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Thread: Getting 110V from a 220V line

  1. #1

    Getting 110V from a 220V line

    Hello All-

    A friend asked me to help him wire his greenhouse. He has a 220v line (it used to be for a hot-tub) out there, but wants to have 2 110V outlets (for heaters, lights, etc).

    I know you can get 110V from a 220V line, but I can't remember exactly how to wire the outlets.

    Do any of you have a drawing or a link to a webpage that shows exactly how to do this?

    Thanks-

    Brad

  2. #2
    yes you can, is it safe? NO!! please pull a dedicated service it`s not very costly or dificult and you might save major headaches down the road. .02 tod

  3. #3
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    I would think if you ran the 220V line into a breaker box in the greenhouse (outdoor rated because of moisture issues) then you could put whatever outlets you wanted out there. I don't claim to be an electrician but that's probably where I would start.

  4. #4
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    I'm not an electrician either, but here is what I'm thinking...

    What kind of wire is it? 12/2?

    If it's 12/2, you could switch the double pull breaker to a single pull 20 amp breaker (black (hot) wire to the breaker, white (neutral) and ground to one of the bars on the side) which would then give you a 110 line. Then just wire the outlets like you would any circuit.

    If it's a 12/3 wire, then I'm not sure. I guess it would work to just not use the extra wire, but that doesn't seem very safe.

    Just be careful - especially in the service box.
    Last edited by Jarrod Nelson; 11-21-2005 at 5:57 PM.

  5. #5
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    Brad.

    Find out what type of cable he has going out there. 2 conductor, or 3 conductor. Ground does not count. The 2 conductor will have a White, and a Black wire, with a ground. The Three will have a Black, White and Red wire, with a ground.
    With the three conductor it will be easy, and safe. With 2 conductor, No dice, without going back to the panel and swapping out breakers and essentially making a new circuit.
    With three conductors there is also a receptacle that splits the loads for you, and still leaves you with a 220.

    Mark Goodall(sp.) has a post where he outlines how to break a 3 condutor 220 out into seperate 115 duplex receptacles. It's safe if done correctly.

  6. #6
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    Like the other folks said, if the original wiring includes both phases plus neutral, you can get 115 between either hot phase and neutral. (Mind you, neutral is not ground. If you don't understand this distinction, perhaps you should get somebody else to work on this task.)

    If you only have two hot phases, one way to get a little 115 is with a transformer. I've done this on woodworking machines which only get 230, so I can use a 115 volt work light. A transformer big enough to run a 60W light is $30 or so. However, if you want to run big stuff (maybe 600W or bigger?), the transformer approach gets real expensive.

  7. #7
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    [quote=Mike Cutler]With 2 conductor, No dice, without going back to the panel and swapping out breakers and essentially making a new circuit.[quote]

    That's what I was trying to describe. If you aren't comfortable working in the service pannel, hire an electrician for that part. It should only take him a few minutes to put in a new breaker.

  8. #8
    Brad - sounds like everybody's nailed it. I'm not an electrician, but I'll put it in my words, maybe that will help. A hottub circuit like that for a 220v dedicated appliance is just two hots and a ground - no nuetral. You need the nuetral for the 110 outlets. We're all assuming there is no more need for 220 out there, right. I'm also assuming you don't need two circuits out there, just two outlets on one circuit. So, given those assumptions, you have two options, both require main panel work. Option 1.) Pull the double breaker and one of the hots off the breaker, mark it as a neutral, connect it to the neutral post. Replace the double breaker with a single and connect the remaining hot to that. Now you have one hot and one neutral heading out - this is what you need. Outside, mark the old hot as nuetral and wire as a normal single circuit.

    Option 2.) If this is in conduit, fish a single neutral wire back to the main box from outside. A properly gauaged single nuetral wire can of course serve as neutral to both circuits. Back in the main, replace the double pole breaker with 2 single breakers. This gives you two circuits out there.

    Sometimes outdoor circuits have their own grounding - just make sure you have the grounding correct all the way through.

  9. #9
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    Okay, everyone is assuming that a hot tub only requires two hots and a ground but mine required a neutral also. So there is no telling what is there without looking at it. In any case a hot tub requires a GFCI next to the tub and I would presume that if you are running electricity to a structure you need some sort of end for the circuit other than just an outlet. I sure would feel safer that way. That's why I suggested a sub panel out in the greenhouse plus it would give you greater flexibility for the future.

  10. #10
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    Lots of good advice here. I would do the same as Jarrod. Wouldn't think twice about. (OK, maybe I would think twice, but not 3 times!) Swap the 220 breaker for a 110 and Bob's your Uncle, you're done. The 220 breaker will probably come in handy for something down the line.

    Neil

    "What do you mean my birth certificate's expired?!"

  11. #11
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    Quote Originally Posted by Steve Cox
    Okay, everyone is assuming that a hot tub only requires two hots and a ground but mine required a neutral also. So there is no telling what is there without looking at it. In any case a hot tub requires a GFCI next to the tub and I would presume that if you are running electricity to a structure you need some sort of end for the circuit other than just an outlet. I sure would feel safer that way. That's why I suggested a sub panel out in the greenhouse plus it would give you greater flexibility for the future.
    Yeah. I kind of didn't want to assume anything about the wiring. If it is to recent codes it is most likely a 3 conductor 10awg cable. I'm kind of surprised that there wasn't a small mini panel somewhere near it, and a GFCI receptacle already, also somewhere near it, but you never know.
    Most new hot tubs have 220 going to them and then split into 115 for lights and such. The 220 has to power the heaters, and sometimes the pump also. I have seen 115 pumps in hot tub setups.
    It's always difficult helping folks with electrical over the net. You are never really sure exactly what they currently have.
    We got into a little "hot water" a few weeks back because of a difference in terminology being used. "ground" vs. "neutral return". kinda threw us for a bit.

    My standard answer is usually to contact a local license in your area when unsure.

  12. #12
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    Actually, many hot tubs are 40 to 50 amp circuits - I know our spa takes a 50 amp, 240v, GFI breaker. If you have something like 8-3 or 6-3 NM ("aka "Romex") that was run to power the spa, you have all the conductors you need to run a 40-50 amp subpanel. You'd need to change no wiring in the feeding panel, assuming it was fed from the main service panel. If the spa was fed from a subpanel, I'd double-check to make sure that the neutral was properly terminated (on an isolated neutral vs the grounding bus).

  13. #13
    Brad,

    If the objective is to provide 120V receptacles and lighting only (i.e., no 240V equipment) without running new wiring, then yes, this is do-able assuming that branch circuit supplying the hot tub is Code compliant in the first place.

    How this would be done depends on the specifics of the current installation; e.g., is it a 2-pole, 3-wire 240V branch or a 120V/240V 3-pole, 4-wire multiwire branch; ampacity, etc. Different tubs require different circuits.

    Some of the advice that has been given on this thread is contradictory, and even I'm just some guy on the internet. Incorrect electrical installations can kill someone or burn down the house; this isn't just a matter of, say, a botched finish messing up the latest project. You might want to consult with a pro, or at least get a book and do some self-education.

  14. #14
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    Brad,

    You can get advise all day long on this and 20-30 posts! Let me try and summarize what has been said and asked in this thread. Namely, you need to answer several question first before any decent advice can be made:

    1. What is the size of the wire in the hot tub circuit?
    2. How many conductors do you have in the outlet?
    3. What are the colors of the conductors that you have?
    4. What is the size of the breaker protecting this circuit?
    Technically, you can just take a 240V plug that fits into the current 240 V outlet and with a small extension cord (of appropriate size/gauge!) and a box, make a 120 V outlet from it. However, as has been said above ad naseum, you MUST have a white neutral contained within the box in order to create 120 V from the 240 V. No white, No dice!

    Now reply back with the above answers and we can get you more sound advice.
    Wood: a fickle medium....

    Did you know SMC is user supported? Please help.

  15. #15
    Only thing I will add is that I would NEVER open up a box at the end of the line w/o first checking the panel. You never know who did the original wiring and if they did it to code
    Jeff Sudmeier

    "It's not the quality of the tool being used, it's the skills of the craftsman using the tool that really matter. Unfortunately, I don't have high quality in either"

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