3-wire 120V 30A Circuit

[MikeHeather]

Hello:

I'm starting to plan for next year's display and been on the search for more electricity. I discovered I have an unused 3-wire 120V 30A circuit. How can I take advantage of this using my controller for 30 AMP. I know how to configure the controller (2 15 amps plugs), but what is the method for installing the outlet(s)? Any reference material would be great.

Regards,

Mike

[columbus27]

I am not a fan of running 30 amp anything. You can pull the 30 amp breaker and put in a tandem http://www.homedepot.com/h_d1/N-5yc1v/R-202253127/h_d2/ProductDisplay?catalogId=10053&langId=-1&keyword=tandum+breaker&storeId=10051

In my area it's not legal but runing a 30 amp with two 15 amp outlets aren't either. I have a few tandem. Next year I am going to run a sub panel

[avsphan]

Are you saying three wires as in white black ground? Or white black red ground? You say three wire and I immediately think its a 220 circuit.

[MikeHeather]

Are you saying three wires as in white black ground? Or white black red ground? You say three wire and I immediately think its a 220 circuit.

white, black, red, ground

[De Trommelslager]

It is illegal and unsafe to construct a circuit with oversized overcurrent protection (breaker or fuse) unless the load served is a motor, but that is out of the realm of this topic. The purpose of the circuit breaker is to prevent the wiring and load served from becoming a match.

Install two 15A or 20A circuit breakers where the two pole breaker (30A) is now. You do not want a tandem breaker serving your receptacles. Make sure you have the two circuits on opposite phases, or you can be creating an overload situation on the neutral. The wires are probably (should be) #10, so in an outlet box they may be a little more difficult to work with. You'll want to install GFCI receptacles and those eat up space in a box. You can put in pigtails (#12 on 20A or #14 on 15A) to make getting the receptacles in the box easier, provided that the box is big enough to begin with. If the box is too small, then add an appropriate extension ring to the box to provide the extra room.

One last thing, you will be coming off of the neutral with two pigtails for the receptacles. Make double sure that connection is good. If it isn't you have the potential to send 220V out to your equipment. It would be a bright show for a moment!

Usual disclaimer: Use this information at your own risk. Never work on an energized circuit. If in doubt, hire a qualified electrician to perform the work for you.

[MikeHeather]

Thanks guys. I think I'll leave this circuit alone for now. I found another 20 AMP one with practically nothing on it, so I'm going with it for now.

Merry Christmas,

Mike

[-klb-]

I thought running 2 circuits on shared neutral requires a double pole breaker to prevent the chance of working on a circuit where hot was dead, but current existed in neutral, and breaking neural would leave an energized neutral wire.

[bob_moody]

white, black, red, ground

That would be a 220 Circuit (?) ... If you have a meter measure between black/White and you should have 110, between Red/White and you should have 110, between black and red you should have 220...

If that is the case, then what gauge is the wire? I'm guessing if its a 30amp then they are (or should be) #10.

Depending on your area... yes you could sub that circuit off into a panel with a pair of 15amps breakers on one leg and a pair of 15's on the other giving you 60amps @110V of Christmas brightness.. Unless your running a lot of LED's then it wont go far, but its a start..

(Note: I'm speaking from my own experiences only. I'm not an electrician but I do my own work and have never burned down my own house or electricuted myself, family or friends, I also live in the county not the city so my restrictions are a lot less..)

Your milage may vary...

Bob

[De Trommelslager]

I thought running 2 circuits on shared neutral requires a double pole breaker to prevent the chance of working on a circuit where hot was dead, but current existed in neutral, and breaking neural would leave an energized neutral wire.

No, a tandem circuit breaker in isn't required nor recommended by NEC. That little "catch all" clause in the NEC that states the "authority having jurisdiction" really negates the whole book and gives the ultimate decision to your electrical inspector. You are correct about the neutral having shock potential if a shared circuit is 1) energized, and 2) carrying current. In the case of a three phase power system, you also have the risk of breaking the neutral (grounded) circuit back to the source and sending two phases (208V or 480V depending on system voltages) into the loads of the circuits. Think smoke! Most of us are dealing with 240V single phase power in our homes.

If you get your body in line with a loaded neutral, understand that your body is trying to carry the full load of the circuit. A lethal shock can be less than .1A (1/10th)! A single 40W light bulb will draw about a 1/3rd of an Amp. If you brush up against a phase wire and are grounded, the current your body will carry is dependant on a variety of factors. That could range from a tickle to a fatal shock. The neutral may not have the voltage, but it does have the current and current is what is is fatal.

If it is a shared neutral and you are going to work on it, turn them both off. You do not want to have any current flow within the box you are working on. No exceptions. For those reading this, if you don't take anything else away from this discussion let this burn into your mind and never forget it: the grounded conductor (neutral) is every bit as deadly as any phase wire. Treat is as such!

Bottom line: If you are going to work on it, turn it off. Having been a professional electrician for more years than I care to mention, there are very few absolute reasons why a circuit cannot be de energized. Turning power off might be a huge hassle, but so is being electrocuted! If you are unsure about something, stop. Get help from a qualified electrician. Electricity is serious business and it doesn't care who you are or how simple it may be.

Use this information at your own risk!

Edited December 21, 2012 by De Trommelslager

[De Trommelslager]

I also live in the county not the city so my restrictions are a lot less.

Bob, I am not meaning to pick on you (nor saying your wrong); just trying to make a point for someone that may come accross this in the same situation.

Electrons flow the same way whether you live in the city, county, under a bridge or whatever. Buildings burn just as well out of town as they do in town. Just because one may not have "big brother" looking over your should doesn't mean electricity is any less dangerous. Because you "can" doesn't make an installation safe. Use good practices and don't cut corners!

[-klb-]

I would suggest that if anything, being outside the jurisdiction of inspectors is, if anything, more dangerous. At least with respect to existing installations.

My father bought 22 acres. It came with 3 meter bases, (one disconnected, but the load served from one of the other services, at least 4 buildings served from 2 bases, one RV pedestal, THHN wire strung in free air from building to tree to lamp post, and one live 220v dryer circuit with the bare ends taped off, no box or anything. Needless to say, cleaning it all up has been a slow, cautious process.

[bob_moody]

Bob

Edited December 21, 2012 by bob_moody

[bob_moody]

Point to add/clarify

Neutral is always a currnet carrying device

Neutral is only a "grounded" device in the main box.

In my example of the sub panel, Neutral and Ground BOTH return seperately to the point of origin (main).

The laws of physics or electricty were never an issue in the comment about living in the country. Simply a matter of I live in an unincorporated area and do not have the additional requirements of obtaining permits or completion inspections to perform any work..

Bob

[steve synek]

I will just say the 2008 and 2011 National Electric codes require a two pole breaker on all shared neutral circuits (black, red, white) . I will provide the code section if someone wants me to look it up, as I am not just saying this as an Authority having Jurisdiction.

Steve

Edited December 22, 2012 by steve synek

[De Trommelslager]

Steve, I would appreciate a reference. I haven't seen that. Then again, the NEC is a known cure for insomnia!

[steve synek]

I will also add, there is a major difference between a tandem and a two pole breaker. As a general rule (I hate using "never" and "always" because there are exceptions) tandem breakers should never be used on a 3 wire circuit. You must always use a two pole breaker on a 3 wire circuit.

Steve

[steve synek]

Steve, I would appreciate a reference. I haven't seen that. Then again, the NEC is a known cure for insomnia!

I am laying in bed now, but will head over to my office right now and pull out the electrical bible ........hold on...........

Edit,,,,,,,,,,,,,I looked in the 2008 NEC and it is section 210.4 sub section B........I keep getting a smiley face here with the parentheses "B"..........I did not look it up in the 2011, but am quite confident it is the same.

Steve

Edited December 22, 2012 by steve synek

[bob_moody]

I will also add, there is a major difference between a tandem and a two pole breaker. As a general rule (I hate using "never" and "always" because there are exceptions) tandem breakers should never be used on a 3 wire circuit. You must always use a two pole breaker on a 3 wire circuit.

Steve

Just for my own edification on terms, a tandem breaker is the two sigle pole breakers that fit in a single slot fed from the same leg and the two pole breaker is the one that has the bar locking the two together?

Bob

[De Trommelslager]

I am laying in bed now, but will head over to my office right now and pull out the electrical bible ........hold on...........

Edit,,,,,,,,,,,,,I looked in the 2008 NEC and it is section 210.4 sub section B........I keep getting a smiley face here with the parentheses "B"..........I did not look it up in the 2011, but am quite confident it is the same.

Steve

Steve, thanks for getting out of bed to dig that up. It's there. Dang, I missed that and don't know how since it is such big change! I knew the rule for a split device on a common yoke but didn't realize it covered all multiwire branch circuits.

Most of what I deal with these days is power studies & evals of distribution systems in heavy industry and at that the most I do is function on the troubleshooting side for branch stuff when the electrician is stumped. I haven't pulled or twisted wire for a paycheck in over six years now (and don't miss it!), so reading the code book isn't something I have to do a lot of anymore. Guess I need to!!

Okay, I understand the reasoning for the regulation and don't necessarily disagree. But between OSHA, NFPA 70, the NEC and the others we are now trying to make too much of this stuff idiot proof. Fall hazard warnings on ladders... arc flash warnings on electrical gear... coffee cup contains hot liquid... one has to be pretty dumb to need a sign for that stuff. The process of natural selection has been disrupted. The only thing that will be produced aside from higher costs is highly improved idiots!!

And back to our normal program!

Just for my own edification on terms, a tandem breaker is the two sigle pole breakers that fit in a single slot fed from the same leg and the two pole breaker is the one that has the bar locking the two together?

Bob

Correct.