GeneralAire DH95 Dehumidifier - Manual (Page 3)

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• Connecting to Existing HVAC Systems: For proper operation, connecting to existing air handler and duct
systems requires the fans of each system to be interlocked utilizing the low voltage interlock method provided
in the DH95 low voltage connection diagram. Refer to low voltage connection diagram in this document and
on the unit.
C. Installation in a Basement or Crawl Space with an Existing Forced Air HVAC System
(Whole House Dehumidification)
If the structure in which the DH95 System is to be installed has an existing forced air HVAC system, utilize the
HVAC system to make the DH95 System installation easier and provide better system performance.
Basement or Crawl Space Installation: Install a separate 10” return for the DH95 in a central area of the
structure or if the return ducting is adequate tap into the existing return duct system near the return air grill. Duct
the supply of the DH95 System to the return ducting of the existing HVAC system. The fan interlock provision
must be utilized for proper system performance.
D. Installation in an Attic with an Existing Forced Air HVAC System (Whole House
Dehumidification)
ALWAYS install a secondary drain pan with a drain or float interrupt for condensation under the DH95
in an attic to prevent condensate overflow that may drip down damaging the ceiling or living space
below.
Install a separate 10” return for the DH95 in a central area of the structure or if the return ducting is
adequate tap into the existing return duct system near the return air grill. Duct the supply of the DH95
System to the return ducting of the existing HVAC system. The fan interlock provision must be utilized
for proper system performance.
E. Installation in a Structure with Two Forced Air HVAC Systems (Whole House
Dehumidification)
Attach the DH95 return to an independent return from the upper level. Attach the DH95 supply to the
return of the basement HVAC system. This will promote circulation of air through the whole structure
from the upper level to the lower level through the DH95. If the DH95 is not connected to both HVAC
systems, it may not control the humidity of the entire structure. The fan interlock provision should be
connected to the lower, ducted, HVAC system and must be utilized for proper system performance.
F. Installation in a Structure with No Existing Forced Air HVAC System (Whole House
Dehumidification)
When installing the DH95 in a structure that does not have a forced air HVAC system, a single return for the DH95
should be installed in central open area of the structure.
DO NOT locate the return in a bathroom or a kitchen.
The supply of the DH95 should be located in the remote areas of the structure (such as bedrooms, den, etc.). By
ducting this way, the air inside the structure will circulate through the DH95 to be filtered and dehumidified. 5”
diameter duct is recommended for branches to the bedrooms, 6” diameter duct is recommended for branches to
larger areas.
G. Installation in a Sealed Crawl Space or Sealed Attic (Spot Dehumidification)
When installing the DH95 in sealed crawlspace or sealed attic, a single return for the DH95 should be installed in
central open area of the structure. If the area is open without partitions return ducting is not necessary. Supply
ducting is recommended to enhance the performance of the system, a minimum length of supply duct, 3’ to 6’
will aid in air distribution. If the area(s) being served are divided by walls or partitions, a supply and return duct
system is recommended. In all cases sound duct design practices must be followed such as those provided in
ACCA manual “D”, or ASHRAE’s “Fundamentals of Air System Design”.