Tip for installation: before wiring up the base plate...install the batteries, attach the base plate and display panel together, and set Mode to Off and Fan to Auto.
I received and installed a new Pearl yesterday, and as soon as I connected the wiring to the base plate my A/C came on. Took me about an hour troubleshooting the wiring connections to figure out that the thermostat was somehow put into cool mode with A/C running before it was shipped to me, and remained that way even without the display panel connected.
In every other thermostat I've used, the wall plate is "dumb" and just used for making the wiring connections. The internal relays or switches are built into the display panel. In the case of the Pearl, it seems that the switches/relays are built into the base plate, and it retains whatever state it was in when the display panel was removed or powered down.
Really? That worries me somewhat. I'm looking at moving to the Pearl and most "smart" thermostats have a "compressor saver" function. Where, when they first get powered up, they will not start the A/C compressor for at least 5 minutes because they don't know when the last time it ran is. This prevents your compressor from burning u[ from excessive start/stops. For example, if your A/C is on and your power goes out for 30 seconds, if when the power came on, the compressor started again, that would be VERY bad for your A/C unit. Like blow up your compressor bad. Even my "dumb" Honeywell thermostat had that function in it. Kinda disappointed the Pearl doesn't. Might keep looking for another t-stat.
Just for future reference. The installation instructions for most thermostats usually tell you turn off the furnace before you start the installation. Once connected to the wiring and placed on the wall, then turn the furnace back on.
