Using 3-way switches as a 4-way

reactancexl wrote on 27/01/2004 :-

For what exactly?

Use a 3 way for a 4way? I for the life left in me do not understand what you are talking about.

3ways are used in pairs to switch from 2 locations. 4ways in the middle of the circuit add another location depending on the number of 4 ways. I await the lords of electricity to explain this one.

Are you sure someone is not pulling your leg?

I remember an article, in a 1960 vintage homeowner's encyclopedia, that showed how to wire _two_ three-way switches to work as a four-way switch. The handles were ganged by runnning a screw through them to make the switches operate together. Electrically, you have same thing, but I don't think it really meets code.

What the contractors may have been talking about is rearranging a lighting circuit with three or more switches into several circuits with only two switches on each one. Why they might need or want to, I have no idea.

Mike

Maybe he's thinking on the basis of two 3-ways make a 6-way...

Sure, simply gang two SPDT switches to make one DPDT switch:

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IANALEB, I'm not sure why it wouldn't meet code. There's no safety issue that I can see. Kinda kludgy though.

OTOH, Any number of X10 "three way" switches can be ganged together. They use one runner for power and the other for signaling.

I think someone is blowing smoke up your...

6 way?!? I think you are smoking dope!

any chance you still have that book? and could scan the article. I would like to add it to my collection

Use two 3-way switches on the beginning and end of the run and switches in the middle will be 4-way. Otherwise, you can't do it.

Beats the heck out of me.

As you probably already know, you need two 3-way (SPDT) switches to totally control power to a load from two different locations. They accomplish this dual control by selection which of two wires is ("runners"?) is currently in use.

To add additional switches requires that the runners be reversed as determined by the settings of as many additional 4-way (DPDT) reversing switches as desired at intermediate run locations.

A 3-way (SPDT) switch alone is incapable of reversing the runners.

Are you sure that what you heard wasn't that they were using three

4-way switches, rather than two 3-way and a one 4-way? This could save the contractor money, at least if he was buying large quantities of all the same type switch.

Harry C.

Easy. See my reply (threaded right above in my reader). Basically it's making two SPDT switches into a DPDT switch. Cross-connect the two "ends" of a DPDT switch and you have a "4- way".

A am not really sure why you would do this. 2 3ways can't be cheaper than 1

4way. I am also not sure where you would find a UL listed handle tie.

Don't be so sure. 4-ways can be expensive (3-ways aren't $.49 either). THought I agree, it's stupid for other reasons.

I don't see why UL would care. There is nothing dangerous here. Stupid, sure. Dangerous? ...at least I don't see it. Perhaps you have a scenario where there is a danger?

Dale Electric will sell you a 4 way commercial grade switch for $6.80. I doubt you can get the double box, two 3 ways and the cover for much less and I am not sure how you explain that duct tape and rusty nail handle tie to the customer.

I said it was ugly, but possible. ;-)

I also don't see the safety issue (thus why would UL care?).

Sorry, I don't have the set. It was my parents' from when they got married and bought their first house. Over the years it got pretty much beat up and was finally tossed out.

There's a 1962 edition, virtually identical, on eBay:

I'd forgotten earlier that the illustration showed the switched mounted outside on a pole next to the driveway, with no weatherproof cover and the happy homeowner reaching from his car to turn on the front porch light. Code violations, anyone?

It's not that UL would care. The inspector uses UL (or other recognized testing group) listing as a major factor in approving things. He/she would not approve the use of 2 3-ways as a four way, without UL listing. Whether you or I think it is safe or not is irrelevant. And imagine the poor homeowner who decides to replace that "4-way". Many homeowners get into trouble replacing a 3-way. This "wack-o" 4-way setup would make it even worse.

Intermatic makes a Decora single-unit timer module (also a switch) that has a single lead that can be used with a simple spst switch at a different location. Thus, you can have 3-way operation in effect with one less traveler wire. I believe the instructions for the timer also indicate how to wire it up for three location control with one timer and two three-way switches.

This might work for you if you're doing outdoor lighting or one of the control points needs to be a timer.

The Intermatic model SS8 Decora Timer Switch also has a cool "astronomic dial" feature so that your lights go on at local sunset, whatever time of the year it happens to be.

Beachcomber

Are you saying that the inspector will supercede his authority and require something that is not called for in the code? I know some do; been there :-(. (A building inspector I had once was a putz.) It's still wrong.

Note that I'm not saying it's a good idea. It'll look like hell and there is no good reason to make such a kludge, but I don't see anything about it make such a thing unsafe. "Unsafe" is all code is worried about (the NEC is written in blood).