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Electrical Help

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    Electrical Help

    If there are any electricians in here I could really use some advice.

    Im trying to use a shed to house multiple grows. The shed has electricity but is protected by a 20A breaker. As it stands it’s a struggle to run just 2 tents and I was hoping to expand to 4 eventually. The shed needs heat and AC and currently (no pun intended) it just isn’t feasible. Breaker has tripped multiple times and it’s just a headache.

    The breaker box that the wire runs to I assume runs to the main box on the other side of the house. In this box there is a 40A dual breaker (20A x 20A). Is it possible for me to run 2 20A lines from my shed and connect it to this breaker? The breaker is labeled as “Attic Fan” but there isn’t one up there (old house) so it just seems like it’s an open line.

    Is this a safe option? I don’t live in a friendly state so finding an electrician to come over is risky business and I’ve done minor electric work before (I know how to shut off power and check for live wires). But if it was safe it would be nice to split the shed’s power load. Any advice would be grateful.

    You could do that but make sure you use cable (wire) that is rated to carry that current or more(better) the breakers are there to prevent the cable from overheating and causing fires.


    • dalvis
      dalvis commented
      Editing a comment
      Yeah I’m aware of that. Thanks.

    Try to find a local electchicken that you can trust. Screwing up on electrical can cost you your house and possibly your life.
    There are 3 things you must check everyday when growing in hydro:
    1) Water level (How much h2o is she drinking in 24hrs)
    2) pH level (change over 24hrs)
    3) ppm/EC level (How much food is she eating in 24hrs)


    • dalvis
      dalvis commented
      Editing a comment
      Yeah not really any electricians in my friend circle. I realize the risks in dealing with electricity that’s why I’m hoping someone on here can guide me.

    Agree with the above. You can take a line from each braker and put a second single 20A breaker at The end of each line and put separate plugs for each line to use in each tent. Its not advanced chemistry either


      Yes matching the wire gauge and the outlets/switches to the current is of the utmost importance. Bigger wire is fine smaller is dangerous.


        It’s not for growing but here’s what I did in my garage/shop. I had a 60amp 240v water heater that I scraped so I took the wire that went to it and put in a small sub panel with a 60a main and dropped in 4 15amp 120v breakers.
        One thing to check out before you get really deep into your setup, I don’t think 2 20a circuits will run that big of a grow. The AC/heat will probably pull one whole circuit and that’ll only leave you one for everything else.


        • dalvis
          dalvis commented
          Editing a comment
          You’re completely right. However I would have to run a 50A line through my house to get to the shed and that would be a ton of work. Probably end up doing it anyways.

        15 amp feed needs 14 ga wire minimum, 20 amp 12 ga minimum and so on. I believe the wire rack at HD or Lowes has the amperage to size info on it. Always use copper in the house not aluminum. Aluminum wire burns houses down.

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          The wire size also depends on the length of the run, on a 20 amp I never go under 10 AWG, better to have fat wire than hot wire! And bigger wire you get less voltage drop over the length.
          BUT, this will still only be 2 20 amp circuits, you will need more, just the heat and AC will use most if not all of one circuit. IF the load center and current wiring can do it, replace the breaker with a 30 amp (2 single breakers not tied together)
          Tell the electrician you are putting a small welder out there (making a small shop), have him/her run the wire to the shed (load center) and you do whats needed once its there. My local laws allow for me to do this work myself, a quarter mile from here no they must hire it done.
          Good luck be safe!


            I replaced a 40 amp double pole single throw breaker at power source( breakers get weak with age). Ran 4 wires 3 were 6 AWG 1 was 10 AWG to my shed 220 volts (2 hot 1 neutral 1 ground). Wired them up to another breaker box with spots for six breakers( 3 for each hot line ). Used those skinny breakers, so that give me 12 breakers to hook up everything to it's own circuit. Hope this helps?
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              I only had 1 open circuit when I decided to grow and it was for upgrading my garage to 20 amps from the 15 it had. From dealing with the Electrical Inspector while rewiring my kids house during rebuilding it I was informed the dual throw single pole breakers met local residential electric codes, and would expand the number of circuits in a given breaker panel. I got the breakers for both houses from Menards they took different styles so you should be able to take one of yours to find the correct one needed. The others are giving good advice on wire gauge but I will add going from the house to your shed you want to use wire rated for direct burial and use PVC conduit to house it, it's much easier to work with over Ridged or EMT conduit. Also from breaker box to the shed should be a continuous length of wire the First break in the line should be where you split it in the shed. I ran down took a picture of my breaker box showing on the right side the dual throw single pole breakers I used.


              • Xena
                Xena commented
                Editing a comment
                Man I had totally forgotten those double breakers. A brain 🧠 is a terrible thing to waste and apparently mine is wasted more times than not. They would be perfect in a sub panel in the shed.

              When you say "40A dual breaker (20A x 20A)" I'm assuming you mean 20Amp double throw 240Volt breaker. If this is the case, then you can remove that breaker and replace with 2 x 20Amp single throw 120Volt breakers, or a different size. The breaker size (amp rating) will determine the potential current available, and will determine the size of the wire you need to carry the current. The wire size calculation is also dependent on other factors such as the length of the wire run from breaker to end point and if you are in a conduit or not. This may necessitate a larger size wire. You need to get a compatible breaker to go with the panel you have. Not all brands are interchangeable.
              Don't worry, be happy, grow sticky buds.


                If you're comfortable replacing the dual breaker with two singles, do it because one tripping will trip the other with it if you don't. The best option for running an air conditioner as well as your tents is definitely the 50 amp sub breaker box in the shed as long as you already have wiring from the house that will support that or you are willing to have it replaced with the proper gauge stuff. DiY is great but you need to know what your limits are and when to bring in a pro.
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                  Loads of great advice here on a topic we are all faced with sooner or later!

                  I'll add that you need to use adequate wire gauge extension cords for your final connection to A/C, lights etc. I had multiple 15A circuits in my grow room, but I still tripped breakers because I had a couple of 16 gauge extension cords in the mix. If an extension cord feels warm it needs to be up sized!

                  It's also helpful to know the Amperage draw from each of your devices so you can divide them up between the available circuits. That's easy if your device indicates power draw in Amps. Many devices only list watts and a simple conversion is needed.

                  For example my new LED growlight draws 150 watts. To convert that to Amps just divide the wattage by the voltage of your circuit: 150w / 120v = 1.25Amps.

                  Apologies if everyone already knows that, but I end up using that simple formula all the time to balance my changing loads.

                  PS, just for fun, Ohm's Law Calculator: enter two values and it calcs the others:
                  I grow exclusively in large pots using soil comprised of the compost I make combined with Foxfarm or other quality commercial soils as an amendment. Appropriate nutes as needed. State of the art LED lighting and an evolving system of environmental controls allows me to pamper my plants and let them tell me what they need.
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                    Thanks for all of the replies everyone. I’ve been meaning to post some pictures of my plans I’ve just been busy with the holidays. Been just running extension cords right now to get by. Will update soon.


                      Finally finished this project a few days ago and I’m simply over it. MAD PROPS TO ELECTRICIANS. Yeah, I saved a ton of money by doing this myself, but I have plenty of cuts and bruises to tell the story. By the end my hands were cramping to the point that I had to physically open them up sometimes.

                      After figuring what breakers were running what to my house, I decided to add a 60A double pole breaker to my main box. Ran that to a 70A sub panel using 4g wire (two live and one neutral) with an 8g ground. In total a little over 300 ft of total wire ran. These run into two 30A breakers that I have running to 2 outlets each with 10g wire. In addition, I ran some new 12g wire from the original 20A breaker that was supplying the shed to run regular lights as well as a single outlet that I may need for yard work or something.

                      So total I now have 5 outlets. 2 on 30A dedicated to heaters and air conditioning and 2 on 30A running the tents and 1 20A extra outlet. Really hoping that this should be enough. Dear god I hope so.


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