10/3 wire to two breakers...

[akdiesel]

? for the sparkies. I am planning on running driveway lights and outlets on the posts for the lights. I am going to use 10 gauge wire.
My question is, Is it legal / safe to run a single 10/3 wire with the black (hot) to feed the lights on a 20 amp breaker and the red (hot) to feed the outlets on a seperate 20 amp breaker, with the white (neutral) being shared in the same panel? Or is it a rule to run them on two individual 10/2 wires.
This question is for ease of pulling the wire and cost.

 

[Ford12508]

If it is a 20A circuit, it requires 12AWG, not 10, but more never hurt anyone

As far as having a multi-branched neutral, you can do that, but I am not sure if there are any special rules when it comes to the gauge it has to be.

 

[nate379]

I'm not sure if you can, but if you have 2 20 amp breakers, that would mean 40 amp protection on the neutral wire. To me (average Joe), that doesn't seem good on a wire rated to 30 amp.

 

[Ford12508]

Yea, chances are with the neutral wire you will have to step it up and go to 8 gauge, but that might not save you any money.

 

[The Motts]

? for the sparkies. I am planning on running driveway lights and outlets on the posts for the lights. I am going to use 10 gauge wire.
My question is, Is it legal / safe to run a single 10/3 wire with the black (hot) to feed the lights on a 20 amp breaker and the red (hot) to feed the outlets on a seperate 20 amp breaker, with the white (neutral) being shared in the same panel? Or is it a rule to run them on two individual 10/2 wires.
This question is for ease of pulling the wire and cost.

This is perfectly legal as long as you follow this from the 2008 NEC:

210.4(B) Disconnecting Means. Each multiwire branch circuit shall be provided with a means that will simultaneously disconnect all ungrounded conductors at the point where the branch circuit originates.

You can use two single pole breakers as long as they have handle ties, or you can use one two pole breaker with internal common trip. This makes it so both ungrounded (hot) conductors are de-energized simultaneously and that the two hot conductors are terminated on opposite phases in the panel, so as not to overload the neutral.

 

[mrb]

remember, your receptacles have to be GFCI protected, so if you are supplying them with a MWBC (shared neutral and two hots) each receptacle will have to be a gfci as opposed to just the first. Or you can run 10/3 to the first location, with a gfci receptacle there, then 10/2 from its load terminals to your downstream receptacles. Better to have a gfci at each location though, so if you trip it the reset button is right there.

why 10/3? is it a long run and you are concerned about voltage drop?

 

[Aceman]

If you want to use 10-3 the whole way, you'll either need to use GFCI receps on each post or put a 2 pole 20 amp GFCI breaker in front of both circuits back at the panel. On the plus side, f you use the breaker, it'll bring your burial depth to 12" otherwise you have to go down to 18 inches.

I'm not sure if you can, but if you have 2 20 amp breakers, that would mean 40 amp protection on the neutral wire. To me (average Joe), that doesn't seem good on a wire rated to 30 amp.

Yea, chances are with the neutral wire you will have to step it up and go to 8 gauge, but that might not save you any money.

How do you guys come up with this nonsense?

You do realize the wires coming into your service panel are 2 hots and ONE NEUTRAL that is being shared between them, right? So how would a branch circuit with 2 hots and one neutral somehow be dangerous?

 

[larry_g]

How do you guys come up with this nonsense?

You do realize the wires coming into your service panel are 2 hots and ONE NEUTRAL that is being shared between them, right? So how would a branch circuit with 2 hots and one neutral somehow be dangerous?

I think what Nate is saying is that two 20a hots are feeding through the load and returning on a single neutral that the neutral could carry up to 40a. Is this not so? So wouldn't the neutral have to be sized for 40a?

Inquiring minds want to know.

lg
no neat sig line

 

[Ford12508]

I know that my service is multiple hots, I was just saying he might need 8 gauge for the neutral because 20A+20A=40A

 

[mrb]

the two hots have to be on opposing phases. the neutral carries only the current imbalance. For example, L1@10 amps, L2@15 amps, neutral will be carrying 5 amps. L1@0 amps, L2@10 amps, neutral will be carrying 10 amps.

 

[shamrock12]

As long as each branch circuit is on a different phase, they can share the neutral. Each phase would cancels out the difference in current. However both breaker handlebars will have to be tied together so both of them can only be on or off at once for safety reason.

 

[akdiesel]

remember, your receptacles have to be GFCI protected, so if you are supplying them with a MWBC (shared neutral and two hots) each receptacle will have to be a gfci as opposed to just the first. Or you can run 10/3 to the first location, with a gfci receptacle there, then 10/2 from its load terminals to your downstream receptacles. Better to have a gfci at each location though, so if you trip it the reset button is right there.

why 10/3? is it a long run and you are concerned about voltage drop?

I am planning on using the GFCI breakers. Not sure if they make the double pole GFCI Square D brand. I will have to check it out.
The run I have is about 350'.

I'm not sure if you can, but if you have 2 20 amp breakers, that would mean 40 amp protection on the neutral wire. To me (average Joe), that doesn't seem good on a wire rated to 30 amp.

I was hoping to keep the 20amp service the same as the rest of the houses/shop exterior outlets for any available car plug ins for winter time. With what you are saying is it would best to go with two 15 amp GFCI breakers.

If you want to use 10-3 the whole way, you'll either need to use GFCI receps on each post or put a 2 pole 20 amp GFCI breaker in front of both circuits back at the panel. On the plus side, f you use the breaker, it'll bring your burial depth to 12" otherwise you have to go down to 18 inches.

This is interesting and good news. I thought you had to be at least 24" down. I do have to go under my driveway so I am planning on using the metal conduit for that part.

Thanks for the help.

 

[mrb]

you do not have to use 15 amp breakers. You may use a 20 amp. You are not putting 40 amps down the neutral, you are putting 20 amps max on it.

You do NOT want to supply a 350ft circuit with a GFCI breaker. You will have problems with it tripping. Furthermore, the cost of a 2 pole 20 amp GFCI breaker will buy you quite a few GFCI receptacles.

 

[nate379]

Ok, if I take a 10/3 line to power a building. To keep it simple it's rated to 30 amps (yes I know there are exceptions).

Now I would make it a 240v feed with a 30 amp breaker.

Let's say I wanted 2 120v runs off that panel, each 20 amp runs. Fine because if I went over 30 amps the main would trip.

In his case he has no main. Lets say he runs those lines to 20 amps... the neutral is not going to see 40??

I'm not a pro, and like I stated in my post that is just how I see it. I honestly don't appreciate your attitude with the "non-sense".

Instead of being insulting and degrading why don't you explain?

If you want to use 10-3 the whole way, you'll either need to use GFCI receps on each post or put a 2 pole 20 amp GFCI breaker in front of both circuits back at the panel. On the plus side, f you use the breaker, it'll bring your burial depth to 12" otherwise you have to go down to 18 inches.






How do you guys come up with this nonsense?

You do realize the wires coming into your service panel are 2 hots and ONE NEUTRAL that is being shared between them, right? So how would a branch circuit with 2 hots and one neutral somehow be dangerous?

 

[mrb]

Ok, if I take a 10/3 line to power a building. To keep it simple it's rated to 30 amps (yes I know there are exceptions).

Now I would make it a 240v feed with a 30 amp breaker.

Let's say I wanted 2 120v runs off that panel, each 20 amp runs. Fine because if I went over 30 amps the main would trip.

In his case he has no main. Lets say he runs those lines to 20 amps... the neutral is not going to see 40??

I'm not a pro, and like I stated in my post that is just how I see it. I honestly don't appreciate your attitude with the "non-sense".

Instead of being insulting and degrading why don't you explain?

see my previous post. The neutral only carries the current imbalance between the two hots. The two hots have to be on different phases. (if you were to put both hots on different breakers on the same phase the neutral could be overloaded, but you would (should) not install it this way) Works the same way as the service to your house.

heres a picture http://www.diychatroom.com/attachme...0-volts-240-volts-oh-my-multiwire-diagram.jpg

 

[nate379]

Yeah I'm retarded. I'm much more used to working on DC systems and pretty much wasn't thinking house is AC.

Almost as bad as earlier today I put a truck for sale by the road and somehow taped the sign facing in the cab. I caught that quick, but then I put it facing out, but upside down. Drove by a bit later and saw that... one of those days I guess!

 

[Norcal]

If you want to use 10-3 the whole way, you'll either need to use GFCI receps on each post or put a 2 pole 20 amp GFCI breaker in front of both circuits back at the panel. On the plus side, f you use the breaker, it'll bring your burial depth to 12" otherwise you have to go down to 18 inches.






How do you guys come up with this nonsense?

You do realize the wires coming into your service panel are 2 hots and ONE NEUTRAL that is being shared between them, right? So how would a branch circuit with 2 hots and one neutral somehow be dangerous?

18" is required not 12" the 12" depth is only allowed for a 120V GFCI protected circuit in residential & a multi wire circuit will req 18" or greater depth.

 

[Aceman]

18" is required not 12" the 12" depth is only allowed for a 120V GFCI protected circuit in residential & a multi wire circuit will req 18" or greater depth.

Unless I'm missing a code article, I'm going to disagree.

210.4(A) states a multiwire branch circuit shall be permitted to be considered as multiple branch circuits. I take that to mean two 120v circuits in this case.

Column 4 of Table 300.5 allows a 12" depth for "One and two family driveways....." utilizing a GFCI breaker for 120v circuits with no more than a 20 amp breaker maximum.

Unless this isn't for a dwelling, I assumed it was.....

This is all a moot point anyhow, if the run is really 350' long I wouldn't recommend a GFCI breaker either.

 

[akdiesel]

This brings up another question.
What is the longest recomended distance run for a 20 amp GFCI breaker?

 

[mrb]

This brings up another question.
What is the longest recomended distance run for a 20 amp GFCI breaker?

i *think* you usually want to keep it under 100ft. Every foot of wire, every receptacle connected adds leakage to the circuit.

why would you want to use a gfci breaker?

 

[akdiesel]

Ease of use and from what I have heard the new rule is that all new constuction bedrooms will have to have a gfci breaker. Maybe they will go the same route for outdoor outlets.

 

[porschedude996TT]

You can use the same neutral as long as the two hot leads come from separate lines in the CB Panel. See attachment.

 

[oleguy]

bedrooms are afci=arc fault.not gfci=ground fault.beginning with 2008 code all bed room,living room,parlors,sunrooms,hall ways,every thing that does not require a ground fault will need afci.nec 210.12(b) all120 volt 15 and 20 amp ckts.

 

[Dragster Racer]

I didn't know that you could do that. Way cool. I learned something.

 

[akdiesel]

bedrooms are afci=arc fault.not gfci=ground fault.beginning with 2008 code all bed room,living room,parlors,sunrooms,hall ways,every thing that does not require a ground fault will need afci.nec 210.12(b) all120 volt 15 and 20 amp ckts.

Yes afci. Thanks for correcting.

 

[Norcal]

Unless I'm missing a code article, I'm going to disagree.

210.4(A) states a multiwire branch circuit shall be permitted to be considered as multiple branch circuits. I take that to mean two 120v circuits in this case.

Column 4 of Table 300.5 allows a 12" depth for "One and two family driveways....." utilizing a GFCI breaker for 120v circuits with no more than a 20 amp breaker maximum.

Unless this isn't for a dwelling, I assumed it was.....

This is all a moot point anyhow, if the run is really 350' long I wouldn't recommend a GFCI breaker either.

As soon as one uses a multiwire circuit you 240 V. between conductors so your in excess of 120 volts maximum, & GFCI protection must be used so that means at the beginning of the circuit or at least before where it goes into the ground, the 12" exemption does not fit the bill here.


If someone does not want to dig, use rigid or IMC steel conduit then 6" burial depth is fine.

 

[mrb]

As soon as one uses a multiwire circuit you 240 V. between conductors so your in excess of 120 volts maximum, & GFCI protection must be used

can you explain this?

 

[walrus]

can you explain this?

Its a 240 volt line therefore the exception doesn't fit? I assume the exception is for a 120v gfci line not a 240v gfci line?