Using a pre-existing light switch to turn on a new circuit

Thread Starter

quattj

Joined Jul 31, 2021
6
I have a pre-existing 15A light switch upstairs in a 3-gang switch box that is connected to outlets in the basement. I want to avoid having to tear the light switch box out of the wall to run a new 20A circuit to the outlets, but I still need to be able to use a switch to turn them on/off. The basement is unfinished, so I have plenty of access down there, plus the circuit panel that I will be running the new 20A circuit from.

How can I go about keeping the existing 15A switch, but have it turn on the outlets on the 20A circuit? I assume some kind of relay or similar? The switch runs to a juction box in the basement that I can use to do the relay. I have only done standard house wiring up to this point, nothing fancy. My original intention was to snake a new line from the 20A circuit up to the switch box and install a new 20A rated switch, but the house was built in the 60's and the wire I would need to replace goes out the top of the box, so would be nearly impossible to get the new wire in without having to redo the whole switch box.
 

Dodgydave

Joined Jun 22, 2012
10,050
Not sure what you want to do here,

You want to add an extra light circuit but use the same switch to turn on both on at the same time ?
Or individually?
 

Thread Starter

quattj

Joined Jul 31, 2021
6
Not sure what you want to do here,

You want to add an extra light circuit but use the same switch to turn on both on at the same time ?
Or individually?
The circuit is currently a 15 Amp circuit that is hooked up to 4 standard outlets upstairs, the front outside light, and a quad outlet in the basement. The quad outlet has a bunch of plant lights plugged in during the winter, less in the summer. They draw too much power from the same circuit, so I am splitting them off on to their own 20A circuit. The current switch is wired together with two other switches (for one of the upstairs outlets and the outside light). The circuit goes through 2 outlets, then the switches/controlled outlets, and ends in the last two outlets. The wiring is all 14GA, and originally I was going to replace the switch with a 20A switch, and the wiring with 12GA wiring, but it looks like I would have to redo to entire switch box and then patch up the wall if I were to do that.

So the new plan is: keep wiring as is to/from the switch. Run a new 12GA wire from a new 20A breaker in the breaker panel to the quad outlet. Connect the wire that goes from the switch down to the basement to a relay on one side, and the new 20A on the other side of the relay. LowQCab's diagram is pretty accurate, except that the existing switched outlet will be "removed" and only the new switched outlet will be present.
 

LowQCab

Joined Nov 6, 2012
1,096
If You use either a Standard type Relay or a SSR,
the "Input" or Coil, gets a Hot and a Neutral.
The Output is Just like a Light-Switch, it is breaking a Hot-Wire, so,
Hot-Wire from Panel coming in, and a Switched-Hot going out to the Load.

All Ground-Wires are connected together at all times.
The Ground does not connect to an SSR because it's Housing is made of Plastic,
an Old-School-Relay "may" have an exposed Metal-Frame with a Ground-Screw on it,
in that case, a Ground-Wire should be attached to it for addition safety.
.
.
.
 

Thread Starter

quattj

Joined Jul 31, 2021
6
I finished the project over the last two days. I had the 20A line (12GA) partially run beforehand. So the 15A circuit remains as it was, with the exception of disconnecting the outlets from the light switch and moving the wires over to the new relay. The new 20A connects to the other side of the relay, and from there feeds three (3) new 2-gang outlet boxes for the assorted lights. I installed a new 20A breaker (200A service panel, 1100 sq. ft. house) for the lights, plus an extra 15A breaker for another circuit I will eventually be splitting. Everything is tested and running great! No more upstairs lights getting brighter when I turn the downstairs ones off for the night ;) There is more space above the relay than the pictures make it seem, about an inch above, and 1/4" from the back of the relay to the floor joist. (My phone camera did its best!)20210817_144315.jpg20210817_144306.jpg20210817_152630.jpg20210817_144630.jpg
 

crutschow

Joined Mar 14, 2008
27,718
It's a little late for this question, but what type of lights do you have that require so much current?
Modern LED lamps don't require that kind of current.
 

Thread Starter

quattj

Joined Jul 31, 2021
6
Modern LED lamps don't require that kind of current.
My brothers have literally a greenhouse's worth of garden and house plants that live outside in the summer and come in for the winter. Currently there are 5 double-tube T8 shop light fixtures with LED plant tubes (designed for that purpose) plus 3 greenhouse-style LED fixtures that are 450W each (normally 4, but one died). There used to be maybe 12 or more flourescent tube fixtures before they were all replaced. If they WERE all standard LEDs it would probably be way overkill. :)
A few others get plugged in on a different circuit, and they are not used during the summer.
 
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