14
5-572.10
UNIT INSTALLATION
Figure 14.1 - Cooling Section (DX Coil Shown)
Optional double
wall construction
DX single circuit (shown) and
dual circuit coils available
Optional Factory
Installed
DX or Chilled
Water coil.
Fin spacings
of 6,8,10,12
or 14 fins per inch
Adjustable
mounting bracket
for 2,3,4 and 6 row
coils
Full coverage
3-way sloping
409 stainless
steel drain pan
1” stubbed drain
connection
Right or left hand coil
header access to match
gas controls
Condensate Drain Pan Trap
The condensate drain line needs to include a P-trap
immediately downstream of the connection to the unit. This
trap should extend at least two inches below the connection
to prevent air pressure from forcing air into the unit. The
trap should be primed with a water/glycol solution to prevent
freezing.
1. Inspect the refrigerant distributor and verify that the nozzle
is in place.
2. All field brazing welding should be performed using high
quality materials and an inert gas purge (such as nitrogen)
to reduce oxidation of the internal surface of the coil.
3. The use of filter-dryers in the system piping is
recommended along with a sight glass that has a moisture
indicator.
4. Connect the suction line and suction connection.
5. Install the expansion valve (by others). Follow the
expansion valve manufacturer's recommendations for
installation to avoid damaging the valve.
6. Connect the liquid line to the expansion valve. Pressurize
the coil, expansion valve assembly and suction connection
to 100 psig with dry nitrogen or other suitable gas. The coil
should be left pressurized for a minimum of 10 minutes.
7. If the coil holds pressure, the installation can be considered
leak free. If the pressure drops by 5 psi or less,
repressurize the coil and wait another 10 minutes. If the
pressure drops again, there are more than likely one or
more small leaks, which should be located and repaired.
Pressure losses greater than 5 psi would indicate a larger
leak, which should be isolated and repaired. Be sure to
check valves and fittings as potential sites for leakage or
bleed.
8. Use a vacuum pump to evacuate the coil and any
interconnecting piping that has been open to atmosphere.
Measure the vacuum in the piping using a micron gauge
located as far from the pump as possible (the vacuum
at the pump will be greater than the rest of the system).
Evacuate the coil to 500 microns or less then close the
valve between the pump and the system. If the vacuum
holds to 500 microns or less for one minute, the system
SUCTION LINE
EXPANSION
VALVE
(BY OTHERS)
REMOTE
SENSING BULB
STRAPS
SUCTION CONNECTION
COIL
SUCTION HEADER
DISTRIBUTOR
EQUALIZER LINE
NOZZLE
LIQUID LINE
Figure 14.2 - General DX Piping
Direct Expansion (DX) Piping
The refrigerant lines should be insulated to prevent warming
or cooling of the refrigerant. If the suction line is allowed to
be cooled, liquid will condense in the line and can severely
damage the compressor. If the liquid line is warmed, the
refrigerant can "flash" into a gas. This will cause erratic
operation of the expansion device and impair the heat transfer
ability of the cooling coil. Long runs of piping need to be
periodically supported to prevent excess vibration that can
damage the piping and joints. It is recommended to provide
dampening supports at intervals of length equivalent to 15 tube
diameters.
Cooling Coil Units
Units with a cooling section (Model Digit 2=C or P) can be
provided with a factory installed direct expansion (DX) coil, a
chilled water (water or water/glycol mixtures) coil, or the coil
can be field supplied and installed by others. For units equipped
with a factory installed cooling coil (Model Digit 23=1), refer to
the packing slip to determine the coil type provided.
The section includes a full coverage, 3-way sloping stainless
steel drain pan to remove condensate from coil headers and
piping components. Insulation is standard on outdoor units
and optional on indoor units. The cabinet includes two doors,
a removable upper door for service access to the coil once the
plumbing has been installed and a lower door which includes
a 1" drain connection to the exterior of the cabinet. Field
connections for coil inlet and outlet piping can be made through
the cabinet corner post or back of the unit. The cooling section
duct transition includes 1-1/2" flanges for fastening the sides
of the coil. The bottom duct transition is angled to remove any
condensation that may be entrained in the supply air stream.
For field supplied coils, do not exceed the maximum coil
dimensions listed in Literature 82-135. If the coil supplied is
smaller than the listed dimensions, field supplied blank off
plates are required to prevent air bypass around the coil. The
coil is supported by two 14 gauge support rails which contain
mounting provisions for fastening 4", 5", 6", 7.5", 8.5", and 10"
deep coils.
