wire sizing

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texie

Senior Member
Location
Fort Collins, Colorado
Occupation
Electrician, Contractor, Inspector
Gentlemen,
I have another question. When installing multi-wire cables in conduit, you are supposed to treat it as one conductor. My question is, where would you find the dimensions of the cable so would could figure out conduit fill?
Someone else asked this question here recently. In my view, this is a good thing to know how to answer this, but in my experience you would never see this in an exam. If you do, they would give you the dimension of the cable in question as there are no tables in the NEC to tell you this (there are no "standard" cables like wire). In the real world you would get the dimensions of a cable from data published by the manufacturer, or if not critical, just measure it in the field and do the math from there.
 
Thanks for the information. You are correct about it not being on a exam without the dimentions being provided. I just want to know for the real world. Almost daily on the job I see foremen and other higher ups just sticking the wires or cables at the end of the conduit and if it fits then thats the size conduit they use.
Its like counting the neutral or grounded conductor as a current carrying wire. Some folks tell me you always count it. Some say if you have three phases and ony use two phases. The NEC is very confusing when it comes to this, at least to me. If you have a lighting circuit then I believe you count it. What about a receptacle circuit, a dryer with a 120v light and timer, a stove with a 120v light, a 204v circuit, 208v, 277v, 480v, etc. Any help would greatly appreciated.
 

jumper

Senior Member
Thanks for the information. You are correct about it not being on a exam without the dimentions being provided. I just want to know for the real world. Almost daily on the job I see foremen and other higher ups just sticking the wires or cables at the end of the conduit and if it fits then thats the size conduit they use.
Its like counting the neutral or grounded conductor as a current carrying wire. Some folks tell me you always count it. Some say if you have three phases and ony use two phases. The NEC is very confusing when it comes to this, at least to me. If you have a lighting circuit then I believe you count it. What about a receptacle circuit, a dryer with a 120v light and timer, a stove with a 120v light, a 204v circuit, 208v, 277v, 480v, etc. Any help would greatly appreciated.
Rob/Infinity wrote this awhile back:

Here's some examples of when to count the neutral as a CCC:

208Y/120 volt system-different circuit types:

A)- 2 wire circuit w/ 1 ungrounded, 1 neutral = 2 CCC's
B)- 3 wire circuit w/ 2 ungrounded, 1 neutral = 3 CCC's
C)- 4 wire circuit w/ 3 ungrounded, 1 neutral = 3 CCC's*

Notes:
A)- A normal 2 wire circuit has equal current flowing in each of the circuit conductors so they both count as CCC's.
B)- In this circuit the neutral current will be nearly equal to the current in the ungrounded conductors so the neutral counts as a CCC
C)- In this circuit the neutral will only carry the imbalance of the current between the three ungrounded conductors so it is not counted as a CCC, with one exception, *if the current is more than 50% nonlinear then the neutral would count as a CCC.

120/240 volt system-different circuit types:

D)- 2 wire circuit w/ 1 ungrounded, 1 neutral = 2 CCC's
E)- 3 wire circuit w/ 2 ungrounded, 1 neutral = 2 CCC's

Notes:
D)- A normal 2 wire circuit has equal current flowing in each of the circuit conductors so they both count as CCC's.
E)- In this circuit the neutral will only carry the imbalance between the two ungrounded condcutors so the neutral is not counted as a CCC.
 

kwired

Electron manager
Location
NE Nebraska
Thanks for all the replies guys. I take it the way the calculations were done correctly.
The reason a counted the neutral for the dryer is because the light inside the drum is 120v, so is it ok to count it? I asked a forman on the job and he said the neutral should always be counted. I thought it is counted for receptacles, lighting, and when your load is unbalanced.
Thanks,
Ivan
This has been answered but I will give a little different perspective. The current is unbalanced for the 120 volt portion of the load. The neutral conductor is only carrying the unbalanced current between the two ungrounded conductors. The effective heating within the raceway is still no more than it would be for two conductors carrying the same current.

Thanks for the information. You are correct about it not being on a exam without the dimentions being provided. I just want to know for the real world. Almost daily on the job I see foremen and other higher ups just sticking the wires or cables at the end of the conduit and if it fits then thats the size conduit they use.
Its like counting the neutral or grounded conductor as a current carrying wire. Some folks tell me you always count it. Some say if you have three phases and ony use two phases. The NEC is very confusing when it comes to this, at least to me. If you have a lighting circuit then I believe you count it. What about a receptacle circuit, a dryer with a 120v light and timer, a stove with a 120v light, a 204v circuit, 208v, 277v, 480v, etc. Any help would greatly appreciated.
If you are just sleeving a cable for physical protection there is no fill requirements to meet. If it is a complete raceway from box to box then you do have to comply with raceway fill requirements.

Understanding some basic electricity concepts a little better makes some of the NEC issues you mention make more sense. Like I said above - knowing why a neutral is considered current carrying in some cases and not others is easier to understand if you understant the right basic electrical theory concepts.
 

texie

Senior Member
Location
Fort Collins, Colorado
Occupation
Electrician, Contractor, Inspector
Thanks for the information. You are correct about it not being on a exam without the dimentions being provided. I just want to know for the real world. Almost daily on the job I see foremen and other higher ups just sticking the wires or cables at the end of the conduit and if it fits then thats the size conduit they use.
Its like counting the neutral or grounded conductor as a current carrying wire. Some folks tell me you always count it. Some say if you have three phases and ony use two phases. The NEC is very confusing when it comes to this, at least to me. If you have a lighting circuit then I believe you count it. What about a receptacle circuit, a dryer with a 120v light and timer, a stove with a 120v light, a 204v circuit, 208v, 277v, 480v, etc. Any help would greatly appreciated.
Unfortunately, if you have leaders that "calculate" fill the way you describe you are getting some poor training. As to your comments on counting the neutral(s), keep in mind that fill and derating are seperate issues. For example, neutrals are always counted for fill if they carry current or not. Grounds also count.
If you are calculating adjusted ampacity due to number of conductors (derating), the you must know if they are considered current carrying. See Jumpers reply.
 
Well thanks for clearing up these issues, I now have a better grip on this now. I know better when it comes to pipe fill but I mind my own business because I never forget who is in charge and makes the decision.
Well many,many thanks again for all your help.
 
Something else that I notice that is being done on the job differently by various is phasing wires. 3 phase 240v is phased black, red, blue. 208v and 277v is phased by some black,red,blue and by others brown,orange,yellow. 480v is phased brown,orange,yellow.
Is there a problem with this? By the way some guys dont phase their wires at all.
 

ActionDave

Moderator
Staff member
Location
Durango, CO, 10 h 20 min without traffic from wing
Occupation
wire pulling grunt
Something else that I notice that is being done on the job differently by various is phasing wires. 3 phase 240v is phased black, red, blue. 208v and 277v is phased by some black,red,blue and by others brown,orange,yellow. 480v is phased brown,orange,yellow.
Is there a problem with this? By the way some guys dont phase their wires at all.
I took the motto that says "Green to everything" and changed it to "Green for everything". (Of course that is not true. But it gets one guy that I work with all riled up when I say it).

The code does not spell out a specific colour code just that you have to stick with one if that is the way you decide to comply with 210.5

Brown, orange, yellow for 277/480V and Black, red, blue, for 208/120 if fairly common but is not the law of the land.

210.5 Identification for Branch Circuits
(A) Grounded Conductor. The grounded conductor of a
branch circuit shall be identified in accordance with 200.6.
(B) Equipment Grounding Conductor. The equipment
grounding conductor shall be identified in accordance with
250.119.
(C) Identification of Ungrounded Conductors. Un-
grounded conductors shall be identified in accordance with
210.5(C)(1), (2), and (3).
(1) Application. Where the premises wiring system has
branch circuits supplied from more than one nominal volt-
age system, each ungrounded conductor of a branch circuit
shall be identified by phase or line and system at all termina-
tion, connection, and splice points.
(2) Means of Identification. The means of identification
shall be permitted to be by separate color coding, marking
tape, tagging, or other approved means.

(3) Posting of Identification Means. The method utilized
for conductors originating within each branch-circuit panel-
board or similar branch-circuit distribution equipment shall
be documented in a manner that is readily available or shall
be permanently posted at each branch-circuit panelboard or
similar branch-circuit distribution equipment.
 

kwired

Electron manager
Location
NE Nebraska
Something else that I notice that is being done on the job differently by various is phasing wires. 3 phase 240v is phased black, red, blue. 208v and 277v is phased by some black,red,blue and by others brown,orange,yellow. 480v is phased brown,orange,yellow.
Is there a problem with this? By the way some guys dont phase their wires at all.
I took the motto that says "Green to everything" and changed it to "Green for everything". (Of course that is not true. But it gets one guy that I work with all riled up when I say it).

The code does not spell out a specific colour code just that you have to stick with one if that is the way you decide to comply with 210.5

Brown, orange, yellow for 277/480V and Black, red, blue, for 208/120 if fairly common but is not the law of the land.

210.5 Identification for Branch Circuits
(A) Grounded Conductor. The grounded conductor of a
branch circuit shall be identified in accordance with 200.6.
(B) Equipment Grounding Conductor. The equipment
grounding conductor shall be identified in accordance with
250.119.
(C) Identification of Ungrounded Conductors. Un-
grounded conductors shall be identified in accordance with
210.5(C)(1), (2), and (3).
(1) Application. Where the premises wiring system has
branch circuits supplied from more than one nominal volt-
age system, each ungrounded conductor of a branch circuit
shall be identified by phase or line and system at all termina-
tion, connection, and splice points.
(2) Means of Identification. The means of identification
shall be permitted to be by separate color coding, marking
tape, tagging, or other approved means.

(3) Posting of Identification Means. The method utilized
for conductors originating within each branch-circuit panel-
board or similar branch-circuit distribution equipment shall
be documented in a manner that is readily available or shall
be permanently posted at each branch-circuit panelboard or
similar branch-circuit distribution equipment.
For the installations where the ungrounded conductors are not marked at all - part (1) only requires marking of ungrounded conductors where there is more than one voltage system present. Many guys like to mark them anyway but it is not required.
 

Smart $

Esteemed Member
Location
Ohio
... 3 phase 240v is phased black, red, blue. ...
If it is a 240V 3? 3-wire system, that would be a delta supply, and code requires one "corner" to be grounded... it would have to be colored or marked as such (e.g. white).

If it is a 240/120V 3? 4-wire system, sometimes referred to as a high leg supply, this would be a delta supply having a transformer winding center-tapped and grounded. The voltage between "phase" B and the grounded center-tap connection is 208V compared to 120V from A or C to ground. Code requires "phase" B conductors of such system to be colored or otherwise marked orange.
 
Last edited:

kwired

Electron manager
Location
NE Nebraska
If it is a 240V 3? 3-wire system, that would be a delta supply, and code requires one "corner" to be grounded... it would have to be colored or marked as such (e.g. white).

If it is a 240/120V 3? 4-wire system, sometimes referred to as a high leg supply, this would be a delta supply having a transformer winding center-tapped and grounded. The voltage between "phase" B and the grounded center-tap connection is 208V compared to 120V from A or C to ground. Code requires "phase" B conductors of such system to be colored or otherwise marked orange.
Last sentence in 110.15:
Such identification shall be placed at each point on the system where a connection is made if the grounded conductor is also present.
They don't have to be marked if the neutral is not present and there is only one voltage system present at the premises.
 

Smart $

Esteemed Member
Location
Ohio
Last sentence in 110.15:

They don't have to be marked if the neutral is not present and there is only one voltage system present at the premises.
For clarity to all readers, you are referring to the "orange" marking requirement for high leg system.
 

Smart $

Esteemed Member
Location
Ohio
I thought it was what you were referring to also:)
I was... in my second paragraph. But you quoted my entire post, and the first paragraph was regarding a 240V "corner-grounded" without neutral, having different marking requirements.
 

kwired

Electron manager
Location
NE Nebraska
I was... in my second paragraph. But you quoted my entire post, and the first paragraph was regarding a 240V "corner-grounded" without neutral, having different marking requirements.
I see. I probably should have only quoted the second paragraph, as that is all I was responding to. Just so you know, I will probably do it again sometime:happyyes:
 
Gentlemen, I dont know if I should start a new thread but I have a coworker that is doing a side job and ran into a problem that is quite puzzling. This home owner has a detached workshop being fed from the main panel. The shop sub-panel is single phase 240v. There are three 240v breakers that feed a small compressor, a small window air conditioner, and something else that I cant remember.
There is a 120v breaker that feeds some lights, and two 120v breakers that feeds some receptacles. The 240v circuits work fine but the 120v circuits doesnt. The lights are very dim but when a electric drill motor is plugged into one of the receptacles and you squeeze the trigger the lights burn bright. He said the home owner said everything worked fine for the past two years and that no changes was made and this problem just started the last two weeks. My friend mentioned that when he test the lights and receptacles with a meter he only gets 72 to 75 volts. He also said that no ground was pulled from the main panel to the sub-panel but a neutral was pulled. He said all the grounds and neutrals in the sub-panel are on the same ground bar.
What gives here.
 

texie

Senior Member
Location
Fort Collins, Colorado
Occupation
Electrician, Contractor, Inspector
Gentlemen, I dont know if I should start a new thread but I have a coworker that is doing a side job and ran into a problem that is quite puzzling. This home owner has a detached workshop being fed from the main panel. The shop sub-panel is single phase 240v. There are three 240v breakers that feed a small compressor, a small window air conditioner, and something else that I cant remember.
There is a 120v breaker that feeds some lights, and two 120v breakers that feeds some receptacles. The 240v circuits work fine but the 120v circuits doesnt. The lights are very dim but when a electric drill motor is plugged into one of the receptacles and you squeeze the trigger the lights burn bright. He said the home owner said everything worked fine for the past two years and that no changes was made and this problem just started the last two weeks. My friend mentioned that when he test the lights and receptacles with a meter he only gets 72 to 75 volts. He also said that no ground was pulled from the main panel to the sub-panel but a neutral was pulled. He said all the grounds and neutrals in the sub-panel are on the same ground bar.
What gives here.
You have an open or partially open neutral. As for the no EGC, that may be OK depending what code year it was installed under. You still need a grounding electrode system regardless of the code year.
 
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