Three-way switching of 240V load

[Natfuelbilll]

I recall this is a no no, but what Code section prohibits this iNsAnItY ?

[charlie b]

I don't know the answer, but I can't think of a reason this would be a no-no, as long as the switches are rated for that voltage. Are you talking about having a wall-mounted receptacle outlet powered by 240 volts with a 3-way arrangement for switching that outlet? Here again, so long as the receptacle is the correct type for that voltage, so that nobody tries to plug in a standard lamp, I think it should be OK.

What is the specific application you have in mind?

[LarryFine]

I recall this is a no no, but what Code section prohibits this iNsAnItY ?Random thoughts:

Control only requires breaking one conductor.

You could always 3-way-switch a 2p contactor.

[j rae]

I would go with larry !!!

[realolman]

I suppose you could use double pole double throw switches.

[ultramegabob]

I suppose you could use double pole double throw switches.

How would that give you a three way? I agree with using a contactor.

[iwire]

How would that give you a three way? I agree with using a contactor.

A normal 3 way is just a SPDT, if you used a DPDT and ran three more wires you could 'three way' switch 240.

[augie47]

A normal 3 way is just a SPDT, if you used a DPDT and ran three more wires you could 'three way' switch 240.

Sad to say but I shudder to think of the discombobulation that arrangement would cause with a number of our local "electricains"

[SEO]

Bob would you draw the switching for the DPDT three-way set up?

[hardworkingstiff]

Sad to say but I shudder to think of the discombobulation that arrangement would cause with a number of our local "electricains"

LOL, yea, get any 2 wires swapped on the terminals and it will never work (or go boom). Finding the problem would be a lot of fun.

[hardworkingstiff]

Bob would you draw the switching for the DPDT three-way set up?

It's just the same as the SPDT switch (x2). The trick is the travlers need to feed through in the same orientation or it will never work.

[charlie b]

Can I get back to the original question, and ask why you thought this was a no-no in the first place? What is the application?

[ultramegabob]

A normal 3 way is just a SPDT, if you used a DPDT and ran three more wires you could 'three way' switch 240.


I wasnt really thinking, I was picturing a DPST

[LarryFine]

Bob would you draw the switching for the DPDT three-way set up?
Just draw two 120v diagrams, and place one in each conductor.

As Lou pointed out, if you flip one pair of travelers, the light will never come on.

[SEO]

I drew it up before I asked Bob to do it, I was trying to give him some homework.:grin:

[LarryFine]

I drew it up before I asked Bob to do it, I was trying to give him some homework.:grin:Oh, okay. Bob, ignore my last post, please. ;)

[gndrod]

Oh, okay. Bob, ignore my last post, please. ;)

Even though running a 240V lighting 3-way is irregular, making a 240V hookup would be no different than a standard 3-way wiring diagram with the exception of the opposite phase leg as a common return to each luminaire lamping rated for a 240V load. There is no grounded neutral return circuit. The travelers switch phase leg A and are isolated from the common phase leg B return in the same 14-3 cable.

[gndrod]

Just draw two 120v diagrams, and place one in each conductor.

As Lou pointed out, if you flip one pair of travelers, the light will never come on.

Switching one phase on the travelers is proof of the pudding to isolate Phase B as the return in that circuit to the other side of the 2 pole breaker. Not practical for the lighting of modern LED low voltage lamping.

[gndrod]

I suspect there are 240 or higher V LED drivers. rbj

[gndrod]

I recall this is a no no, but what Code section prohibits this iNsAnItY ?

I believe there is none as long as the component listed ratings comply. Did Charlie b ever get his question answered? (What is the application?) rbj

[Natfuelbilll]

The application is 240v fixtures being controlled by a typical three-way switch pair. One phase would be treated as the common neutral and the remaining phase as the switching leg.

Code requires switching the ungrounded conductor. Is the intention to switch all ungrounded conductors?

[LarryFine]

Code requires switching the ungrounded conductor. Is the intention to switch all ungrounded conductors?
For controlling, no; for disconnecting, yes.

[Natfuelbilll]

Good answer and thanks.

[gndrod]

The application is 240v fixtures being controlled by a typical three-way switch pair. One phase would be treated as the common neutral and the remaining phase as the switching leg.

Code requires switching the ungrounded conductor. Is the intention to switch all ungrounded conductors?

Can anyone really call a common phase return a common neutral? Watch out....rbj

[sameguy]

drum switch i don't have a diagram to look to see if it would work anyone?

[LarryFine]

drum switch i don't have a diagram to look to see if it would work anyone?One? :confused:

[kleinstoller]

Specifically -- yesterday i was working with a different group -- making up service equipment in a panel room.

3 sets of paralell conductors in emt extended outside and along the wall of the building.

their location in the panel made it difficult to land the grounded (neutral) conductors with out bending too tight a radius.

Also they were landed top center overe the breaker and bus bars.

Accordingly -- i decided to turn loops in the gutter (plenty of space) and sweep them into place.

When i asked why i did that -- i responded with what i just described -- and added that i had been taught that turning that loop in the gutter served a second purpose..., when condensation woukld occur in the pipe (and it WILL)
the build-up of water would fall harmlessly in the gutter -- rather than accumulate on the main breaker etc.

They acted as if i'd dremt that one up -- would you comment