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INSTALLATION - COOLING COIL UNITS
Cooling Coil Units
Models with a cooling section can be provided with either a
factory installed direct expansion (DX) evaporator, a chilled
fluid (for use with water, ethylene glycol, or propylene glycol
fluids) coil, or the coil can be field supplied and installed by
others. For units equipped with a factory installed cooling coil
(Digit 23 = 1), refer to the packing slip to determine the coil type
provided.
The cooling section includes a full coverage, 3-way sloping
409 stainless steel drain pan to remove condensate from coil
headers, thermal expansion valves, and refrigerant piping.
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 factory supplied 1"
stubbed 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. The dimensions listed
are for the maximum coil dimensions. 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.
Figure 18.1 - Cooling Section
Optional double
DX single circuit (shown) and
wall construction
dual circuit coils available
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.
18
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
5-594.10
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.
Figure 18.2 - General DX Piping
SUCTION HEADER
DISTRIBUTOR
EQUALIZER LINE
LIQUID LINE
NOZZLE
EXPANSION
VALVE
(BY OTHERS)
SUCTION LINE
STRAPS
REMOTE
SENSING BULB
1. Inspect the refrigerant distributor and verify that the nozzle
is in place.
2. All field brazing and 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. For DX coils, 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
is ready to be charged or refrigerant pumped down in
another portion of the system can be opened to the coil.
A steady rise in microns would indicate that moisture is still
present and that the coil should be further vacuumed until
the moisture has been removed.
COIL
SUCTION CONNECTION
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