Results 1 to 4 of 4
  1. #1
    Join Date
    Jan 2007
    Posts
    20

    Proper t-stat mode for Rheem modulating

    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.

  2. #2
    Join Date
    Oct 2006
    Location
    So. NH
    Posts
    746
    MY understanding of it is it will still act as a 2 stage, energize w2 and go to full cap, say if you manually raise the setpoint 2 or more deg. Plenty of more knowlegable folks here and I'm sure they will have more info than me. I'm still figuring it out myself but it sounds like you have other issues. Mine for the most part seems to work great.

  3. #3
    Join Date
    Jan 2007
    Posts
    20
    But according to the installation manual, W2 is not supposed to be hooked-up for a modulating t-stat!

    Besides, I find that on my t-stat it will nearly always signal the furnace to go to 100% when I raise the temperature 2 degrees or more. And it does this even when the t-stat is set to SS1 mode.

  4. #4
    Join Date
    Oct 2006
    Location
    So. NH
    Posts
    746
    Your right, its not connected on w2 but does still act like it is though. just w and v. I'm sure the pros will shed some light. Too many threads for this topic!

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
Comfortech Show Promo Image

Related Forums

Plumbing Talks | Contractor Magazine
Forums | Electrical Construction & Maintenance (EC&M) Magazine
Comfortech365 Virtual Event