Mammoth 2 to 6 Tons: High Efficiency, Superior IAQ Single Circuit Vertical (B-Vintage) - Manual (Page 6)

6
MAMM-WSHP-IOM-1BA (February 2012)
Ductwork and Attenuation
Discharge ductwork is normally used with B-vintage
single circuit units. Return air ductwork may also be
required.
Discharge ductwork should include a non-insulated
transition from the unit connection to a flexible
connector at the full duct size, a short run of duct and
an elbow internally lined with insulation but without
turning vanes. The main duct tees into branch circuits
with discharge diffusers.
Return air is typically brought in through a grille in a
mechanical closet door. The unit should be located
ninety degrees from the door return to eliminate any
“line of sight”. Return air can be brought in through the
grille and ducted to the unit.
Return ducting is facilitated through use of a filter rack
that is designed to accept return air ducting. Return
ducting will likely increase the required width of the
closet.
Outside air may be required for ventilation. The
temperature of the ventilation air must be controlled so
that the mixture of outside air and return air entering
the unit is within application limits. It is typical to close
off the ventilation air system during unoccupied periods
(i.e. night setback).
The ventilation air system is typically a separate
building subsystem with distribution ductwork. Simple
introduction of the outside air into each return air
plenum chamber reasonably close to the unit air inlet is
recommended. Do not duct outside air directly to the
unit inlet. Provide sufficient distance for the thorough
mixing of outside and return air.
Ventilation Air