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Application Guide / FLEXAIR-AGU-1505-E
UNIT WITH NO EXHAUST AIR OPTION
1 → 2 : ESP (external static pressure) given in eLencal (LENNOX
units selection tool) corresponds to the static pressure between
inlet and outlet of the unit and includes all options and accessories
delivered with the unit with the exception of the ductwork. This
external static pressure will be used to push the air through the
supply and the return ductwork installed on site.
ESP =
Supply duct pressure drop + return duct pressure drop
Example :
With an eLencal ESP = 350 Pa and a return ductwork pressure
drop of 150 Pa ▬► Remaining available static pressure for the
supply ductwork = 200 Pa
In any case, on a basic unit, the return ductwork pressure drop
should be lower than 150 Pa.
The airfl ow is usually set during start up for a given fresh air
rate. During normal operation the fresh air ratio will change and
eventually the unit will go to full fresh air during free cooling
operation. If the pressure drop in the return ductwork is high,
the fan may trip on over current protection when it operates with
full fresh air where the pressure drop is much lower.
If the return ductwork pressure drop is higher than 150 Pa :
• Select an extraction roofcurb which will include an extraction
fan and the appropriate drive kit for the given airfl ow and
pressure drop.
• FLEXAIR with eDRIVE includes constant airfl ow operation
that can control and limit the airfl ow as the pressure drop
reduces.
Building air tightness Low air tightness
Fresh air & Free cooling
Medium fresh air rate
Free cooling possible
Pressure drop in the
return ductwork
Medium < 150 Pa
Building pressure control NO control
Typical applications
Existing hypermarkets and supermarkets
(old buildings with high leakage rates)
GRAVITY EXHAUST DAMPER
1 → 2: ESP “Supply” in eLencal
Gravity exhaust dampers are used to relief pressure when outside
air is being introduced in a building with good air tightness.
Building air tightness Medium
Fresh air & Free cooling
High fresh air rate
Free cooling
Pressure drop in the
return ductwork
Low < 50 Pa
Building pressure control Low control
Typical applications Warehouses
2- OPTIONS DESCRIPTION
2.9- EXTRACTION OPTIONS
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