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Mark P
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The main disconnect and panel are outside below the meter. There is a 200 amp main breaker w/ appropriate sized wire running from the meter. Inside the house there is a subpanel that services the majority of the house. The wire(s) running from the outside main panel to the inside sub-panel are 2 #4 secured under the same lug, not a breaker. See picture. Is there anything technically wrong with this?

I know that #4 is rated for 100 amp and that 2 #4 does NOT = 200 amp. So I understand there is not 200 amp going to the subpanel inside the house; so no reason to revisit the discussion for my benefit.

This is the 1st time I have seen this arrangement, so I’m looking for another opinion, which is what TIJ is so great at.

Yes I know there are other issure: double tapping, neturals not isolated, etc.

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Hi Mark,

Running parallel conductors is not allowed unless they are at least a certain size. Problem is that I can't remember what the min. sized conductor is. I know it's big, like 2/0 or something. I'm in the middle of a report, but figured I'd chime in with the "parallel conductor" wording to help you in your search. I'm positive that this has been covered before on this site.

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The main disconnect and panel are outside below the meter. There is a 200 amp main breaker w/ appropriate sized wire running from the meter. Inside the house there is a subpanel that services the majority of the house. The wire(s) running from the outside main panel to the inside sub-panel are 2 #4 secured under the same lug, not a breaker. See picture. Is there anything technically wrong with this?

I know that #4 is rated for 100 amp and that 2 #4 does NOT = 200 amp. So I understand there is not 200 amp going to the subpanel inside the house; so no reason to revisit the discussion for my benefit.

This is the 1st time I have seen this arrangement, so I’m looking for another opinion, which is what TIJ is so great at.

Yes I know there are other issure: double tapping, neturals not isolated, etc.

Aside from the double tapping issue, you're not supposed to run parallel conductors with wires that are smaller than 1/0.

310.4 (A) General. Conductors in Parallel. Aluminum, copper-clad

aluminum, or copper conductors of size 1/0 AWG and

larger, comprising each phase, polarity, neutral, or grounded circuit

conductor, shall be permitted to be connected in parallel

(electrically joined at both ends to form a single conductor).

Several exceptions follow, none of which apply to your situation.

- Jim Katen, Oregon

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The main disconnect and panel are outside below the meter. There is a 200 amp main breaker w/ appropriate sized wire running from the meter. Inside the house there is a subpanel that services the majority of the house. The wire(s) running from the outside main panel to the inside sub-panel are 2 #4 secured under the same lug, not a breaker. See picture. Is there anything technically wrong with this?

I know that #4 is rated for 100 amp and that 2 #4 does NOT = 200 amp. So I understand there is not 200 amp going to the subpanel inside the house; so no reason to revisit the discussion for my benefit.

This is the 1st time I have seen this arrangement, so I’m looking for another opinion, which is what TIJ is so great at.

Yes I know there are other issure: double tapping, neturals not isolated, etc.

Click to Enlarge
tn_20091215201053_050.jpg

43.21 KB

Click to Enlarge
tn_2009121520126_055.jpg

92.68 KB

Terminals shall listed for the use. If the terminals are not listed for two conductors, it is a violation of 110.3(B).

Also, #4 CU is rated for 70A per 310.16 and 110.14©(1)(a)(1). #3 CU is rated for 85A. #2 CU is rated for 95A. #1 CU is rated for 110A.

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Also, #4 CU is rated for 70A per 310.16 and 110.14©(1)(a)(1). #3 CU is rated for 85A. #2 CU is rated for 95A. #1 CU is rated for 110A.

This doesn't make the double-tapped set-up right, but we are talking about service feeders here with regards to ratings and 310.15 (B)(6) would be the appropriate table....

#4 cu - 100-amps

#3 cu - 110-amps

#2 cu - 125-amps

#1 cu - 150-amps

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Also, #4 CU is rated for 70A per 310.16 and 110.14©(1)(a)(1). #3 CU is rated for 85A. #2 CU is rated for 95A. #1 CU is rated for 110A.

This doesn't make the double-tapped set-up right, but we are talking about service feeders here with regards to ratings and 310.15 (B)(6) would be the appropriate table....

#4 cu - 100-amps

#3 cu - 110-amps

#2 cu - 125-amps

#1 cu - 150-amps

I agree that two wires under a lug is a violation of 110.3(B). However, 310.15(B)(6) is only applicable when the conductor carries the total load of the dwelling unit. Therefore, my statement of ampacities still stands. My guess is that whoever did the initial install mis-applied 310.4 and compounded the mistake by applying 310.15(B)(6).

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However, 310.15(B)(6) is only applicable when the conductor carries the total load of the dwelling unit.

I can't find the reference to "total load" but 310.15(B)(6) does state 3-wire feeds. I stand corrected although, for all practical purposes, it would seem the table should still be applicable (if everything was allowed).

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However, 310.15(B)(6) is only applicable when the conductor carries the total load of the dwelling unit.

I can't find the reference to "total load" but 310.15(B)(6) does state 3-wire feeds. I stand corrected although, for all practical purposes, it would seem the table should still be applicable (if everything was allowed).

310.15(B)(6) states;

(6) 120/240-Volt, 3-Wire, Single-Phase Dwelling Services

and Feeders. For individual dwelling units of onefamily,

two-family, and multifamily dwellings, conductors,

as listed in Table 310.15(B)(6), shall be permitted as

120/240-volt, 3-wire, single-phase service-entrance conductors,

service-lateral conductors, and feeder conductors

that serve as the main power feeder to each dwelling unit

and are installed in raceway or cable with or without an

equipment grounding conductor. For application of this section,

the main power feeder shall be the feeder between the

main disconnect and the panelboard that supplies, either by

branch circuits or by feeders, or both, all loads that are part

or associated with the dwelling unit. The feeder conductors

to a dwelling unit shall not be required to have an allowable

ampacity rating greater than their service-entrance conductors.

The grounded conductor shall be permitted to be

smaller than the ungrounded conductors, provided the requirements

of 215.2, 220.61, and 230.42 are met.

The term "total load" was edited out and the wording was changed to state "main power feeder". In order for this table to be applied the conductors must be the main power feeder (ie. service entrance). Who ever installed this service looked at the table first, saw #4 CU was rated for 100A, mis-applied the intent of the NEC, then figured if the conductors were installed in parallel they would be rated for 200A. Couple that with two wires under one terminal and presto this is what we end up with.

AN unsafe installation that should never have passed inspection if there was one.

[;)]

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  • 2 weeks later...

The main disconnect and panel are outside below the meter. There is a 200 amp main breaker w/ appropriate sized wire running from the meter. Inside the house there is a subpanel that services the majority of the house. The wire(s) running from the outside main panel to the inside sub-panel are 2 #4 secured under the same lug, not a breaker. See picture. Is there anything technically wrong with this?

I know that #4 is rated for 100 amp and that 2 #4 does NOT = 200 amp. So I understand there is not 200 amp going to the subpanel inside the house; so no reason to revisit the discussion for my benefit.

This is the 1st time I have seen this arrangement, so I’m looking for another opinion, which is what TIJ is so great at.

Yes I know there are other issure: double tapping, neturals not isolated, etc.

Click to Enlarge
tn_20091215201053_050.jpg

43.21 KB

Click to Enlarge
tn_2009121520126_055.jpg

92.68 KB

Terminals shall listed for the use. If the terminals are not listed for two conductors, it is a violation of 110.3(B).

Also, #4 CU is rated for 70A per 310.16 and 110.14©(1)(a)(1). #3 CU is rated for 85A. #2 CU is rated for 95A. #1 CU is rated for 110A.

To quote amperage ratings for these conductors we need to know more information! Are these conductors in a cable or conduit? What is the insulation type?

If they are in conduit then #4 could be 85 amp, # 3 could be 100 amp.

To just throw out amperage ratings without the proper information can be just as wrong as the installation itself.

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