half inch emt with # 8

[hardworker]

For a number of reasons, I am forced to use an existing half inch emt run that feeds an rooftop a/c condenser. I need to run two conductors of #8 for a 40amp circuit. I have three 90 degree elbows in the 70ft. run, so the pull might get tight. Will code allow a smaller ground than #8?

 

[mcclary's electrical]

for a number of reasons, i am forced to use an existing half inch emt run that feeds an rooftop a/c condenser. I need to run two conductors of #8 for a 40amp circuit. I have three 90 degree elbows in the 70ft. Run, so the pull might get tight. Will code allow a smaller ground than #8?

250.122.......

 

[jumper]

250.118 says you can use the emt as an EGC.

 

[mcclary's electrical]

250.118 says you can use the emt as an EGC.

Now that's saving room!:grin:

 

[hardworker]

The emt changes to seal tight before it passes through the roof, so using the conduit as ground won't work. Can I use #12 or #10 as ground? Do you think three conductors of #8 will pull?

 

[mcclary's electrical]

The emt changes to seal tight before it passes through the roof, so using the conduit as ground won't work. Can I use #12 or #10 as ground? Do you think three conductors of #8 will pull?

Yes, (2) 8's and a 10 will go in a 1/2" assuming THWN

Is there a box at the changeover to flex. If so, just ground from there to unit, not the whole run.

 

[hardworker]

Yes there is a box, so grounding from it to the unit is an option. Does code allow the #10 to be used as ground?

 

[mcclary's electrical]

Yes there is a box, so grounding from it to the unit is an option. Does code allow the #10 to be used as ground?

If cu then yes. Up to 60amps

 

[hardworker]

ok, thanks

 

[Dennis Alwon]

I would add a JB as McClary said to avoid the run in the emt.

 

[HuskyDog18943]

Article 350 of ANSI/NFPA 70, "National Electrical Code" (NEC).

Article 350 of ANSI/NFPA 70, "National Electrical Code" (NEC).

Where terminated in fittings investigated for grounding and where installed with not more than 6 ft (total length) in any ground return path, liquid-tight flexible metal conduit in the 3/8 and 1/2 (12 and 16) trade sizes is suitable for grounding where used on circuits rated 20 A or less, and the 3/4, 1 and 1-1/4 (21, 27 and 35) trade sizes are suitable for grounding where used on circuits rated 60 A or less. See Conduit Fittings (DWTT) with respect to fittings suitable as a grounding means.

The following are not considered to be suitable as a grounding means:

1. The 1-1/2 (41) and larger trade sizes.
2. The 3/8 and 1/2 (12 and 16) trade sizes where used on circuits rated higher than 20 A, or where the total length in the ground return path is greater than 6 ft.
3. The 3/4, 1 and 1-1/4 (21, 27 and 35) trade sizes where used on circuits rated higher than 60 A, or where the total length in the ground return path is greater than 6 ft.

 

[kwired]

For a number of reasons, I am forced to use an existing half inch emt run that feeds an rooftop a/c condenser. I need to run two conductors of #8 for a 40amp circuit. I have three 90 degree elbows in the 70ft. run, so the pull might get tight. Will code allow a smaller ground than #8?

Is the overcurrent device 40 amps or is the load 40 amps?

If feeding an AC unit, a unit requiring 40 amp overcurrent device will often have a load of around 20-25 amps. If you are installing larger than otherwise needed conductors for voltage drop you need to increase equipment ground conductor by a similar increase in size.

 

[Cow]

You want to pull #8's into 1/2" emt and your username happens to be "hardworker."

It's perfect.

 

[Chamuit]

You're probably gonna need someone pushing on the other end!


3 #8 THHN = 0.1098 in?
40% on ?" EMT = 0.122 in?

or

3 #8 THHN = 70.83 mm?
40% on ?" EMT = 78 mm?

2 #8's and a#10 for the ground would be a little easier and coderific.

 

[mcclary's electrical]

Where terminated in fittings investigated for grounding and where installed with not more than 6 ft (total length) in any ground return path, liquid-tight flexible metal conduit in the 3/8 and 1/2 (12 and 16) trade sizes is suitable for grounding where used on circuits rated 20 A or less, and the 3/4, 1 and 1-1/4 (21, 27 and 35) trade sizes are suitable for grounding where used on circuits rated 60 A or less. See Conduit Fittings (DWTT) with respect to fittings suitable as a grounding means.

The following are not considered to be suitable as a grounding means:

1. The 1-1/2 (41) and larger trade sizes.
2. The 3/8 and 1/2 (12 and 16) trade sizes where used on circuits rated higher than 20 A, or where the total length in the ground return path is greater than 6 ft.
3. The 3/4, 1 and 1-1/4 (21, 27 and 35) trade sizes where used on circuits rated higher than 60 A, or where the total length in the ground return path is greater than 6 ft.

and?

 

[iwire]

You want to pull #8's into 1/2" emt and your username happens to be "hardworker."

It's perfect.

I was thinking the same thing. :grin: