With the new Rheem touchscreen t-stat, what is the proper mode (Menu Reference #1 in the Installer Menu) setting when used with a modulating furnace?
The company who installed my furnace set it to MS2. But I discovered this may not be the best setting to use.
When the mode is set to MS2, the t-stat behaves like a 2-stage thermostat-- making extra "click" sounds and printing messages on the screen saying it is firing the second stage. These messages don't make any sense at all for use with a modulating furnace.
So I changed it so the SS1 setting and noticed the furnace modulation and firing scheme behaves identically! Except now all the meaningless messages and clicks about the 2nd stage are gone.
It looks like the PWM signal on the V line is correctly generated regardless of which mode (multi-stage or single-stage) the t-stat is configured for.
The manual provided with the t-stat gives no suggestions about how this should be set. And when asked, my dealer doesn't seem to know. Though based on my tests, SS1 is the correct setting for someone with a modulating furnace only (no heat pump or A/C).
All this is just confirming my suspicion that the touchscreen t-stat is a product that's not fully polished. Ideally this t-stat should display the current firing rate and the menus should include options for the mod furnace. But it has none of this.