Hello. Welcome to Just Answer.
Please post your questions, and I'll do everything I can to assist you.
Great...we recently moved into a house. There was a circular cover plate in the ceiling which led me to beleive that there was wiring for a light there that had been covered over. I opened up and sure enough there is a box and wiring...I want to install an overhead light in this spot and connect it to a light switch already on the wall. Inside the box there are two black wires (connected when I opened it up) two white wires (connected when I opened it up) and a copper grounding wire. So...what do to connect a new light here and still keep the circuit working properly so an existing light on the same light switch doesn't get messed up.
You would just add the black wire from a new fixture to the splice of 2 blacks, and add the white wire from the new light to the splice of 2 whites. Do the same with the ground wires, and you'll be all set.
However, have you done any testing to confirm the wires you're tapping into are controlled by the wall switch in question?
No...how would I go about doing this?
You need some type of electrical tester. You can use a basic multi meter. Or, you can get a noncontact tester.
I prefer a multi meter, because it is so much more versatile than the other tester.
A basic meter will cost around $20 or so. The noncontact tester is about $15.
I have one
You have the noncontact tester?
Or a meter?
OK, perfect. Just set it to AC volts, and then place one probe inside the white splice, and the other inside the black splice. Have someone turn the switch off and on a few times, and watch the meter to see if it reacts.
Make sure the metal tips on the probes don't touch each other.
OK...will do...and it if it reacts I assume that I'm good to go. If it doesn't I assume that it is a much bigger project to get the proper wiring ready to go.
Yes, exactly. However, if the wiring you want to tap into isn't controlled by the existing switch, you and I can work through that to a solution you are happy with.
Great...last question for now. The switch is a dimming switch and the overhead light I bought says that it shouldn't be powered by a dimming light. I have changed light switched before with no problem so it doens't concern me...just wanted to see how crucial something like this actually is
I would follow the fixture's recommendations, just because of insurance issues. If there were ever a problem, and a violation of manufacturer recommendations was discovered, you could have trouble with an insurance claim.
Got it....well thank you very much...this has been very helpful.
I'm glad to hear that. I'm here quite a bit... basically when I'm not at work at my full time day job. Happy to assist with this, and any future questions you may have.
Many thanks...have a great day.