Fact Sheet

 
1. Are PVC strips and automatic doors a substitute to air curtains?

  • PVC strip curtains are NOTan alternate for air curtains. Strip curtains are physical barriers which tend to obstruct the passage of material through doors / openings. Material movement becomes cumbersome through strips and at times are responsible for accidents on shop floors. Generally, in day to day use, workers tend to tie up loose ends of strips on sides of the openings to avoid physical hindrances caused due to hanging strips, which lowers their productivity during material movement.

  • Automatic doors / fast moving roll-up doors are not a substitute to air curtains. For large work spaces with ample openings a combination of air curtains & auto doors can be complimentary to each other. A buyer can benefit immensely by using this combination in maintaining any desired work space environment spaces air curtains alone may suffice.
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    2. Are air curtains a substitute to vestibules [ air locks ] in buildings ?

  • YES. Green building codes and ACMA# recommends air curtains over expensive air lock spaces.

  • Expensive floor spaces used to create air locks, may alternately be used for some more productive activity or can be totally done away, by air curtain installation. Installing effective air barriers will offer same benefits as that of an air lock, but at a much cheaper cost.

          # AIR MOVEMENT & CONTROL ASSOCIATION INTERNATIONAL INC. [AN AIR SYSTEMS PRODUCT TESTING AUTHORITY]

  • 3. Should the Acme air curtain be mounted inside or outside the doorway?

  • An air curtain will operate with equal efficiency on either side of doorway. However, there are general rules to remember as follows:
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  • Going by a thumb rule, an air curtain should be installed - for best results without any air draft absorption duct at floor level - on opposite side of the source of what needs to be prevented i.e. for prevention of conditioned air losses, on warmer side only.
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  • Whenever installing an air curtain, door should preferably open on rear side of installed air curtain without rupturing the unit’s air draft. Exceptional situation can be, when the door is to remain open for a very long time.
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  • When used over freezer doors or cold rooms, outside installation is preferable because if mounted on the cooler side, blower fans tend to gather moisture which freezes and eventually forms a snow ball around tangential flow fans causing it to lose operational efficiency.
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  • If people are working inside, near the door opening, an outside installation is suggested because of air frictional sound from unit in operation, as this will keep the noise out and allow any functional sound to dissipate in open environment.
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  • As a dust barrier, we suggest to install the air curtain preferably on cleaner side.
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    4. How far above the doorway should an air curtain be mounted?

  • It is advisable to install an air curtain around one & half / two inches [ max. ] above the door opening whenever possible. An installation nearer to door top will be more effective in curtain formation.

  • An air curtain can also be hung away from wall, if there is any hindrance to the air flow in curtain formation. But adequate care should be taken to cover the sides between the wall and actual curtain formation. An extended length [ overlapping ] air curtain unit may also be considered for such situations.
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    5. What happens, if Acme air curtain used is much smaller than the door opening?

  • It is wrong to install an air curtain smaller than the width of door as there will be unprotected areas on sides which will allow inside air to pass out and outsides air to get in. In an ideal situation an air curtain unit should cover the door width completely with one inch overlapping on either sides of door frame to ensure total protection.

  • Competitive manufacturer sometimes supply incorrect units when bidding. These units may have extreme side deflectors to spread the air draft towards uncovered sides. In such air curtains, air draft will go across the width but has irregular & inconsistent pattern as it travels down towards the floor. Further, due to inconsistant air pattern this air draft looses much of its velocity by the time it reaches floor level.
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    6. How far beyond the edge of the curtain chassis does the air spread extend and what is the depth [ thickness ] ?

  • This depends more on discharge nozzle width. Wider the nozzle, thicker is the air draft.

  • Moreover, when the air leaves discharge nozzle at high velocity, once out of the nozzle, this air draft tends to extend up to two inches on each side. The depth of curtain air is about one feet when measured 6 ft. away from discharge nozzle. It generally increases and this air draft attains an inverted cone shape as it travels to floor level.
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    7. When would a vertical mount be feasible?

  • When installation is not possible over the top of any doorway, an air curtain may be side mounted along the door opening with it’s air flow horizontal to floor. Such installations are recommended for openings exceeding 5.0 meters heights and having a width not exceeding 4.5 meters.
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    8. How long does it take to install an Acme air curtains?

  • The average time required to install a unit on firm wall surface is around two hours. After the second or third installation the time can usually be cut to 1 1\2 hours.

  • This time may vary for installations on MS structures or Aluminum & glass panels.
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    9. Why does an air curtain have adjustable air directional vanes?

  • Directional vanes aid in improving efficiency of air curtain’s air draft. Vanes are helpful in adjusting air draft tilt for keeping away strong air currents, dust, fumes, insects or to lower floor level air turbulence.

  • When using Acme air curtains for insects and dust control, directional vanes in air discharge nozzle should be tilted outward not only to repel insects and dust, but also to allow least amount of air to come inwards when the air draft reaches floor.

  • If mounted on outsides of doorway and used for the purpose of holding cold air in refrigerated rooms when the door is open, the directional vanes should be slanted slightly outward. If mounted on insides of freezer or coolers, vanes should be turned slightly towards refrigerated area.
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    10. When an air curtain is mounted over a cooler doorway, can the door be removed and air curtain allowed to operate continuously ?

  • YES. All Acme air curtains are equipped with continuous duty motors and can be run 24 hours all round the year, with minimum preventive maintenance efforts.
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    11. What happens to the air draft, when it reaches the floor level ?

  • When air draft reaches the floor level, it will divide, sending air partially inwards and outwards simultaneously and causing a drift both ways at the floor line. The inner side will experience Venturi effect of inside air whereas the outsides will experience Venturi effect of outside air. Based on site conditions, location of installation & purpose of air curtain installation, a judicious tilt to air draft will help deliver best efficiency.
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    12. If velocity of an air curtain is more than optimum, how can it be slowed down?

  • Velocity can be slowed down by using pre-filters at suction side to restrict air intake from suction grill. This restriction should not be used while using air curtain for repelling insects or for stopping high speed winds.
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    13. Are there any situations, which could cause an air curtain to operate poorly or not at all?

  • YES.

    There are situations to be avoided while selecting & using an air curtain.

    a. Wrong place of installation can prove counter productive.
    As a thumb rule an air curtain must be installed on opposite side of the source of what it is being used to prevent, or else its performance will be affected. There can be exceptions in this rule where split level floor-line is provided OR curtain absorption ducts are provided to prevent air draft splitting, which causes ingression.
    b. Improper installation of unit due to which air draft of the unit is formed away from the actual opening, this leads to unprotected sides from where air ingression can take place.
    c. c. An air curtain will not perform satisfactorily if there is an exhaust fan or exhausting system in operation, in any defined work area. An exhaust system without fresh incoming air, to substitute the quantum of exhausted air, will tend to create negative pressure within the building. This negative pressure will rupture air draft of any air curtain unit. If pressure difference is high then unit’s air draft may not reach the floor level.

    Same applies to positive pressure areas too. Air draft will tend to rupture beyond a certain point in withstanding positive pressure.

    It’s best to allow conventional air curtain units, for energy savings, to function in a balanced environment condition.
    d. Units with insufficient velocity and cfm air draft, will offer a weak air barrier that will not allow it’s air draft to reach floor level. Resulting in ineffective curtain formation.
    e. Improperly designed units may have very high variation in velocity, at any horizontal point of the air draft, hence will remain ineffective to deliver results.
    f. External pressures occurring due to wind tunnel effect will rupture the air draft of any air curtain. A wind tunnel occurs when there are two open doors ---- one on each side of the building corridor or passage.
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    14. What happens when man or material pass through air barrier ? Is the air curtain still effective ?

  • An air curtains efficiency will not be affected by passage of man or material through it. An air draft will be created all around the profile of human being or object passing through it.
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    15. What is a micro switch and when is it used?

  • A micro switch is used to synchronize functioning of air curtain with the working of doors, to avoid continuous operation of curtain. There are various types of micro switches used - such as plunger type, roller type etc.. Preferably, a good quality, heavy duty switch should be used for peace of mind.

  • However, if there is too frequent opening and closing of the doors it is always advisable to avoid the micro switch and allow Acme air curtain to operate continuously. This is because any and every air curtain motor takes couple of seconds to reach full speed, from zero RPM to full load RPM, by which time any human being is well past through the opening.
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    16. Can a micro switch be used on all types of doors?

  • NO. They will not work on swinging doors that open both ways. They are suitable for swinging doors that open one way, sliding doors and roll-up doors/shutters.
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    17. Are there any other options which may be tried for auto actuation of the air curtains with the functioning of the doors or high speed roll-up shutters ?

  • Yes. Options of magnetic sensors / photo sensors with or without delay timers are available. This will require a control panel for the incorporation of any of these features.
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    18. If air leaving the nozzle does not seem to have much velocity what could be the reason?

  • a.The cause may be probably of incorrect rotation of tangential flow fans. This usually occurs with three phase motors. If this is the problem, change power phase sequence of motor power supply connector.

  • b.The tangential flow fans / pre-filters are choked, hence air displacement does not take place sufficiently. If this is the case, blow off dust or other material choking the fan with a high velocity industrial blower.
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    19. Can filters be used in front of a suction side?

  • YES. Filters may be used in conjunction with suction grilles, but care should be taken in getting the filters celaned periodically. Filters are used when there is an excessive amount of dust and dirt in the air. Further, pre-filters will lower air draft speed. Hence, a stage higher model, may be preferred while opting for pre-filters.
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    20. Can the Acme air curtain be used to hold in extreme heat inside conveyorized industrial ovens?

  • YES. As long as air curtains are mounted on outsides of the oven. Specifications of such units need to be upgraded to address the site conditions.
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    21. When there is a foyer, where do you mount the air curtain?

  • To be more effective, an air curtain should be mounted inside the foyer over doorways leading to insides. Depending upon climate conditions either a heated or unheated model may be used.
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    22. Can an Acme air curtain be used over a blast freezer?

  • YES. Use models with enhanced specifications for the purpose.
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    23. What type of maintenance does the Acme air curtain require?

  • All air curtains and it’s motors have lifetime lubricated [ with 100% synthetic lubricant ] sealed ball bearings which do not require frequent lubrication. Blowing or wiping dust off the fans and motor whenever lint is visible is advisable to ensure maximum performance.