Thread: Question about pigtails in a breaker box

I know you are allowed to pigtail 2 wires into 1 wire so you don't have a double tapped breaker, but my question is does it work in reverse? Can you pigtail 1 wire into 2. I am planning a standby setup of my generator and I have 2 main panels in my home, my panel, and an in-law apt. panel, I want to feed both bus bars on each panel, and since I don't have anything that requires 220 I was curious if I could pigtail 1 hot wire into 2 inside the panel to energize both bus bars.

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Originally Posted by John Naehring

I know you are allowed to pigtail 2 wires into 1 wire so you don't have a double tapped breaker, but my question is does it work in reverse? Can you pigtail 1 wire into 2. I am planning a standby setup of my generator and I have 2 main panels in my home, my panel, and an in-law apt. panel, I want to feed both bus bars on each panel, and since I don't have anything that requires 220 I was curious if I could pigtail 1 hot wire into 2 inside the panel to energize both bus bars.

John,

You really, really, really do not want to do that.

Not as I am understanding what you are asking.

Originally Posted by Jerry Peck

John,

You really, really, really do not want to do that.

Not as I am understanding what you are asking.

Jerry, I don't want to split 1 110 leg across both bus bars? or the reverse pigtail?

John,

First, let's start here: Where is the transfer switch located in the circuit and how is it wired to the panels? What size neutral is there in relation to what size hot conductors?

Originally Posted by Jerry Peck

John,

First, let's start here: Where is the transfer switch located in the circuit and how is it wired to the panels? What size neutral is there in relation to what size hot conductors?

I'm going to be using the square D generator interlock, #8 neutral and hots

Edit: this was just a preliminary question, all this work will be done with permits, I wouldn't attempt to do something that was unsafe or non code compliant

John,

This is just one problem with what you are describing:
- When using 120 volts / 240 volts, the panel has 120 volts from each 120 volt leg on each bus bar, with 240 volts between the bus bars. That means the neutral *only* carries the unbalanced load between the 120 volt loads placed on the two hot phase legs. Your connection would place *double* the neutral current on the neutral as *all* current on both bus bars would *double* up on the neutral ... because the "neutral" is really no longer serving as a "neutral", it is now serving as a full current carrying grounded conductor.

Think of it this way: Everyone refers to 120 volt branch circuits as having "1 neutral and 1 hot", and the same full current which flows on that hot also flows on that neutral, so it is not "neutral" it is simply a grounded current carrying conductors.

While it is "common trade practice" to refer to that grounded 120 volt conductors as a "neutral" is it anything but a "neutral", it is no different than the ungrounded conductor as regards to the amount of current being carried on it, that conductor is simply "grounded" at the service equipment while the ungrounded conductor is not.

What you are proposing to do is not good.

When connecting a generator, you MUST have some means of disconnecting the buildings electrical system from the utility power grid BEFORE connecting the generator power to that building, otherwise you risk energizing the entire utility power grid by back feeding through the meter and the transformer.

That is where the transfer switch comes in. The transfer switch FIRST disconnects BOTH services (utility power and generator power) from the structure, the transfer switch then throws to EITHER source (utility power or generator power), IT CANNOT connect both at the same time. Think of a transfer switch as a double throw switch with a center off, only the center off is a "momentary off", meaning that NEITHER is "on" in the center of the throw from one to the other - therefore BOTH CANNOT be energized at the same time.

However, back to your question, you will be doubling the current in the neutral when doing as you are thinking of doing, even if you did install a proper transfer switch.

Besides dangerous to the entire circuitry, it is not legal here in the states. I mention the states because that is the way many people have their residential electrical set up in Mexico. I had to wire a small church which had only one 120V hot leg and one neutral. In that case, I had to split the 120V hot leg coming from the outside meter to the indoor panel. In Mexico that is the energy company's standard set up unless you request a three wire service set up which will cost many too much. Till this day the two-wire set up it is still servicing that small church in Mexico but, that set up will not be accepted here in the states because of the potential hazards it presents.

John, U have good responses so far and i would agree w/them, wouldn't recommend this idea.
But, as far as an Electrical Inspector, i would require a complete diagram and would then have to research the code as I've never had a request for something of this nature.??
One item not mentioned is whether the transfer/gen setup is a separately derived or non-separately derived system....and there would be more after doing the plan review for the permit.
Bob Smit, County Electrical Inspector

Thank you everyone for your responses, I do have another question though. My first idea of branch feeding 1. 110 leg to both bus bars was a bad idea, but can i bring both legs of 110 from the generator into a junction box and branch each 110 line to feed 220 to each box? would we still run into the problem of an overloaded neutral?

EDIT: And I don't know if I was clear of my transfer switch, I will be using a Square D Mechanical interlock which is a device that turns my whole panel into a transfer switch via a mechanical slide device that only allows the generator breaker to close if the main breaker is open via a slide motion. It is an economical solution at $70 But as safe as any independent transfer switch... as with anything of this nature it is only safe if installed properly.

Hello John,

This is most likely a bad idea.

There are really good reasons for installing listed and approved equipment for specific purposes. I have found that saving money can limit safety in instances like this. It sounds like you are adding an element that the inter-lock kits were not designed for.

If you set a junction box to connect both panels to the generator feeding through the inter-lock kits it would function.

I think your main concern is safety though. A 400amp transfer switch is the best option (automatic or manual). I am assuming by your statment of having two main panels that you have a 400amp or 320amp service.

Another thing you should figure out is if your generator is big enough.

I have been a licenced/working electrician for ten years (just to give credentials

Good luck
And definitly get it inspected, there are a ton of linemen that would appreciate it.

Darrell

Darrell thanks for your input.

I have a 200A weatherhead feeding down to 2 seperate meters, each panel is 100A

I will try to re- explain my proposal, I apologize in advance for my lack of correct electrical terminology.

Inside the proposed junction box i would have an incoming 8-3 line, both 110 legs would be branched as well as the neutral and ground.

From there i would send 220 into each box via a 2 pole 30A breaker. The 30A breaker would occupy slots #2 and #4 in both boxes. and because we have seperate meters there is no chance that by energizing 1 panel you would energize the service line


Does this make it any clearer?

Originally Posted by John Naehring

and because we have seperate meters there is no chance that by energizing 1 panel you would energize the service line

John,

As I am understanding what you just said, unless you pull the meters ... I don't understand how you would not energize the service line going to the meters - the very real danger ... which happens all the time ... is back feeding through the meter to the utility service and energizing the utility service with the generator.

THAT is what a properly listed and labeled transfer switch does - it eliminates the possibility of back feeding into the utility lines by physically and electrically removing the connection from the utility lines from the service.

Unless you physically and electrically disconnect the utility lines from the service YOU WILL back feed through the meters and energize the utility lines, potentially killing a lineman working on the utility lines, or someone elsewhere working on another electrical service.

Originally Posted by Jerry Peck

John,

As I am understanding what you just said, unless you pull the meters ... I don't understand how you would not energize the service line going to the meters - the very real danger ... which happens all the time ... is back feeding through the meter to the utility service and energizing the utility service with the generator.

THAT is what a properly listed and labeled transfer switch does - it eliminates the possibility of back feeding into the utility lines by physically and electrically removing the connection from the utility lines from the service.

Unless you physically and electrically disconnect the utility lines from the service YOU WILL back feed through the meters and energize the utility lines, potentially killing a lineman working on the utility lines, or someone elsewhere working on another electrical service.

Jerry, imagine you are looking at your panel with this interlock installed and your generator running, the only energized wires in your box at this moment is the 2 hot legs connected to your 2 pole 30 A breaker, and because you have the interlock installed the breaker remains open because your main is still closed. your physically cannot closed your generator breaker until your main has been opened due to a mechanical metal plate, you must first open your main, then slide the interlock plate up to close the generator breaker.

This is a UL listed piece of equipment
http://static.schneider-electric.us/...281-691-02.pdf
[IMG]file:///C:/Users/John/AppData/Local/Temp/moz-screenshot.jpg[/IMG]

John, I know what interlock U are refering to. If u have a Square D panel and use the listed interlock U are ok so far. I should know...but don't, whether there is a field install kit from the manufacturer. All the one's i've seen (and used once), came as part of a new panel assembly and therefore listed as such.

As I mentioned previously, I would require a plan for review prior to granting a permit if i were your AHJ. It has been my experience that giving advice or preliminary OK's over the phone has sometimes come back to bite when i finally get the plans.

Jerry, U might have a better picture of what is proposed here??
I have a concern if I'm picturing this correctly. If one meter were to be pulled, or any other reason power was lost to one panel only; The generator being put on line would then back feed through the 'TAP' and collide with utility power.

Again, I am not sure as to how and where all the connections are proposed. Location points of the grounding electrode conductor and main bonding jumpers are of concern also. Improper locations of these can cause objectionable currents on the service grounded conductor(s).
Bob Smit, County Electrical Inspector

Originally Posted by bob smit

John, I know what interlock U are refering to. If u have a Square D panel and use the listed interlock U are ok so far. I should know...but don't, whether there is a field install kit from the manufacturer. All the one's i've seen (and used once), came as part of a new panel assembly and therefore listed as such.

As I mentioned previously, I would require a plan for review prior to granting a permit if i were your AHJ. It has been my experience that giving advice or preliminary OK's over the phone has sometimes come back to bite when i finally get the plans.

Jerry, U might have a better picture of what is proposed here??
I have a concern if I'm picturing this correctly. If one meter were to be pulled, or any other reason power was lost to one panel only; The generator being put on line would then back feed through the 'TAP' and collide with utility power.

Again, I am not sure as to how and where all the connections are proposed. Location points of the grounding electrode conductor and main bonding jumpers are of concern also. Improper locations of these can cause objectionable currents on the service grounded conductor(s).
Bob Smit, County Electrical Inspector

Bob the do have a retrofit kit, My local inspector has not gotten back to me yet but I am sure he will require a diagram, I will post it up here when I draw it out