High Velocity/Pressure fans & Ducts

Discussion in 'HVAC' started by gerry_g, May 8, 2011.

  1. May 8, 2011 #1

    gerry_g

    gerry_g

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    I have a Leisure Line thermostatic controlled coal stove in my family room at one end of the basement of a long ranch. It can automatically adjust room temperature via wall thermostat by varying the fire from 5,000 to 80,000 BTUs/hr.

    Since this stove is fully automatic, only needing feeding every 1-3 days, anthracite coal very clean and inexpensive (per unit of heat) I wish to distribute heat from that room about the house. Pick up warm air through the suspended ceiling and duct it about the house. I need to observe local fire codes and use fire dampers where I penetrate the floors.

    My problem is lack of basement head room for conventional size ducts. I am aware high velocity / high pressure warm air HVAC systems exist but can not find fans for use as the primary blower of such a system. Conventional duct booster fans are not designed for such.

    Any suggestions on where to locate in line, variable speed fans to move significant air through 4" or less duct?

    gerry
     
    Last edited: May 8, 2011
  2. May 9, 2011 #2

    inspectorD

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  3. May 9, 2011 #3

    paul52446m

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    You are not talking about ducting right to the stove Right?. You are talking about picking the hot air up by the ceiling Right?. First question is where does the stove get it burner air from? It could be dangerous if you pull air from this room and pull a vacuum on the room. Is this unit sealed combustion? or does the burner air come from this room? They do make blowers that develop higher static pressure. You did not tell me how big your home is so i can guess at how much air you are talking about moving.
    If you are just moving air from the ceiling through the house, then you don't need fire dampers. If i could see a floor plan off the basement and the main floor, that would help. If you can get me more info and then we can go from there. Paul
     
  4. May 9, 2011 #4

    gerry_g

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    The room already has free air flow to the rest of the house (open stairwell) and hot air central system returns. It is in conditioned space, I merely wish to circulate air in the existing conditioned space. Convection would help a two story house but convection doesn't help much on a long single story home.

    I wish to pick up air off the ceiling of the downstairs family room and move it horizontally on a 72'x24' ranch and then through to the main floor.

    Despite the fact that I have an open stairwell, my local inspector will not approve through floor (level change) ducts without fire dampers at each floor penetration. This is a tad ridiculous since the warm air heating system already has approved duct work that feeds the basement level family room and penetrates floors on the main floor! I'm just adding a second metallic air path! I can't use the existing duct since it would disturb pressures of my gas furnace.

    The fire code he is citing regarding fire dampers (national code) is clearly written for commercial buildings, hospitals, multiple story apartments... since it is in the same section that requires fire doors on stairwells, fire rated walls and floors...

    However, this section of the code does not include an explicit exemption for residential buildings. If the inspector is not happy, my fire insurance is void.

    The existing warm air ducting is explicitly exempt (re fire dampers) under a clause that it is directly connected to a residential furnace with a 165F max safety cut off. Again, this duct system already connects the family room through he warm air ducts to main floor registers without fire dampers and meets code! Fire could follow that duct work or just go up the open stairwell!

    My inspector will approve fans and ducts that penetrate the floor only with fire dampers. He rules!

    I did cover the safety issues and keeping my home insurance valid. so back to the QUESTION!

    Where can I find in line variable speed fans to move significant air through small diameter (4") horizontal ducts. Not just "booster fans", these will be the sole "air handler" fan for these ducts. High velocity/pressure is required to keep duct size small.

    gerry
     
  5. May 9, 2011 #5

    paul52446m

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  6. May 10, 2011 #6

    gerry_g

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    I know and have an account at Granger, although their prices are high compared to the supply house I deal with most often.

    Perhaps I should have phrased the question more explicitly. What specific fans are suitable as primary air movers, not boosters or small diameter multiple bathroom exhaust (not 100% duty cycle). The latter are usually have plastic shells and thus a no go per my inspector. That is another interesting inspection interpretation.

    Specs desired:

    Metal shell

    Not larger than 4" diameter

    Can be connected with a remote a variable speed control.

    Capable of 300+ cfm when used as sole air mover in 30' straight run with a flare out to 6' or 8" elbow and floor register

    gerry
     
    Last edited: May 10, 2011

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