Is this a legal use of a 3 way switch

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Jim W in Tampa

Jim W in Tampa

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Tampa Florida
Could i use a 3 way swith to change a load from side A to side B.
The common would go to the load and other 2 screws to a breaker from A and other from B

That would have made a quick fix for last nights problem of 1 leg going dead.
Anything in nec that prohibits it or do any see any hazards ?
 
The only issue that I can think of is you would have 240 applied to what is likely a 120 volt rated switch. Maybe ask for a 277 volt 3 way?
 
iwire said:
The only issue that I can think of is you would have 240 applied to what is likely a 120 volt rated switch. Maybe ask for a 277 volt 3 way?
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Thanks, I did not think of that. I was bit concerned about the 240 but 277 is easy way out.
My thinking is only for a few selected loads that i need and usefull at same time when we have huricanes. Easy way to balance load on gen.
 
It is a 110.3(B) violation. Standard snap switches are not listed for that application.
Snap switches have not been investigated for switching a load between two alternate sources of supply. Double-throw enclosed switches (see Switches, Enclosed [WIAX]) or switches Listed as transfer switches (see Transfer Switches [WPTZ] and Emergency Lighting and Power Equipment [FTBR]) should be used for this purpose.
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The above is from the UL Guide Information for snap switches
 
Others here have used 3 ways where they feed the common and put the garbage disposal on one load screw and the insta hot water on the other load screw. That way one circuit for two appliances, disposal only runs for short amount of time and insta hot is not really affected by the short time it is off.
 
Flipping it around and having one source on the common which supplies two separate loads such as light #1 and light #2 alternately would imho be a legal and ok use of a three way switch. Reverse the switch and have two separate feeds to control one single load and you have a listing issue as Don points out.
 
I think Don is correct.
Coming from another leg or phase is a second source.
I understand switching loads and I 100% agree thats safe. It may or may not meet the requirements of required circuits but that is not what i am doing.
What i would have is 240 volts across the switch.
Bobs idea of 277 volt rated switch might solve that.
Now we have issue of is this safe. They would be switched sometimes under a load.
Likely seldom used

What happened Saturday placed me under a very unusual situation.
I could have used manuel transfer switch and solved part of problem by gaining back 240 volts but at same time but then would have only 5 kw. That would have shut off all the AC units as some are 1 ton 120 volt units.

What i did do was quickly open up one of my sub panels and moved a load for pool table to a working side. Just a temp. fix

Other than dance foor lights and a few other area lights we managed the short outage.
If i had a system to move the loads i could have solved that. So this is soulution i came up with. Power outages are rare here so might not even be worth the cost.

All my emergancy battery back up lights did come on so no areas where in total dark. Had it lasted for much more than 1 hour then might been issue. Do they make any replacement lamps for the old style incandesant lamps to led for combo type exit/ emg lights ?
 
I don't know that adding 3 way switches to change what is supplying the circuit would do much to fix your issue. Since you had one phase burn clear due to the load it seems silly to raise the load on the unburned side at that point. If the panel was balance correctly to start with (and I believe it was) you would just be putting the second (unburned phase) conductor at risk, or even the neutral conductor.
 
I agree you would probably need to use a switch rated at 277 ,20 amp.

But I don't see how you would consider changing from X1 to X2 of the transformer a different source.

Ronald
 
Are you sure a 3-way switch always guarantees that the two switched legs will never simultaneously be connected to the load (and therefore each other) at the same time? This would short out the two feeds if they are not from the same source pole. You could test it by slowly moving the switch to its center position and see if it shorts out.

People have considered using these as poor mans transfer switches. This same issue was pointed and and they recommended using center off type double throw switches as a bare minimum.
 
Are you sure a 3-way switch always guarantees that the two switched legs will never simultaneously
be connected to the load (and therefore each other) at the same time?
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No Mark,no guarantees but they are a mechandical switch. But the way Jim is going to be using this switch is because the power on that leg is dead.
But all things considered that why the switch will be rated at 277 volts, 20amps. so it will trip the breaker.
 
My thinking is?this would be considered two circuits connected to a single yoke and these two circuits would have to originate on a two pole breaker or two single pole breakers with a listed handle tie per 210.7(B). This section would prevent using an alternate source of supply.
 
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