ROOM AIR DISTRIBUTION MSYS4480 1 Louvre Selection Issues 1. - - PDF document

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ROOM AIR DISTRIBUTION

MSYS4480

Louvre Selection Issues

1. Airflow versus water ingress 2. Minimizing pressure loss 3. Beware free area 4. Know your location 5. Controlling noise 6. Stick to the design

Louvers

200 Water Street, Vancouver

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Louvres

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Sloped Plenum Detail

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• Traditional louvres provide protection

from non-storm rain

• Wind Driven Rain Resistant louver provide

storm condition protection

• Let’s look at the differences…

Louvre Types

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Traditional Louvres:

• Horizontal blades
• Drain Gutters
• Wide Spacing
• High free area
• Low cost
• Stops some rain
• Not effective in storms

Louvres

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Louvres

Traditional Louvre Sizing:

• AMCA water penetration test – Beginning point of water

penetration free area velocity (FAV)

• Determine design FAV considering AMCA test data
• CFM/FAV = Total free area required
• Reference louvre free area guide to determine appropriate

louvre size

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.01 oz./ft,

• f free

area

Water Penetration Graph

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Air Performance Rating

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Traditional Louvres

Where to use:

• Properly drained applications
• Sloped plenums & ductwork
• Floor drains
• Protected areas (overhangs, barriers,

interiors, non-prevailing wind elevations)

• “Screen” applications (vision barriers)

Sizing

• Use safety factor of 15 to 20%

Note

• Does not stop storm rain

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1/21/2019 6 Wind Driven Rain Louvres

• Horizontal or Vertical blades
• Drain Gutters on horizontal
• Hooks on vertical
• Close spacing
• Lower free area
• Higher velocity
• Effective in storms

New Louvres

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Horizontal blade models Vertical Blade Models

40% - 50% free area 2” to 8” deep Class A @ 800 to 1200 fpm Moderate ∆p Traditional appearance 40% - 45% free area 3” to 7” deep Class A @ 1500 to 2100 fpm Low ∆p Best performance

Wind Driven Rain Louvres

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Wind Driven Louvre Benefits

Prevent rain infiltration

• Lessens interior water damage & mold growth
• Helps keep walls & floors dry
• Helps keep filters dry
• Excellent for penthouses

Allow higher intake velocities

• Use smaller louvres

Reduce future problems & liability

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48” x 48” & 7,000 cfm

• 6” Traditional

710 fpm

• .07”

∆p 60% Wind Driven Rain Effectiveness (29 mph)

• Cost 1.0
• 5” Horizontal

1,002 fpm WDR

• .16”

∆p 99.8% Wind Driven Rain Effectiveness (29 mph) Cost 1.7

• 6” Vertical

1,030 fpm WDR

• .09”

∆p 99.8% Wind Driven Rain Effectiveness (50 mph)

• Cost 2.7
• 48”

x 36” (25% smaller) 1,488 fpm

• .18”

∆p 99.8% Wind Driven Rain Effectiveness (50 mph)

• Cost 2.3

Sizing Example

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Traditional style, allows rain penetration Wind Driven Rain Design, prevents rain penetration

Rooftop Intakes

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What About Snow?

Prevent snow infiltration

• Heated screens behind

louvres

• Reasonable pressure drop
• Relatively slow airflow – 350

FPM face velocity

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Common Accessories

Bird and insect screens prevent louvres from becoming nests Insulated blank off plates are used when future capacity is planned but yet needed Acoustic Screens

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Air Exhaust

Water Droplets Waterdrop Manifold Wetted Wall Manifold Test Unit

Air Entrained into chamber through louver

Air Flow Measurement Collection Zone Exhaust Fan “Still Air” Condition!

Standard 500-L Louvres

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Wind/Rain Machine Test Louver Wind Driven Rain plus Air Entrained Into Chamber Through Louver Air Exhaust Exhaust Fan Collection Zone Rain Water Discharge Nozzles

Std 500-L Wind Driven Rain Test

5.11 Water Rejection Wind Driven Rain

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• Rejection EffectivenessClasses

A 99% to 100% B 95% to 98.9% C 94.9% to 80% D below 80% (std. louvers)

• 3” rain/29 mph wind
• 8” rain/50 mph wind

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Std 500-L Wind Driven Rain Test

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Rear view, 29 mph wind, 3”/hr rain, 2,000 fpm intake velocity

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How Much Water Is Applied?

• 3” Per Hour Rain On 1m X 1m
• 21 Gallons Applied Over 1 Hr.

– Class A (99% or better) allows 27 fl. oz penetration – Class D (80% or worse) allows over 4 gallons – Std Louvers (60% or lower) - over 7 gallons

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1/21/2019 12 Test Conditions

• 48” x 48” size
• 15 minute intervals
• Manifold (raindrops) - 4” per

hour (3.15 gal/15 min)

• Wetted wall - .25 gpm (3.75

gallons/15 min)

• Ventilation airflow only – no

wind

• 1250 fpm max free area

velocity

Standard 500-L Louvres

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AMCA “Still Air” Water Test

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“Still Air” Test with Non-drainable Louvre

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Traditional Drainable Louvre 29 mph wind, 3”/hr rain, 1,000 fpm intake velocity

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