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  1. #1
    Join Date
    Jul 2011
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    2
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    Questions about bringing in fresh air through return in a bar

    Hi All! I've been using HVAC talk for many years, but I've always found what I've needed without posting any questions. My luck has run out. I've got a customer that is remodeling a building that has an adjacent wall to his already in operation pool hall. The new bar will have a door that goes between both establishments. The old bar is a smoking allowed facility, and the new one is non-smoking. We are just doing a little bit of re-ducting, nothing major. They are reusing the old equipment that is above the drop ceiling. On the building remodel plans it shows to add a 10" duct from the roof, into the return air plenum, with an actuated damper, and 120v fan. This is exactly what it says...."Extend a 10" sheet metal outside air duct up thru a storm collar at roof to outside and terminate duct on a goose neck fitting with insect screen and provide a motorized damper model #MA-405 with actuator equal to Greenheck model # VCDR-50 with 120 volt is normally closed. Interlock indoor A/C fan and it's O.A. damper actuator so that actuator opens damper whenever fan is activated." I have a few questions about this. 1. Is this for the sole purpose of creating positive pressure to keep smoke from coming in when the connecting door is opened? 2. Does this HAVE to be 120v or will 24v work, and will I get tagged for not using 120v? 3. What is suppose to control this damper and fan? There is no zoning system of any kind, just a regular old Tstat. (I'm a refrigeration guy, having never done commercial A/C work, if it were up to me, I'd put an 8145-00 in there and call it good). 4. Do I have to use Greenheck parts here, or can I just go to the supply house and get an actuated damper and a inline fan and put that in there? I've attached a copy of the Mechanical plan itself, hopfully it will help shed some light. Looking forward to understanding this! Thanks.
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  2. #2
    Join Date
    Sep 2007
    Location
    edmonds wa
    Posts
    1,731
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    Looks to me to just be a outside air to help keep that side with more air, i take it these are split systems? The one over the bar, thats a good spot! If all the PE is trying to do is bring in outside air, i would just use a 24 v actuator, power off of g at the stat. Run it by the powers who be. to cover your butt.

  3. #3
    Join Date
    Jan 2010
    Posts
    8,005
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    If you decide to use 24v, make sure the existing transformer can handle the additional load.

  4. #4
    Join Date
    Aug 2002
    Location
    Southold, NY
    Posts
    7,329
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    If he's specifying 120 volt so be it. its his stamp on the plans. Install a relay in the air handler, when the fans on the damper is open.

  5. #5
    Join Date
    Apr 2011
    Location
    North Florida
    Posts
    275
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    Bringing in outside air thru the Air Handler serves to meet the Ventilation code based on number of Occupants , to dilute odors and smoke, to replenish the indoor air that is being exhausted thru bathroom exhaust fans ,etc... and to provide a fresher environment . It also reduces mold buildup in the space . It will provide some free cooling of the interior instead of running the mechanical cooling equipment . A 10" AUTOMATIC Damper will give you about 400 cfm of airflow from outside which of course will get heated, cooled, and filtered as it passes thru the Air Handler . I recently used a 16" Fresh Air Damper as shown here : http://www.ebay.com/itm/SD-10-or-9-i...item1c26f3b71a . I found this Mfgrs Damper to be very durable and its motor strong -- better than the typical Honneywell equivalent . I used the 16" fresh air damper on an AirHandler located above a Restaruant kitchen ceiling to provide free cooling during spring, fall, and winter months to the Kitchen and it worked superior and is saving a lot in mechanical cooling savings. I interlocked it with the space thermostat , so upon a call for cooling if the outside air temperature is 60 f. or below, the fresh air damper opens fully and mechanical cooling is prevented from starting ; it the outside air temperature is 61 f. or higher then the fresh air damper closes fully and mechanical cooling is energized. In the event the Air Handler is shut down, the fresh air damper automatically closes ; same for a power loss.

    The link I gave you is for a 3 wire arrangement but they also offer a simple 2 wire arrangement which is for their spring return Dampers (damper opens on a 24 v. signal and is spring closed when 24 v. signal ends) . In your application, you would simply install a separate 20 va Transformer for the Damper and tie it into the Blower Motor circuit so anytime the blower starts the fresh air damper will go fully open . Very simple . You wouldn't even need to touch the thermostat or its wiring.

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