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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.'
'
.,R/*,"%?(4@"''(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.''In]line'dampers'must'be'installed'so'that'the'exhaust'air'flow'will'open'the'
butterfly'blades.'''
'
For'N0'*M0,$(/%31)$%'1,#,'the'damper'must'be'installed'so'that'the'hinge'between'the'two'butterfly'blades'is'S"'$*)(/—the'hinge'pin'
must'point'up'and'down.''Otherwise,'because'of'gravity,'the'damper’s'blades'will'not'close'and'the'damper'will'not'prevent'
backdrafts.'''
'
For'S"'$*)(/%31)$%'1,#,'the'in]line'damper’s'hinge'will'be'N0'*M0,$(/'(sideways),'which'is'correct'for'vertical'duct'runs.''Gravity'will'help'
close'the'damper'blades'after'each'use.''
'
For'1@E('3%#/(,$"3%31)$%'1,#,'the'in]line'damper’s'hinge'must'point'to'the'top'and'bottom'sides'of'the'duct.''In'his'position,'gravity'
will'help'close'the'damper'blades'after'each'use.''Otherwise,'because'of'gravity,'the'damper’s'blades'will'not'close'and'the'damper'
will'not'prevent'backdrafts.'''
'
T< 700G%=(@#%(,3%I(//%=(@#%
The'roof'cap'or'wall'cap'is'the'termination'point'of'the'venting'system'that'allows'the'exhaust'air'to'exit'to'the'outdoors.''All'sections'
of'this'fitting'must'have'an'equal'or'greater'air'path'area'than'the'ventilator’s'discharge'port.'''If'any'section'of'the'roof'cap'or'wall'
cap'is'smaller'than'the'ventilator’s'discharge'port,'the'entire'ventilation'system'will'lose'efficiency'and'the'restriction'will'cause'
increased'static'pressure'and'decrease'performance.'
'
.5&678298:''Even'though'the'intake'side'of'the'roof'cap'or'wall'cap'may'be'properly'sized,'roof'caps'or'wall'caps'with'built]in'
dampers'must'be'made'so'that'when'the'damper'is'fully'open,'the'actual'open'area'of'the'final'air'path'is'equal'to'or'greater'than'the'
discharge'port'of'the'ventilator.''Any'undersized'portion'of'a'roof'cap'or'wall'cap'will'cause'excessive'static'pressure'that'may'result'in'
rattling,'vibration'and'air'buffeting'noises,'as'well'as'inadequate'ventilation.'''
%
?0%90$'use'“goose]neck'style”'caps'as'they'significantly'restrict'natural,'heated'air]flow.''?0%90$'use'caps'with'dampers'for'BBQ'
Hoods.%
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The'air'exit'opening'on'the'roof'cap'used'needs'to'be'at'or'above'78.5'square'inches.'See'illustrations'above.'9"S"''use'a'roof'cap'like'
the'one'shown'in'Figure'1.'Instead'use'a'style'similar'to'the'one'shown'in'Figure'2.''
'
U< 2$$()N*,-%?1)$%$0%V01#"%A'(4"E0'W%
The'ventilation'system'should'be'attached'to'the'framework'in'such'a'manner'that'the'weight'of'the'duct'and'fittings'is'supported'
with'no'stress'on'the'duct'joints,'fittings'or'on'the'ventilator.''All'ducting'should'be'attached'so'as'to'avoid'any'possible'duct'vibration'
from'being'transferred'to'the'house’s'framework.'
%
X< V003#%E*$N%6@$*0,(/%80@%0'%!()W%+",$*,-'
.5&678298:''On'all'models,'the'open'holes/slots'around'the'unused'venting'port'5YL8%!C%LC2PC?%E*$N%2/14*,14%A0*/%5"$(/%?1)$%
8(@".''Otherwise,'exhaust'air'and'smoke'will'be'vented'through'the'unused'Vent'Knockout’s'holes/slots.''Y9YLC?%&678L%LV6YP?%!C%
82&C?%!CA67C%8VC%729ZC%V66?%.L%56Y98C?%86%8VC%I2PP%67%=2!.9C8.'