fan/light common ground

Discussion in 'General Electronics Chat' started by tamarack, Nov 25, 2011.

  1. tamarack

    Thread Starter New Member

    Feb 22, 2011
    9
    0
    Hi
    I have done a lot of house wiring but this is a new one for me.
    I have wired a fan/light combo using a 3 way switch circuit for the light and a separate switch circuit for the fan. The unit has a black for the fan, blue for the light and a common white ground.
    After wiring it like this I had all kinds of strange things happen. I know the 3 way switches was correct as was the single fan switch.
    I then wired it using just one switch for the light and it is working fine.
    I have read that the problem lies with the use of a 3 way light circuit and the common ground, related to the electrical "phasing"???
    Is there a way I can overcome this problem and go back to using the 3 way light circuit...I understand both the light circuit and fan circuit must be "out of phase". How would I achieve this??
    Don
     
  2. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
    6,357
    718
    Diagram?

    For 4 way, normally all 3, BLK, WHT, RED are needed, and only BLK (hot) and WHT (neutral) are needed to switch the fan.

    What is your location? These are US conventions, so your country may have different conventions.

    I'm unsure about the fan being wired "out of phase", is that in the installation instructions, could you provide more context with that?

    Since you have a Blue wire, you may have an odd setup, or aren't in the US.

    See if This link w/Video is of any help, it has a link for "odd and rare setups" as well.
     
  3. tamarack

    Thread Starter New Member

    Feb 22, 2011
    9
    0
    Thanks for your reply. I have no trouble with the 3 way switching circuit but it does not work with a fan/light unit with common ground....the fan unit has a blue, black and one white "common neutal or ground". I found on this site the statement below regarding phasing....this is a new term for me also but I do know that household current is said to be 2 phase as opposed to the 3 phase used in industy. I have tried to separate the motor and the lighting white grounding wires which I'm sure would solve the problem but it's hard to do and I don't want to tamper with the unit.

    http://www.google.ca/imgres?imgurl=http://www.blurtit.com/var/question/q/q4/q46/q461/q4617/q461762_284108_3_way_wiring_1.jpg&imgrefurl=http://www.blurtit.com/q461762.html&usg=__hxuGQSRnPI2qaCdCwOGzZ_L_Bdo=&h=343&w=514&sz=47&hl=en&start=17&zoom=1&tbnid=FGI0SjumbYF3DM:&tbnh=87&tbnw=131&ei=F6_OTqKmDYT10gHS-vn-Dw&prev=/search%3Fq%3Dwiring%2Ba%2Bfan%2Blight%2Bwith%2B3%2Bway%2Bswitches%26hl%3Den%26sa%3DG%26gbv%3D2%26tbm%3Disch&itbs=1

    Here in Canada, our electrical wiring for household use is virtually the same as yours in the U.S.
    It is this following statement from that site that confuses me. Note that the site is used to describe 3 way circuits and the exact fan arrangemant I have.
    Please see the "Note" in the paragraph(in red) below, from the ariticle.

    Normally, combination devices such as ceiling fans with lights are wired with separate control wires colored black and blue, with black usually being the control wire (or power source) for the fan and the blue being for the light.
    When wiring a combination fan/light with each being switched separately, you would have the switched conductor, neutral, and ground for each coming into the box. NOTE - you cannot use a common neutral unless you have two separate circuits originating in your panelbox which have the circuit breakers installed on different phases (i.e. Breakers installed at spaces 1 & 3, 2 & 4, etc.) You need to understand that the breakers installed directly across from one another are on the same phase (A); the next two will be on Phase B; and then the cycle will repeat. This is standard for all residential electrical.
     
  4. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
    6,357
    718
    They are referring to "Split Phase". The step down transformer outside your house is center tapped, with neutral in the center, and two legs 180 degrees out of phase from each other. These are split up in the breaker box on left and right. It is best to balance your breakers so each phase/side of transformer has the same load. 220V outlets are obtained by pulling from both phases and returning on the Neutral.

    With me so far?

    What they are saying is you cannot wire the fan with a common neutral, unless your hot comes from two different breakers, one for light and one for fan.

    You CAN wire it with a common HOT, and switched neutral, however. Both the 3 way light and the single fan switch would need to be switched on the Neutral. This is one of the situations in wiring where neutral is not the same as ground inside the house.

    Does that help?
     
  5. GetDeviceInfo

    Senior Member

    Jun 7, 2009
    1,571
    230
    Specifically breakers from opposing phases.

    In Canada, you cannot switch the neutral unless you simultaneously switch the hot(s). As well, neutral is never the same as ground, nor referred as such. In a 2 wire circuit, the white wire is referred as the 'identified conductor' to distinguish it from the neutral.
     
  6. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
    6,357
    718
    So it appears you cannot run the light independently of the fan unless you run a cable from the other side of the circuit breaker box to a fan switch that is isolated from the hot used for the light switch.

    That's a bit of an odd setup, e.g. the fan uses the full current on that circuit/15A, so the light bulb needs to be on a separate one. Similar to the 220V electric dryers where one leg is for the heating element and the other is for the tumbler motor.
     
  7. GetDeviceInfo

    Senior Member

    Jun 7, 2009
    1,571
    230
    I don't think that the problem lies in the supply or return however, be it single or two phase. I suspect the OP is having a problem wiring his 3 way.

    If you consider the practicallity of implementing such a combo device, picking up sources for the different functions may be a natural, ie; light source borrowed from neighbouring switch in gang box, fan spliced or fished from a receptacle supply. In such a 'grab what's easiest' approach, neutral sizing may be implied.

    The OP should realize that there are two basic 3 way arrangements, one with power supplied to device, and the other with power supplied to switch. The former can power both devices with a common hot/neutral, the later needs another source for the fan, where you get it from now determines if the return is a neutral or an identified.
     
    Last edited: Nov 26, 2011
  8. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
    6,357
    718
    This could be easily tested by tying the BLK and BLU together at the fan, and running them to a single switch.

    If that works, then splitting them and switching should work as well.
     
  9. tamarack

    Thread Starter New Member

    Feb 22, 2011
    9
    0
    Eureka!!!
    Thanks so much for the help....I now understand!! Both circuits did originate at the panel from the same side of neutral so I simply moved a couple of breakers to separate them(one on each side of neutral), hooked the 3 way circuit back up, as before, and it works fine.
    I think I understand everything about 3 and 4 way switching circuits but this common ground thing was a new one for me.
    I still don't fully grasp why it works for single switched circuits but not with 2 - 3 way switches!! I have a little more studying to do.
    Thanks again guys
    Don
     
  10. GetDeviceInfo

    Senior Member

    Jun 7, 2009
    1,571
    230
    sounds fishy. Now the question really needs to be asked, do you have adequate return? Phasing implies if you use a neutral or identified wire, not if your switching arrangement works. I suggest you draw out and post your schematic. This exercise will surely help you fully grasp the 'whys'.

    True, but the confusion was in red, concerning the return. If sourced from a similar phase, the return (identified wire in Canada) must accompany the entire circuit path, for each circuit. If sourced from alternate phases, then a single neutral is only required for both circuits.

    3 way switching arrangements implement a single phase, and for the light that's a seperate circuit. The fans another independant ciruit, regardless if same or different phase. If switching phases makes the difference in operation or not, something is wrong.

    There is one caveat, and thatoneguy alluded to it earlier. The white wire in a 3 wire cable, MAY be used to switch hots in a 3 way switching arrangement. In this application, it is not referred to as neutral, common ground.
     
    Last edited: Nov 26, 2011
  11. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
    6,357
    718
    Do you have a clamp type meter?

    I'd be interested in the current readings in the hot and neutral wires in fan positions, Fan On, Fan Off (hot and neutral in each of the following): 3 way switch on, what the hot/neutral show for current, and when another 3 way is on.

    That should help clear up how it is working for everybody. The neutral will be carrying more load if it is all tied to a common point.

    Makes me wonder if the outside of the ceiling fan would be carrying a voltage, if it is made from metal.
     
  12. GetDeviceInfo

    Senior Member

    Jun 7, 2009
    1,571
    230
    Bonding, being a must, will deal with that. But, if the bulb broke for instance and the neutral was switched, that would leave an uncomfortable task for changing things out.
     
Loading...