thecrazyezel
Member
I had a question with an electric engineer at my office today so I thought I would pose the question to the group for their thoughts.
The engineer is showing a new 150 KVA transformer and showing 170 demand kW on the panel schedule attached to this transformer. I state that he has overloaded the transformer and that you can't show more than 150 for the demand kW on that transformer. The engineer states that you are allowed to go up to 125% of the transformer rating and that we have not gone over the 600A OCPD for the panel so we are ok. I counter that this is something that utilities routinely do but they are not bound by the NEC but we are. We consult the NEC, specifically section 450 but neither of us can find anything relating to how much load we can show on the transformer.
As engineers, we both know that the transformer will probably see half of the 170 kW peak demand and that even if it is run to 125% (187,500 KVA) it will still operate.
So the question becomes, is this code legal and what codes are involved here?
The engineer is showing a new 150 KVA transformer and showing 170 demand kW on the panel schedule attached to this transformer. I state that he has overloaded the transformer and that you can't show more than 150 for the demand kW on that transformer. The engineer states that you are allowed to go up to 125% of the transformer rating and that we have not gone over the 600A OCPD for the panel so we are ok. I counter that this is something that utilities routinely do but they are not bound by the NEC but we are. We consult the NEC, specifically section 450 but neither of us can find anything relating to how much load we can show on the transformer.
As engineers, we both know that the transformer will probably see half of the 170 kW peak demand and that even if it is run to 125% (187,500 KVA) it will still operate.
So the question becomes, is this code legal and what codes are involved here?