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BX Armored Cable - Solid vs Stranded Wire and Ground vs Ungrounded

BX Armored Cable - Solid vs Stranded Wire and Ground vs Ungrounded

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Old 10-08-17, 07:00 AM
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BX Armored Cable - Solid vs Stranded Wire and Ground vs Ungrounded

I want to make a few "whips". I need to upgrade my wiring. I have a circulator pump on a boiler to my aquastat, another wire from my aquastat to a motor, and another wire from one aquastat to another .

The available cable at the store are 14/2 and 14/3 and each come in either solid or stranded wire.

I'm assuming I would use the stranded. I'm not sure when you would use 14/2 over 14/3. Can someone explain the this. Also, when would you use solid over stranded? Thanks
 
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Old 10-08-17, 09:00 AM
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14/2 actually has 2 conductors and a ground wire. 14/3 would be used on 3 phase equipment.
 
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Old 10-08-17, 11:13 AM
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Also, when would you use solid over stranded?

It's personal preference. My opinion is that the solid conductors are much harder to work with.
 
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Old 10-08-17, 11:44 AM
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For furnace work I've always use what's called Greenfield. It comes as a very flexible steel cable just like BX but it comes empty. Then I pull in my own flexible conductors.

The solid type metal clad you are probably looking at is called MC Lite and uses an aluminum metal jacket. The wiring inside is solid and there is an insulated green ground. BX is probably still available and also uses solid wire, no insulated ground but the jacket is steel.

Three wires are used when you need to carry additional switching circuits thru the same cable.
Solid or stranded...... whatever.... stranded is more flexible.
 
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Old 10-08-17, 02:06 PM
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Looks like I have a few options but stranded is what I'll use.

Are the "anti-short bushings" required? It seems like the old lighting wiring didn't have these. They're cheap enough to buy, I just didn't know if it was required. Thanks
 
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Old 10-08-17, 02:56 PM
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The disadvantage to stranded wire versus solid wire is that it's harder to make connections to terminals using the stranded. You either need to crimp the ends into connectors or tin them. Without wire can just wrap it around the terminals. To me the decision should be based on how long the runs are and how flexible you need the wire to make the runs.
 
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Old 10-08-17, 02:58 PM
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Red heads are required for type AC cable but not for MC cable.
 
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Old 10-09-17, 04:58 AM
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PCBOSS,I always use Redheads on both never realized they weren't required for MC.
 
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Old 10-09-17, 10:52 AM
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PCBOSS,I always use Redheads on both never realized they weren't required for MC.

PCBoss is absolutely correct, but many electricians will argue that point. That being said, a package of redheads comes attached to most full 250' rolls of MC cable and most electricians use them religiously.
 
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Old 10-09-17, 10:55 AM
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Most of the union guys don't use the red heads. I don't install any metal clad cable without using one. It eliminates possible shorting problems.
 
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Old 10-09-17, 02:51 PM
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Can I pull out the solid wire from the MC and replace it with stranded?

How come the metal sheathing on the MC is a smaller diameter than the empty flex conduit yet each say 3/8th inch?
 
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Old 10-09-17, 06:00 PM
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PCBOSS ,where does it say they are not required? as Joe mentioned they come in a bag with every 250' coil of MC, this would indicate they are required by the mfg. and should be used.
Jimmy, 3/8" Greefield is much better to use then trying to pull the conductors out of the MC,I don't think MC is 3/8",Greenfield is more flexible and makes a better job, in my opinion.
Geo
 
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Old 10-09-17, 08:00 PM
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PCBOSS ,where does it say they are not required?

http://www.bptfittings.com/Public/Do...MC%20Cable.pdf


This is the short version.

Anti-short bushings are not required for Type MC cable in accordance with the listing for
the product. The termination fittings approved for use with Type MC cables are designed
such that the wires will not come in contact with the cut edge of the armor; the throat of
the fitting is small enough to prevent contact with the armor. Type MC termination
fittings perform the same function for Type MC cable as Type AC terminations plus the
anti-short bushing do for Type AC cable.
 
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Old 10-10-17, 03:55 AM
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The conduit on the left is (I'm assuming) greenfield and the right was the mc. The mc was clearly smaller in diameter but both were listed as 3/8".

It's not a big deal I'm just trying to understand why they are both listed as 3/8". The mc is close to 3/8" inside diameter when the other is closer to 1/2".
 
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Old 10-10-17, 04:35 AM
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The rolls are both flexible metal conduit one steel and one Al not MC .
Geo
 
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Old 10-10-17, 05:01 AM
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Both use a 3/8" connector that fits in a 1/2" knockout.
 
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Old 10-10-17, 06:05 AM
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one steel and one Al not MC
So the "greenfield" is the AL/Steel 2 rolls on the left in the pic? (The MC Lite was at the store but I guess I didn't put it in the first picture).

I was going to ask when steel vs AL would be used but I can look that up. For boiler whips would it matter which one I used? Besides getting your hands black I've read with AL you can't use set screw connectors. Anything else to consider? Thanks
 
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Old 10-10-17, 06:20 AM
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Generally a ground wire must be strung through flexible spiral conduit. There is an exception if metal outlet boxes are used and the conduit interior is not painted/ plastic coated and a metal strip runs the full length inside, outside any paper lining. The spiral conduit all by itself does not count as an equipment grounding conductor. Such a metal strip need not come into outlet boxes and be wire nutted to other equipment grounding conductors.
 
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Old 10-10-17, 06:42 AM
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Hopefully this is the last question. I tend to save all my old electrical fittings and these are from an older demolition. Some of the ends are triangle shaped, some are round, and some round but a little different shaped.

Is there a reason for the shapes or is this just a manufacturer design? thanks
 
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