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  1. #1
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    Help with duct smoke detector

    I need help wiring in a d4120 smoke detector what wire goes to what I know 9 and 10 are my 24v but then what not using anything else but a shut down so red into 9 and red out of 10 to thermostat?

  2. #2
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    Sep 2008
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  3. #3
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    Aug 2006
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    Is this being used on a RTU or AHU to ONLY shut the blower off?

    I usually break the 24v off the transformer to kill the entire unit unless the unit has a smoke detector set of contacts on it.

    #9 and #10 get 24v

    #6 and #16 would be your 24v hot from the units transformer or the aux. set of wires from the main board designated for a duct smoke head.

    It would help if you could post the model and make of the unit you are installing it in.

  4. Likes ferminrey1227 liked this post
  5. #4
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    Quote Originally Posted by zw17 View Post
    Is this being used on a RTU or AHU to ONLY shut the blower off?

    I usually break the 24v off the transformer to kill the entire unit unless the unit has a smoke detector set of contacts on it.

    #9 and #10 get 24v

    #6 and #16 would be your 24v hot from the units transformer or the aux. set of wires from the main board designated for a duct smoke head.

    It would help if you could post the model and make of the unit you are installing it in.
    Thanks that what im going to ended up doing been a long while since i had to wire one up. do i need to run a common for the 10? or can i just wire a 24 from the trans then jump to NC 16 come out of 6 to the tstat?

  6. #5
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    Jun 2004
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    St Paul, minnesota
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    no you must run common to #10 and 24v hot to #9. you can get away with using 3 wires. 24v common to #10, 24v hot from transformer to #9 then jumper #6 and #9 and then hook #16 up to the wire that was coming off the transformer 24v hot (switched hot)

    The old school rule of breaking the red to the thermostat won't fly anymore (at least in my neck of the woods) as in most cases the control boards are still powered and fire marshalls and most inspectors won't approve it

  7. #6
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    Dec 2011
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    Quote Originally Posted by superfittertech View Post
    no you must run common to #10 and 24v hot to #9. you can get away with using 3 wires. 24v common to #10, 24v hot from transformer to #9 then jumper #6 and #9 and then hook #16 up to the wire that was coming off the transformer 24v hot (switched hot)

    The old school rule of breaking the red to the thermostat won't fly anymore (at least in my neck of the woods) as in most cases the control boards are still powered and fire marshalls and most inspectors won't approve it
    Can't break red here either. In most cars the blower continues to run. Breaking at the transformer is ok ish. But most newer units have terminals on the board dedicated for smoke detectors

    Sent from my HTC_Amaze_4G using Tapatalk 2

  8. #7
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    Jan 2012
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    This is a trane tch180f300

  9. #8
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    Apr 2016
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    I have this same sensor. I am trying to control my furnace power with it in the event it detects smoke. So I need a relay to go from 24vdc to 120vac?

    Sent from my LG-H812 using Tapatalk

  10. #9
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    Quote Originally Posted by atoned4.byhim View Post
    I have this same sensor. I am trying to control my furnace power with it in the event it detects smoke. So I need a relay to go from 24vdc to 120vac?

    Sent from my LG-H812 using Tapatalk
    Hard to say, we don't know what furnace you are putting this on?

    Almost all new residential units have a 24vac transformer you could break into.

  11. #10
    Join Date
    Apr 2016
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    I have a power source for the duct sensor. I need the sensor to shut down the carrier 59sc5. So no burner no blower.

    Sent from my LG-H812 using Tapatalk

  12. #11
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    May 2004
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    Salt Lake City/Tooele
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    Why break 120v power source? Just break the 24v off of the furnace transformer or break the R between the furnace and thermostat. Any who your only powering the detector with 24v from the furnace, the built in relay in the detector is nothing but a normally closed dry contact so can break the main power through it. Instructions should come with the sensor dictating this.

  13. #12
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    Apr 2016
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    I did that. The inspector doesn't want the blower to run after burner shuts off. It runs for sayyyy 90 seconds after burner shut down. He doesn't want any smoke pumped through the duct after the sensor detects it

    Sent from my LG-H812 using Tapatalk

  14. #13
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    May 2004
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    Salt Lake City/Tooele
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    If your dealing with the same sensor as the original poster is talking about back in 2012, then your talking about the System Sensor D4120, correct?
    The current models should beable to be powered by either 24v or 120v based on the input terminals used. At the same time you will have two sets of DRY contacts (A & B), so should have no issues breaking 120v or 240v as needed through either contact set. Thus, your killing power to the furnace.

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