Unusual use of a three way.

[jes25]

I have a customer who has a row of light poles he has controlled by a feed thru timer( the ones with the trip switches) What he wants to do is be able to throw a switch down at the timer to go from "manual" mode to timer mode. In manual mode he wants to control the lights from a standard wall switch.

So I thought of this, its hard to explain but i will try. I will put an offset nipple off the timer to a handi box with a three way switch in it. I wiil then remove the load wire to the lights off the timer and thru the nipple to the common terminal on 3way. A new wire from the load on the timer will go to one of the traveler terminals on the 3way. When the switch is in this a postion where these contacts are closed we will have timer mode.

Now for "manual" mode I will run a wire from the line in the timer thru the nipple and splice on to a two wire switch loop up to a single pole upstairs. The other end or the switch loop will go to the remaining travler terminal. Now when the 3 way is moved from the postion it was in the upper paragraph, it will be controlled by the switch loop of the single pole only.

I have never done anything like this and was wondering if anyone sees a problem.

 

[iwire]

Re: Unusual use of a three way.

It will work fine, three ways make good high low switches for two speed fans or in my own house a "Hand / Auto" switch for a attic exhaust fan.

 

[jes25]

Re: Unusual use of a three way.

Hey thanks, I thought so I just needed to be reassured. Since we are kind of on the subject how about this one for a furnace generator transfer with a DP DT switch. Poco in normal postion and switch the hot and neutral to a disposal cord when the power is out so a cord can be plugged in.

 

[cselectric]

Re: Unusual use of a three way.

That install will work fine. But, if this is a commercial install, you might consider a single pole, double throw, center off switch, to provide a positive off position for maintenance purposes.

 

[iwire]

Re: Unusual use of a three way.

Electrically yes code wise probably not.

I assume you are talking about an optional stand by generator.

If that is true we have to look at 702.4

702.4 Equipment Approval.
All equipment shall be approved for the intended use.

This means the AHJ has to say it is approved.

Then there is also 702.6

702.6 Transfer Equipment.
Transfer equipment shall be suitable for the intended use and designed and installed so as to prevent the inadvertent interconnection of normal and alternate sources of supply in any operation of the transfer equipment. Transfer equipment and electric power production systems installed to permit operation in parallel with the normal source shall meet the requirements of Article 705.............

Again the AHJ would have to say the transfer equipment is suitable.

I might switch to a cord and plug on the furnace but that is also questionable.

 

[George Stolz]

Re: Unusual use of a three way.

See 424.10. I don't think cord-and-plug installation is covered in Article 424.

 

[jes25]

Re: Unusual use of a three way.

The problem is when somebody has a 220V 3 wire generator. The N and G are bonded so you have to switch the neutral, and the inexpensive Gen panels do not switch neutral. So there has to be a way without installing a very expensive generator transfer switch for a customer to plug in the furnace.

 

[iwire]

Re: Unusual use of a three way.

Who said it was fixed electric space heating equipment?

When I read furnace I think of an oil or gas fired hot air maker.

Very few electric furnaces get installed in homes, well at least in this area.

 

[jes25]

Re: Unusual use of a three way.

George I dont think a gas furnace is "fixed electrical space heating equipment"

 

[jes25]

Re: Unusual use of a three way.

I would say my switch would meet 702.6.

 

[iwire]

Re: Unusual use of a three way.

Originally posted by jes25:
I would say my switch would meet 702.6.

I might too, but it is not up to us, it would be within the discretion of the inspector to ask for a switch that says transfer switch.

Or is red or is special in what ever way the inspector wants it. :roll:

Look in article 100 at approved.

 

[jes25]

Re: Unusual use of a three way.

What might I ask, is "questionable" about the cord and plug technique other the fact when someone sees it they will immediately think DIY.

 

[iwire]

Re: Unusual use of a three way.

Originally posted by jes25:
What might I ask, is "questionable" about the cord and plug technique other the fact when someone sees it they will immediately think DIY.

I don't think a typical furnace fits any of the allowances in 400.7 Uses Permitted for cord connection, at least not without saying you did it to for the prevention of the transmission of noise or vibration.

Dishwashers and garbage disposals get specific allowances for cord and plug connection.

 

[George Stolz]

Re: Unusual use of a three way.

My mistake.

gas fired hot air maker[/QB]

This is what I was picturing. Do these have a section devoted to them?

 

[iwire]

Re: Unusual use of a three way.

Not devoted to them but 422 applies, specifically 422.12

 

[pierre]

Re: Unusual use of a three way.

Just a note
in the original post, he mentions using a handy box - that box will be to small for the application of the device and number of conductors he proposes to use.

 

[charlie tuna]

Re: Unusual use of a three way.

many years ago i was called to a high rise condo where the control section of an automatic transfer switch was burnt up! i wired a board that controlled the sequencing of the ats's functions. then placed the switches in order with a instruction sheet on how to "go to emergency power" and how "to return to normal power"! most of the switches were normal three ways! worked for a few weeks until the new control section could be built.

 

[rattus]

Re: Unusual use of a three way.

Seems to me that a single pole, single throw switch is all that is needed. You merely wire this switch in parallel with the switch in the timer. That is, wire this switch between the hot wire and the load and leave the timer connected.

 

[iwire]

Re: Unusual use of a three way.

Originally posted by rattus:
Seems to me that a single pole, single throw switch is all that is needed. You merely wire this switch in parallel with the switch in the timer. That is, wire this switch between the hot wire and the load and leave the timer connected.

Yes of course that would work also, you might have issues with the ON and OFF marking. OFF would not be off.

 

[rattus]

Re: Unusual use of a three way.

Bob,

It's like this: Fellow had a 40-year old combine which had lost all the chain and belt guards. When asked if that was dangerous, fellow replied,
"Well, you have to know not to put your hands in there!" Must have been pre-OSHA.