Need help with wiring

[ticobird]

I need help with wiring a 2477D dimmer switch. After the house was built I had an electrician add a switch to control a new outdoor post light and the ordinary switch has been working fine for years.
The new switch box has three 2-strand wires (each strand has one black and one white plus a bare ground). Two 2-strand wires come from below and one comes from above which is where existing switches already resided and I assume he obtained power. One side of the old switch had two black wires one from the bottom strand and one from the top strand attached to the same side of the switch. The other side of the switch had one black wire from the bottom strand. All three white wires were wire tied together.

I apologize in advance if I am using improper terminology. I also need help.

[stusviews]

If you have a switch with three screws (one black screw), then that's part of a 3-way configuration (same load controlled from two locations). Does that describe your situation?

BTW, you have 2-wire Romex (the ground wire is not counted).

[ticobird]

No. My switch is a simple 2 screw. One of the three black wires going to the switch used a screw and the other 2 black wires used the push-in connectors. Thanks for the nomenclature update.

[stusviews]

The connection that has two black wires (one push-in plus one screw) is the line. The connection with only one wire (push-in) is the load. The bundle of white wires is the neutral. As a test, connect the Insteon device to line and neutral only. If the device lights up, then the wires are correctly identified.

A better test is to use a meter. Even the least costly voltmeter is fine. A voltage indicator (e.g., neon light) is not adequate.

[ticobird]

Thanks stusviews for the advice although you might want to edit your answer from "bundle of black wire" to "bundle of white wire." I think my biggest problem the first time was a bad wire connection because when I tried it again the switch worked like a champ.