Replacing existing single pole bathroom fan switch

Discussion in 'Electrical Forum discussion & Blog' started by Wen72, Sep 12, 2020.

  1. Wen72

    Wen72 New Member

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    Sep 12, 2020
    Location:
    Montreal
    Hi Experts,

    It is my first post here, sorry if this has been discussed before.

    Last year I tried to replace my bathroom single pole fan switch with a timed or humidity control fan switch. Inside the existing switch box I can see two inputs, one 3-wire (black, white and copper) and one 4-wire (black, white, red and copper). The red wire goes to the switch and the white wires goes together and then to the switch as well. The two black wires are capped off and they are not connected to the switch.

    On the switch, the red wire goes in has a tag marked "high" and the white wire goes in has a tag marked "com".

    The new switch that I bough has 4 wires, black, white, red and copper. I couldn't figured out how to wire the new switch so I returned it to the store. Recently I saw this forum and would like to see if I can get your advice
    so I can try again.

    Appreciate anyone can tell me how do I wire the new switch?
     

    Attached Files:

  2. wwhitney

    wwhitney Active Member

    Joined:
    Mar 17, 2019
    Location:
    Berkeley, CA
    The existing wiring arrangement you show is somewhat unusual. What is the make and model of the fan? (Edit: start with just posting this info. It may be one of these Panasonic fans that is not switched like a normal fan.)

    A terminology note: generally when discussing building wires (as opposed to a flexible cord on an appliance), the bare wire is not counted. So you have a 2-wire cable and a 3-wire cable.

    Also, when you say "the two black wires are capped off" do you mean individually, or do you mean they are connected to each other under one wire nut?

    Lastly, your picture shows more wires in the box than you've described. You might think that if the fan switch is on the right, only the cables entering the box on the right are fan related, but that need not be the case. So what you really need to do is draw a diagram of all the cables entering, and how each non-bare wire is connected to a device or another wire within the box.

    Cheers, Wayne
     
    Last edited: Sep 12, 2020
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  4. Wen72

    Wen72 New Member

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    Hi Wayne,

    I opened the fan cover and it says it's an Epurair EP100G2V, this is what I found online:

    http://www.epurair.com/pdfs/Epurair fiche information EP100G.pdf

    It says it is two speed, the red wire is high speed and black is low speed. Actually this reminds me that our apartment do have a build-in humidity control that I almost never use (and so I have forgot about it completely). When I turned on the humidity control (photo attached), I can hear the low speed fan running. Didn't realize this until now that it is the same bathroom fan.

    Yes, the two black wires are connected together in one wire nut.

    It is a 3-switch box, not sure if it is the right way to call it, but yes, there are two light switches beside. I ran the wires for the fan switch and I am certain that the fan switch's wires are not inter-connect to the two light switches beside. Although the two light switches do have some wires inter-connected together. So for the fan switch, it is just two feeds, 2-wire and 3-wire (learned something new today:) , two black wires go together and not connected to anything, two white wires go together and connected to the switch, the one red wire connect to the other pole of the switch.

    Do I still have hope to replace the switch to a timed switch or I will have to live with the on and off switch?:)

    Thanks,
    Wen
     

    Attached Files:

  5. wwhitney

    wwhitney Active Member

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    Location:
    Berkeley, CA
    There's no dealbreakers yet for using a timed switch, but we don't yet have the full picture of the circuit. The two speed fan explains the 3-wire cable.

    Now, how is the humidity control wired into the circuit?

    Also, it is unusual that you have white wires on the switch. White wires are used for the neutral conductor, and the switch should be breaking the hot or ungrounded conductor. So I am wondering if somewhere the wires color are reversed.

    Based on the wiring diagram you posted, it should normally be wired like this: 2-wire feed into switch box (B1, W1), 3-wire out to humidity control (B2 W2 R2), 3-wire from humidity control to fan. In switch box, W1 & W2 tied together; B1, B2 and jumper to switch tied together ; jumper and R2 going to switch. In the humidity control (if it's a 2 wire control), W and R go straight through; B is broken by the humidity control. At the fan itself, W to W, B to low speed, R to high speed.

    That arrangement will give the humidity control constant power; when the humidity control says its too humid, it will power the fan on low. And the switch runs the fan on high when on.

    Since you didn't find it wired that way, more investigation is required.

    Cheers, Wayne
     
  6. Wen72

    Wen72 New Member

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    Sep 12, 2020
    Location:
    Montreal
    The humidity control unit is outside of the bathroom, I opened the box and only see one feed (black, red and green).

    I tested the fan switch box with a voltage circuit tester. When the fan switch is in the off position, I can detect current in the red and white wires connected to the switch, but when I switch it on, there are no current detected in both red and white wires.

    Thanks,
    Wen
     

    Attached Files:

  7. wwhitney

    wwhitney Active Member

    Joined:
    Mar 17, 2019
    Location:
    Berkeley, CA
    Well, if the humidistat cable with the black/red runs straight to the fan, and the 3-conductor cable from the switch box runs straight to the fan, that would also allow the expected wiring configuration.

    So if you are comfortable checking if you can access the fan junction box and take a picture of the connections in there, that would hopefully complete the investigation. I would suggest turning off the breaker first.

    Inferring connectivity from a non-contact voltage tester is difficult. And arguably you should not open up the boxes unless the breaker is off.

    And just to reiterate, the main obstacle here is that the black and the white are reversed in the existing circuit in that switch box. So it's important to understand what's going on before you just try to change it to a timer. BTW, does the timer have just two wires (in and out), or 3 wires (also requires a neutral connection)? Again this count ignores the bare grounding conductor.

    Cheers, Wayne
     
  8. Wen72

    Wen72 New Member

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    Montreal
    Hi Wayne,

    Sorry I couldn't reply you back earlier.

    I finally have some time today to see if I can get to the fan junction box. Yes, I did turn off the breaker first. I also did turn off the breaker last weekend when I open the switch box, only turned the breaker back on when I tested the current.. I guess the voltage tester is to test and make sure there is no current but not to see if there is current? oh well..

    I cannot get to the top of the fan through the opening of my bathroom ceiling. The fan was boxed in by some drywall above the ceiling, not sure why, maybe the furnace and A/C unit is next to it? The apartment I live in is a pretty new and modern building built in 2010 so didn't want to break it open just yet. I had to work from the fan opening on the ceiling instead.

    So I removed the fan motor and next to motor is a wiring box inside the housing, couldn't remove the cover of the wiring box completely as it had another screw screwed in from the outside of the box. The housing itself also has a few screws screwed from the outside in, I could not find a way to remove the housing. So I guess this is as much as I can get to. Since I cannot remove the cover of the wiring box completely, I couldn't see how many wires feed into the wiring box clearly.. But this is what I see in the wiring box.

    Connected to the fan motor are 3 wires (not counting the green wire), black, white and brown.

    Black wire goes out of the wiring box directly.

    White wire goes to a wire nut together with another white wire and a blue wire for which both of them go out of the wiring box.

    There are two small black box (BB) each has two black wires (in and out). The brown wire connects to the one of the black wire goes into the first black box (BB1-in) and BB1-out goes to a wire nut with a red wire and BB2-in. The red wire goes out of the wiring box. The BB2-out joined with a orange wire in a wire nut and go out of the wiring box.

    I bought and returned the timer last year, can't remember how many wires were there. But I'm pretty certain it is not just 2 wires. Are there 2-wire and 3-wire timer? What are the differences between them?

    Here is a diagram I drew, doesn't look like a technical wiring diagram but I tried:)

    Thanks,
    Wen
    fan wiring box.jpg fan 1.jpg fan 2.jpg fan 3.jpg fan 4.jpg fan 5.jpg
     
  9. Wen72

    Wen72 New Member

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    Oh and also, this seems like not giving us a clue on whether the black and white wires are reversed, does it?
     
  10. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    Retired Systems engineer for defense industry.
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    New England
    A mechanical timer only needs two wires: power in to switch, power out when on.

    An electronic timer will need those same wires, but also neutral so that it would have a complete circuit so it could run itself.

    In a switch leg of a normal 2-wire cable, power is on one lead all the time, and power is applied to the other lead when the switch is on...so, both the white and black would have power on them when the switch was on...identifying a switch leg from a cable with power and neutral can sometimes be difficult.

    The sensor you have is not detecting current, it is detecting voltage potential, I think. Now, you can't have current without voltage, but it's easy to have voltage without current.
     
  11. Wen72

    Wen72 New Member

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    So normally I think a bathroom fan timer switch is an electronic timer and has 3-wire (black, white and red) so it could run itself, right?

    How does this kind of switch usually connects? May I assume there are usually two wires coming from the fan? Or how does it work?

    Thanks,
    Wen
     
  12. wwhitney

    wwhitney Active Member

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    Mar 17, 2019
    Location:
    Berkeley, CA
    Hello,

    Your photos are very good. However, all the wiring you are showing looks like factory wiring, not the field wiring. If I knew more about dual speed fans, I could figure out what it all means, but it's almost certainly not relevant to the black/white reversal issue.

    What you'd like to find is a wiring compartment with one (possibly more, but most likely one) NM cable (Romex, in the US it would be white or yellow sheathed) coming into it from outside the whole unit, and look at the connections that the field wiring makes to the factory pigtails.

    Now it is possible that the cavity you've opened up has both the factory wiring and the field wiring, and the field wiring is just way up higher. You can try get an angle to peer in the back or take a photo. And you can try tracing those green grounding wires coming from that one stud--I find it unlikely the manufacturer would bother to install more than one stud like that, so one of those green wires should be connected to the supply cable's grounding (bare) wire.

    But you say the black wire just goes straight through and goes out of the box you can see--it may be that it enters a different wiring compartment that has all the field wiring, and that's the compartment you'd like to open up. And it may be that compartment is only accessible from the backside of the unit. And since you say the backside is drywalled in (could be a fire code requirement if there's another unit above yours), we might get stymied on accessing the field wiring compartment now, I don't think it's worth opening up drywall at this point.

    If that's the case, and if you are qualified at using a multi-meter on live circuits, then you could do some further diagnostics on this white/black reversal. However, I wouldn't suggest doing that if you've never done it before. In that case you might need to get an electrician in to diagnose the white/black reversal issue. Which is really the only thing holding up your timer installation.

    [On 3-wire versus 2-wire timers: a mechanical timer and some electronic timers (maybe?) only need two connections (plus ground), one for the constant "hot" and one for the hot going to the load. Some electronic timers have a third connection, they need a neutral connection as well. So just a little more complicated to install.]

    Cheers, Wayne
     
  13. Wen72

    Wen72 New Member

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    Sep 12, 2020
    Location:
    Montreal
    Hi Wayne,

    I see. The factory and field wiring you mentioned makes sense to me. Oh well, guess I'll leave it as it.

    One other thing I forgot to mention, last year when I bought the timer switch, I remembered I just connected without thinking and connected the black wire from the timer switch to the two existing black wires in the switch box (the wires that go into a wire nut and not connected to anything else), the white wire from the timer switch to the white wires, and the red wire to the red wire. With this configuration, when I turned back on the breaker, the lower speed fan was always on, no matter if I turn the switch on or off.

    Will this give any clue? Or I was just lucky I didn't blew it off? Sorry, trying one more time before I throw in the towel..

    Thanks again, really appreciate your analysis.

    Wen
     
  14. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Joined:
    Sep 2, 2004
    Occupation:
    Retired Systems engineer for defense industry.
    Location:
    New England
    Just following the colors of the wiring may not work, as you found when you had the low fan speed on constantly.

    Wiring can have many permutations. It depends somewhat on how new the wiring is. Today's code requires neutral at the switch (although, it may not be used) so that it can handle smarter switches. Older codes often did not have neutral in the same box as the switch as the power sometimes is easier if it goes to the fixture first. Then, they run a switch leg to the switch...one lead will be connected to the hot lead up by the fixture, go down to the switch, and when on, go back up to the fixture to turn it on when you flip the switch.

    So, you need to figure out where the power is sourced, either up at the fixture, or in the box by the switch.
     
  15. wwhitney

    wwhitney Active Member

    Joined:
    Mar 17, 2019
    Location:
    Berkeley, CA
    Was that the first time you opened the switch box? Do you have any photos of how the switch was wired before you made any modifications to the circuit?

    And what was the behavior of the timer?

    If the two cables you identified initially (the 2 conductor and the 3 conductor) were power in and then feed to the fan, and the colors reflected their standard function/connectivity, then the way you initially wired the timer would be correct. [And BTW, that's a 3-wire electronic timer, since it has white, black, and red connections.]

    Can you explain what you mean by the word "ran" here? Do you mean "traced"?

    Also, one more piece of information you can easily provide. Presumably the two switches next to the fan switch control lights? When you shut off the breaker to kill power to the fan, and only that breaker, do the lights still work? If not, then those switches are on the same circuit as the fan, and it would be beneficial to trace out all the wires in the switch box, rather than just the 2-conductor and 3-conductor cables you initially identified. (Although that's more trouble than my other suggestions, and may not be necessary, so you may want to hold off for the moment.)

    Looking at this post again and at the picture you provided, I am thinking that again you have only found the factory wiring of the unit. I would think that the rear off-white plate is mounted over a junction box, and that you want to (with the power off) unmount the unit and the backplate and look in the junction box to see what cables are coming in and going out, and how they are connected. I'm not 100% sure because it's a bit hard to diagnose over the Internet, but I'm pretty sure.

    Cheers, Wayne
     
  16. Wen72

    Wen72 New Member

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    Montreal
    I wasn't thinking about all this when I tried it last year. Thought it was just a simple switch change, shouldn't have underestimated this work.

    Thanks,
    Wen
     
  17. Wen72

    Wen72 New Member

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    Yes, that was the first time I opened the switch box. I didn't take a photo, but I'm pretty sure it was how it was wired before. I meant I saw one white and one red wires connected to the fan switch.

    I remembered when I turned the breaker back on, the low speed fan just went on constantly no matter the switch is on or off. I don't remember if I tested the timer or not, cause I thought it just didn't work. The timer if I remembered correctly, it has timer with different pre-set timed buttons and a on-off switch. It didn't took me long before I decided to take the new switch off and put the old one back. It has been awhile, can't remember much of the details except the lady at Home Depot was mad when I return the switch with the plastic package all teared open:) Hmm.. I could go buy a new timer switch and try again.

    Sorry to the confusion, I did mean "traced".

    Yes, the two lights in the bathroom are still working when I turned off the fan breaker. The fan's power is controlled by the furnace breaker. The furnace unit is located next to the fan and they are both on top of the bathroom ceiling.

    And from what I see as I mentioned before, the two light switches have no wire connect to the fan switch wires.

    So the 2-wire feed (or the 2 conductor as you said) is most likely the power in?

    You're right! I was able to unmount the humidity control unit and get to the junction box. Wow, the wiring in there is a lot more complicated than I thought.. I took some pictures and here is the wiring diagram. Below the humidity control unit is the thermometer for A/C plus furnace.

    Humidity Control Junction box wiring.jpg H_C_1.jpg H_C_2.jpg H_C_3.jpg H_C_4.jpg H_C_5.jpg

    Thanks,
    Wen
     
  18. Wen72

    Wen72 New Member

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    I checked the bathroom ceiling again to see if there is anyway I can access to the outside of the fan housing. Took some more pictures.

    It is pretty drywalled in, I can see there are two cables going in or out of the drywall box. Don't think there is a way to get to the fan junction box, it must be inside the drywall box and outside of the fan housing.

    bathroom fan 1.jpg bathroom fan 2.jpg bathroom fan 3.jpg bathroom fan 4.jpg
     
  19. wwhitney

    wwhitney Active Member

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    Later tonight I'll look more closely at all the info you've posted, particularly the great wiring diagram of the box behind the humidistat. A couple initial responses:

    OK, good, that supports the assumption that only the two cables in the switch box are fan related, which simplifies things a lot.


    That would normally be a good assumption but I need to possibly reconsider that.

    OK, it would be helpful to know if both the cables going in to the drywalled box are 2-conductor cables. The simplest way to do that would be to read the printing on the sheath (I can see some of it in the photo), somewhere along there it should say some like 14/2 or 12/2 or 14/3 or 12/3, or 2 conductor or 3 conductor or something like that.

    P.S. Just to double check, the way it worked originally was this: flip the switch and the fan comes on high; with the switch off, turn the humidistat to a low humidity and the fan comes on low. Correct?

    Cheers, Wayne
     
  20. Wen72

    Wen72 New Member

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    My ladder is not in the apartment, so it is a little hard for me to reach to the two cables.. These are the most I can see:

    1. UNDER PAT. NOS. 7557301 7411129" 5/10/10 M.CLAR...

    This one looks pretty clear to me is a 2-conductor cable. You can feel the two wires and it has a grove in the middle.

    2. CORS NMD90 NYLON ROMEX(R) BRAND SIMPULL(TM) 300 VOLTS FT1 COVERED...

    This one looks like it is a 3-conductor cable The wrapping are tight, but you can somehow wiggle the wires inside.

    Correct. And if the fan switch is on (fan is on high), turning the humidistat to a low humidity does nothing, the fan is still on high.

    wire 1-1.jpg wire 1-2.jpg wire 2-1.jpg wire 2-2.jpg wire 2-3.jpg

    Cheers,
    Wen
     
  21. wwhitney

    wwhitney Active Member

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    OK, I agree that it looks like your fan is fed by a 3-conductor and a 2-conductor. And in the switch box, we have a 3-conductor and a 2-conductor. And behind the humidistat we have a 3-conductor and multiple 2-conductors.

    Which leaves a bit of a mystery: each 3-conductor cable segment has 2 ends, but we've only found 3 ends. There has to be another box somewhere with a 3-conductor cable going to it. [Unless we're wrong about the fan feed, but I don't think we are.]

    There's not another switch that controls the fan or anything else relevant that you can think of, is there?

    This thing is not wired in anything like the normal way. So far I haven't had any aha! moments.

    Cheers, Wayne
     
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