Running your own 40amp Line.

Discussion in 'Do It Yourself' started by Walliby, Mar 17, 2012.

  1. Hey guys, i am going to be building a room that i need to wire. i have a 100 amp service and i was going to replace some breakers with 40 amp breaker and run a line to my room. Room will ultimately consist of 1350w of HPS and a 400w MH, 400cfm Exhaust Fan, Two of Budslingers recirc bubblers (4 buckets each for flowering... so i can do two different strains.)

    Perhaps a custom rig for veg, 6" net pots put into 2ft long 6" PCV sealed at the bottom to make long slender bubbler rig... hopefully allows root mass to grow enough before being transfered to one of 8 5gal buckets.

    3-4 Fans for Air Circ
    Dehumidifier and/or Air Conditioner
    Humidifier (for veg room)

    Think that should be all of what i am running.

    Now for the actual part of the Wiring.

    My Electrical Panel, almost everything is being used with the exception of the two that are off on the bottom right, which i will replace with a 40amp and run the wire from the box

    the wire will run down this pre-drilled hole and to a room where it will come up the floor vent (will be disconnected for air exhaust) and wired to a box that will be built into the room wall.


    Now i need to know what type of line i should be running. 12/3 wire or 12/2 wire if anyone has experience with this would be much appreciated.
  2. 12/3 brother 12/2 is for 120v I'm not an electrician but I just wired my 6000 watts from a light controller to a 40 amp breaker I'm pulling 27 amps 4.5 amps per ballast and then ran 12/2 wire to a single pole 20 amp 120v line for 2 8" max fans and a 6" max plus 5 circulating fans a 9000btu a/c, dehum, and a 5000btu I'm pulling almost 15 on that one , with how small your grow will be a 20 amp 120 would be more than enough, run it to a sub panel so u can still split the 240v and still have more room to get bigger , gl with it bro it was dimple for my first time and should be the same for u ,
  3. Are you doing 120v or 240v? It also looks like you have free space above your breakers?

    Instead of adding a break you might be able to use the existing wiring in your house. Do you have a dryer in your house? or a dryer outlet? you can defiantly use that!
  4. Was thinking about it, did a load of research yesterday. i was gonna run 240v because i heard it saves you money. Wrong.... it trades double voltage for half amperage. thus i'll run a 8 guage 3 wire cable 120v and wire it to a electrical socket. i am only running 3 lights (2000watts or so) 40 amps will be more than enough for me to do that. when the time comes to get bigger, 240v is only one positive connection away in the breaker box.

  5. Use three wire if you have two three way light switches to operate in your grow room, otherwise I'd just use two wire. A hot, neutral, and ground would be sufficient :D
  6. I think in your case 120V will be fine...but:

    The concern I have is that you first considered running 12 gauge wire for a 40A circuit. 12 gauge copper wire wouldn't be acceptable because it cannot carry that much current safely. Your last post says you'll run 8 gauge, which is OK for a 40A circuit -- but to wire it directly to an electrical socket (generally 15A) is not acceptable. Remember, standard outlets are usually rated for 15A, but you'll be trying to protect it with a 40A breaker at the main panel. The rating of your outlets and wire has to meet or exceed your breaker rating.

    One option, is to wire in a small subpanel in your new room (a 70A panel like in my photo will cost maybe 20 bucks). Run wire from your 100A main panel that is sized to carry 40A (8 gauge will work) and use a single 40A breaker. Then, you can install two 15A breakers (or two 20A breakers) in your new subpanel, and you can use 12/2 for each new 15A or 20A circuit. One can handle the AC, the other the lights and fans, etc.

    There is a lot more to this, though. I just wanted to address the immediate hazard I read, that you do not run wire that is undersized.

    When wire is stated as 12/2, there are two 12 gauge conductors and a 12 gauge ground (that is, three total wires). 12/3 has three conductors and a ground (4 total wires).

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  7. Using 240 doesn't HALF your amperage. The total amps you can pull is regulated by a 40 amp breaker. Working with higher voltages is always more efficient if possible. I would definitely use 12/3 over 12/2 because that 3rd wire is your ground which you will definitely need.
    You can run 4800 watts on a 40 amp breaker @ 120 V
    You can run 9600 watts on a 40 amp breaker @ 240 V

  8. 2 wire is a hot(black), neutral(white), and ground, 3 wire is a black, white, red, and ground.

    Use 2 wire unless you are going to have three way/four way switches. And come in with 12/2.
  9. Great advice. You must run wire related to the size of breaker and only load the breaker to 80%!

    You could also run 12/3 with shared neutral to two 20Amp receptacles and it would be two circuits (just balance your load because the neutral carries the unbalanced load from the two circuits). Also note it on your panel that it is a multiwire branch circuit and check local code to see if its allowed.
  10. Run #8/3 w/ Ground copper or #6 SER aluminum from your panel to a Sub-Panel. From the sub-panel you can distribute as needed. I personally would run a #6/3 SER feeder to a Sub-Panel and install a 60 amp sub-main breaker at the main panel. Make sure to use an Ox-Gaurd if you go Aluminum. AL, will be much, much cheaper then running a 6/3 Copper. Only use AL for your feeder.
  11. Bakrr also has offered sound advise, and yes, make sure your use a double pole 20 amp breaker w/ a handle tie if running a multi-wire branch circuit.

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