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Addition of Whole House Attic Fan Timer and Three Way Switches Trips Breaker

Addition of Whole House Attic Fan Timer and Three Way Switches Trips Breaker

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  #1  
Old 11-04-15, 05:49 PM
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Lightbulb Addition of Whole House Attic Fan Timer and Three Way Switches Trips Breaker

On a very light-load circuit, I have an existing single-pole light switch wired to an attic pull light, although admittedly I don't understand why there's 12-2 coming into the single gang box, and 12-3 going up to the light.

Over the weekend, my father and I install a whole house attic fan, controlled by a 3-way "High/Low/Off" switch and an upstream timer. Given the easily accessible single gang light switch below, I added a separate double gang box on the other side of the wall. I ran 12-2 cable from the hot/neutral/ground nuts in the existing single gang box to the double gang box, and then wired the timer and 3 way (High/Low/Off) switches, and ran 12-3 up to the attic fan.

I thought I had this correct, and cannot flip the breaker, so something is obviously amiss in terms of a short? I've attached a diagram showing the existing setup and my additions.

Thanks in advance!!

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  #2  
Old 11-04-15, 09:14 PM
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Are you sure about where the power comes in. Did you disconnect the cable and measure it with a multimeter (a non contact tester can't be used)?
 
  #3  
Old 11-04-15, 09:44 PM
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Does the position of the fan switch or the timer affect whether or not the breaker trips?

Check the wiring of the timer. If the wires are connected to the wrong lugs, you are shorting out the power.

Check the wiring of the fan. If the speed control is connected wrong, it will be almost a short circuit.

What is the ampere rating on the fan?
 
  #4  
Old 11-04-15, 10:23 PM
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Running a three wire from the attic switch to the attic light is common practice. With that type of wiring you have a switched line to the light and an always live line for a future exhaust fan.

Your diagram is shown correct.... however the devices connected may be miswired.
 
  #5  
Old 11-05-15, 03:56 AM
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I'll post some pics later of all the connections after I get home from work. Thank you for the responses. Baffling.
 
  #6  
Old 11-05-15, 12:43 PM
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Attached more photos...

The timer has 4 wires coming out of it. According to the manual green is ground, black is hot (power from circuit), red is load (power to fan/lamp) and white is neutral.

As you can see pictured I did the following:
Green is connected to ground wire coming from power circuit and connected to ground screw on high/low speed switch.

Black is connected to black wire coming from power circuit (orange nut), and connected to black wire nut in the existing 1-gang switch box.

Red is connected to the input load on the high/low switch

White is connected to neutral (yellow nut) coming from power circuit, and connected to white wire nut in the existing 1 gang box, as well as the neutral white wire coming from the fan.


Next is the High/Low/Off switch for the fan.

The top left is the input load (red wire coming from the timer switch).
Top right is the red wire for high
Bottom right is the black wire for low.

As instructed,
White wire from fan goes to neutral bundle in the wire nut.
Black wire goes from fan's black wire to the black wire (high speed) on the 3 way toggle switch
Red wire goes from fan's red wire to the red wire (low speed) on the 3 way toggle switch
Ground wire goes from the fan's green wire screw to the grounding screw on the 3 way toggle.
That's the 12-3 bundle on the right hand side of the 2 way gang box.

And the 12-2 bundle on the left hand side of the 2 way gang box goes to the same-color wire bundles in the 1 way gang box (picture 3).

In the 1 way gang box... you can see the switch (red = on, black = off).... 12-3 running to the attic pull string light. Otherwise, all whites nutted together, all blacks nutted together, all grounds tied together.


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Last edited by kcwxforecaster; 11-05-15 at 01:16 PM.
  #7  
Old 11-05-15, 01:20 PM
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Disconnect the connections at the fan and see if it still trips.

If it still trips reconnect at the fan and disconnect at the load side speed switch.

If it still trips reconnect at the load side of the speed switch and disconnect at the line side of the speed switch.

If it still trips disconnect the timer and try connecting power directly to the speed switch.
 
  #8  
Old 11-05-15, 02:56 PM
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Grabbed the multimeter...one of the neutral wires is shorted to ground. Now to figure out how. Definitely think I've got this wired correctly.
 
  #9  
Old 11-05-15, 03:02 PM
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I thought I had this correct, and cannot flip the breaker, so something is obviously amiss in terms of a short?
one of the neutral wires is shorted to ground
Unless the breaker is a GFCI breaker that would not cause a trip.
 
  #10  
Old 11-05-15, 04:31 PM
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OK, now I'm admittedly a little more than bit concerned - or a blithering idiot.

I unhooked everything, leaving only the original input and output wiring to/from the single light switch in the hall closet... basically returning it to "as was". To my surprise, the neutral to ground continuity is found in the incoming line -- which was never touched!! Everything else on that circuit behaves the same way. The breaker is "off".

As far as I know, this circuit controls two hallway lights (linked by 4 separate switches), the lights and exhaust fan in the upstairs bathroom, a floor outlet in the hallway outside the bathroom, and the attic light. The GFCI outlets in the house that I'm aware of are all in the bathrooms -- all working -- and none on this circuit.

So at this point I'm like WTF. How do I have a neutral to ground continuity in a circuit that worked moments before I went to wire up the fan, didn't have any load turned on to the fan (timer off and high/low/off was off), and then removed back to its original state?? Is this correct with the breaker in the off position and I'm panicking for no reason?
 

Last edited by kcwxforecaster; 11-05-15 at 05:29 PM.
  #11  
Old 11-05-15, 05:52 PM
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How do I have a neutral to ground continuity in a circuit
Neutral and ground are connected to the same bar in the first panel so that is to be expected. Does it still trip the breaker back in the original configuration?
 
  #12  
Old 11-06-15, 12:26 PM
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OK good. I didn't want to flip the breaker until that was confirmed. Yes, we're all good in the original configuration.

Now I will start adding stuff in one-by-one.

Evan
 
  #13  
Old 11-06-15, 01:12 PM
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OK, so I disconnected the load (fan) wires, and reconnected the timer and 3-way switch. All is well. I get no continuity to the 3-way switch unless the timer is on. And when the timer is on, I get no continuity to either output if off, low if low and high if high. So far so good.

Now at the fan motor there are 3 wires coming off -- white, red, and black. White is connected to via white to neutral (white) in the gang box, red is connected via red to red (lo fan) on the 3 way, and black is connected via black to black (hi fan) on the 3 way.

With the fan motor isolated, I'm getting continuity across all 3 wires coming out of the motor. Does that seem correct? I don't want to hook this back up for nothing.
 
  #14  
Old 11-06-15, 01:57 PM
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I would be checking at each step to see if the breaker trips. That is the simplest easiest surest way to do it IMHO.
  • Connect to the line side of the timer.
  • If it doesn't trip. Connect the speed switch but not the cable to the fan.
  • If it doesn't trip connect only the cable to the fan (fan not connected to the cable).
  • If it doesn't trip connect the fan.
 
  #15  
Old 11-07-15, 07:37 AM
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Ray,

I connected the last remaining leg... the fan motor, and all works.

The only thing I can think of that caused the short and tripped the breaker, is that the grounding wire in one of the gang boxes was touching the hot screw on either the timer switch or the light switch in the closet? I took special care to keep the grounding wires isolated on the reconnect.

I'm glad to know that I had this wired properly from the get-go, and appreciate your assistance! Fan works great and will be a welcomed addition next Spring/Summer.

All the best,
Evan
 
  #16  
Old 11-08-15, 09:17 PM
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There should be a form of continuity between the three wires on the fan motor, because the two windings in the motor are connected to each other at some point within the motor.
 
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