>9.,&-/?$&)*#&@/,,/*:&K/L$+&(Continued)&
>9.,&29*+&N&O$*:,M&
a. Configure'the'ventilation'duct'run'to'be'as'short'and'as'direct'to'the'outside'as'possible.''Minimize'
the'number'of'elbows'and'transition'fittings'used.''Complex'or'long'runs'should'be'reviewed'by'a'
qualified'installer.'
'
b. No'portion'of'the'ducting'should'be'run'so'that'the'exhaust'air'flows'downward.''Since'exhaust'heat'
rises,'forcing'the'air'to'flow'downward'will'cause'increased'static'pressure.''As'previously'mentioned,'
improperly'installed'duct'pipe'will'cause'excessive'static'pressure'(air'resistance),'that'may'result'in'
rattling,'vibration'and'air'buffeting'noises,'as'well'as'inadequate'ventilation.'
'
c. Duct'runs'for'390CFM'ventilator'models'should'not'exceed'20'linear'feet'with'two'90-degree'elbows'
(or'four'45-degree'elbows),'a'damper'and'a'roof'or'wall'cap.''Longer'runs'or'additional'elbows'will'
result'in'decreased'ventilation'performance.'''Each'90-degree'elbow'is'the'equivalent'of'8'linear'feet'
of'duct'pipe;'each'45-degree'elbow'is'equivalent'to'4'linear'feet'of'duct'pipe.'
'
d. Always'run'ventilator'ducts'to'the'outdoors.''DO'NOT'terminate'a'duct'into'an'attic,'basement,'
garage,'crawl'space'under'a'house,'a'chimney,'other'ducting'or'an'enclosed'room.'
'
'
P8 >)Q?$(+&
0!-1234536''DO'NOT'USE'SCREWS'TO'ATTACH'ANY'TYPE'OF'DAMPER'AS'THE'SCREWS'MAY'BLOCK'THE'
DAMPER'BLADES.'
'
0!-1234536''DO'NOT'USE'MORE'THAN'ONE'DAMPER'IN'THE'VENTILATION'SYSTEM.''513B:''Many'styles'of'
roof'caps'and'wall'caps'have'built-in'dampers.''See'2""F&;)?+&)*#&H)%%&;)?+'section'for'more'detail.'
&
Always'use'carefully'crafted,'tightly'wrapped'Aluminum'Foil'Metal'Duct'Tape'on'all'connections'and'physically'
view'and'test'the'damper'blades'to'make'certain'they'are'opening'and'closing'correctly.''Make'sure'that'the'
damper'blades'do'not'touch'the'duct'walls'and'that'there'is'no'debris'blocking'the'free'movement'of'the'
damper'mechanism.''Common'things'to'look'for'include'screws'protruding'into'the'blade’s'path,'overspray'of'
paint,'plaster'and'insulation.''If'using'rectangular'duct,'be'sure'that'all'four'sides'of'the'duct'are'on'the'
outside'of'the'damper’s'start'collar'or'frame.'
&
JRS;@!&!"#$%+&
390CFM'models'have'a'7"'round'duct.'''
DO'NOT'USE'SCREWS'TO'ATTACH'THE'DUCT'TO'THE'DAMPER'FRAME'AS'THE'SCREWS'MAY'BLOCK'
THE'DAMPER'BLADE.''ALWAYS'use'Aluminum'Foil'Metal'Duct'Tape'on'all'connections'and'physically'
view'the'damper'blade'to'make'certain'it'is'operating'correctly.''On'ventilator'installations'designed'
to'recirculate'the'exhaust'air'back'into'the'kitchen,'be'sure'to'remove'the'aluminum'damper'blade'
before'attaching'the'duct'to'the'damper'frame.'
'
>)Q?$(&/*&2""F&;)?&"(&H)%%&;)?&
In'ventilation'systems'utilizing'a'roof'cap'or'wall'cap'with'a'built-in'damper,'do'not'install'an'
additional'in-line'damper.'Two'dampers'are'unnecessary'and'will'cause'increased'static'pressure'(air'
resistance),'that'may'result'in'rattling,'vibration'and'air'buffeting'noises,'as'well'as'inadequate'
ventilation.'
&
0*<%/*$&>)Q?$('(for'ventilation'systems'utilizing'a'roof'cap'or'wall'cap'without'a'built-in'damper)&
In'cold'weather'areas,'installing'an'“in-line”'damper'may'be'the'preferred'type'of'installation.''This'is'
because'in-line'dampers'installed'just'above'the'perimeter'of'the'heated'space'(the'ceiling)'will'
reduce'the'amount'of'cold'air'traveling'down'the'duct'into'the'heated'space'and'into'the'kitchen'
through'the'ventilator.'