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  1. #1
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    Mar 2014
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    Carrier Comfort Link Need Local Mode

    I have recently had 2 48A3 RTU's installed and I need to just install a regular Honeywell thermostat to control them. Unfortunately the contractor skipped out on us and we are stuck with this. The units came with Bacnet controllers and I want to bypass all that and just control the units from a regular thermostat. Can anyone assist with the settings in the Comfort Link to make this work. I can't find anything and Carrier Tech Support wasn't much help either. Any assistance would be greatly appreciated. If someone has a link to a manual that would help also. I can't find anything online.

  2. #2
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    Apr 2010
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    Is it a Comfortlink controller with the scrolling marquee? The one with the led readout, escape and enter, up and down buttons, and a bunch of mode LEDs?

    If it is, the path to the correct parameter is UNIT>U.CTL>4.

    The 4 is for thermostat control, which is the factory default setting.

    There may be many other that need to be changed depending on how the unit was set up in the field, and to be honest, don't ask me about that, cause I only know enough about these units to be dangerous.

    http://siglercommercial.com/wp-conte..._4850a-10t.pdf

    The information you're looking for is on page 27 of this manual, assuming it's the right one, which will make all the difference. Not all of those use the same number, different models may have different numbers for that same setting.
    Last edited by CHAINIK; 05-11-2017 at 06:54 PM. Reason: wrong information corrected


  3. #3
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    Quote Originally Posted by mwr1203 View Post
    I have recently had 2 48A3 RTU's installed and I need to just install a regular Honeywell thermostat to control them. Unfortunately the contractor skipped out on us and we are stuck with this. The units came with Bacnet controllers and I want to bypass all that and just control the units from a regular thermostat. Can anyone assist with the settings in the Comfort Link to make this work. I can't find anything and Carrier Tech Support wasn't much help either. Any assistance would be greatly appreciated. If someone has a link to a manual that would help also. I can't find anything online.
    Is there vavs? Or does it just dump into a space?

    Sent from my SM-G900V using Tapatalk

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  5. #4
    Join Date
    Mar 2014
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    Thread Starter
    It is a VAV RTU. Fan has a drive, but there are no VAV's just dumps into the space. Carrier came out yesterday and couldn't get the Fan to work off the thermostat. The tech wasn't very knowledgeable at all so someone else is coming on Monday. The gas heaters worked as well as the compressors, but just not the fan, which is obviously not good. I don't want control per say of the VFD. Only a start/stop. The unit can control the VFD.
    These units were spec'd by an engineer and no one told me about it. Our project manager just went ahead with it until he final realized that all this was just overkill for a school cafeteria. Now we are stuck with them. I am just trying to dumb them down.
    We are in a suburb of Houston very humid here. Units came with Economizer option also which doesn't work her but maybe a few days out of the year. Units are powered down for now until Monday. I am thinking that since there is a VFD on the Fan that the "G" terminal for the Fan in the unit is not useable on that terminal block in the unit. It may need a signal at the VFD itself to enable and disable the fan. I guess I will know Monday.
    Carrier said it can be done, so just getting a tech who knows what he is doing is what I'm up against.

  6. #5
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    I would use tstat multi then, option 3 under same menu as posted by CHAINIK. Either option 3 or 4 will operate the unit from thermostat inputs as CHAINIK stated. You will need to remove any jumper across r and the w terminals if they are there.

  7. #6
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    4 supposedly just goes back to 3, but again he could not get the Fan to operate per the thermostat. See what happens on Monday when they hopefully send a competent tech that knows what he is doing.

  8. #7
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    Sometimes you have to go back to basics, too.

    Was 24 volts measured coming back from the thermostat at a board input in the unit?
    [Avatar photo from a Florida training accident. Everyone walked away.]
    2 Tim 3:16-17

    RSES CMS, HVAC Electrical Specialist
    Member, IAEI

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  9. #8
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    Type - 4 is no longer an option with the version of software you have on your new units.

    What I would recommend is to configure the unit this way.

    Configuration menu > SP menu
    SP.CF > 0 for none
    CV.FD > 1 for yes
    SP.FN> 1 for yes
    Then set your:
    SP.MN to 67% which is the max for low cool

    All of this is in the manual .

    Quote Originally Posted by mwr1203 View Post
    4 supposedly just goes back to 3, but again he could not get the Fan to operate per the thermostat. See what happens on Monday when they hopefully send a competent tech that knows what he is doing.

  10. #9
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    Thread Starter
    Carrier got it done.

  11. #10
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    Quote Originally Posted by mwr1203 View Post
    Carrier got it done.
    It might be helpful for you to tell us what they did.....
    [Avatar photo from a Florida training accident. Everyone walked away.]
    2 Tim 3:16-17

    RSES CMS, HVAC Electrical Specialist
    Member, IAEI

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