Power to a double switch

Discussion in 'Electrical Forum discussion & Blog' started by lee polowczuk, Aug 4, 2007.

  1. lee polowczuk

    lee polowczuk New Member

    Messages:
    63
    Location:
    Florida
    I had a bathroom ceiling fan on a switch.

    i replaced the fan and hooked it up to a new switch -- with two off and on's on one post

    please forgive my electrical ignorance.

    i want to run a separate light fixture off the second switch... so i ran the wire from the switch to the light... the light has no power.

    do each of these switches need to have their own power source?

    i guess i am thinking the circuit to the fan would supply power to the light as well.
  2. frenchie

    frenchie Jack of all trades

    I can think of so many different ways this might be configured... where is the power coming in from - the switch box, or the fan box? A diagram would help...
  3. Mikey

    Mikey Aspiring Old Fart, EE, computer & networking geek

    Messages:
    2,714
    Location:
    Central Florida
    In general, the power source (e.g., black wire from the panel) goes to the common side of the dual switch, and the other two (switched) sides go to the appliances' hot sides. The appliances share the neutral. As Frenchie points out, the topology is slightly different if the power comes from the panel to the switchbox or the fan's box, but a few minutes spent with a pencil and the back of an old envelope will be well spent to get the picture of what's going on.
  4. lee polowczuk

    lee polowczuk New Member

    Messages:
    63
    Location:
    Florida
    boy, I am sure both of you guys would be a tremendous help.

    I just have to figure out some of the terminology.

    Some of this is difficult because the fan wiring is in the attic... since it worked fine, i just hooked it up to the top switch

    then i put a can light in the ceiling and ran wiring from it down to the lower switch, black to brass colored screw, white to black colored screw, ground to green colored screw.


    my guess is either that white wire or the black wire from the can light has to be tied to the fan switch

    you can laugh a little... i am patient.
  5. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,539
    Location:
    Cave Creek, Arizona
    light

    I can't follow your wiring, but by hooking the white to the switch, it in effect became a black, red, or blue wire, not a white one. You still need to find a source for a white neutral wire to the fixture. And that is assuming the "black" wire is actually connected to a "hot" wire.
  6. Mikey

    Mikey Aspiring Old Fart, EE, computer & networking geek

    Messages:
    2,714
    Location:
    Central Florida
    Since you "just hooked it up to the switch", I assume there were only two wires going from the fan box to the switch box -- probably a black/white pair. Another black/white pair should have brought power from the panel to the fan box. The black wire from the panel (the "hot" wire) should have carried current via the black wire to the switch, where it was switched on and off to the white wire (which should have been marked with black paint or tape). Back in the fan box, the white wire from the panel (the "neutral") should have been connected to one of the fan wires, and the white wire from the switch box (which also should have been marked with black paint or tape) should have been connected to the other fan wire. The complete circuit is then hot from the panel, through the switch, through the fan, and return to the panel via the neutral.

    Now we introduce the double switch. If you look at the switch terminals, one side of the switch will have two black screws in 2 brass strips connected by a small tab, the other side will have two brass screws in two separate brass strips, each obviously associated with one of the individual switches. The black wire from the fan box should be connected to one of the black screws, and the white wire (which should have been marked with black paint or tape) should be connected to one of the screws on the other side of the switch. Notice that the black ("hot") wire from the fan box is now actually feeding both switches, via the little tab connecting the two halves of the brass strip -- the 2nd switch is all dressed up with no place to go, i.e., nothing's connected to it.

    Now to connect the light, you've somehow got to get a wire from the other separate screw on the switch to one side of the light, and the other side of the light to the white neutral wire from the panel in the fan box. How you do this is up to you, but in new construction I'd run a three-wire cable from the fan box to the switchbox (one "hot", 2 switched) and another 2-wire cable from the fan box to the light box (one switched, one neutral).

    Draw some pictures and it might make sense. Of course if any of my initial assumptions is wrong, none of this works. If that's the case, do what Frenchie suggested and draw us a picture, or describe what's going on in all 3 boxes (fan, switch, and light) in detail.
  7. Mikey

    Mikey Aspiring Old Fart, EE, computer & networking geek

    Messages:
    2,714
    Location:
    Central Florida
    Okay, I just studied your description a bit. I think you can make all this work by disconnecting your existing light-to-switch white wire at both ends. Then connect another white wire (the white wire in a two-wire cable works OK) from the light to the white wire from the panel in the fan box. Logically, we're moving the end of the light-to-switch white wire from the switch to the system neutral.
  8. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,539
    Location:
    Cave Creek, Arizona
    wire

    That description is not much better than the original one. He is probably already using the "white wire in the romex" for the switched lead to the fixture, and what does he do with it once he disconnects both ends? But he probably does need another white wire for the neutral, we just don't know how he is going to run it.
  9. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,950
    Location:
    New England
    WIthout being there and measuring things, it is hard to say, but this is my guess.

    At the fan, there's two cables coming into it; one from the power panel, the other going to the switch. The white wire coming from the power panel is connected directly to the fan. The black wire from the panel is jumpered to the other wire that is going to the switch. It goes down to the switch, and when the switch is closed, it comes back to the fan on the white, which is connected to the black wire to the fan, providing it with power. BTW, this wire is supposed to be labled with a red marker to indicate that it is a switched hot lead, but is ignored way too often.

    So, you need to verify this, and you need to continue the white wire from the power panel to the white wire of the new light. Then, with the new lead from those lights to the new switch, at the switch for the fan, connect both black leads together with a couple of pigtails, and then go to each of the switches, providing power to both items when their respective switches are closed. Leave the white wires where they are, but mark them with red tape or a red magic marker.

    The grounds need to run all the way through each item, but I left that out.

    If you don't own one, you need either at the minimum a test lamp, or a meter.
  10. frenchie

    frenchie Jack of all trades

    You were doing so well - but that "one hot 2 switched" is wrong - it'd be one hot, one switched, and one neutral. Like HJ said, what Lee's probably missing is a neutral for the light circuit. Assuming that by wiring in the attic, he means the power enters there...

    By the way, ALL of you are wrong about the white wire marked as hot. If you re-designate a white, it can't be the switch leg returning to the light, it has to be the constant "always hot" wire.

    http://forums.jlconline.com/forums/showthread.php?t=38064&page=2

    (I always hesitate to link to JLC... it's a pro-only site, and we/they can be mean about it. If you're not in the trades, feel free to lurk, but do not post unless you like getting flamed.)

    The idea is that, at the fixture's connections, you're always going black-to-black, white-to-white, no matter what, it saves on confusion for the next guy.


    Lee - describe each box, will ya please? How many wires in each box, and where do they go?

    Do you have access to the attic? Or are the walls open? It'd help to know where it's easier for you to add a wire, because you're gonna have to do it somewhere.
    Last edited: Aug 5, 2007
  11. lee polowczuk

    lee polowczuk New Member

    Messages:
    63
    Location:
    Florida
    I will print and follow these posts..

    here's the best i can tell... power came from the basement panel..up the wall to the ceiling to a junction box... then it split... to the fan... and then back down the wall to the original switch.. there, a pair of wires was attached to the switch..

    everything worked well.

    then i took out the single switch and attached the fan to the top switch.. fan works great..

    then i put the can in the ceiling and ran romex from it down to the other switch.

    Please allow some patience for my ignorance.. I will take a Sunday break... and thank everone for their help...

    i'll let you know next week, where I am ..... even with A/C ,,,it seems to hot to work today...

    regards,

    Lee
    Greenville, SC
  12. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,539
    Location:
    Cave Creek, Arizona
    light

    Those two wires down to the switch are both "hot" when the fan is on. You do not have a white neutral to the light, so it cannot work. If the black wire is the switched leg, then the white one is "hot" which can be more confusing, and dangerous to a DIY person. I would rather have him confused by the wiring than in the emergency room because he touched a "safe" white wire. And if it happened to me, I would be looking for the idiot that wired it that way.
  13. lee polowczuk

    lee polowczuk New Member

    Messages:
    63
    Location:
    Florida
    Just to let everyone know some more info..... the ceiling is more or less buttoned up now.

    the wall is still open. And, there is romex coming up from the basement into a wall plug box (the plug is in the adjoining bathroom) A wire comes out of that same box and feeds another light switch.

    I presume that's a possible solution to complete the circuit. I need to take a breather.

    They should teach this stuff in high school rather than another history class. I tried to decipher it in books, but forget it.

    HJ--- i'll play it on the safe side, I keep running up and down the stairs from the basement, turning the breaker off an on...

    Actually most of the wiring looks decent.. it's a 1930's bungalow...but all of the knob and tube has been replaced...
  14. Mikey

    Mikey Aspiring Old Fart, EE, computer & networking geek

    Messages:
    2,714
    Location:
    Central Florida
    I stand corrected... partly

    I said "one hot, two switched", and that is in fact the situation, although I would have been wrong about the colors. Having read through the Code (God, I wish they had had an English major on the team that wrote the damned thing) and the JLC thread, I now see that my "one hot" would be the reidentified white conductor (coming from the black in the light outlet and going to the common switch terminal), and the "two switched" would be the black and red conductors (coming off the switched terminals and returning to the fan and light) in a "standard" 14-3 cable.

    Someday I'll figure out how to draw pictures for this forum and save a hell of a lot of words.
  15. frenchie

    frenchie Jack of all trades

    If he runs a 3-wire, there's no need redesignate the white, anyways - it'll be one hot, one switched, one neutral. I think you missed what I was saying.

    Anyhow...


    Drawings? Google Sketchup!

    Give me a few minutes... here we go!


    Lee - replace the 2-wire cable between the fan & the switch with a 3-wire cable. This is how it should look when you're done.

    Attached Files:

    Last edited: Aug 5, 2007
  16. lee polowczuk

    lee polowczuk New Member

    Messages:
    63
    Location:
    Florida
    frenchie...do you want me to pigtail the two whites?

    I have tried that (then the brass side has no connections)

    the blacks are each tied to their respective black screws.

    the fan still works that way....

    i am sure it won't be too difficult with all this advice coming in...

    First thing monday morning... I will draw a sketch, scan it...and post it.
    Last edited: Aug 5, 2007
  17. frenchie

    frenchie Jack of all trades

    Yup, pigtail the whites. That's the critical connection you're lacking, right now.

    If the 2 screws on the "hot side" of your switch is still connected by the little tab, it only needs one black wire connected to it - the one bringing power to the switch. If the tab's been broken off and thay are completely independant, then you need to pigtail that black, and connect to both screws.

    Making sense, yet?

    The other black, that goes to the light, is now a switch leg - like the red is for the fan - it goes on the OTHER side.


    ...if this still isn't making sense to you, I really think you should call in a pro.
    Last edited: Aug 5, 2007
  18. lee polowczuk

    lee polowczuk New Member

    Messages:
    63
    Location:
    Florida
    Let's see if this makes any sense.

    Frenchie... i think i am catching on.

    Pigtail whites.

    Attach fan black to upper switch

    Attach light black to other side of lower switch

    Attached Files:

  19. frenchie

    frenchie Jack of all trades

    Sorry, man, I can't make out your drawing, it's too small - and I can't seem to zoom it. And what I can see, ain't making much sense... Can you zoom it in & crop a bit or something?

    WAIT A MINUTE! There's a junction box somewhere in all this? Please explain, with a LOT more detail...

    I had thought there were only 3 boxes involved, kinda like this:

    Attached Files:

    Last edited: Aug 6, 2007
  20. jwelectric

    jwelectric Electrical Contractor/Instructor

    Messages:
    2,532
    Location:
    North Carolina
    Frenchie

    I copied his drawing to paint and enlarged it and it still makes no sense.

    No he hasn't got it yet!!!

    Edited to add;

    Does this help you understand why some of the people at JLC get the answers that they get in The Electric Shop?

    Over there the people are supposed to be professionals trying to do the same thing that is being done here. Do you think that a real professional would try something this far outside their knowledge?

    Keep up the hard work and he will get it sooner or later.
    Last edited: Aug 6, 2007
Similar Threads: Power double
Forum Title Date
Electrical Forum discussion & Blog Cost estimate for Generator Power Transfer Switch installation Nov 12, 2013
Electrical Forum discussion & Blog Power Out From Electric Space Heater Jan 25, 2013
Electrical Forum discussion & Blog Old fuse box blowing large fuses but turn on dryer and power is back on? Dec 20, 2012
Electrical Forum discussion & Blog How to run power to a shed that is 16 inches away from my house... Sep 8, 2012
Electrical Forum discussion & Blog Dishwasher Power Cord Jun 30, 2012

Share This Page