15 vs. 20 Amp 3-Way Wall Switches

[Wade Gattett]

Two 3-way switches controlling a big Hunter Original ceiling fan on a 20 amp circuit worked fine for 33 years of occasional use. A week or two back, they quit working properly...both had to be "on" for the fan to run.

I decided to replace both switches and picked up two 20A Leviton 3-ways. When I pulled the old switches, they were slightly different models- but both were marked "Slater 15 amp".

One of them had what looked like the beginnings of some mild surface corrosion on its metal support bracket- though I guess it could have just been a scuzzy-looking mill finish. The other one was bright and looked fine. Unfortunately, I didn't test them and just tossed them out.

With the new switches installed, the fan is working right.

At the local Home Depot, the 20A switches were twice the cost of the 15A ones. I'm thinking if the price difference was the same 33 years ago, maybe that's why the electrical sub used them.

We ended up having a lot of problems with the general contractor for the room addition where the fan was installed. What do they say about apples not falling far from the tree?

So- is it OK to use a 15A switch on a 20A circuit? Could that have had anything to do with the switch failure? Or are Slater switches not so hot?

[trader_4]

I believe the answer is that the switch is sized to the load, not the breaker. So 15A is OK. It's hard to imagine a fault condition where a 15A switch is going to create a safety hazard in that application. As to whether a 15A switch contributed to your switch failure, I'd say yes and no, mostly no. Your small fan load is nowhere near the limit of either a 15A or 20A switch. But a 20A switch may be built a bit heftier, might take more openings and closing, etc than a 15A one, so a 20A one might have lasted longer. There are also differences among 15A switches, ie a cheap chinese one or a better spec grade one, (probably from China too :)

[Home Guy]

Why would a ceiling can need a 20-amp switch?

Why would a sub use a switch that's twice the price - just because it costs more?

Why would he not use a switch that would work just fine (a 15 amp switch) and put the difference in his pocket?

On a side note -

When you say "3-way" - do you mean 2-pole center thow - with center off? A switch that can be set to 3 different physical positions?

I was looking for either a paddle or decora-style 3-way (with center off) but they're not available at home despot (canada) but they are in the US, and they're like $50. I seem to remember them being more common years ago (and not so expensive) - ?

[Ralph Mowery]

In the US what is normally referred to as a '3 way switch' in a building is a single pole double throw. They do no thave a middle off, but just an off/on position like any light switch would normally have. From the outside of the switch you could not tell the difference. They are most often used for lights. You have a room with 2 doors. You put one switch at each door. Then you can turn the light off and on from either switch. That is you could walk in one door, turn the light on, walk out the other door and turn the light off.

There is also a '4 way switch' . That is for more than 2 places to turn on/off a light (or anything else). You usually put a 3 way switch at each end of the circuit and as many 4 way switches in the middle as you need.

[Clare Snyder]

A "three way" switch is a SPDT switch used in pairs to switch a device from 2 different locations.

Have never seen a center off SPDT switch in paddle or decora in Canada

- the odd momemtary contact (click one way for on and one way for off for low voltage remote control - or this one:

Which is an "industrial grade" switch - can't think offhand where one would use one in a house - - - -

[micky]

Maybe, but it seems to have lasted 33 years.

This is one of a series of conservative sentiments attributed to the US founding fathers or other great historical figures that they never said.

And which were actually first said by conservatives in the 2nd half of the 20th century or later.

One screen down on this page, a sentence with the same meaning is attributed to De Toqueville, but he never said it either. Nor did Alexander Hamilton, another one to whom it's attributed.

[gfretwell]

I have seen them but they are god awful expensive and only in decora.

[gfretwell]

This is another one bouncing around on the interweb with dubious citation

"About the time our original thirteen states adopted their new constitution in 1787, Alexander Tyler, a Scottish history professor at the University of Edinburgh, had this to say about the fall of the Athenian Republic some 2,000 years earlier:

"A democracy is always temporary in nature; it simply cannot exist as a permanent form of government."

"A democracy will continue to exist up until the time that voters discover they can vote themselves generous gifts from the public treasury."

"From that moment on, the majority always vote for the candidates who promise the most benefits from the public treasury, with the result that every democracy will finally collapse due to loose fiscal policy, which is always followed by a dictatorship."

"The average age of the world's greatest civilizations from the beginning of history, has been about 200 years"

"During those 200 years, those nations always progressed through the following sequence:

1. from bondage to spiritual faith;

1. from spiritual faith to great courage;

2. from courage to liberty;

1. from liberty to abundance;

2. from abundance to complacency;

1. from complacency to apathy;

2. from apathy to dependence;

1. from dependence back into bondage"

[Home Guy]

There is a leviton constant-contact (not momentary contact) center off and like I said home despot US has them ($50 - $60 if I recall).

I wanted to control an attic fan. I wanted 3 options: Off, On, and Auto. Auto means the fan is controlled by the thermostat in the attic. A SPDT with center off would do this, but none are available. I ended up using one of those double switches (2 SPST single-gang). Available in paddle and decora, and relatively cheap (I think $17).

[Mark Lloyd]

[snip]

It is essentially a DPDT (double pole, double throw) switch with 2 pairs of terminals connected internally, so switching exchanges 2 connections.

[SPAM snipped]

[Mark Lloyd]

What I heard is that its called "3-way" because wires are run to 3 locations (2 switches and light/fan). If you have three switches, its 4-way.

A double-throw switch does have center off, although it can be difficult to get the switch into that position (a spring tries to pull it away from the center). I have had this happen accidentally, one switch in this (center) position means the light can't be turned on at the other location.

[trader_4]

+1

That's not really true. Sounds like you had a particular switch that could be positioned in between, in an unstable position. Some switches have a center-off and if they do, it's clearly a detent position and the switch is spec's as having a center off. If they don't then I guess it depends on the design, how easy it is to get it into a position it's not really meant to be in.

[dpb]

...

But if there are four or more switches, they're not "N-way"...

[trader_4]

Seems to me that they are all N-way. We come up with a definition for the N-way case and uniformly apply it. And like Mark said, N was determined by how many locations the wires had to be run to, eg one light, two switches is 3 way. Which then leads to what really is a light with one switch? I'd say that if you analyze it, apply a uniform definition, then it's two ways, though for whatever reason, it's not commonly referred to as that.

[gfretwell]

My deal was a two speed ceiling fan (whole house deal). It was common, hi, lo. so a 3 way was a natural for speed (SPDT) but you still need an off. I had a 4" box there anyway so I went with 2 switches. Being a motor load I did go for spec grade, motor rated switches but I was still out the door for $5 or so for two (a regular 3 way and an SPST) snap switches in Decora.

[gfretwell]

When they are 59 cents in a barrel on the end cap, who would think it could just be bad? Or part of batch of a 1000 bad ones because even the Chinese have trouble finding good help. Mass production = Mass mistakes. (See any recall)

[Clare Snyder]

some time or other "off the record"

[Clare Snyder]

What would you use such a switch for??? I can think of many industrial uses.

[Clare Snyder]

Generally that would be accomplished using a bat-handle type switch supplied by the fan manufacturer or the control manufacturer - but 2 switches in parallel would do the job too

[gfretwell]

I gave you one, switching a single phase 3 wire multi speed motor.