Help with debate at work.

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I have a situation at my work. That I would like some input on. That is if you do not mind?


First one is this. My boss wants me to run an electrical service for a flashing light, and a regular light. Both of which will be controlled by a toggle switch (one for each light). Now the regular light is 120v, but the flashing light is 24VDC. I pointed out that we need a 120V flashing light, so as that we would not need to install a power supply. Another electrician pointed out that we could take the DC from the press panel. Now the 120V is coming from a load center. So I said we would a method of disconnecting both power sources at one time (and from one place). That if we used the press?s power supply this would be nearly impossible. The other electrician then pointed out that this is only for devices on the same yoke, and that both light switches could use 120V. It?s just that we would have to use a relay for flashing light. I debated that both power sources should still be disconnect able from place. He then came back with the yellow wire in a control panel means it is getting its power from some where else.

Now am I reading this wrong? I thought they both had to be disconnected from one place, and that the yellow wire came form different code (i.e. ANSI or NEMA). Also doesn?t the yellow wire still get its power from the main disconnects of machine, and can not be from some other panel not attached to this machine?

If you have answer great, but even better if we can find code to support my theory.

Then again maybe I am just wrong. :confused:


Thanks
Dan
 

highkvoltage

Senior Member
Re: Help with debate at work.

Same yoke one source. Why not use one source two switches one relay two lamps one junction box. Trying to use the 24V just creates more work. Two conduits one for low voltage on for 120 Voltage. Why would you even want to use DC? Sometimes small projects are just over thought and engineered.

[ June 25, 2005, 03:56 PM: Message edited by: highkvoltage ]
 

jim dungar

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Staff member
Location
Wisconsin
Occupation
PE (Retired) - Power Systems
Re: Help with debate at work.

For what it's worth.

If you are following NFPA79 then the color yellow means "foreign voltage" not disconnected by the panel switch. In simpler terms, yellow wires would mean possible live voltage.

Also, voltages below 50V are not consider "live" according to NFPA70E.

IMHO, use the 120V switch and a relay.

[ June 26, 2005, 11:10 AM: Message edited by: jim dungar ]
 
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