pnorb409
Member
- Location
- Carthage, MO
I have been working with some engineers at a local plant on upgrading some service equipment.
Currently the equipment consists of a 1200 amp panel board with a main breaker fed from the utility company's transformer outside the building. The conductors are three sets of 500s thhn in three inch conduits. These conduits are encased in concrete. Due to down time concerns, they would like to use the existing conduits and splice onto the cables. The plan is to demo the existing equipment, mount a gutter on the existing conduits, splice the cables in the gutter, and feed a stand alone 1200 amp breaker. From the breaker we would nipple through to a new 1200 amp main lug panel board. The end result would be a safe way of turning the panel off for adding circuitry in the future without having anything energized in the panel, therefore eliminating the company's concern for arc flash risk.
Problems;
The 75 deg rating on the equipment makes the 500s undersized. We could pull new 600s in, but then the three inch conduit is undersized for four cables in each conduit.
The idea has been mentioned to splice on to the existing 500s to 600s with 90 deg rated connectors in the gutter and from there feed the new 1200 amp breaker, thus satisfying the 75 deg requirement of the breaker. I haven't brushed up on what the code says yet, but figured I would ask for some thoughts/feedback from you guys. Thanks in advance.
Currently the equipment consists of a 1200 amp panel board with a main breaker fed from the utility company's transformer outside the building. The conductors are three sets of 500s thhn in three inch conduits. These conduits are encased in concrete. Due to down time concerns, they would like to use the existing conduits and splice onto the cables. The plan is to demo the existing equipment, mount a gutter on the existing conduits, splice the cables in the gutter, and feed a stand alone 1200 amp breaker. From the breaker we would nipple through to a new 1200 amp main lug panel board. The end result would be a safe way of turning the panel off for adding circuitry in the future without having anything energized in the panel, therefore eliminating the company's concern for arc flash risk.
Problems;
The 75 deg rating on the equipment makes the 500s undersized. We could pull new 600s in, but then the three inch conduit is undersized for four cables in each conduit.
The idea has been mentioned to splice on to the existing 500s to 600s with 90 deg rated connectors in the gutter and from there feed the new 1200 amp breaker, thus satisfying the 75 deg requirement of the breaker. I haven't brushed up on what the code says yet, but figured I would ask for some thoughts/feedback from you guys. Thanks in advance.
