Replacing old wire

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Old 12-04-03, 08:38 PM
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Question Replacing old wire

My house was built in the late 1940s and I just upgraded from 60 amp service w/fuses to 100 amp service w/circuit breakers. The original service was grounded, but the individual circuits did not have a grounding wire. They were only grounded thru the rigid metal conduit (basement & garage) or flexible conduit (rest of house). All of the boxes are metal.

I'm slowly replacing much of the old original wiring, adding a ground wire to individual circuits and maybe adding add'l circuits.

Question 1: Is there any difference between Bx cable and flexible conduit for the purpose of rewiring? How can I tell which I have? (Some areas have 2 circuits running thru them [4 wires], so I assuming that it isn't Bx cable.) I'm hoping to use this conduit since it will make it much easiest to pull new wire.


Question 2: If all of my wire is within rigid metal or flexible metal conduit, do I have to use Romex wire or can I use individual hot/neutral/ground THHN or THWN wire? The reason is that the flexible conduit is not big enough to fit 2 circuits of Romex 14-2 NM-B w/Ground. I can't use 14-3 for the 2 circuits because in some areas the conduit carries wires for a 3 way switch and a separate circuit.


Question 3: I have one 20 amp circuit to my garage. Do any light switches and wires on that circuit need to be rated for 20 amps? Or can I use a 15 amp switch w/14 guage AWG for lights? Nothing is "downstream" from the switch on that circuit. The wiring to the 20 amp outlets is 12 guage AWG.


Question 4: The light switches in the garage are in a metal box w/metal cover and are not currently grounded. I going to add a ground wire, but do I need to have the light switch GFCI protected?

Thanks a bunch.
 
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Old 12-04-03, 09:19 PM
merfturtle
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First, I hope you upgraded the service wire to the new panel to handle 100 A. Assuming that is the case, lets move on. Any circuits in rigid meatl conduit are already grounded by way of the pipe. Flexble metal conduit must have a ground wire run itin it. Thhn wire can be used in both, with the addition of the ground wire in any flexible.switches on any circuit do not have to match the total circuit draw, only what they(the switch) are to control. If the circuit to the garage is run in rigid conduit, all you have to do is add a ground wire in the box and attach to the switch, I do not believe switches are required to GFCI protected. also remember breaker size must be matched to wire size. ie. a 20 A circuit must be run in #12, #14 = 15 A. Marc
 
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Old 12-04-03, 09:31 PM
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Re: Replacing old wire

Originally posted by BHB_RHG

Question 1: Is there any difference between BX cable and flexible conduit for the purpose of rewiring? How can I tell which I have? (Some areas have 2 circuits running through them [4 wires], so I assuming that it isn't BX cable.) I'm hoping to use this conduit since it will make it much easiest to pull new wire.
The difference is that Armored Cable (UL type AC) which we commonly call BX is installed with the wires already in the armor and it is completely impractical to remove them. The wires will be twisted around each other and will have an overall covering of kraft paper tightly wound around them.. If your installation has individual conductors with no overall wrapping then it is Flexible Metallic Conduit.

Question 2: If all of my wire is within rigid metal or flexible metal conduit, do I have to use Romex wire or can I use individual hot/neutral/ground THHN or THWN wire? The reason is that the flexible conduit is not big enough to fit 2 circuits of Romex 14-2 NM-B w / Ground. I can't use 14-3 for the 2 circuits because in some areas the conduit carries wires for a 3 way switch and a separate circuit.
Not only do you not have to use romex in conduit but it is considered bad practice and some code authorities believe it is a code violation.

Question 3: I have one 20 amp circuit to my garage. Do any light switches and wires on that circuit need to be rated for 20 amps? Or can I use a 15 amp switch w/14 gauge AWG for lights? Nothing is "downstream" from the switch on that circuit. The wiring to the 20 amp outlets is 12 gauge AWG.
Wires yes. Light switches no. Wires are tested and rated for the current they can carry. And switches are tested and listed for the current they can safely interrupt without damage to the switch. Most switches can carry far more current than they can interrupt. If the garage is detached you must have a single switch or set of three way switches that will open all ungrounded conductors and although the code does not require this those switches should be listed for the ampacity of the circuit.

Question 4: The light switches in the garage are in a metal box w / metal cover and are not currently grounded. I going to add a ground wire, but do I need to have the light switch GFCI protected?
Only the receptacle outlets in the garage are required to be GFCI protected.
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Tom H
 
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Old 12-05-03, 09:15 AM
brickeyee
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AC cable is slightly different than old BX. AC has a thin metallic bond wire to ensure ground continuity. The original BX did not have the bond wire and the armor was not listed as a grounding means. The bond wire does not need termination in any way. Flexible Conduit does not have a bond wire and a ground wire must be run in the conduit.
If you can see the thin bond wire, the cable is AC, and is an acceptable grounding method. You may still want to replace it since much of the old AC used rubber insulation (often with a cloth jacket for color) that is brittle and easily damaged.
 
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Old 12-05-03, 10:23 AM
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A couple of follow-up questions:

Can anyone tell me why it is bad practice to run romex in conduit? I ask because I ran 12-2 NM-B w/ground in rigid metal conduit for a dedicated circuit to my washing machine. It's only about 6 ft. from the service panel, so replacing it isn't a problem.


Hornetd wrote "If the garage is detached you must have a single switch or set of three way switches that will open all ungrounded conductors and although the code does not require this those switches should be listed for the ampacity of the circuit."

I'm not exactly sure what that means, but it might not be applicable since my garage is attached - sort of. The garage is connected to the house by a breezeway. The breezeway is a permanent structure, but is isn't finished. From a code standpoit, does this make my garage attached or detached?


BTW- From the answers here, it appears that it is flexible metallic conduit instead of armored cable. And the 60 to 100 amp service upgade was done by a qualified electrician and inspected by my municipality.
 
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Old 12-05-03, 12:35 PM
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The biggest problem running NM cable in conduit is the risk of damage to the cable while getting it through the conduit. For only six feet, I wouldn't give it another thought -- leave it be.

Whether or not a breezeway connected garage is considered "attached" is subject to the interpretation of the inspector. It goes both ways.

Tom, you referred to a "single switch." Does it really need to be just one switch. Does the "six sweeps of the hand" rule apply here? I don't have my code book with me, so I can't look up the exact wording.
 
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Old 12-05-03, 02:48 PM
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"Snap" switches as building disconnects.

The way I read 225.36 the only acceptable building disconnecting means are "suitable for use as service equipment" or "a snap switch or a set of 3-way or 4-way snap switches." Since "a" is the singular adjective I take it to mean only one switch or only one circuit controlled by three and or four way switches. That is totally consistent with the exception that allows us to serve an outbuilding with a single branch circuit without building a grounding electrode system at the outbuilding. If you use multiple switches that are not listed as service equipment your only reason for doing that would be a violation of 225.30 in that you would have run multiple circuits to the out building when the rule permits one branch circuit or one feeder. If the branch circuit is multiwire then I believe the use of the singular adjective "a" would require the use of a single double pole "snap" (toggle) switch or a disconnect listed as service equipment.
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Tom

225.30 Number of Supplies.
Where more than one building or other structure is on the same property and under single management, each additional building or other structure served that is on the load side of the service disconnecting means shall be supplied by one feeder or branch circuit unless permitted in 225.30(A) through (E). For the purpose of this section, a multiwire branch circuit shall be considered a single circuit.

225.36 Suitable for Service Equipment.
The disconnecting means specified in 225.31 shall be suitable for use as service equipment.
Exception: For garages and outbuildings on residential property, a snap switch or a set of 3-way or 4-way snap switches shall be permitted as the disconnecting means.
 
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