Was wondering if someone could shed some light on this. In reference to Exhibit 250.13, p199 of NEC 2005. Is the system bonding jumper to be sized based on 250.66? Base on size of the secondary conductors for step down transformers or primary conductors for the step up transformers?
transformer grounding
- Thread starter reko19
- Start date
- Status
Your terminology is a bit diffent from that to which I am accustomed.
The "output" side of the transformer to me has always been the "secondary" be it step-up or step-down. In any event, your bonding jumper is sized per 250.66 for the "output" of the transformer (the conductors which do not have an overcurrent device ahead of them).
The grounding for the power conductors supplying the transformer can be protected by an equimemt ground sized by the "feed" overcurent device.
The "output" side of the transformer to me has always been the "secondary" be it step-up or step-down. In any event, your bonding jumper is sized per 250.66 for the "output" of the transformer (the conductors which do not have an overcurrent device ahead of them).
The grounding for the power conductors supplying the transformer can be protected by an equimemt ground sized by the "feed" overcurent device.
Thank you for the reply. Now that 250.66 is confirmed, I'll try to clarify the second part of my question. 250.66 is to be applied based on the size of the largest ungrounded service entrance conductor. For a step down transformer this is secondary conductors, no questions here. For a step-up transformer the primary conductors are larger than the secondary. So for the step up transformer do I use transformer secondary or primary conductors with 250.66. Once again thank you.
- Status