Wiring Question

Posted on
Mon Feb 22, 2010 2:43 pm
eme jota ce offline
Posts: 618
Joined: Jul 09, 2009
Location: SW Florida

Wiring Question

I currently have a keypad dimmer, the main load of it controls a ceiling light (Light A, 65 watts). The ceiling light is the "end of the line" so only the neutral (white) and load (black) wires reach the ceiling light's box. The (blue) line/hot wire goes no further than the box into which the keypad dimmer is installed. It's all in conduit, which serves as the ground.

I'd like to install a second light (Light B, 20 watts) very close to the existing ceiling light, but want to control their brightness levels separately.

Anyone have thoughts on the two possible approaches:

Option 1:
Leave the keypad dimmer connected to Light A, pull a new, blue (line/hot) wire to the ceiling light's box, then connect an inline dimmer which will control Light B using the existing neutral (white) and the new line (blue) wires.
(The disadvantage is that I'd have pull the wire, which I haven't done)

Option 2:
    Disconnect the black load wire from the keypad dimmer's red load wire and cap the red load wire;
    Mark the black load wire as "HOT" on both ends and connect it to the blue wires in the junction box;
    (Now, I'd have a hot wire and a neutral wire running through the conduit to the box at the ceiling light);
    Use those two wires to connect two inline dimmers, one to Light A and the other to Light B
This seems much easier to me.
    No pulling of wires.
    All the new wiring would be easy access.
    I could just use Indigo to create a link between the current keypad dimmer and the new inline dimmer for Light A, then I could link Light B's inline dimmer to a different button on the keypad (or whatever).
    I already have a couple inline dimmers that are not being used.

But, I'm not an electrician and would like to avoid doing something regrettable.

Posted on
Mon Feb 22, 2010 3:29 pm
kalisphoenix offline
User avatar
Posts: 50
Joined: Feb 01, 2010

Re: Wiring Question

Okay, if I understand correctly you currently have:

Code: Select all
House -[Neutral]-> Dimmer -[Neutral]-> Light A
House -[Line]-> Dimmer -[Load]-> Light A


And your options are:

Option 1:
Code: Select all
House -[Neutral]-> Dimmer -[Neutral]-> Light A
House -[Neutral]-> Inline Dimmer -[Neutral]-> Light B
House -[Line]-> Dimmer -[Load]-> Light A
House -[Line 2]-> Inline Dimmer -[Load 2]-> Light B


Option 2:
Code: Select all
House -[Neutral]-> Dimmer
House -[Line]-> Dimmer
House -[Neutral]-> Inline Dimmer 1 -> Light A
House -[Neutral]-> Inline Dimmer 2 -> Light B
House -[Line]-> Inline Dimmer 1 -> Light A
House -[Line]-> Inline Dimmer 2 -> Light B


Disclaimer: I am not an electrician. I know very little about NEC code. What I advise may be unsafe, stupid, and likely to burn down your house. What follows is my completely uneducated opinion.

Given those options, I'd pick Option #2. It should work as well as Option #1 and save you the trouble of running wire. Just link the dimmer switch to the inline dimmer for Light A and you should have your old functionality back as well as dimmable control of Light B.

As long as everything is capped and labeled properly, I believe it's safe and code-compliant. It's just a "pigtail." Just be sure Light B is grounded, make sure your wires are labeled correctly, and everything should be fine.

Posted on
Mon Feb 22, 2010 5:19 pm
bjojade offline
Posts: 285
Joined: Aug 03, 2005
Location: Wausau, WI

Re: Wiring Question

Either option sounds acceptable to me. Whichever is more convenient for you should be fine.

Brian Jojade
HappyMac Digital Electronics
http://www.happymacshop.com

Posted on
Mon Feb 22, 2010 5:40 pm
seanadams offline
Posts: 489
Joined: Mar 19, 2008
Location: Saratoga, CA

Re: Wiring Question

Do #2. A couple points:

- Never run a single conductor by itself as you've described in #1. Always use Romex inside walls, or conduit where applicable, but even then you must NOT use the hot without connecting ground and neutral. This is to ensure that both the return current (neutral) and fault current (ground) have a low impedance, parallel path back to the panel.

- Do not label black wires as "hot" - this is redundant at best will leave someone scratching their head. Black is always hot unless marked otherwise*. So are red and blue, although red is often the switched hot, and blue is seldom seen except in 3-phase.

* In certain situations (NOT gang boxes) an appropriately identified black wire may used as ground, neutral, or either of the other phases. For example larger gauges of wire are only sold in black. The correct way to label it is with several turns of colored electrical tape. NEC prescribes when this is allowed, and exactly how and where it must be wrapped - but in the home it is usually seen just at the service entrance.

Posted on
Tue Feb 23, 2010 8:39 am
eme jota ce offline
Posts: 618
Joined: Jul 09, 2009
Location: SW Florida

Re: Wiring Question

Thanks for the three excellent responses. Option 2 sounds like the winner.

Posted on
Wed Feb 24, 2010 10:49 pm
bjojade offline
Posts: 285
Joined: Aug 03, 2005
Location: Wausau, WI

Re: Wiring Question

He said the wire is already in conduit. In that case, pulling the additional pice of wire would be an acceptable solution.

Brian Jojade
HappyMac Digital Electronics
http://www.happymacshop.com

Posted on
Thu Feb 25, 2010 6:26 am
seanadams offline
Posts: 489
Joined: Mar 19, 2008
Location: Saratoga, CA

Re: Wiring Question

bjojade wrote:
He said the wire is already in conduit. In that case, pulling the additional pice of wire would be an acceptable solution.


agreed, I missed that

Posted on
Thu Feb 25, 2010 6:57 am
eme jota ce offline
Posts: 618
Joined: Jul 09, 2009
Location: SW Florida

Re: Wiring Question

Does that change the preferability of either option?

Posted on
Thu Feb 25, 2010 7:33 pm
seanadams offline
Posts: 489
Joined: Mar 19, 2008
Location: Saratoga, CA

Re: Wiring Question

There are a lot of things an electrician would observe in just a few seconds that are hard to determine except in person. Maybe a picture would help. For example how full are the boxes and the conduit, how long is the conduit, and how many bends? What type and gauge of wire, etc etc etc. Pulling a new conductor probably means pulling out the existing ones, taping the new wire to the bundle, and pulling them through again. It's not that hard really.

PS the internet is a terrible place to get wiring advice. Even people who know what they're talking about (which is very few of them) are going on limited information and can not give as good an answer as they would in person. For example, Mike Holt's web site has great forums, but posting is closed except to professionals for this reason. Sometimes you can hook something up and as far as you can tell everything is working fine until there is, say, some fault that doesn't trip the breaker or GFI like it would have if the wiring were done right. Homes and lives are lost over wiring mistakes.

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