Greenheck ERCH - Energy Recovery Unit with Packaged DX (468151) - Manual (Page 5)

5
Energy Recovery Unit with Packaged DX
Rooftop units require curbs to be mounted first . The duct
connections must be located so they will be clear of structural
members of the building .
1. Factory Supplied Roof Curbs
Roof curbs are Model GKD, which are shipped in a knockdown
kit (includes duct adapter) and require field assembly (by others) .
Assembly instructions are included with the curb .
2. Install Curb
Locate curb over roof opening and fasten in place . (Refer
to Recommended Roof Openings) . Check that the diagonal
dimensions are within ±1/8 inch of each other and adjust as
necessary . For proper coil drainage and unit operation, it is
important that the installation be level . Shim as required to level .
3. Install Ductwork
Installation of all ducts should be done in accordance with
SMACNA and AMCA guidelines . Duct adapter provided to support
ducts prior to setting the unit .
4. Set the Unit
Lift unit to a point directly above the curb and duct openings .
Guide unit while lowering to align with duct openings . Roof curbs
fit inside the unit base . Make sure the unit is properly seated on
the curb and is level .
All dimensions shown are in inches . Weights are for 12 inch high curbs .
Curb Outside Dimensions
Roof curb details, including
duct location dimensions, are
available on ERCH roof curb
assembly instructions,
Part #468280.
Curb Outside Dimensions and Curb Weights (lbs)
Model L W Weight
ERCH-20 104 .88 51 310
ERCH-45 115 .75 60 .63 400
ERCH-55 129 .88 71 .5 510
ERCH-90 148 .13 90 .75 720
ROOF CURB MOUNTING
INSTALLATION CONCERNS
Unobstructed airflow to the condensing section must be maintained at all times to ensure proper operating
efficiency and capacity of the cooling system . Unit placement should allow proper airflow over the condensing
section . The unit may not operate properly and damage may occur to the system if there is coil starvation (lack of
air over condenser) or warm air recirculating back through the condensing coil . Recirculating air is caused when
the unit is placed near obstacles that can redirect exhaust air from the condensing fans, back around to the coil
inlet . Overhangs or walls near the condensing section are two examples .
Another consideration when placing the unit is prevailing wind direction . The condensing coil operation can be
significantly affected when winds are blowing continuously and directly at the condensing coil . On hot days, the
wind will help the system by providing extra flow over the coil . But on cooler days, that same wind may overcool
the refrigerant, and cause hot gas bypass to operate more frequently, causing higher operating costs . Therefore,
avoiding direct winds will provide a more stable operation of the system throughout the cooling season .
Lack of air over the coil can reduce efficiencies and affect system operation . Do not allow debris (such as leaves
and trash), to accumulate on or near the unit . Keeping debris clear of the unit will ensure minimal obstruction to
the coils, keeping efficiencies and operation closer to design . The unit typically should not operate when snow
is present . In the event this is possible, make sure all snow is clear of the coil and condensing fans prior to
operating the unit .
If more than one unit is being installed, make provisions so discharge air from either the condensing fans or
exhaust fan of the unit do not discharge towards another unit’s intake . Also, OA intake and condensing sections
should be spaced as too allow proper airflow to each unit helping ensure the units operate as intended .
When cutting only duct openings, cut opening 1 inch (25mm) larger than duct size to allow clearance for
installation . Area enclosed by roof curb must comply with clearance to combustible materials . If the roof is
constructed of combustible materials, area within the roof curb must be ventilated, left open, or covered with
non-combustible material which has an “R” value of at least 5 . If area within curb is open, higher radiated sound
levels may result .
Where the supply or warm air duct passes thru a combustible roof, a clearance of one inch must be maintained
between the outside edges of the duct and combustible material in accordance with NFPA Standard 90A .