Codes & Standards InfoZone

Because of our extensive participation and knowledge of Codes and Standards, we provide the opportunity for our customers to ask questions regarding the application of Codes and Standards. Continue to check back to the site on a regular basis to review a new question and answer. The questions presented are fundamentally in the same context and format as submitted to us.

If you are supplying a building from a 480/277 WYE transformer, can you derate the neutral and have a smaller wire size than your phase conductors? This is a common practice in our area. However, I was reading in Section 220.61 (C1) and it seems to me that in a WYE connected system, the reduction of the neutral is not allowed. Please clarify.

I have a new 500kW generator, with 3000A Square D transfer switch and I-line panel located exterior from the building on a separate pad. Five main panels are located at separate locations with mains located in the I-line panel. The feeders are in underground PVC conduit. Each panel has its own electrode. The contractor pulled and equipment grounding conductor to each panel, removed the bonding jumpers and installed ground bar kits. Should he have actually bonded the neutral at each panel and removed the equipment grounding conductors?

The HVAC crew asked that the circuit conductors be sized according to the maximum circuit capacity given on the unit. The units give a minimum and maximum circuit ampacity. I was reading in article 440 and my interpretation is that you size your circuit conductors according to the minimum circuit ampacity, and your overcurrent protection, whether being a fuse or a circuit breaker at the panel, would be the maximum circuit ampacity. For example, a unit that has a maximum circuit ampacity of 40amps and a minimum of 27amps would have a number 10 copper conductor with a 40amp breaker. Is this correct or what is the correct way?

Can you please comment on the following three statements:

• It is our understanding that the 2008 Code now requires that if we use 3 L-N circuits with one Neutral, we would need to provide a means at the source to simultaneously disconnect all 3 circuits. (ie essentially a 3 pole breaker).
• It is our understanding that this is also true for convenience receptacle feeds, that if we use 3 L-N circuits with one neutral, then all 3 need to be simultaneously disconnected if one trips.
• It is our understanding that if we want to continue with our philosophy we now need to pull separate neutrals for each L-N circuit.

I have a couple of questions for you regarding wiring. I am being told that an AFCI circuit and a GFCI circuit cannot share a neutral conductor, even though they are on separate phase legs of the panel box. Is this correct?

My next question is also regarding the wiring of receptacles. I suspect this one is merely good practice, but not a code requirement. When wiring a series of receptacles on the same circuit in a daisy-chain fashion, can the neutral and phase conductors both be wired to the device in both in and out configurations, or does the neutral need to be pigtailed to the receptacle such that the next receptacle in line will have is neutral in tact if an upstream receptacle is removed? Obviously, if they are configured to attach to both the in and out sides of the receptacle, when both are removed upstream, all those downstream are disabled.

Section 110.16 requires an arc-flash warning label on equipment. Is this a field applied label or does the manufacturer of the equipment provide that when they build the equipment at the factory?