I ordered some sidewalk heating mats from HeatTrak and I want to automate them with HA so that they come on when it makes sense to do so based on the data from my Tempest Weather Station.
According to HeatTrack my mats will have a combined resistive load of 5A which is well within the spec of the Zooz ZEN05 or ZEN14, both rated for 15A resistive loads, but when I asked them about it they did not recommend using either of them with heated mats. They couldn’t, or wouldn’t, explain why and it doesn’t make sense to me why this wouldn’t work.
My next thought was to simply swap the outlet to something smart but this is an outdoor outlet so it needs to be GFCI and there’s essentially no Z-Wave GFCI outlets made.
Do I really need to use something like an Enbrighten Z-Wave Plus 40-Amp contactor for this or am I missing something here?
If they don’t trust their specifications, do you? Pick up a Kill-a-Watt or some other way to measure them.
The only thing that comes to mind is that most resistive heaters eventually fail and might draw significant additional current when they do. But you should have plenty of extra margin with a 15A switch.
I will say, I’ve had an old mechanical window AC trip the ZEN15’s overload detection when the thermostat short cycled and the compressor was stalled. So I would trust it for that in a pinch, and especially with a resistive load. But for an outdoor heating element application, I still would oversize the switching device (and get the 40A contactor), and put 15A circuit breakers before the contactor. Also, that 40A device can drive either a two pole 240V device (unison contacts) or two 120V devices, so you could just put each heater on its own pole and heat up your wiring a little less. Or probably just wire only one pole, I haven’t read the manual.