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Some, but not all, three-way light switches are marked with a "Top". Why?

Here are some examples. These pics are all taken from ordinary three-way Decora light switches.

Leviton:
enter image description here

Cooper:
enter image description here

Legrand:
enter image description here

It's easy enough to search for photos of ones that do not have the marking.

The first one I saw was the Cooper one and I thought maybe it's so the UL marking will be prominent and right-side-up for inspection. But the others don't have the UL marking in the same place.

Perhaps it is because regular on/off switches must be marked with a top, and these manufacturers want to accustom installers to looking for the marking and getting it right? So marking three-way switches reenforces a good habit? Just a theory, not very likely.

The Legrand one has "Legrand" marked on the paddle (visible to users) so if it's mounted upside down that writing is upside down. But the others don't have exposed writing. And as far as that goes, if it were the only reason, if some fool is going to install the obvious "Legrand" mark upside down, I don't think a much more subtle and hidden "top" will change anything!

jay613
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3 Answers3

15

One possibility is that the manufacturers simply maintain a single die for stamping all their yokes of a given size, rather than one with the "top" mark and one without. It doesn't hurt anything to mark 3-way switches with a "top", and it simplifies the manufacturing line a tiny bit.

nobody
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3

In addition to the very likely answer already posted of simplifies manufacturing, it may be so that screw positions can be defined for that particular model. There is no standardization across the industry, or even necessarily within a particular product line. But every device comes with instructions and for those instructions to make sense, screw position and device orientation matter.

In this Leviton from Home Depot, the screw configuration (pictures on Home Depot web page and instructions) are:

  • Green = Ground = Upper left
  • Black = Common = Lower Right
  • Travelers = Brass = Lower Left and Upper Right

That is actually an interesting combination. It might seem more logical to have the travelers be one of:

  • Top Left/Right
  • Bottom Left/Right
  • Top/Bottom Left
  • Top/Bottom Right

but this particular configuration has the neat side-effect that if you do rotate 180 degrees (a.k.a., install upside down), the travelers are still Lower Left and Upper Right. Of course, then you need to look at the screw colors to determine where to connect the common (Hot or Switched Hot) wire, but all you need to remember for that is "Green = Ground", which is the one thing guaranteed everywhere.

manassehkatz-Moving 2 Codidact
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-1

Simply - its an aid at re-assembly time. Presuming the switch was assembled with "TOP" at the top originally, subsequent reassembling doesn't require the wiring to be traced, or the switch to be tested live to make sure it is going back in the right way around.

It can be quite annoying to re-do work you just finished reassembling because of something simple like assembling it upside down.

Criggie
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