kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
ROMEX IN PVC
- Thread starter j rae
- Start date
- Status
- Occupation
- Licensed Electrician
I was just stating that because a previous poster mentioned if you were using NM that you could use #6 for the Ungrounded Conductors and #8 for the the Neutral and #10 for the Ground, evidently he didnt realize that #6 NM comes with a full size neutral not a #8.
I'm too industrial oriented and we always pull full size neutrals to any loads for the simple fact that the load it is serving today (although it may not require a full size neutral) may change tomorrow.
Today it may be feeding a 50 amp piece of equipment, Tomorrow it may be turned into a Subpanel to distribute power to some 120v Loads, and this just carries over for me when I do a residential install but like I said that's just me.
i dont really consider running pipe and pulling wire unless its for a Hot Tub or something like that when doing residential.
Otherwise I'll usually use NM.
Jap.
petersonra
Senior Member
- Location
- Northern illinois
- Occupation
- engineer
I have not ever spec'd in reduced neutrals. It is not common in industrial settings at least IME, that they are especially useful, and the cost of running a full size set of wires over making one of them a little smaller is rarely an issue.
I might be more inclined to do so if there was significant cost involved, but it just has never been an issue with what I do.
I might be more inclined to do so if there was significant cost involved, but it just has never been an issue with what I do.
- Location
- Simi Valley, CA
I'm in the "I never reduced the neutral" camp also.
kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
Well I often do reduce neutral and often see no good reason not to. I do a lot of work on farms and other small industrial places with primarily motor loads. If you have a majority of the load as line to line and very limited neutral load, like I often do, I don't see any advantage to using much more than a 250.122 minimum sized conductor. I have seen numerous 100 amp or larger services or feeders in these kinds of places and if you clamp an meter on the neutral you are seldom going to see more than 30 or 40 amps.
Most 120 volt loads in these places are limited lighting and convenience outlets, the major load is line to line connected motors.
If you are in a place where most of the load is 120 volt - I have no problem with larger neutrals - you will have more current on the neutral most cases.
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
I almost always reduce the neutral on a residence form 2/0 or 3/0 copper to 1/0 copper. Most of the homes here are all electric esp. now with the cost of fuel. In fact most homes get a 400 amp service because of their size and the heating. Why bother with a full neutral if more than half the load is 240V- we usually are not worried about harmonics like you must in some commercial jobs.
Same here and would go as far as saying "most of the time" in place of "often do".
Roger
- Location
- Massachusetts
Same here but mostly due to never thinking of it. I have nothing against it, just never seem to remember I can when ordering wire.
petersonra
Senior Member
- Location
- Northern illinois
- Occupation
- engineer
I don't get involved at all with services, and rarely with feeders that have neutrals. Most feeders I deal with are 3 phase and I don't use the neutral at all so it is not even run.
The exception is load banks that are all L-N loads, but I have no responsibility for running the wiring to them or spec'ing it out. The end user mostly runs reduced size neutrals on these based on their own criteria.
The exception is load banks that are all L-N loads, but I have no responsibility for running the wiring to them or spec'ing it out. The end user mostly runs reduced size neutrals on these based on their own criteria.
kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
One situation I run into a lot is crop drying fans. The fan will be 10 hp or more @ 240 volts single or three phase, and the manufacturer will include a motor starter with 120 volt coil. Now I have a 120/240 volt circuit but the max current on the neutral is just the contactor coil that is less than 1 amp. Why run say a 3 AWG for this neutral just because that is what the ungrounded conductors are?
My complaint to the manufacturer is why not install 240 volt coils? But my guess is they just buy 120 volt contactors for every unit they make, that way if the supply voltage is other than 120/240 they just add a control transformer and still use same 120 volt contactors. For example, a 20 hp 480 volt unit uses the same contactor as a 10 hp 240 volt unit and there are less parts in inventory this way.
My complaint to the manufacturer is why not install 240 volt coils? But my guess is they just buy 120 volt contactors for every unit they make, that way if the supply voltage is other than 120/240 they just add a control transformer and still use same 120 volt contactors. For example, a 20 hp 480 volt unit uses the same contactor as a 10 hp 240 volt unit and there are less parts in inventory this way.
- Location
- Simi Valley, CA
Same here but mostly due to never thinking of it. I have nothing against it, just never seem to remember I can when ordering wire.
Probably the same reason for me. Just one less thing I had to think about.:happyyes: I think my first boss did it once and the inspector wanted a calc to justify it. Just seemed like mor trouble than it was worth.
kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
Well if you can say look at the loads, and a majority of the load is not even connected to the neutral, I think you can easily do a certain amount of calculating in your head.
Typical grain storage bin on a farm around here with 120/240 single phase supply may have a 10 hp fan, a 10 hp unloading auger, maybe an additional 10 hp auger for transferring to a truck, all 240 volts and maybe only 2 or 3 20 amp 120 volt circuits max I will have probably at least 100 amp supply up to 200 amp supply to this bin, and can very quickly see that the neutral load is not going to be anywhere significantly beyond the absolute minimum of a 250.122 sized conductor. And with all the larger motors connected to this there is not a lot of capacity to add much load so I am not too concerned about that either. If sufficient load gets added my supply conductors need changed anyway.
- Location
- Massachusetts
Any multiwire circuit that supplies a variable load.
I have a 20 amp MWBC that supplies 40 - 1 amp fixtures, 20 on each phase, I turn off all the lights on phase A and now phase B and the neutral have 20 amps of current on them.
kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
If you have a circuit with overcurrent 30 amps or less minimum allowed size is same size as ungrounded conductors.
Although I guess I should have given it a little more thought, I was just kinda taken by the statement that somebody never uses a reduced neutral. I guess I was thinking more of a 200 a. 3 ph. load with practically no neutral load... or maybe not thinking at all
Last edited:
- Occupation
- Licensed Electrician
I see where you are coming from and agree with you.
The odds of overloading a neutral in either a branch circuit or a feeder are rare. Narrow the discussion to feeders, even if all the load is 120V, and I think they would be greater than getting struck by lightning twice; three times even.
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