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Discussion Starter · #1 ·
Hi guys, first post here. I'm looking at hooking up a whole house fan and the electric portion of the project is leaving me with some questions. Couple parameters...

1. My panel is 100% full and in active use, forcing me to T into an existing circuit.
2. The circuit in question is 15 amp with 14 gauge solid wire
3. Circuit in question hooks only to lights and draws 3.4 amps with everything in use.
4. Fan motor in question is 1/3 hp and says 3.8 amp on it.
5. Instructions say to use 14-3 wire to hook up high and low settings.

Now the questions

Am I correct in my understanding that I can T into a branch on the circuit before a light switch and power the fan with it's own switches?

Will running the fan on high with 14-3 (power from 2 hot 14 gauge wires) draw too much power from the 14-2 I plan to splice into?

Thanks in advance everyone.
 

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That circuit is fine. You will need a 2 speed switch, not 2 single pole switches. You do not have both hots on at the same time.
 

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You may not be able to T into a light switch. It could be a switch loop with no neutral.
 

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Based on your drawing you will be fine. Be aware that cutting into an existing run most times does not provide enough cable to make connections in the new box. You must at least 6 inches of cable in the box from each direction.
 

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Discussion Starter · #9 ·
Based on your drawing you will be fine. Be aware that cutting into an existing run most times does not provide enough cable to make connections in the new box. You must at least 6 inches of cable in the box from each direction.
Thank you for the help.
 

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Discussion Starter · #12 ·
Thought of something that would save me some time. Can I use the existing switch itself as a junction box? Something like this?
654802
 

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Thought of something that would save me some time. Can I use the existing switch itself as a junction box? Something like this? View attachment 654802
You may be able to go from switch junction box if there is room. Also there may not be a common in the switch box. There are normally just two terminals on a switch. The switch just interrupts the load (black wire) going to the light. The reason you would need a lot of room in the junction box is because you would be doubling the amount of wires in the box.
You would need to pigtail on to the load and common wires to use the light switch box.
 

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I would have ran a separate circuit. I would have done what was needed in the panel to free up one space. Maybe a tandem? That results in one free space.
Clearly its compliant to tap into an existing circuit. But its a motor load and I personally would run a circuit for it.
What does the manufacturers instructions say.
 

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Discussion Starter · #15 ·
I would have ran a separate circuit. I would have done what was needed in the panel to free up one space. Maybe a tandem? That results in one free space.
Clearly its compliant to tap into an existing circuit. But its a motor load and I personally would run a circuit for it.
What does the manufacturers instructions say.
I'll have to look into it. I'm not super comfortable messing with the box itself though.

On the first page it says

4. Installation work and electrical wiring must be performed by a qualified person in accordance with all applicable codes and standards, including fire-rated construction.

Wiring instructions in their entirety are as follows.

654816
 

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I would not worry about that small of a motor to need a dedicated circuit.
 

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Some codes require whole house fans to be interconnected with a smoke detector near the fan. If the fan is on and there is a fire, it will consume the house fast. Without a detector, I would not run the fan while I am sleeping. And if you have fuel burning equipment make sure to have CO detectors. Whole house fans can cause backdrafting.
 

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Discussion Starter · #18 ·
Update: I hooked the fan up basically as shown in post #12. Everything is working as it should. Thanks for the help everyone.

Old Thomas: thanks you for the advice. I do have CO monitors by the furnace and top of the basemen stairs for a backdraft warning.
 
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