Originally Posted By: kmcmahon This post was automatically imported from our archived forum.
After inspecting this home and finding virtually nothing substantial to report on because the home was virtually new and well constructed and maintained, I find myself second guessing this.
Aren’t the hot and neutral service conductor wires supposed to be of the same guage? Maybe I’m missing something when reading the NEC book. I’m used to seeing them all the same guage, so when I saw this I started second guessing.
I also have a difficult time judging service wire sizes. These were 1/2" and 3/8" dia aluminum conductors measured at the insulation. They seem undersized for a 200amp, but want to make certain before I call for an electrician. I usuall read the size on the insulation, but wasn’t marked on this one. Your guesses?
Originally Posted By: phinsperger This post was automatically imported from our archived forum.
Kevin,
Up here the neutral may be reduced in size but it is not clear (at least to me) how much it can be reduced.
Basically the neutral can be reduced because it only carries the remainder of the unbalanced load. Most of your heavy loads are 220V and don't use the neutral. A smaller neutral may also allow you to get away with a smaller conduit.
Originally Posted By: kmcmahon This post was automatically imported from our archived forum.
That’s why I’m second guessing myself and haven’t submitted the report. I wish I could find something in print that could define it one way or the other.
Originally Posted By: Thomas Ogryski This post was automatically imported from our archived forum.
I agree with Joey, do a calculation for the neutral, there are examples in the back of the NEC.
As for the wire size, it does look small but there are conductors, especially aluminum, that are called "compact stranded." All the space has been squeezed out & each individual strand in the cable is no longer round. Some of these can fool you when you look at them.
Originally Posted By: bking This post was automatically imported from our archived forum.
[quote=“kmcmahon”]After inspecting this home and finding virtually nothing substantial to report on because the home was virtually new and well constructed and maintained, I find myself second guessing this.
Aren’t the hot and neutral service conductor wires supposed to be of the same guage? Maybe I’m missing something when reading the NEC book. I’m used to seeing them all the same guage, so when I saw this I started second guessing.
I also have a difficult time judging service wire sizes. These were 1/2" and 3/8" dia aluminum conductors measured at the insulation. They seem undersized for a 200amp, but want to make certain before I call for an electrician. I usuall read the size on the insulation, but wasn’t marked on this one. Your guesses?
I found this thread after looking for some related info. Are you sure those SE wires were 3/8 and 1/2 ? They look like they are larger.
If the hot is in fact 1/2 in. including the insulation, then it is 0 awg and only good for 125A.
This is what it looks like in the picture:
The following sizes are approx. and include the insulation.
If the hot is 9/16 or 16mm then they are 4/0 awg and ok for 200A.
If the neutral is 17/32 or 14mm it is 2/0 and ok for 150A.
A smaller neutral is ok unless the property had an unusual amount of 120V circuits that were connected to dedicated equipment.
Most of your high current will be via 240V circuits and not put any load on the neutral.
Originally Posted By: kmcmahon This post was automatically imported from our archived forum.
I cannot remember the exact conversation with the power company, but there is newer compact wiring, and that’s what this is. I really wish I could remember the conversation better.
Originally Posted By: jpope This post was automatically imported from our archived forum.
NEC 250.24(B)(1)
The neutral (grounded conductor) cannot be smaller than the required size of the GEC (per table 250.66) and is not required to be larger than the largest ungrounded conductor.
Originally Posted By: kmcmahon This post was automatically imported from our archived forum.
Jeff, that’s saying that the neutral cannot be smaller than the ground. That wasn’t the original question. The question was whether the neutral could be smaller dia. than the hot.
Originally Posted By: bking This post was automatically imported from our archived forum.
If that is compact wiring it is not anything new. That size wire has been around for years and the hot conductors are good for 200A.
I really doubt the diameters including insulation are 1/2 in. looks like standard 9/16 with visual reference to the lug sizes that are common.
Did you use a caliper to measure or a ruler held next to it?
Using a ruler is not accurate for round objects.
If there is new compact wiring we need to know more about it because it will make all the inspector "service entrance plastic gauges" obsolete that are sold everywhere.
Originally Posted By: bking This post was automatically imported from our archived forum.
on another note, since that is not a subpanel, does the bare ground wire really have to be there? The neutrals and grounds were all connected together right?
Originally Posted By: jpope This post was automatically imported from our archived forum.
Quote:
NEC 250.24(B)(1) Routing and Sizing
This conductor shall be routed with the phase conductors and shall not be smaller than the required grounding electrode conductor specified in Table 250.66 but shall not be required to be larger than the largest ungrounded service-entrance phase conductor. In addition, for service entrance phase conductors larger than 1100 kcmil copper or 1750 kcmil aluminum, the grounded conductor shall not be smaller than 12 ? percent of the area of the largest service-entrance phase conductor. The grounded service conductor of a 3-phase, 3-wire delta service shall have an ampacity not less than the ungrounded conductors.
My interpretation of this is that the grounded conductor can be smaller than the ungrounded conductors in the service entrance, as long as we are talking about single-phase and not three-phase.
Originally Posted By: jpope This post was automatically imported from our archived forum.
bking wrote:
on another note, since that is not a subpanel, does the bare ground wire really have to be there? The neutrals and grounds were all connected together right?
I am assuming that the "bare ground" is the grounding electrode conductor in which case, yes, it really has to be there 
Originally Posted By: bking This post was automatically imported from our archived forum.
I was referring to a case where the GEC is at the meter base which is typical when the SE panel is indoors. If the GEC is present then the SE panel only needs a 3-wire feed. Of course the extra ground is ok and better but 3-wire feed would meet code right?
Originally Posted By: Greg Fretwell This post was automatically imported from our archived forum.
Extra wires are not always “better”. You will get a red tag here in about half the jurisdictions if the meter base has the neutral bonded and you have a parallel path to the service disconnect. They want a plastic raceway and 3 service conductors. Otherwise they call it a parallel neutral.
Originally Posted By: bbadger This post was automatically imported from our archived forum.
Downsizing the neutral is more common that we notice.
Many times a service supplied with SE cable will have have a smaller neutral.
A common AL SE would be 2 AWG SE with a 4 AWG neutral.
Commercial services in my area used to have greatly reduced neutrals, that practice has pretty much stopped due to harmonic current issues that can toast the neutral of 3 phase systems.
In a house service the neutral will carry very little load if the panel is balanced, however the neutral must be sized for the greatest imbalance possible or the GEC which ever is larger.
-- Bob Badger
Electrical Construction & Maintenance
Moderator at ECN