Conduit Fill

S

Silky1

Member
Location
Ohio
Occupation
Electrician
Hello, I’m installing a Level 2 Electric Car charger. The max amp draw is 48 amps, so I’ll be installing a 60 amp 240 volt circuit. I’m going to use 2 #6 THHN with 1 #10 THHN for a ground. So I would need .122 of area in a 1/2 inch EMT (this will be all inside) once I completed the math I have .125 of fill area in the 1/2 inch, my question is, would .003 make a big differences. Reason for the 1/2 inch is the conduit will be installed in a finish basement so I was looking at trying to keep the conduit less obtrusive. As a side note I’ll be changing to 1/2 inch flex with has an area of .127 so we are good for flex. Thank You for your input on this matter.
 
Silky1 said:
Hello, I’m installing a Level 2 Electric Car charger. The max amp draw is 48 amps, so I’ll be installing a 60 amp 240 volt circuit. I’m going to use 2 #6 THHN with 1 #10 THHN for a ground. So I would need .122 of area in a 1/2 inch EMT (this will be all inside) once I completed the math I have .125 of fill area in the 1/2 inch, my question is, would .003 make a big differences. Reason for the 1/2 inch is the conduit will be installed in a finish basement so I was looking at trying to keep the conduit less obtrusive. As a side note I’ll be changing to 1/2 inch flex with has an area of .127 so we are good for flex. Thank You for your input on this matter.
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According to http://conduitfillcalculator.com/ in 1/2" EMT you are over 40% by 0.32%.
 
as am alternative you could change the EGC to a bare conductor or add a j box at the transition and use the EMT as the EGC up to to J box then a grounding conductor thru the flex.
 
Silky1 said:
I’m going to use 2 #6 THHN with 1 #10 THHN for a ground. So I would need .122 of area in a 1/2 inch EMT (this will be all inside) once I completed the math I have .125 of fill area in the 1/2 inch
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I get 0.1225, so you're only over 0.0005 in^2.

Edit: also, if I use the OD in mils from Southwire's website, I get areas slightly under the NEC Table values, so the total area becomes less than the the 0.122 in^2 allowable.

Cheers, Wayne
 
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Silky1 said:
Hello, I’m installing a Level 2 Electric Car charger. The max amp draw is 48 amps, so I’ll be installing a 60 amp 240 volt circuit. I’m going to use 2 #6 THHN with 1 #10 THHN for a ground. So I would need .122 of area in a 1/2 inch EMT (this will be all inside) once I completed the math I have .125 of fill area in the 1/2 inch, my question is, would .003 make a big differences. Reason for the 1/2 inch is the conduit will be installed in a finish basement so I was looking at trying to keep the conduit less obtrusive. As a side note I’ll be changing to 1/2 inch flex with has an area of .127 so we are good for flex. Thank You for your input on this matter.
Click to expand...

Can you post the wire diameters and conduit diameters you are using for your calculation?

I get that the wire will require 0.118 in^2, the conduit has an internal area of 0.304 in^2 and a conduit fill of 39%. Close to the max but still code legal.

-Jonathan
 
augie47 said:
winnie, with THWN-2 I get 0.1225
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And that agrees with @wwhitney . I think I see where the difference comes from.

I went to the southwire calculator site, and they use a diameter of 0.249" for #6 THHN, and 0.161" for #10 THHN. Table 5 gives 0.254" and 0.164" respectively.

IMHO this install would be kosher on the basis of manufacturer wire dimensions, but agree with @augie47 , just use a bare EGC or use the EMT itself as the EGC.
 
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