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Thread: Splitting generator output question

  1. #1
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    Splitting generator output question

    Hi guys Iím trying to get power into the laundry room in preparation of whenever our next storm will hit. What I would like to do is bring the 240/30amp side output through a wall (10Ēconcrete) and then split it into 2 15amp circuits. This will all be independent of the house wiring so no need for the backfeed discussion. I just want to make sure what Iím doing is as safe as possible. I will post some pics of the parts I have on hand. I donít mind constructive criticism so please fire away. Thanks!
    BCEAF067-C5EB-42AA-8F97-A25D4120922D.jpg
    9E85DACC-1B87-464D-8964-0552DA205CB2.jpg07FF26B8-6FC4-4E90-A494-9E2D97B048E1.jpg

  2. #2
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    You need to use the four wire side of the 240v output to provide two 120v circuits because you need the neutral for those circuits. So you will need an appropriate matching 240/120 four wire male plug, a hunk of appropriate cable that has two hots, a neutral and a ground and a quad box with two dual 120v receptacles and appropriate cable clamp for the cable coming from the generator. Assuming that the box is metal, your ground must connect to both the receptacles and the box. The 'borg should have rubber coated cable that's great for this kind of thing and they sell it by the foot. You could also cannibalize a four wire generator supply cable and replace the female end with the box, et al, that I've already described.
    --

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  3. #3
    You cannot put 15A receptacles on a 30A circuit, it is just wrong from a safety & code prospective, a better is to get a small loadcenter, and put in 15 or 20A circuit breakers in it with GFCI receptacles, or GFCI circuit breakers, there are more details to do it right.

  4. #4
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    Quote Originally Posted by Jim Becker View Post
    You need to use the four wire side of the 240v output to provide two 120v circuits because you need the neutral for those circuits. So you will need an appropriate matching 240/120 four wire male plug, a hunk of appropriate cable that has two hots, a neutral and a ground and a quad box with two dual 120v receptacles and appropriate cable clamp for the cable coming from the generator. Assuming that the box is metal, your ground must connect to both the receptacles and the box. The 'borg should have rubber coated cable that's great for this kind of thing and they sell it by the foot. You could also cannibalize a four wire generator supply cable and replace the female end with the box, et al, that I've already described.
    this is basically what Iíve done using the output shown on the right in the pic above. I have #12 wire but was wondering if I needed #10 for the neutral because it would be shared between the two circuits. My other concern is that I have plastic boxes and conduit so Iím not sure about grounding the generator itself? The reason I wanted plastic is everything metal goes to rust down here even galvanized stuff.

    Rollie, Ií Leaving the left (3 prong 30 amp) outlet as is to feed the dryer which I was going to address next if this discussion got any traction. If that was the only outlet I would have used a sub- panel and breakers as you suggest

    Thanks for your input guys

  5. #5
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    I haven't used this product, but have seen it several times and would probably at least consider it for an application like yours.

    https://www.amazon.com/Reliance-Cont.../dp/B0743BQDT4

    Scott

  6. #6
    Quote Originally Posted by Steve Fish View Post
    this is basically what I’ve done using the output shown on the right in the pic above. I have #12 wire but was wondering if I needed #10 for the neutral because it would be shared between the two circuits.
    If I understand what you're doing - that is you have a 240 volt circuit with a neutral and you want to tap 120 volts off of each side (hot to neutral) - then your neutral is fine with #12 wire. The two hots are out of phase so the currents subtract on the neutral.

    For example: If you have a 10 amp load on one side and nothing on the other, you have 10 amps on the neutral.

    If you have a 10 amp load on both sides, you have zero current in the neutral - not 20 amps.

    Mike
    Go into the world and do well. But more importantly, go into the world and do good.

  7. #7
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    Like Rollie said, you can't put a 15A or 20A receptacle on that 30A circuit and expect to stay safe. Doesn't matter if you use #10 wire, the receptacle is still good for only 15A. If you proceed with this, you may well have a burned down hours to add to your power outage worries.

    You can get a cheap, small 4 circuit panel, fill it with 15A breakers, & connect it to 4 receptacles. The other 30A circuit can't be used for the dryer because it has no neutral. Most dryers need 120V for the motor & controls.

  8. #8
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    I spoke with Caterpillar customer service. They are very helpful and on call 24/7 which is good to know. I pretty much got the green light for what I need to accomplish. I just need to keep loads balanced across both sides. Hereís their cord that splits the 240........
    6B13BD02-64DE-446B-9A29-0355A6702D83.jpg

  9. #9
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    If you can get a pre-made cable like that, jump on it. Much safer than rolling your own, IMHO. But yes, pay attention to balancing between the two sides and keep in mind this is absolutely for short-term, emergency use.
    --

    The most expensive tool is the one you buy "cheaply" and often...

  10. #10
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    Yeah for sure Jim. Eventually I will have the service panel replaced and I will probably go with a little bit bigger generator and an interlock system. Unfortunately I have to gut half the kitchen to get access to where the proper generator feed needs to go. Our walls are all concrete and block down here so itís not easy. Thanks for the input everybody especially you guys that wouldnít let me burn the house down. I do appreciate the heads-up

  11. #11
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    Doesn't your generator have two 120 out lets mine has one from each side of the 240

  12. #12
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    Quote Originally Posted by Jerome Stanek View Post
    Doesn't your generator have two 120 out lets mine has one from each side of the 240
    Some generators only have 240v output.
    --

    The most expensive tool is the one you buy "cheaply" and often...

  13. #13
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    Quote Originally Posted by Jerome Stanek View Post
    Doesn't your generator have two 120 out lets mine has one from each side of the 240
    Yes it does, currently those are already feeding into the main level. I’m just trying to avoid running outside in the middle of a storm to switch wires and extension cords around at the generator. All outlets are “hot “ all the time, no selector switching. So I’m only planning on drawing power from one source (120,240 etc) at a time to avoid overloading
    Last edited by Jim Becker; 09-06-2019 at 7:08 PM. Reason: Fizzed quote tagging

  14. #14
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    Quote Originally Posted by Steve Fish View Post
    . My other concern is that I have plastic boxes and conduit so Iím not sure about grounding the generator itself? The reason I wanted plastic is everything metal goes to rust down here even galvanized stuff.

    Thanks for your input guys
    Steve
    What type of generator do you have? Is it a "Bonded Neutral to Frame", or unbonded. Regardless of plastic box or not, the ground still has to be carried through your "system". When using plastic boxes the ground wire is attached, electrically, to the yoke of the duplex receptacle, or switch. In a metal box, it is attached to both.
    You run a significant risk of encountering a differential ground potential with what you are describing.
    Most generators made after 2012 have to meet the OSHA requirements for a "Bonded to Frame Neutral". What this means is that the neutral return, the ground, wire(s) and the frame of the generator, are all at the same electrical potential. Some generators have a switchable neutral, most do not. In a "bonded to frame" generator the frame of the generator itself, is now "the reference". It's an odds on bet that your generator manual will tell you to drive a ground rod at the generator and attach a ground cable between the frame of the generator and the driven rod.
    If you are going to be bringing power from an independent source into your house, everything better be at the same ground potential.
    The extension cord, power inlet box, and stand alone breakout panel, are available through Generators Direct.
    If you will have the ability to touch the metal part of any appliance plugged into your temp power system, and the bare metal of any appliance in your house not powered by your temporary power, but still electrically referenced to your main service panel ground, you will probably get a shock due to the difference in ground potential.
    You really need to sort out the grounding requirements though.
    Last edited by Mike Cutler; 09-06-2019 at 1:42 PM.
    "The first thing you need to know, will likely be the last thing you learn." (Unknown)

  15. #15
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    Quote Originally Posted by Steve Fish View Post
    Yes it does, currently those are already feeding into the main level. I’m just trying to avoid running outside in the middle of a storm to switch wires and extension cords around at the generator. All outlets are “hot “ all the time, no selector switching.
    That's interesting...the portable generator I had prior to getting my whole house unit would only permit "either" 120v or 240v, but not both simultaneously.
    --

    The most expensive tool is the one you buy "cheaply" and often...

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