Main Switch box to a Small Subpanel Question.

[TURTLE]

This is Turtle.

I would like to know about the wiring being run from a main switch box to a smaller subpanel and to the ground or neutral wire you use. If you had a 200 main switch box and wanted a 100 amp subpanel installed up stairs. What type wire would you have to run to get the configuration right. Now wire size has nothing in my question here. Here is the three choices to pick from.

1) Run #2/ 3 wire and use third wire / white as ground and netrual !

2) Run #2 / 2 wire with naked ground. Use the naked ground as netrual and ground wire.

3) Run #2 / 3 wire with naked ground. Use the naked gound and the insulated white wire as ground and netrual.

I will always use the #2 / 3 wire with insulted ground but what about the #2 / 2 wire with a naked ground. Can the naked ground be used as netrual and ground suppling this subpanel or used in this application in residentiual or other in anyway. It might sound a little stupid but I got to know if there is any exception for this to be used?

I'm just checking up on a electrician around here that is doing it outside the city where there is no inspection of wire or wire codes. I just did not think you could do it but hey there maybe some exceptions somewhere I don't know about.

TURTLE

[Speedy Jim]

Hello TURTLE. This is Jim. Hope you are having a nice day.

This is a Feeder. Feeders are not permitted to use a combined Neutral and Equipment Ground, whether covered or naked. Use a 3-wire feed (2 Hot & 1 Neutral), all of them insulated.

The Equipment Ground can be either covered or naked. If covered, it must be colored Green. In your hypothetical case of a 100 Amp Feeder, the Ground would be #8 minimum.

There are other choices for the current-carrying conductors rather than #2, but I understand you're not concerned with that. Jim

[Tom Horne]

If the sub panel is supplying 120 volt circuits then the Grounded Conductor (neutral) must be run with the feeder conductors; along with the Equipment Grounding Conductor (EGC); and it must be insulated. If the panel that the feeder is supplying will have only 240 volt loads then only the Equipment Grounding Conductor is run with the ungrounded conductors (hots).

-- Tom H

[TURTLE]

residentiual or

This is Turtle.

I always over do everything and use 2 # / 2 wires for 100 amp feed to a 100 amp subpanel and a #2 covered wire for the Netrual , too. If i install a 100 amp subpanel, the wire will be able to handle 100+ amps anyday. Too small of wire or on the limit of the wire is not in my volcabulary. The Wire , switch box , and the main breaker is all going to match barring what NEC says. Now i do commercial work where you do not want any mistakes.

Thanks for the thought here. I had to just get it straight in my mine for I don't even think about near or half ass at all.

TURTLE

[TimS]

Where I live you have 1 and only 1 connection between a ground and a neutral in a dwelling, in the original service panel. Any downstream panels have all 4 conductors carried to it, 2 "phases", the grounded conductor (neutral), and the ground. The local supply houses have subfeeder cables with 4 conductors, all sized appropriately.

Tim S.

[TURTLE]

residentiual or

This is Turtle.

Let me get this straight here. I have 3 wires feeding the subpanel all #2 wire. White is used for netrual and the red and black feeds the two hots. I have all these hooked up to the respective places. Now I have a naked ground [ looks to be a # 8 or so ] in the wire bundle too. What do I do with the Naked ground in the three insulated # 2 wire use on the subpanel ?

1) Tape it up.

2) Hook it also to the grounding bar.

3) What do i do with it?

TURTLE

[Mark or Sue]

At the source "main" panel, put the neutral and naked ground on the same bus (but different holes -- neutrals must use their own hole but nakes wires can be doubled up if #10 or smaller). At the subpanel, buy a separate grounding bar and attach the naked ground to it. It is very important in the subpanel that you DO NOT use the green bonding screw the bonds the neutral bus to the chassis. The nuetral bus must be electrically isolated from the subpanel chassis. The grounding bus, where all the naked ground wires go, must be bolted to the panel chassis so it makes good electrical contact with the chassis.

-- Mark Kent, WA

[TURTLE]

This is Turtle.

i'm getting brain damage tring to figure out the wide range of answers here so i called my Commercial Electrician who works for me , to tell me about it and he said he would hook it up for me when he finishes the 63 tons of gas packs he is hooking up the electric service for me. He does a little residentiual stuff for me and some others and he does know the ropes on residentiual stuff. I know the commercial stuff on electric but this residentiual stuff is a horse of a different color. To me Small wire is # 6 / 4 wire in conduit or 3 hots and a ground all insulated. To me big wire is

400MC / 4 wires insulated in conduit. This unconduited wire just do seem right to me.

TURTLE

[Tom Horne]

In the sub panel you will install a separate Equipment Grounding Buss bar. That buss bar will be bonded to the panel cabinet by it's mounting screws. You will remove the bonding screw or strap that connects the insulated neutral buss to the panel enclosure. This will isolate the current carrying grounded conductors (neutrals) from the panel's enclosure so that neutral currents will not be flowing in exposed metallic parts of the wiring or other mechanical systems such as plumbing or duct work. The code requires that no grounding connection be made to the grounded conductor (neutral) on the load side of the Service Disconnecting Means (SDM). The SDM is usually the main breaker in the houses main panel.

Note: In some panels the factory installed buss bar can be separated into two separate buss bars one of which is insulated from the cabinet and one of which is bonded to the cabinet. If your sub panel is one of those then you can remove the bonding strap between the two buss bars instead of installing an additional buss bar. The only draw back is that you will need to route your neutrals to one side of the panel and your grounds to the other.