Wiring 2 stage thermostat - Page 2
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  1. #14
    Join Date
    Jun 2003
    Location
    Florida
    Posts
    9,548
    If you want to have batteries to replace, let them use the common wire to control your second stage.With the common wire installed, your t-stat is powered by the furnace's transformer(no batteries needed,unless for back-up). Just tell them to run new wire,and hopefully they're smart enough to use 8 strand minimum,to help if a future problem occurs( wire shorted,etc.)
    If everything was always done "by the book"....the book would never change.

  2. #15
    Join Date
    Oct 2005
    Posts
    16
    UPDATE:

    Ok guys, i had the company send the installer back to wire it properly. Luckly they sent another installer so i got a 2nd opinion on the furnace install. He said it was good and fixed some minor spots that were missed...like missing screws.

    Anyways when he was looking at the wiring, he found out that the wiring had 6 wires so new wiring wasnt needed. (Damn lazy first installer) All i wanted was to have a two stage thermostat wired properly so all is good.

    Question: How do i know if its the furnace or thermostat that is controlling the first and second stage? When the tstat was installed as a single stage, it started on low and then high heat came out after a while. What should i look for now?


    Thanks again for everyone who posted and helped me out.

  3. #16
    Join Date
    Apr 2003
    Posts
    248
    thesober,

    With a 2 stage stat, you should now notice a couple of thing (both of which a single stage stat is not capable of):

    1. The furnace should run a looooong time in low stage on milder days. It should rarely come up to high stage unless its really cold and windy or coming out of setback. This is the number one difference you will notice. With a single stage stat the furnace is limited by a timer to run in low stage for up to about 16 minutes or so. Then it will always go to high stage.

    A 2 stage stat senses the rate at which the temp is changing in the room and will kick the furnace into 2nd stage ONLY if required. My furnace will sometimes run in low for over an hour before shutting off.

    2. Your 2 stage stat will now allow the furnace to run in Low, then go to High (if needed) then BACK TO LOW again. A single stage will only go from Low to High then OFF. This may not be as obvious unless you are sitting around timing the stages on the furnace..

    And yes, I'm a geek. I have sat around and monitored my furnace. I have no life!

  4. #17
    Glad I found this thread. I just had a Carrier 58CTA installed. Among some other issues with the installation, I noticed that the furnace only seems to burn at one level of fire. I looked at the wiring on the two-stage capable thermostat (Totaline P474) and the screw labeled W2 is not attached to anything. They pulled a new 5-wire bundle. From what I am reading here - five wires is not enough to support thermostat controlled staging when the thermostat has no batteries. Can someone confirm this before I explain to the installer why he can't have any money just yet?

    Also - Given that it appears to be set up as a single stage, why would the furnace not be burning low for some period and then burning high? Is that not what it is supposed to do? I sat next to the thing for 15 minutes after it kicked on - it made the same amount of noise and the pitch didn't change at all.

  5. #18
    Join Date
    Mar 2002
    Posts
    5
    W1 and W2 may be jumped at control board resulting in full time high fire.

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