Confused on Switch Ratings

[sherlocktk]

I have been playing with home automatin recently and am getting to the point I am looking to "fix" the lights in the garage and I am getting confused on the switch ratings

I am looking at a GE 45609 zwave swith with the below ratings. Its not a "dimmer" switch, just a fancy contolled on/off relay.
"This switch is designed for use only with permanently installed fixtures. The device controlled by this Z-Wave switch must not exceed 600 watts (Incandescent); 15 Amps, 1800W (Resistive); or ½ HP (Motor)."

Looking to run the shop lights (10 dual t8 type) fixtures, which run on a "normal" light switch. I think the load of these fixtures is about 80w a piece, for a total of 720w.

Now I realize that flourescent is not "incandescent" but I was confused with 3 ratings of 600 watts incandescent which is purely resistive. 15 amps, which is 1800 watts, or 1/2 hp which is around 375 watts (probably de-rated due to spike current).

Looking to do the flourescents on one circuit, and probably 4 "security" lights at 300 watts a piece (or 1200w total) on another circuit.

Anybody know why there are the different ratings?

 

[Greatbear]

Incandescent lamps have a big inrush current on powerup. This is made much worse with multiple lamps on a single switch. This is the reason for the apparent low rating of your switch on incandescent loads.

Purely resistive loads such as heaters have little or no inrush current compared to incandescent lamps. This allows the switch to operate near its maximum ratings since the ratings won't be exceeded at turn-on.

Inductive loads such as motors have a wildly fluctuating inrush demand, as well as power factor variations and kickback EMF that can put a hurting on a switching device. This is why you see some switches with a decent resistive and tungsten (incandescent) rating yet a paltry few amps at best for motor loads.