Main Lug labeled 2-250

[Sam Morris]

Can you put 2 wires underneath this lug. house was built in 1980 ?? Should this be reported or is this acceptable. (and yes I see the door bell) Thanks in advance

[Roy Lewis]

Can you put 2 wires underneath this lug. house was built in 1980 ?? Should this be reported or is this acceptable. (and yes I see the door bell) Thanks in advance

No it is double lugged.

[Jerry Peck]

Sam,

I zoomed in on that terminal and it is identified for:

CU-AL (copper or aluminum ... either/or, but not both mixed together)

2-250 (2 AWG to 250 kcmils conductor size range for the single conductor the terminal is rated for)

Note, if ... IF ... if the terminal was identified as: (2) 2-250, the it would be identified for either one or two conductors in the terminal, but the conductor material must be the same type (copper or aluminum), not mixed.

Note that there are MANY terminals in your photo which show multiple tapped (two or more conductors in a terminal rated for one conductor only).

Note that there are several terminals in your photo which copper and aluminum mixed (not allowed).

[Gunnar Alquist]

Oooo... I would have said the same as Roy.

Jerry, how do you find this stuff out? 1) That CU-AL means "or" rather than "and" (can't mix copper and aluminum). Is there any case where you can mix the two? I know about the Ideal 65 and the Tyco crimp, but I'm referring to the lugs in the panel. I think I saw a split bolt that was approved at one time, but don't know if that's still the case.

Also, please clarify... I don't understand if 2-250 means 2 conductors at 250 kcmils or if it means a single conductor that can be a maximum of 2 AWG or 250 kcmils.

Frankly, I never learned the kcmils chart and relation to AWG. Can you point me to a chart? (I bet there's one in Hansen's "Electrical Inspection of Existing Dwellings". Maybe I should look).

[Roy Lewis]

I've never heard of any code that would allow different sized conductors under the same lug.

[Jerry Peck]

Jerry, how do you find this stuff out?

Things I have read and 'learned' over the years (acknowledging that some things I 'learn' over the years turn out to be 'incorrect' when I 'learn' something new).


1) That CU-AL means "or" rather than "and" (can't mix copper and aluminum). Is there any case where you can mix the two?

First, I will clarify the above and the "CU-AL" and shown on that terminal lug - "CU-AL" is the old/original marking used to identify terminals which were rated for either copper or aluminum conductors. That marking has been replaced with "CO/ALR" and "AL/CU" shown in the excerpt from the UL White Book (the UL White Book is known as the 'Second Volume of the NEC' as it tells what things are actually approved for and their uses. The UL White Book is available, free of charge, here: http://www.ul.com/wp-content/uploads/2014/09/UL-White-Book.pdf?utm_source=multiple&utm_medium=vanity&utm_campaign=codeauthoritieswhitebook ).

This is from the 2015-16 UL White Book: (on page 48) (underlining is mine)
"Terminations — Copper pigtail leads may be used with aluminum or
copper-clad aluminum supply wires in dry locations if 1) the splicing
devices are certified for use in joining copper to aluminum, 2) there is sufficient
wiring space, and 3) the means provided for connecting the wiring
system are acceptable for the wire size used.
Supply terminals of 15 A and 20 A switches and receptacles not marked
‘‘CO/ALR’’ are for use with copper and copper-clad aluminum conductors
only. Terminals marked ‘‘CO/ALR’’ are for use with aluminum, copper and
copper-clad aluminum conductors.
Screwless pressure terminal connectors of the conductor push-in type are
for use only with copper and copper-clad aluminum conductors, both solid
and stranded unless otherwise limited by marking.
Terminals of switches and receptacles rated 30 A and above not marked
‘‘AL/CU’’ are for use with copper conductors only. Terminals of switches
rated 30 A and above marked ‘‘AL/CU’’ are for use with aluminum, copper
and copper-clad aluminum conductors.
Combination of dissimilar conductors in terminal or splicing connectors is
acceptable only in dry locations and when the connectors are identified as
suitable for such intermixing."

I have not seen any special marking for intermixing, so this afternoon I sent an email to UL asking about what such marking would be/look like. Hopefully, I will have an answer early next week.


Also, please clarify... I don't understand if 2-250 means 2 conductors at 250 kcmils or if it means a single conductor that can be a maximum of 2 AWG or 250 kcmils.

"2-250" means that the terminal is rated for one conductor sized from 2 AWG to 250 kcmils

"(2) 2-250" would indicate that a terminal is rated for up to two conductors sized from 2 AWG to 250 kcmils

I arrived at this by the different labels I have seen which state (examples):
- "14-10 AWG" and nothing on the label indicates more than one conductor
- "(2) 14-10 AWG" and sometimes the labels additionally state that two conductors are permitted, the "(2)" is the quantity of the conductor size shown, the "14-10 AWG".

This afternoon I also sent UL and email asking if they have a marking guide related to the standard markings indicating the above - I will hopefully have that answer early next week as well.


Frankly, I never learned the kcmils chart and relation to AWG. Can you point me to a chart? (I bet there's one in Hansen's "Electrical Inspection of Existing Dwellings". Maybe I should look).

The NEC, in the tables in 310, show a column titled "AWG and kcmils" once you get larger than 0000 (which is 4/0 in modern marking) you get above AWG sizes and the sizes are identified in the "circular mils" (and the older codes actually referenced those larger conductors as "circular mils"), the newer codes, I could look back and see when the change was made, changed "circular mils" to "kcmils'.

"Circular mils" is a unit of area: CM - Circular Mil Area (http://www.engineeringtoolbox.com/mil-circular-mil-area-d_817.html)

If you want to convert AWG sizes to circular mils, go here: AWG - American Wire Gauge and Circular Mils (http://www.engineeringtoolbox.com/awg-wire-gauge-circular-mils-d_819.html)

- - - Updated - - -


I've never heard of any code that would allow different sized conductors under the same lug.

The code does not say yes or no to that, the listing of the terminal would say yes or no to that.

I recall someone posting, a few years ago, a label from Cutler-Hammer (I recall it was C-H) which gave the number and sizes of equipment grounding conductors allowed in each terminal, and that label (as I recall) allowed intermixing of sizes within the same terminal (which surprised me).

In fact, the label allowed (3) equipment grounding conductors in the terminals, not just two.

At least, that is as I recall it - anyone remember see something like that posted here?

[Jim Port]

All that information would be on the label in the panel. C-H does allow up to 3 grounding conductors in some terminals of a neutral or ground bar.

[Gunnar Alquist]

I am going to have to re-read this (probably repeatedly) in order to fully comprehend and retain this information.


Things I have read and 'learned' over the years (acknowledging that some things I 'learn' over the years turn out to be 'incorrect' when I 'learn' something new).

Ya, me too.


The UL White Book is available, free of charge...

Thanks for this. I just downloaded and saved it. Took a quick look through it, but it's kinda huge. That is going to be really helpful.


I recall someone posting, a few years ago, a label from Cutler-Hammer (I recall it was C-H) which gave the number and sizes of equipment grounding conductors allowed in each terminal, and that label (as I recall) allowed intermixing of sizes within the same terminal (which surprised me). In fact, the label allowed (3) equipment grounding conductors in the terminals, not just two.

Included is a C-H label that I happen to have. It allows, in specific holes, up to 3 conductors, but all have to be the same size and material.

[Jerry Peck]

I just received an answer to one of my two inquiries to UL (see my post below).

The email is attached. There is a link in the email, and photos in it also.

[Jerry Peck]

I just received a reply from UL to my second question (see below).

I do not recall ever ... Ever ... EVER ... having seen the "(intermixed - dry locations)" marking ... granted, on 6 AWG and smaller connectors the marking is permitted to be on the box/container or paperwork, but on one the size in the photo under discussion ... that would be marked on the connector itself.