IM 178 / Page 17
The unit is provided with a 1.5" male NPT condensate drain
connection. Refer to certified drawings for the exact location.
The unit and drain pan must be level side to side and a P-trap
must be installed for proper drainage.
RDS units may have positive or negative pressure sec-
tions. It is recommended that traps be used in both cases
with care given to negative pressure sections. In Figure 12,
dimension A should be a minimum of 8" (203 mm). As a
conservative measure to prevent the cabinet static pressure
from blowing or drawing the water out of the trap and causing
air leakage, dimension A should be two times the maximum
static pressure encountered in the coil section in inches w.c.
Drainage of condensate directly onto the roof may be
acceptable; refer to local codes. It is recommended that a
small drip pad of either stone, mortar, wood or metal be
provided to protect the roof against possible damage.
If condensate is to be piped into the building drainage
system, the drain line should be pitched away from the unit
at a minimum of
1
⁄
8
" per foot. The drain line must penetrate the
roof external to the unit. Refer to local codes for additional
Condensate Drain Connection
requirements. Sealed drain lines require venting to assure
proper condensate flow.
Where the cooling coils have intermediate condensate
pans on the face of the evaporator coil, copper tubes near
both ends of the coil provide drainage to the main drain pan.
Check that the copper tubes are in place and open before the
unit is put into operation.
Because drain pans in any air conditioning unit will have
some moisture in them, algae, etc. will grow. Periodic clean-
ing is necessary to prevent this buildup from plugging the
drain and causing the drain pan to overflow. Also, the drain
pans should be kept clean to prevent the spread of disease.
Cleaning should be performed by qualified personnel.
Biological hazard. May cause disease.
Cleaning should be performed by qualified personnel.
Figure 12. Condensate drain connection
}
4" (102 mm)
Minimum
Minimize This
Dimension
Note: Drain line
must not
be run higher
than this level.
“A”
[8" (203 mm) Min.
or 2 x “P”]
Copper Tube
(one each end of coil)
See View “A”
View A
Drain Pan
Static Pressure “P”
(in. w.c.)
RDS units that ship from the factory with DX coils installed do
not include refrigerant piping or refrigerant controls. The coil
assembly is ready for field connections at the distributors
and at the suction headers. Piping kits that provide the
necessary liquid and hot gas piping and control components
are available for field installation.
Field installed refrigerant piping may exit the unit cabinet
at one of the following locations:
1. Through the floor of the unit.
2. Through the discharge and bulkhead of the unit.
3. Through a cabinet door near the DX coil that is not
required for service areas.
Caution: For any of the above cabinet penetrations, the hole
must be tightly sealed to prevent water or air leakage.
In preparing for field piping, the plastic plugs on the
distributor must be removed and the copper caps at the
suction header connections must be unsweated.
Piping design, sizing and installation information pre-
sented in the “ASHRAE Handbooks” should be followed in
the design and installation of interconnecting piping. The
RDS and condensing units are intended to be set at the same
elevation as close as possible to each other to minimize
Field Refrigerant Piping and Charging of DX Coils
The pounds of refrigerant in the system may exceed the
capacity of the condenser, depending on the amount of
refrigerant in the liquid lines between the DX coil and the
condensing unit. Refer to condenser manufacturer for
information about refrigerant capacity. Suitable means of
containing the refrigerant is required.
refrigerant pressure drop. The piping must be designed and
installed to prevent liquid refrigerant carryover to the com-
pressor and to assure a continuous return of compressor oil
from the system.
On systems with optional hot gas bypass, it is important
that the bypass solenoid valve be located at the condens-
ing unit and not at the DX coil to prevent liquid return and
damage to the compressor.
!
WARNING
!
CAUTION
!
WARNING
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