Cannibalizing 240V Circuit

Discussion in 'Electrical and Wiring' started by Quatrix, Dec 17, 2019.

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  1. Dec 17, 2019 #1

    Quatrix

    Quatrix

    Quatrix

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    Good Day,

    I need your help and advise regarding installation of a 20A, HTB series fuse holder (with fuse) inside of a box. The project will be done in a residential home, 240/120V, in the United States.


    Scope of Application
    : I have a NEMA 10-30R receptacle in one of my bathrooms for what used to be the clothes dryer before I got rid of it. I do not use the clothes dryer, therefore my plan is to use one leg of the 240Vrms to connect to one of my 120V receptacles next to the sink in the same bathroom. In the NEMA 10-30R box I have the following: 1 Black Hot wire, 1 Red Hot wire, 1 White Neutral wire, 1 bare Ground wire. I have measured with DMM the voltages across the red to white = 120V, across the black to white = 120V, and across the red and the black = 240V. With such a combination I believe I am blessed to continue as planned, splice the #10AWG with a #12AWG, but please confirm on that. My question is how shall I aesthetically mount the fuse holder? By a simple search I have found the following link below which does not really express full details on the install, but does show an in-line fuse installation into a 6x6x4 box. Perhaps other experts on this forum may suggest even a better, more aesthetically pleasing installation. Please provide guidance and suggestions.

    http://waterheatertimer.org/Fuseholder.html
     
  2. Dec 17, 2019 #2

    Snoonyb

    Snoonyb

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    Is the 10/3 in metallic flex, conduit or romex?
     
  3. Dec 17, 2019 #3

    nealtw

    nealtw

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    Change the double 30 breaker to a double 20 breaker and just run 12/2 from that junction box.
     
  4. Dec 17, 2019 #4

    Jeff Handy

    Jeff Handy

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    Yes, great idea.

    And leave the existing outlet alone, just add another one.
    Always a need for more outlets, with hair dryers, toothbrushes, shavers, curling irons, etc.

    Or change a duplex outlet to a box with two duplex outlets.
    Of course, all of them should be gfci.
     
  5. Dec 18, 2019 #5

    Quatrix

    Quatrix

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    Nealtw,

    Yes, that is a good idea. But if we only had the option to install a fuse, which one would you go with? Panel mount vs. in chassis mount?

    P.S. this is a photo of my box with the wiring inside. Also, I have sample images of fuse carriages with two types of mounting methods. I just wanted to see what would you select as the best way to mount it in this application?
    part0.jpg
    Panel Mount Fuse Holder.png
    Internal Chassis Mount Fuse Holder.png
     
  6. Dec 18, 2019 #6

    bud16415

    bud16415

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    First off I’m not a pro.


    If it were mine and I no longer needed the 240v power I would do something similar to what Neal suggested. I would convert the breaker at the panel to the lower amp breaker and select one suitable for what is called a multi wire branch circuit. In that box then I would add two GFCI outlets one on each branch.


    No way would I mount any kind of fuse and holder in that box as you are suggesting. Not to code.
     
  7. Dec 18, 2019 #7

    kok328

    kok328

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    Yea, I'd have to veto the fuse and go with reducing the breaker amperage to two 20 Amp circuits with a shared neutral.
    However, I don't think reducing wire size is allowable.
     
  8. Dec 18, 2019 #8

    bud16415

    bud16415

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    As long as he pigtailed on #12 to feed two GFCI outlets I don’t see a problem. He’s really not reducing wire size he will just be feeding the multi wire branch with and oversized wire gauge.


    I don’t think code has a problem with over spec on wire size.


    He does need a breaker where both circuits are on a tied or common handle though so when one is opened they both open.
     
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  9. Dec 19, 2019 #9

    nealtw

    nealtw

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    this is not a car, bus or truck. there is no way in hell i would use inline fuses.
     
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  10. Dec 19, 2019 #10

    Quatrix

    Quatrix

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    Neal,

    Thanks for the feedback. This is the breaker I will purchase.
    https://www.homedepot.com/p/Square-D-QO-20-Amp-2-Pole-Circuit-Breaker-QO220CP/100032386
    Also, would you suggest to feed one receptacle from one of the legs (e.g. from black and white, plus GND) and another receptacle in a different bathroom from the other leg (from red and white, plus GND)? That way, the current draw will balance out if both bathroom receptacles are being used at the same time, vice connecting both receptacles all from one of the legs, tying back and insulating the unused HOT wire.
     
  11. Dec 19, 2019 #11

    bud16415

    bud16415

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    At this point I’m going to suggest (with all due respect) that you hire a professional electrician and tell them your intended outcome and let them provide the products and do the work as to code. Just from what I’m reading I think this project is outside what I feel is safe and practical for you to do.
     
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  12. Dec 19, 2019 #12

    Quatrix

    Quatrix

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    bud16415,
    That is why I am here, to get the feedback and learn about the process. I just asked a question in my previous post and would like to get a reasonable answer.
     
  13. Dec 19, 2019 #13

    bud16415

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    Well I gave you my input in post 6, 8 & 11. You were given some similar good advice in the rest of the answers.


    Have you worked behind the panel before changed breakers etc?


    If you feel comfortable change the breaker run from your Jbox to all new locations install a suitable Jbox / boxes and follow code as to proper wire size and GFCI outlets. The Jbox where this is now cannot be hidden but if you don’t want an outlet there it will need a blank cover. If you need more than one location as in a second bathroom I would make it a multi wire branch circuit and use both sides of the 240v.


    https://www.twielectric.com/safety-...nal-electrical-code-multiwire-branch-circuit/


    https://www.ecmweb.com/content/article/20886177/multiwire-branch-circuits-can-be-dangerous


     
  14. Dec 19, 2019 #14

    nealtw

    nealtw

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    That looks like the right idea, breakers do have to match the breaker box you have. But yes a double pole 20 would be the answer.
     
  15. Dec 19, 2019 #15

    Jeff Handy

    Jeff Handy

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    I think Square D makes at least two types of breakers, QO and Homeline.
    There should be a big chart inside the panel that lists the compatible breakers for that box.
     
  16. Dec 20, 2019 #16

    kok328

    kok328

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    Good catch on the tied breakers.

    I fully realize the gauge of existing wire will now be considered over sized for the circuit and that code does not have a problem with over sizing your wire BUT, it does have a problem with reducing the size of the wire in the run. Even though this reduction will be perfectly safe for the 20amp outlets, it still violates code.

    P.S.- Just saying. I'd do the same with pigtails. Safer than trying to attach 10AWG to a 20AMP GFCI?
     
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  17. Dec 20, 2019 #17

    Michael Armstrong

    Michael Armstrong

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    Can one of the pros tell me the code section that prohibits reducing conductor size?
     
  18. Dec 20, 2019 #18

    kok328

    kok328

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    I think we are good to go here. Reduction in wire size IS allowable as long as the reduction of wire size does not go below the rated amperage of the breaker.
     
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  19. Dec 21, 2019 #19

    Michael Armstrong

    Michael Armstrong

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    That's my feeling as well, but in #16 you said "[the code] does have a problem with reducing the size of the wire in the run. Even though this reduction will be perfectly safe for the 20amp outlets, it still violates code." I haven't been able to find that violation explicitly called out, and if it exists I'd love to know where.
     
  20. Dec 21, 2019 #20

    kok328

    kok328

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    Yea, thought about code and how it applies to this situation and realized we do not have a violation here, and posted a correction to my previous statement. Just me talking before thinking; again.
    It would be a different story if we were going to pigtail from 10awg to say 14awg to a 20 or 30 amp outlet. This is the type of situation that code is preventing and in this case does not apply.
     

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