We have a situation where a motor heater is part of 4160v compressor control circuit. We have a standard that any critical control circuit should be supplied with UPS. Question is, if there is a fault in motor winding (4160v), can fault current find it's way into 120v heater circuit (UPS)? Is...
Are motor MCCs with Mechanically held coils (one close, and one trip) common? Vendor said those are mainly used on breakers, or starters feeding transformers. The only reason I can think of is safety concern, as you need to be able to stop motor remotely if needed, but that can be solved. Any...
NEC permits using transformers in parallel operation and switching as one unit. Is switching as one unit a mandatory? Does that mean I have to use a 6 pole switching application, or I don't have to do that if proper tagout procedure is used? This is for 480v, 300KVA XFMRs application. Does...
A client with no spare MCC capacity needs to add a spare motor. The only option available is to use the same starter for two motors (main and spare). I was thinking of using a transfer switch so that only one motor can be operated at one time. Does NEC article 430.87 which states that: "Each...
I just realized that the vendor is using a thermal-magnetic breaker to feed a VFD/Motor application rated at slightly above 125% FLA. Looking at motor starting curve Vs breaker curve, it seems pretty tight. My question is, what would be the maximum starting current drawn by a 753 Powelflex...
My question is regarding a branch breaker in a large 480v Power Panel. The circuit feeds a 36A heating load. Can a 40A breaker be used, knowing the following:
- This is at a small generating Station
- Space Heater is supposed to turn on only when ambient temperature is below 50F (10C)
- #8 AWG...
I have a situation where LV-MCCs are installed in a structure with a skid/pumps. I couldn't tell for sure in the NEC what LV-MCC location requirements are. Even thought MCCs are located indoors, a possible leak from the skid could occur. My questions are:
1- Is there a minimum distance...
