Need help with bathroom exhaust fan/light box

otch

Hi everybody,
I'm doing a bathroom reno. Need to replace existing ceiling light box with a new fan/light unit.
When I opened up ceiling there were three wires connected to the light box. Two hot wires and one from the control switch.
I have no idea where come these two hot wires from.
When I connected all three to the fan/light box, the fan/light is on constantly. No reaction to the switch.
How should I re-connect the wiring, so that the box works from the switch.
I would greatly appreciate any help.
Thank you.

Jim Port

You need to find the hot controlled by the switch and connect it to the black from the fan housing.

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Answers based on the National Electrical Code. Local amendments may apply. Check with your local building officials.

otch

Thanks Jim,
Just to clarify...
I'm a carpenter by trade and not so familiar with electrical terms.
What do you mean "hot controlled by the switch"?
You mean two blacks from two hot wires..?

andrew79

well most likely what you have is an incoming two wire, an outgoing two wire and a two wire to the switch, what jims saying is that you need to hook into the "switch leg" from the switch, a picture will probably help but i assume that there's three black and three whites in the box from your description. Most likely the two "always on" blacks get hooked together with the white from the switch(should be identified as black) and the other two whites get wire nutted together with a pigtail out to the neutral for the light fan combo, the black comming from the switch gets hooked to the black for the light fan combo. This is how it should have been wired previously, if it wasn't then you may need to identify where the other two wires go before going any further.

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Sarcasm is my friend
I'm here to learn too, i do mostly commercial/industrial/new construction and this place is a great way to pick up tips on residential from some good electrical minds. Excuse the spelling, my phone has a mind of it's own.

otch

Thanks Andrew,
Very informative and helpful.
I did some Google search and got some ideas.
Looks like what I have is Power from the Fixture Connection.
Will try it on Monday when get back to the customer's house.
Thanks again.

rjniles

DANGER! Will Robinson.

A carpenter should not be doing electrical work on someone else's house.

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Location:
Coastal South Carolina