250.122(F)

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luke warmwater

Senior Member
Looking at drawings of a 2500amp service. From transformer to 2500amp disconnect, 6sets of 4" with 4:600mcm. From disconnect to MDP 6sets of 4" with 4:600mcm and 1:3/0. The ground wire size in each conduit seems wrong as per Table 250.122 or am I reading the table wrong?
 

gwz2

Senior Member
Location
Indiana
Re: 250.122(F)

This may be off of the original question topic, but the info was provided of the Service Entrance conductors.

If the Service entrance raceway(s) have and any part of the raceway is metallic, then 250.102(C) must be applied.

Was on a site that was a 4000 amp service and the installers had just daisy chained a 4 AWG through the bonding bushings on the metal 90?'s stub-ups.

Installers very upset that they had to abide by 250.102(C), a 3/0 from each stub-up.
 

luke warmwater

Senior Member
Re: 250.122(F)

Dereck, I'm sorry, it's PVC. It appears that they based the ground on the basis of 3:600mcm per conduit with ampacity of 1260 amp and listed 3/0 and not on the ampacity of the overcurrent device.Or that they based it on Table 250.66. Todd
 

dereckbc

Moderator
Staff member
Location
Plano, TX
Re: 250.122(F)

Todd, that is why I asked. If it had been RMC, I would have said the EE was probable supplying a supplemental equipment bonding jumper per 250.102(C) for added safety.
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
Re: 250.122(F)

Dereck,
If the EGC is installed in the raceways between the main disconnect and the panel, it must be installed per 250.122(F), and this would require a 350 kcmil in each raceway. I don't know of any code setion that permits a smaller EGC in a raceway that is in itself suitable for use as an EGC.
Don
 

dereckbc

Moderator
Staff member
Location
Plano, TX
Re: 250.122(F)

Don, maybe you did not read my first reply. I agree a 350 MCM is required in each raceway. If it had been RMC used rather than PVC, then no EGC would have been required. At that point the EE could elected to use anything, and I was just guessing what the intention might of been. Assuming gets me in trouble. :D
 

gwz2

Senior Member
Location
Indiana
Re: 250.122(F)

I do not understand " - - - . At that point the EE can elect to use anything, - - -. "

Do you mean if the raceway is metal than the EE can elect to use a 6 AWG EGC in the metal raceway for any amperage involved ?
 

dereckbc

Moderator
Staff member
Location
Plano, TX
Re: 250.122(F)

All I meant was it was a mute point, the requirement would have been met with rigid. An EE might of wanted to add a supplementary EGC as an extra margin of safety, and a logical choice would be in my oppinion is to apply 250.102(C). If busted or questioned by AHJ, remove it, it's not required. But since it is PVC a 350 MCM minimum is required in each raceway to meet 250.122(F)(1). I have been snowed in the whole week just rambling on.

[ February 26, 2003, 03:19 PM: Message edited by: dereckbc ]
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
Re: 250.122(F)

Dereck,
Even if the conduit is rigid, if the EE wants a grounding conductor in the raceway, it must be 350 kcmil. There is no provision to install a smaller conductor just because the conduit is an EGC. If you install it, it must e sized per code.
Don
 

jmc

Member
Location
Massachusetts
Re: 250.122(F)

The conductors in the raceway for a service are not "equipment grounding conductors" because there is no overcurrent device ahead of the circuit. The conductors for grounding the equipment are "equipment bonding conductors" and are sized in accordance with 250.102(C). The size of the equipment bonding conductor is sized in accordance with the phase conductors in the raceway, in this installation, 600 kcmil, therefore, Table 250.66 requires not less than 1/0 conductor in each raceway.
 

jmc

Member
Location
Massachusetts
Re: 250.122(F)

Where there is an overcurrent device, on the load side of the service point, it will govern the size of the equipment grounding conductor in accordance with 250.122(F), which is sized in accordance with the overcurrent device of 2500 amperes which results in 350 Kcmil in each raceway.
 

hbendillo

Senior Member
Location
South carolina
Re: 250.122(F)

I agree that a 350 MCM ground is needed on the load side of the disconnect for the feeder to the MDP. However, the supply side conduit is configured properly. No equipment ground is needed.
 
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