Electrical talk: 12-3 power cord vs romex

bobs409

 
Administrator
In my research for the grinder build, I decided on 12 gauge wire to go from VFD to motor. (using 10 gauge to power VFD)

I was told that 12-3 wire actually has 4 wires so that's what I ordered in cord form. I checked the Home Depot site and the Romex 12-3 IS showing 4 wires but the 12-3 power cord (wire by the foot) that I purchased only has 3 wires. (never noticed it until now that I OWN it!)

Is that a common thing??? I did want the ground wire inside the cord but screw it, now I'll just ground the motor to the grinder/cart and another ground at the VFD location to the cart. Since the motor is bolted on anyway, it's all grounded but I'll do the wire for good sportsmanship. :D I tried! :angry

Google search says 12-3 wire is 4 wires! Guess either cord is different or Home depot is in error.

Curious what our electricians here have to say. :D Do we have any????:waiting1:
 

bobs409

 
Administrator
Yeah that's what I wanted but... surprise! :D

Obviously for some reason, cord 12-3 and Romex 12-3 do not contain the same amount of wires. :wacko :bonk Now the big question is WHY????? :rub :read
 

rstreet

Well Known Member
Supporting Member 17
Yeah that's what I wanted but... surprise! :D

Obviously for some reason, cord 12-3 and Romex 12-3 do not contain the same amount of wires. :wacko :bonk Now the big question is WHY????? :rub :read

Different applications Bob;) But... what you are doing the local codes would determine which wiring scheme is correct and those VFD's can be "touchy" just saying.
Robert
 

rstreet

Well Known Member
Supporting Member 17
Go for it. Don't let the smoke out!

No don't let any smoke out! A well meaning neighbor will call the fire dept. Then on the fire dept logs they will log it as an electrical source fire. The 911 call center will have the State Fire marshal "stop by" for final opinion. Fire marshall young whippersnapper will log in that the issue needs further investigation and send it to the county planning and zoning for permitting violations and or master electricain error on the part of the licensed master electrical contractor who pulled the permit. Then the state certified electrical inspection agency will be called in to determine the cause. Since the permitting wasn't complete the county planning and zoning will send out a mandatory cease and desist while sending the report to the statres attorney's office for setting a court date for the many violations.
Remember Bob I was a county department head for a bunch of years and like the Farmers Insurance ad says we've seen that before.:D
Robert
 

409gang

Well Known Member
Supporting Member 1
In my research for the grinder build, I decided on 12 gauge wire to go from VFD to motor. (using 10 gauge to power VFD)

I was told that 12-3 wire actually has 4 wires so that's what I ordered in cord form. I checked the Home Depot site and the Romex 12-3 IS showing 4 wires but the 12-3 power cord (wire by the foot) that I purchased only has 3 wires. (never noticed it until now that I OWN it!)

Is that a common thing??? I did want the ground wire inside the cord but screw it, now I'll just ground the motor to the grinder/cart and another ground at the VFD location to the cart. Since the motor is bolted on anyway, it's all grounded but I'll do the wire for good sportsmanship. :D I tried! :angry

Google search says 12-3 wire is 4 wires! Guess either cord is different or Home depot is in error.

Curious what our electricians here have to say. :D Do we have any????:waiting1:
SO cord or what you call rubber cord always includes the ground wire (example 12-3 equals 1 Black, 1 white and 1 green wire) where as romex and mc cable 12-3 is 1 black, 1 red, 1 white and 1 bare or green wire. I don't know why this is but Home Depot was right, also if you use stranded wire verses romex (solid wire) the wire will carry a greater amperage. The finer the strands and the more of them gives the wire a greater ampacity rating due to what is called the skin affect.
 

bobs409

 
Administrator
Don't worry about the wire size, I went bigger than it called for. Said 14 gauge for vfd to motor but I went with 12. It's only a very short piece anyway, probably about 2' when all done. :D
 

409gang

Well Known Member
Supporting Member 1
That is correct. A few years ago I buried most of the wires here using mostly 4/0 alum. To 2 of the buildings I reduced it to 2/0.
The rule of thumb is once you know the proper size wire for the intended load you should up it one size for every 100' of run. This is for voltage drop also along with amperage draw.
 

409gang

Well Known Member
Supporting Member 1
For all you do it yourselfers out there here is a simple chart to properly size the wire you need for a given amperage (load). You use the 60 degree C column for loads under 100 amp and the 75 degree C column for loads 100 amp and up. This chart is the same for any voltage even 12V as you are sizing the conductor for amperage, also you need to use the proper over current protection. Remember you should only load a conductor to 80% of its listed amperage so a 20 amp circuit ran on 12ga wire should carry a maximum of 16 amps.IMG_4847.JPG
 
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