@kishmich - great find! 

The manual is a bit disappointing as it still does not give any clues as to whether it will be a single unit install or a require pair (as the image shows) 
Although I'm beginning to think since it is referred to as a 'kit' that it will be two switches (makes makes sense if you want to be able to have manual control at both locations) - however will undoubtedly make it doubly expensive!  The 'other' (TL) brand only requires one and personally I would have been happy with that situation, I mean it's a SMART switch - why do you need MANUAL control at both locations? We'll find out soon I guess 

I think its frustrating to many users that there is no actual physical installation instruction in ANY of the manuals and just told to follow the on-screen guide in the app. 

BaumSquad wrote

 It has 5 wire connections. Line, Ground, Neutral, and Traveler 1 and Traveler 2 labeled seperately. 

@BaumSquad Well of course - that was a given - it's a 3-way switch! My question remains as to whether it goes at line or load end but more importantly if it REQUIRES two with one at EACH end. 

I don't see any possible reason why you would want to use it with an HS210 - that would not add any more capability than a 'dumb' switch and the circuit would already be being Smart Controlled by the other (the exact same reason as why you only need one HS210 in a non-dimming 3-way application)

Nor would it be a single pole switch as that would cut the circuit completely and would need to be flipped back manually in order to restore. 

So I think it comes down to will there be one or two required. 

Even if it says to install two, I will definitely be doing some experimenting to see if/how it will operate with one and if/what the limitations might be if it does

Oops - just noticed your post-script edit - that would be most unfortunate. Unless they are only marginally more expensive, I think that would make it prohibitive for me. 

MizzouMan2k wrote

 

1) I have one of the TPLink smart 3-way (non-dimming) switches in my garage.  I have a standard 3-way switch at the other end of the circuit, so this definitely works.

2) However, I think I have noticed some limitations.  The biggest one is that I have a timer on the smart switch to turn off automatically after being on for 30 minutes.   If i turn on the light at the 'dumb' switch, the smart switch doesn't recognize it's on and turn it off.  I haven't specifically tried this to confirm, but I think this has been my observation so far.  I may have to run a specific test to confirm.

 

3) I also don't know if the app would correctly reflect the actual state of the light if you control it from the dumb switch.  With the way my garage is wired, I had to put the dumb switch by the door from garage to the house and the smart switch by the door from garage to outside.  If the garage light is off and I turn it on at the dumb switch, does the smart switch recognize it's on and reflect the correct status accordingly in the app?  Another test I can run.

@MizzouMan2k 

1) Yes, this is the standard way to connect the HS210 

2) There are no 'on or off' positions with 3-way switches - each will invert the current state of the actual lamp whether that be on or off

These switches - whether smart or dumb - are changeover - so what might have turned on the light in one position does not necessarily mean that is always the on position as if you lets say leave the dumb switch alone and toggle the smart switch, that dumb position (where it was previously on) in now the 'off' position; 

Your timer turns on the lamp (when it was previously 'off') - regardless of that timer function on the Smart Switch, if you toggle the dumb switch, the Light WILL turn off. 

Run your test and it should prove accordingly. 

3) The LED on the Smart Switch will always reflect whether the actual lamp is on or off - when it does not detect any current flow (i.e. when the lamp is off) then the LED (and the App) will always show the correct state of whether the lamp is on or off. 

So the latter part of your question - yes, the app will show the light is on. (and you will also see it on the physical LED on the Smart Switch) 

It's important to understand that the LED - and App status - have nothing to do with which traveler is selected by the internal relay (i.e. relay energized or not) and only whether current is actually flowing to the load. 

So let's say the internal relay is turned on to couple the Common (Line) to the T2 Traveler - then (if light was previously off, that MUST mean that the T1 was the active line and that the dumb switch must already be linking the Load to the T2); so when the T2 becomes active from the Smart Switch, the Light comes on.

When the light comes on, the app reflects this status and now the LED on the Smart Switch turns off (LED is inverse of the actual light state) 

Now - T2 is still active right? Toggle the dumb switch - again, T2 status out of the Smart switch does NOT change i.e. still active; However by toggling the dumb switch, it now breaks the connection of the load with T2 and flips the switch to connect the Load to T1 - so the light goes OFF. Again, the relay state of the Smart Switch did NOT change, however because no current is flowing to the load, it reflects in the app that the Light is Off AND turns ON the LED on the Smart Switch.