CONDUIT FILL

[ohmhead]

What is the the max amount of no# 2 copper thwn-2 wires I can get in a 1 inch flex metal conduit ? I see 3 total can I run the ground on the out side of the flex which would be a number 8 thwn-2 and if so can it be bare copper wire .

 

[infinity]

For argument sake if you could run the EGC on the outside how would you connect it at each end?

 

[ohmhead]

For argument sake if you could run the EGC on the outside how would you connect it at each end?

Well lets see drill a hole in the bottom of VFD pass it thur a fitting made for a single wire that size which would be 8 #awg install a grounding bushing on the flex connector that the 3 number 2 #awg pass thur that with a listed grounding bushing so I have a bond also on the flex . Now if its not a grounding electrode conductor would I have to bond both ends to the raceway or just the one end .

Or should I not connect to flex bushing do to a choke condition ?

 

[Dennis Alwon]

I don't think you can run the equipment grounding conductor outside the conduit-- 300.3(B)

 

[Fulthrotl]

I don't think you can run the equipment grounding conductor outside the conduit-- 300.3(B)

they used to make sealtight fittings that had a ground lug
on the outside of the compression nut, and you could spiral
a piece of #12 on the outside of the sealtight to bond it,
and i've seen them on old installs, but it's not been allowed
for maybe 30 years or so......

 

[pjholguin]

May I ask, what are circuit requirements i.e. amps and OCP size?

What is the the max amount of no# 2 copper thwn-2 wires I can get in a 1 inch flex metal conduit ? I see 3 total can I run the ground on the out side of the flex which would be a number 8 thwn-2 and if so can it be bare copper wire .

 

[don_resqcapt19]

they used to make sealtight fittings that had a ground lug
on the outside of the compression nut, and you could spiral
a piece of #12 on the outside of the sealtight to bond it,
and i've seen them on old installs, but it's not been allowed
for maybe 30 years or so......

If there is a metal raceway that the flexible metal conduit is connected to, then the FMC would need a bonding jumper, and those fittings are fine for the bonding jumper connection.

We use them all the time for LFMC connections to motors, but we also have an internal EGC. The code would permit us to eliminate the internal EGC and just use the bonding jumper as the conduit the LFMC is connected to is rigid.

The question as to installing the bonding jumper in spiral around the flex has been the subject of a number of threads.

 

[ohmhead]

I don't think you can run the equipment grounding conductor outside the conduit-- 300.3(B)

What about article 250.102 (d) (e) (1) (2) if less than 6 foot exhitbit 250.43 2014 code book

 

[ohmhead]

If there is a metal raceway that the flexible metal conduit is connected to, then the FMC would need a bonding jumper, and those fittings are fine for the bonding jumper connection.

We use them all the time for LFMC connections to motors, but we also have an internal EGC. The code would permit us to eliminate the internal EGC and just use the bonding jumper as the conduit the LFMC is connected to is rigid.

The question as to installing the bonding jumper in spiral around the flex has been the subject of a number of threads.

Well i would never sprial the ground around the flex if i gave that impression. I planned on running it straight attached to the flex with plastic tie raps . What we have is three number 2#AWG CU 3 phase conductors no neutral which enter a VFD the reason we need 1" is because the VFD doesnt alow a 1 1/4" conduit on the bottom so we need a 1 " i think i may also just use the nipple rule less than 24 " of conduit then i can install 60 % conductors .
Do you think that might be a better option Don . When i was asking about a choke effect we were thinking a ground current loop between the outside EGC and the flex itself but it would be less than 6 foot that was my question to the forum . Even if the code alows this what could happen in a fault current wise using that method of grounding . :huh:

 

[Dennis Alwon]

Can't you use an 11/4" fmc?

 

[pjholguin]

May I ask, what are circuit requirements i.e. amps and OCP size?

Well i would never sprial the ground around the flex if i gave that impression. I planned on running it straight attached to the flex with plastic tie raps . What we have is three number 2#AWG CU 3 phase conductors no neutral which enter a VFD the reason we need 1" is because the VFD doesnt alow a 1 1/4" conduit on the bottom so we need a 1 " i think i may also just use the nipple rule less than 24 " of conduit then i can install 60 % conductors .
Do you think that might be a better option Don . When i was asking about a choke effect we were thinking a ground current loop between the outside EGC and the flex itself but it would be less than 6 foot that was my question to the forum . Even if the code alows this what could happen in a fault current wise using that method of grounding . :huh:

 

[infinity]

Can't you use an 11/4" fmc?

Sounds like he's trying to get away with using only 1" FMC and his conductor fill is over the 40% limit. If he can keep the length to 24" or less then maybe he can use 60% fill and include the EGC on inside,

 

[ohmhead]

Sounds like he's trying to get away with using only 1" FMC and his conductor fill is over the 40% limit. If he can keep the length to 24" or less then maybe he can use 60% fill and include the EGC on inside,

Yes the problem is we have a AHU which has three fans each has a VFD they only accept a 1 inch conduit so three no.2# & one no.8# EGC is not code . But we will most likely do the nipple because there all on one rack close to one another .

 

[pjholguin]

I guess you don't want answer my question; however, will the AHU allow you to use the 24" rule...my understanding is that for a nipple, not the extension of a raceway. Are the VFDs group? If so use a gutter, if not maybe some sort of transition point using a box or a conduit body. JSI

P.S. just saw your last post, than a gutter and nipples would be the to go.

Yes the problem is we have a AHU which has three fans each has a VFD they only accept a 1 inch conduit so three no.2# & one no.8# EGC is not code . But we will most likely do the nipple because there all on one rack close to one another .

 

[pjholguin]

Are you going to run separate feeds from the OCP? If you use a single feed you can use the tap codes...JMO...
Accidently hit the smilely face and can't remove it ...does anyone know to remove them?

I guess you don't want answer my question; however, will the AHU allow you to use the 24" rule...my understanding is that for a nipple, not the extension of a raceway. Are the VFDs group? If so use a gutter, if not maybe some sort of transition point using a box or a conduit body. JSI

P.S. just saw your last post, than a gutter and nipples would be the to go.

 

[Ponchik]

Assuming the OCPD is 115Amps your EGC needs to #6. Then your conductor calc comes out to .3981 and the 40% for FMC is .3270.

If you use #8 for EGC your conductor calc comes out to .3840

If you use a nipple the 60% fill is .490


IMO, even though it violates the code, I don't think it will be a safety issue if you install your EGC in the conduit.

 

[ohmhead]

Assuming the OCPD is 115Amps your EGC needs to #6. Then your conductor calc comes out to .3981 and the 40% for FMC is .3270.

If you use #8 for EGC your conductor calc comes out to .3840

If you use a nipple the 60% fill is .490


IMO, even though it violates the code, I don't think it will be a safety issue if you install your EGC in the conduit.

I never said it was a 115 amp breaker its a 60 amp 3 pole 480 v 3 phase circuit so were NEC fine here . With NO. 2# AWG we should be just fine the name plate states 59 fla crt amp the max over current device is 60 amps max .

The wire doesn't rule what amp size you have the breaker does. What my first question posted was how to use 1 " conduit and I think were going with the 24 inch nipples which will be flexed into VFD,s

Thanks for the input which I think was already answered two post ago .

 

[ohmhead]

Are you going to run separate feeds from the OCP? If you use a single feed you can use the tap codes...JMO...
Accidently hit the smilely face and can't remove it ...does anyone know to remove them?

Well yes we are using a gutter under units total of three VFD,s were going to use the full size feeder and tap each with 24 " nipples of flex .
each VFD will get the full size number 2# awg each VFD has a fused disconnect located inside factory installed at 40 amp class J fuses I was thinking if I could reduce the tap to say a number 8# awg I would have to fuse that ahead of the VFD ? yes/ no Or is it ok per code to just use the VFD as the protection ahead of the tap . What you thoughts ?

 

[Ponchik]

I never said it was a 115 amp breaker its a 60 amp 3 pole 480 v 3 phase circuit so were NEC fine here . With NO. 2# AWG we should be just fine the name plate states 59 fla crt amp the max over current device is 60 amps max .

The wire doesn't rule what amp size you have the breaker does. What my first question posted was how to use 1 " conduit and I think were going with the 24 inch nipples which will be flexed into VFD,s

Thanks for the input which I think was already answered two post ago .

I never said you did. Hence "I assume" based on your wire size.

The most important information about your installation was your last post. You should have posted that in your first post.

 

[Dennis Alwon]

Why do you need #2 wire? Can't you use #6 from the disconnect to the unit?