300.20

[dan 456]

Been reading posts on here for quite awhile, first new thread I am starting. Service 3 phase 4 parallel 500 kcmil. conductors entering the end line box phase isolated. The conduit is fre with a change to gal for 3 feet entering the end line box. ( a pre fab 90 and short nipple) the conduits enter the end line box with lock nuts and migbs. power company said this is no good with isolated phase entry because conduits must be non ferrous for the entire length. my question. are there other ways to do this with either cutting slots in the conduit or cabinet, an isolation plate installed between the conduits and box or an open bottom box where the conduits are less than 3" into the box? last, I understand the heating issue, hysteresis and the need for the non ferrous conduit, but what is the heating concern? is it because of the short distance of gal pipe or is it that this gal is grounded and bonded to the box? another words would this install be ok if the pipe was isolated from end line box or they want no metal pipe what so ever? any advice much appreciated

 

[iwire]

There is no way to leave the steel in place and go isolated phase.

 

[dan 456]

appreciate quick response. not even open bottom or non ferrous isolation plate? soares by the iaei seems to relay that message

 

[david]

appreciate quick response. not even open bottom or non ferrous isolation plate? soares by the iaei seems to relay that message

you said short pieces Gal. steel, are you still using Galvanized for the entry?

 

[dan 456]

gal entry yes. will a non ferrous isolation plate or an open bottom gear be a possible solution

 

[Smart $]

gal entry yes. will a non ferrous isolation plate or an open bottom gear be a possible solution

You said you understood heating issue, hysteresis and need for nonferrous conduit but yet ask what the heating concern is???

Could it be conduit required to be grounded, conduit gets hot, conductor insulation melts or otherwise degrades. Result is _____?

 

[dan1234]

my question smart member was if the short gal section isolated from the cabinet or the gal section grounded and bonded to the cabinet was the heat issue. do you know what can happen pulling 500 kcmil 1000 kcmil or 2000 kcmil thru non metallic 90's? reread my question and please don't tell me are you a romex slinger, maybe a stat guy? or a basement dweller with hi hats? did u know u can bury a metal 90 ungrounded isolated 18 inches? can someone answer can metal pipe be used for isolated phases with the metal pipe insulated and isolated from the cabinet it enters? no romex guys need apply

You said you understood heating issue, hysteresis and need for nonferrous conduit but yet ask what the heating concern is???

Could it be conduit required to be grounded, conduit gets hot, conductor insulation melts or otherwise degrades. Result is _____?

 

[GoldDigger]

Using a non-ferrous end plate or cutting slots will only take care of the iso-phase wires entering the box through the ferrous box wall. It will do nothing to fix the inductive heating in the galvanized pipe sections.
And if you cut a slot the full length of each piece of pipe you will not have a code approved raceway any more.
You have to replace the galvanized steel with brass, aluminum or nonmagnetic stainless if you cannot go completely non-metallic.
That is the bottom line last word.

 

[iwire]

You have to replace the galvanized steel with brass, aluminum or nonmagnetic stainless if you cannot go completely non-metallic.
That is the bottom line last word.

The NEC will not allow any of those metals for isolated phase installations.

From 2011 NEC

300.3(B)(1)
Exception: Conductors installed in nonmetallic raceways
run underground shall be permitted to be arranged as isolated
phase installations. The raceways shall be installed in
close proximity, and the conductors shall comply with the
provisions of 300.20(B).

So with metal raceways we can't even think about 300.20(B)

 

[Smart $]

my question smart member was if the short gal section isolated from the cabinet or the gal section grounded and bonded to the cabinet was the heat issue. do you know what can happen pulling 500 kcmil 1000 kcmil or 2000 kcmil thru non metallic 90's? reread my question and please don't tell me are you a romex slinger, maybe a stat guy? or a basement dweller with hi hats? did u know u can bury a metal 90 ungrounded isolated 18 inches? can someone answer can metal pipe be used for isolated phases with the metal pipe insulated and isolated from the cabinet it enters? no romex guys need apply

I will be direct. Yes, metal conduit is a heating issue. The electric field is circular for round conductors. It may be oblong or lobed with multiple grouped round conductors. Nevertheless, isophase results in eddy currents being driven at high velocity through the cross section of metallic conduits.

 

[iwire]

my question smart member was if the short gal section isolated from the cabinet or the gal section grounded and bonded to the cabinet was the heat issue.

Yes and a code violation

do you know what can happen pulling 500 kcmil 1000 kcmil or 2000 kcmil thru non metallic 90's?

Yes, and if you have to use metal 90s due too sidewall pressure you cannot use isolated phase arrangements.

reread my question and please don't tell me are you a romex slinger, maybe a stat guy? or a basement dweller with hi hats?

:lol:

Wow, you are really clueless on those thoughts.

If you are so sharp why did you screw up this installation? :lol:

did u know u can bury a metal 90 ungrounded isolated 18 inches?

Yes we know that and we also know if you do that you can't run isolated phase conductors through it.

can someone answer can metal pipe be used for isolated phases with the metal pipe insulated and isolated from the cabinet it enters?

No, see NEC 300.3(B)(1) and its exception.

no romex guys need apply

I am a 'romex guy' and I know the rules.

 

[dan1234]

aluminum conduit is the answer thanks for all replys

I will be direct. Yes, metal conduit is a heating issue. The electric field is circular for round conductors. It may be oblong or lobed with multiple grouped round conductors. Nevertheless, isophase results in eddy currents being driven at high velocity through the cross section of metallic conduits.

 

[dan1234]

thanks for all replies no screw ups job on going presently but I do appreciate your concern and input

Yes and a code violation



Yes, and if you have to use metal 90s due too sidewall pressure you cannot use isolated phase arrangements.



:lol:

Wow, you are really clueless on those thoughts.

If you are so sharp why did you screw up this installation? :lol:




Yes we know that and we also know if you do that you can't run isolated phase conductors through it.



No, see NEC 300.3(B)(1) and its exception.



I am a 'romex guy' and I know the rules.

 

[kwired]

my question smart member was if the short gal section isolated from the cabinet or the gal section grounded and bonded to the cabinet was the heat issue. do you know what can happen pulling 500 kcmil 1000 kcmil or 2000 kcmil thru non metallic 90's? reread my question and please don't tell me are you a romex slinger, maybe a stat guy? or a basement dweller with hi hats? did u know u can bury a metal 90 ungrounded isolated 18 inches? can someone answer can metal pipe be used for isolated phases with the metal pipe insulated and isolated from the cabinet it enters? no romex guys need apply

You may want to refrain from accusations until you get to know some of the members here. This particular member is fairly highly respected with his content, and is often difficult to prove wrong on issues that are not clear cut to answer.

 

[dan1234]

absolutely do not want to prove anyone wrong just looking for an answer of a code issue

You may want to refrain from accusations until you get to know some of the members here. This particular member is fairly highly respected with his content, and is often difficult to prove wrong on issues that are not clear cut to answer.

 

[don_resqcapt19]

aluminum conduit is the answer thanks for all replys

From a technical standpoint, that is correct, but from a code standpoint, it is a violation.

 

[dan1234]

ahj wants phase isolation to comply with 310.4B the length issue being the sticking point and to avoid a rats nest that can possibly happen. so the bottom line there is no way to do this with a short distance metal, ferrous or not and comply with nec?

 

[jim dungar]

absolutely do not want to prove anyone wrong just looking for an answer of a code issue

You have been given the answer multiple times, starting with post #2.
It is a code violation to use isolated phases with any metallic conduit per 300.3(B)(1).

Grounding and bonding is not the problem.

Oh, and welcome to the forum. Please continue to participate.

 

[dan1234]

thanks I was waiting for answer to change I may do the job that way anyway just need dead presidents in an envelope

You have been given the answer multiple times, starting with post #2.
It is a code violation to use isolated phases with any metallic conduit per 300.3(B)(1).

Grounding and bonding is not the problem.

Oh, and welcome to the forum. Please continue to participate.

 

[jim dungar]

...just need dead presidents in an envelope

Don't we all.