garyfitzgerald
Member
Concerning derating. Are both travelers considered as current carrying conductors even though only one of the travelers is carrying current at any given time?
3 and 4 way travelers
- Thread starter garyfitzgerald
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jimwalker
Senior Member
- Location
- TAMPA FLORIDA
Re: 3 and 4 way travelers
Im not touching that with a 10 ft pole
Im not touching that with a 10 ft pole
jimwalker
Senior Member
- Location
- TAMPA FLORIDA
Re: 3 and 4 way travelers
Changed my mind
All current carrying wires count, used or not.
Answer is yes till im proven wrong.
Changed my mind
All current carrying wires count, used or not.
Answer is yes till im proven wrong.
Re: 3 and 4 way travelers
My vote is that only one of the travellers is a conductor.
A brief thorough glance at the index of my big code book informs me that the Code is mute on the subject. Perhaps this would make a sensible request for a new rule or clarification.
The man says, "All current carrying wires count, used or not." Since the Code doesn't seem to say anything, one way or the other, then we can resort to electrical theory and common sense. The derating rules are based on heat build up with maybe a little EMF[?] tossed in. The logic of a 3- or 4- way system is such that only one conductor is carrying current, therefore the other conductor is not a "current carrying wire...". Thus there would be no heat build up from the unused wire.
~Peter
My vote is that only one of the travellers is a conductor.
A brief thorough glance at the index of my big code book informs me that the Code is mute on the subject. Perhaps this would make a sensible request for a new rule or clarification.
The man says, "All current carrying wires count, used or not." Since the Code doesn't seem to say anything, one way or the other, then we can resort to electrical theory and common sense. The derating rules are based on heat build up with maybe a little EMF[?] tossed in. The logic of a 3- or 4- way system is such that only one conductor is carrying current, therefore the other conductor is not a "current carrying wire...". Thus there would be no heat build up from the unused wire.
~Peter
garyfitzgerald
Member
Re: 3 and 4 way travelers
Bennie
Lets just say there are other current carrying conductors in the conduit and one of the conductors not counting could make the difference in sizing the conductors.
I knew this would be a fun one. I tossed this out to my empolyees.
Bennie
Lets just say there are other current carrying conductors in the conduit and one of the conductors not counting could make the difference in sizing the conductors.
I knew this would be a fun one. I tossed this out to my empolyees.
pierre
Senior Member
- Location
- Westchester County, New York
Re: 3 and 4 way travelers
Bennie
In most typical installations you may be correct as to your reasoning, lets say there are two multigang boxs and there are more than 9 conductors, including the travelers in a raceway inbetween the two boxes.
Than what?
Pierre
Bennie
In most typical installations you may be correct as to your reasoning, lets say there are two multigang boxs and there are more than 9 conductors, including the travelers in a raceway inbetween the two boxes.
Than what?Pierre
jxofaltrds
Inspector Mike®
- Location
- Mike P. Columbus Ohio
- Occupation
- ESI, PI, RBO
Re: 3 and 4 way travelers
314.16(B)(1) last line----"A conductor, no part of which leaves the box, shall not be counted."
When I device none of my wires leave the box. ??? Does that mean I can jamb 8 12-2wg into a single gang, use it as a junction box, and place a blank cover on it?
LOL
Mike P.
314.16(B)(1) last line----"A conductor, no part of which leaves the box, shall not be counted."
When I device none of my wires leave the box. ??? Does that mean I can jamb 8 12-2wg into a single gang, use it as a junction box, and place a blank cover on it?
LOL
Mike P.
tonyi
Senior Member
Re: 3 and 4 way travelers
The no part leaves the box would be for things like the gnd wire now required from a receptical to a metal box. If you were using AC cable, no gnds would be entering and this jumper wouldn't count.
Another situation would be pigtailing on a capped off set of spare leads in a j-box for future use so the original splices don't have to be disturbed to make an addition.
The no part leaves the box would be for things like the gnd wire now required from a receptical to a metal box. If you were using AC cable, no gnds would be entering and this jumper wouldn't count.
Another situation would be pigtailing on a capped off set of spare leads in a j-box for future use so the original splices don't have to be disturbed to make an addition.
al hildenbrand
Senior Member
- Location
- Minnesota
- Occupation
- Electrical Contractor, Electrical Consultant, Electrical Engineer
Re: 3 and 4 way travelers
Supporting this are 310.15(B)(4) and 310.15(B)(5) which describe conductor uses, while present in a raceway, that are not counted for Table 310.15(B)(2)(a) adjustment purposes.
This is aimed at, IMO, ensuring the temperature inside the raceway does not exceed the insulation rating. The current-carrying conductor is the one that heats from the I?R and adds to the heat concentrating in the confined space of the raceway, thus resulting in the temperature increase.
Therefore, only one of the 3- and 4-way travellers should be counted.
The one exception to this general statement for travellers that I can think of is that of the 4-wire Travelling Bus Threeway which has one setting where all four conductors are carrying current simultaneously.
Edit to update the Link to the Travelling Bus - Al
[ March 17, 2005, 09:53 AM: Message edited by: al hildenbrand ]
In the quote I emphasize the active present tense of the adjective used to describe the type of conductor to be counted. The conductor is not the conductor that will, or that has carried current, but is carrying current.
Supporting this are 310.15(B)(4) and 310.15(B)(5) which describe conductor uses, while present in a raceway, that are not counted for Table 310.15(B)(2)(a) adjustment purposes.
This is aimed at, IMO, ensuring the temperature inside the raceway does not exceed the insulation rating. The current-carrying conductor is the one that heats from the I?R and adds to the heat concentrating in the confined space of the raceway, thus resulting in the temperature increase.
Therefore, only one of the 3- and 4-way travellers should be counted.
The one exception to this general statement for travellers that I can think of is that of the 4-wire Travelling Bus Threeway which has one setting where all four conductors are carrying current simultaneously.
Edit to update the Link to the Travelling Bus - Al
[ March 17, 2005, 09:53 AM: Message edited by: al hildenbrand ]
Re: 3 and 4 way travelers
Al: I agree completely. The thermal flow calculations used for determining the number of heat producing conductors are based on the conductors carrying full rated load.
It is also not often the switch legs will be 100% loaded. Both travellers will never be loaded at the same time.
[ December 20, 2003, 06:17 PM: Message edited by: bennie ]
Al: I agree completely. The thermal flow calculations used for determining the number of heat producing conductors are based on the conductors carrying full rated load.
It is also not often the switch legs will be 100% loaded. Both travellers will never be loaded at the same time.
[ December 20, 2003, 06:17 PM: Message edited by: bennie ]
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