How do I wire a box with 3 dimmers (with neutral) from a single line?

[gamp945]

Hi all,

My terminology might be off, so apologies about that - I'd appreciate corrections where I'm off.

I'm trying to replace a few switches with dimmers. These dimmers require a neutral wire. If it matters, the dimmers have two straight connectors (term? push-in with screw) for each terminal.

I'm using a 3-gang box with one incoming line and one outgoing line that feeds other boxes (term?).

How do I wire these 3 dimmers (with neutrals) using just one incoming line?

I have a crawlspace so I could actually put a junction box for the incoming line and supply 3 separate lines going up to the box, but I doubt that's the recommended way of doing it (although it might eliminate a bunch of pigtails in the box).

I've attached a diagram of the dimmers below (Legrand H703PTU universal dimmer).

Any advice appreciated

 

[ard]

Some clarifications:

When you say 'one incoming line' is that ONE or TWO conductors?

When you say 'one outgoing line" do you mean ONE or TWO conductors ..>AND, IMPORTANT, is that to EACH of the THREE Lights you seek to control?

If there were three switching controlling three separate lights, then there still ought to be 3 wires headed out.

But unless you have a neutral in that box, that dimmer will not work.

 

[gamp945]

Hi ard,

Thanks for your patience with my lackluster description and terminology

There is one 14/2 wire coming in (hot from the electrical panel), so I guess that means 2 conductors - one hot and one neutral (plus ground).

When I say "one outgoing line" I mean another 14/2 wire (unswitched) that is carrying power to other lights further downstream. I do not need to do anything with this wire other than make sure it remains hot for the other items connected downstream.

I also have 3 separate 14/2 wires run to each of the 3 lights that I want to control with the 3 dimmers. If it matters, they are all 120V LED (two fixtures using about 50W and one using about 30W).

 

[Git]

jumpers

All your white wires (neutral) get wire nutted together in the box along with 3 'jumper wires' long enough to reach your three switches.

 

[ard]

Well. We just went from 4 wires in the box to 10.



All neutrals in the box now get tied togteher. Add one single wire to this 'bundle' (now 6 wires total) and have it go to the first, then second then third dimmer. (ie daisy chain)

Tie the two hots together- this is the one in and the one out. Add one wire to this (so now 3), same daisy chain to the three dimmers on the 'line' connection.

The three remaining wires each go to a single dimmer on the 'load' connection point.

Dimmers are big, it is a PITA to get this inside a 3 gang. Good news is that it is #14. Some may not like wiring in daisy chain, but I believe it makes for a more compact box, when needed.

 

[gamp945]

ard,

Thanks for the detailed explanation. That makes perfect sense.

As you mentioned, the dimmers are big, and I am concerned about being able to get everything inside the 3-gang. I see 2 solutions:

1. Since I am replacing the box, I can use a 4-gang box for a bit more room, and just use a face plate with one gang blanked out.

2. As I stated in my first post, I could put a junction box in the crawlspace, and then run 3 separate 14/2 wires up to the switch box. This would also move the "outgoing" hot from the switch box to the junction box.

Do either of those solutions sound like a good idea to you? What would you do?

 

[ard]

I would NOT do a 4 gang w a blank...just offends my sense of propriety.

Can you change the box? 3 gang deep boxes, done. Google around, find a box with the largest internal volume.

But you should be able to get this into a 3Gang, watch wire lengths, tuck them to the back carefully, etc.

I'm not sure a junction elsewhere will help appreciably unless you can fully route the wires to that box and not at all to the 3gang.

So, larger box would be *my* preferable if you just cannot get them into the existing. (How big IS the existing? Should have ** cu.in. On the inside....)

 

[cabranch47]

On occasion I have had two or three dimmers in one box and they interfered with each other (RF?). They would turn each other off and on. I had to separate them in order to get them to work. Heat dissipation might also be another problem depending on the load.

 

[Radix2]

Often times you need to break off the heatsink wings on the front if dinners when they are placed side by side to fit properly. This should not be a problem since your loads are low.

You can use WAGO connectors to make fitting the wire splices in the box easier.