriate at first glance.

The original 200 amp main breaker panel remained, there was just a new 200 amp fused disconnect added next to it.

The service conductors leave the meter (3) 3/0's , go into the loadcenter and terminated on a PDB.
From the PDB 3 3/o's feed the 200 amp main in that panel, and from the PDB 3 3/0's exit the loadcenter and feed the new 200 amp fused disconnect that was nippled into the side of the loadcenter.

They basically created a splice point in the service conductors that originally came from the meter to the 200 amp main to be able to jumper to the fused disconnect.

JAP>

 

[Smart $]

Exactly what do you believe to be non-compliant? None of the information provided indicates a direct violation. The only one I see as possibly ignored at this point is 312.6.

PS: With multiple service disconnecting means, the only thing that determines service conductors to have their ampacity exceeded is the load. Sum of OCPD's are permitted to exceed the service rating.

 

[jap]

Exactly what do you believe to be non-compliant? None of the information provided indicates a direct violation. The only one I see as possibly ignored at this point is 312.6.

PS: With multiple service disconnecting means, the only thing that determines service conductors to have their ampacity exceeded is the load. Sum of OCPD's are permitted to exceed the service rating.

I don't know that anything is non compliant to say. It just seems that the calculated load at any given time may not be what it could be in the future. Making sizing the conductors at the calculated load and the overcurrent protection protecting the wire makes it hard to wrap my head around.

I guess as long as the conductors on the load side of the service disconnects are protected correctly, we don't need to worry about the load that could be put on the service conductors?

If the school became active again, during the event, the service conductors from the meter to the line side of both overcurrent devices could very easily be overloaded seeing as how you have the ability of going full tilt with both 200 amps services (400 Amps) with only a 200 amp rated service wire feeding them.

JAP>

 

[Smart $]

I don't know that anything is non compliant to say. It just seems that the calculated load at any given time may not be what it could be in the future. Making sizing the conductors at the calculated load and the overcurrent protection protecting the wire makes it hard to wrap my head around.

I guess as long as the conductors on the load side of the service disconnects are protected correctly, we don't need to worry about the load that could be put on the service conductors?

If the school became active again, during the event, the service conductors from the meter to the line side of both overcurrent devices could very easily be overloaded seeing as how you have the ability of going full tilt with both 200 amps services (400 Amps) with only a 200 amp rated service wire feeding them.

JAP>

Your assessment and concerns are correct... but Code permits it up to the point where calculated load exceeds ampacity, with no consideration for what may be done in the future.

 

[petersonra]

Correct me if I am wrong in reading what you wrote.

The service wires from the poco to the meter are 3/0.

downstream of the meter is a splice block that the 3/0 hooks to.

there are 2 sets of 3/0 leaving the splice block. both go to 200A OCPD.

thus the 3/0 going the meter is protected by effectively a 400A OCPD.

is that the situation?

 

[kwired]

Correct me if I am wrong in reading what you wrote.

The service wires from the poco to the meter are 3/0.

downstream of the meter is a splice block that the 3/0 hooks to.

there are 2 sets of 3/0 leaving the splice block. both go to 200A OCPD.

thus the 3/0 going the meter is protected by effectively a 400A OCPD.

is that the situation?

Those conductors are not protected by a 400 A OCPD, they are selected based on calculated load - though they can be easily overloaded if future load is added without concern for re-figuring whether or not the service conductors are sufficiently sized. This is not anything new and has been allowed for a very long time for multiple service disconnecting means. AFAIK there is not that much trouble with it either as long as new calculations are done when more load does get added.