We are replacing some existing process equipment at an existing facility. The facility has a backup generator on site. The backup generator feeds a separate, backup power bus within their MCC which is isolated from the normal power bus.
Certain equipment (including the equipment we are replacing) is fed with dual kirk-key interlocked breakers so that the equipment can be run either on normal or backup power, but not both.
There is some newer equipment that was added approx 15 years ago. For this new equipment, dual 800A switches (one from normal one from generator) have their load side terminals "jumped" to feed a separate MCC. There is no interlock or method (other than operating procedure) to prevent paralleling the genset and utility power. There is no method to prevent backfeeding of utility with genset power.
The "newer" equipment is not part of our workscope, but I intended to discuss this arrangement with our customer. Most (all) of my genset installation experience is with break-before-make auto transfer switches.
1. I'm assuming that 702.6 prohibits this installation. Are there any sections/exceptions that would permit it?
2. Would it have been permitted in 1990 NEC?
3. Are there situations where "operating procedure" is an acceptable method (acceptable to NEC) to prevent inadvertant connection of backup to utility power?
Certain equipment (including the equipment we are replacing) is fed with dual kirk-key interlocked breakers so that the equipment can be run either on normal or backup power, but not both.
There is some newer equipment that was added approx 15 years ago. For this new equipment, dual 800A switches (one from normal one from generator) have their load side terminals "jumped" to feed a separate MCC. There is no interlock or method (other than operating procedure) to prevent paralleling the genset and utility power. There is no method to prevent backfeeding of utility with genset power.
The "newer" equipment is not part of our workscope, but I intended to discuss this arrangement with our customer. Most (all) of my genset installation experience is with break-before-make auto transfer switches.
1. I'm assuming that 702.6 prohibits this installation. Are there any sections/exceptions that would permit it?
2. Would it have been permitted in 1990 NEC?
3. Are there situations where "operating procedure" is an acceptable method (acceptable to NEC) to prevent inadvertant connection of backup to utility power?