Yes I still use. I have measured the neutral of balanced three phase MWBC's serving electronic ballasts and only see an amp or two for a fully loaded (16 amp) 20 amp circuit. I have no concerns about using a standard size neuter
How often are people loading said light circuits to near circuit ampacity, other than maybe where high bays or other high output luminaires are being used? The smaller room applications possibly using similar number of circuits as with older technologies even though less load, they don't want to take out every room or every room on a floor, or similar when fault occurs in one lumminaire, or to not have to shut everything off to service something in one room.
don't see why you couldn't. Is design decision and not any sort of requirement.
I've done some sizable retail spaces with all electronic ballasts and used 4 wire MWBCs throughout without problem or worry. Most had fixtures that came pre wired with relock configured with MWBC. Been back to do service work over ten or more years and haven't seen any problems
Pretty often in Oregon actually. 1000W HPS grow lights are pretty common here.
Thank you, good to know.
Well I suppose it does come to that but since I've always used double pole breakers for those in homes anyway it does not make a difference for me. In terms of trouble shooting I just disconnect one energized conductor at a time and see which one is tripping the breaker. I would do the same thing with an AFCI and have done so. If both energized Conductors still trip the circuit then I have a neutral to ground fault and I am really on a treasure hunt.
For the sake of my continuing education how do you get a "nuisance trip" on a Wet Pipe Domestic Automatic Sprinkler System. There are only 2 ways that I can think of to make a wet pipe sprinkler system discharge water. One is to subject one or more of its sprinkler heads to a temperature greater than ~130 degrees Fahrenheit long enough to overcome the thermal lag of the fusible element which is holding the cap tight to a sprinkler heads discharge port. The other is to physically damage the sprinkler head or the piping. In the first case the system is doing exactly what it is supposed to do. It is keeping the temperature of the compartment down to a survivable level and markedly reducing the smoke production by directly suppressing the fire. In the second case I would hardly call a would be golfer's back swing through the sprinkler head a nuisance trip.
I got a marked reduction in harmonic current when we switched Fluorescent lighting to LEDs. Was I measuring that wrong. I didn't know that LEDs produced a lot of harmonics.
Probably the worst case for neutral current would be if you switched off one phase of a 4-wire 3-phase MWBC. Then the fundamental 60Hz current in the neutral would be the same as each phase current (assuming they're equal), and the harmonic current would add to that.
