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Old 08-28-2010, 11:25 AM   #1
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How to wire momentary switch in house?


I need to install a push button momentary switch or push to break switch for an enclosed light inside a cabinet. The idea is that when the door is close, the circuit is broken and the light cannot come on. When open, the light will come on (I plan to have a normal switch to turn on/off the light past this point).

Anyway, my question is can this be done and if so, do I need to have the right size of momentary switch to be compatible with standard house wiring? Most of these switches I have seen look very small and my guess is that with regular 110V electrical wire in a house, I'd have some issues.

any help, much appreciated. thanks.

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Old 08-28-2010, 12:40 PM   #2
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How to wire momentary switch in house?


The switch itself has a voltage and amperes rating. To be connected directly to house current, it must be installed in a standard junction box with the activating lever coming through a hole just big enough, or must come in an appropriate UL approved enclosure.

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Old 08-28-2010, 02:23 PM   #3
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How to wire momentary switch in house?


So find a switch that matches the volts and amps and install in a box and I'm good to go?
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Old 08-28-2010, 04:44 PM   #4
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How to wire momentary switch in house?


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Originally Posted by Hoodzi View Post
So find a switch that matches the volts and amps and install in a box and I'm good to go?
You also need a switch that is rated for a tungsten [lamp] load if you are switching incand. lamps.
They are hard on switches because the instantaneous current is 10x or 15x the steady-state current. LEDs and CFLs, not so, they are more like 'resistive' loads.
Motor loads are the worst.

Last edited by Yoyizit; 08-28-2010 at 05:01 PM.
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Old 08-28-2010, 06:11 PM   #5
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How to wire momentary switch in house?


This is for an 18" fluorescent bulb.
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Old 08-28-2010, 07:56 PM   #6
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How to wire momentary switch in house?


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Originally Posted by Hoodzi View Post
This is for an 18" fluorescent bulb.
It's probably 13 W.

13 W/110 V = 0.12 A. The load is primarily resistive but the fluorescent ballast is inductive and may spark when the switch is opened.
Almost any 110 VAC switch with an inductive load rating of more than 0.12 A will do the job.
http://www.hosfelt.com/contents/en-us/d158.html
You may have to ask the manufacturer. Digi-Key is pretty good about publishing switch ratings for different loads but most are silent on this issue. A switch rated at 1 million cycles with a resistive load gets less with an inductive load and even less with a motor load.

Your electrical code may have a few things to say about how exactly to safely implement this arrangement.

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Old 08-28-2010, 11:28 PM   #7
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How to wire momentary switch in house?


If you run a raceway or conduit from the fixture to the switch setup you can use 18ga wire rather than 14 ga.
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Old 08-28-2010, 11:44 PM   #8
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How to wire momentary switch in house?


Quote:
Originally Posted by hayewe farm View Post
If you run a raceway or conduit from the fixture to the switch setup you can use 18ga wire rather than 14 ga.
Please tell me what code Article would allow this.
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Old 08-28-2010, 11:59 PM   #9
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How to wire momentary switch in house?


It would become fixture wiring just like a power strip. The NEC 14ga minimum is for in wall wiring.

Last edited by hayewe farm; 08-29-2010 at 12:38 AM.
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Old 08-29-2010, 09:42 AM   #10
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How to wire momentary switch in house?


I've heard of lower gauge wiring when it comes with the fixture
Never heard you can add on yourself whenever you want ?
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Old 08-29-2010, 12:00 PM   #11
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How to wire momentary switch in house?


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I've heard of lower gauge wiring when it comes with the fixture
Never heard you can add on yourself whenever you want ?
Wiring for pendent lights 18ga. wiring in water heater 16 ga. lamp cords 16 ga. some 18 ga. The requirements for 14 ga. minimum is for "in wall" wiring. Take a look at vent hoods, light and blower in box tube running from box to switch cover with 18 ga wiring. By the way I was answering the question about the size o0f the wire for the switch loop used in this case not the incomming power.
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Old 08-29-2010, 12:09 PM   #12
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How to wire momentary switch in house?


You could also put an inline fuse upstream of your circuitry, say 2/10 A.
If most similar commercially available fixtures do not have such a fuse then your implementation is probably safer than theirs.

Don't tell UL. Best not upset them.

Last edited by Yoyizit; 08-29-2010 at 12:13 PM.
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Old 08-29-2010, 12:44 PM   #13
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How to wire momentary switch in house?


If everything has to have a UL label, when do you call for their inspection and testing of the electrical system you install in a house? You don't, you just need to use UL approved devices.
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Old 08-29-2010, 12:55 PM   #14
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How to wire momentary switch in house?


Quote:
Originally Posted by hayewe farm View Post
Wiring for pendent lights 18ga. wiring in water heater 16 ga. lamp cords 16 ga. some 18 ga. The requirements for 14 ga. minimum is for "in wall" wiring. Take a look at vent hoods, light and blower in box tube running from box to switch cover with 18 ga wiring. By the way I was answering the question about the size o0f the wire for the switch loop used in this case not the incomming power.
still waiting for a code section that allows field installed wiring to be sized as you say. The examples you provide here are for manufactured appliances that the manufacturer has spent thousands of dollars to obtain a UL label for. A field installer cannot use that justification to use smaller wire unless they too are going to apply for a UL listing.

we need a code citation to support your contention.
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Old 08-29-2010, 03:01 PM   #15
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How to wire momentary switch in house?


210.19(4) Exception No. 2 Fixture wires and flexible cords shall be permitted to be smaller than 14 AWG as permitted by 240.5

240.5(B)(2) Fixture Wire. Fixture wire shall be permitted to be tapped to a branch-circuit conductor of a branch circuit in accordance with the following:
(1) 20-ampere circuits-18 AWG, up to 15 m (50 ft) of run length.


402.10 Fixture wires shall be permitted (1) for installation in luminaries and in similar equipment where enclosed or protected and not subject to bending or twisting in use, or (2) for connecting luminaries to the branch-circuit conductors supplying the luminaries.
 

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