Service manual

2-11
T-294-01
2.5 REFRIGERATION CIRCUIT WITH THE
WATER-COOLED CONDENSER
Starting at the compressor, the suction gas is
compressed to a higher temperature and pressure.
When operating with the water-cooled condenser, the
gas flows through the discharge line into the pressure
regulator valve that is normally open. The pressure
regulator valve may restrict the flow of refrigerant to
maintainaminimumdischargepressureof5kg/cm
2
(70
psig).
Refrigerant gas then moves through the air-cooled coil
to thewater-cooled condenser. As the refrigerant flows
across the water chilled coiled tube bundle, it is cooled
to saturation temperature and exits the condenser as a
high pressure/saturated liquid.
Fromthewater-cooledcondenser,theliquidrefrigerant
continues through the filter-drier (which keeps
refrigerant clean and dry), and a heat exchanger that
increases subcooling of liquid refrigerant to the
thermostatic expansion valve. As the liquid refrigerant
passes through the orifice of the hermetic expansion
valve,someofitvaporizesintoagas(flashgas).Heatis
absorbedfromthereturnairbythebalanceoftheliquid,
causing it to vaporize in t he evaporator coil. The vapor
then flows through the stepper motor suction
modulation valve to the compressor.
Thehermetic thermostaticexpansionvalvebulb(onthe
suctionlineneartheevaporatorcoiloutlet)controlsthe
expansion valve, maintaining a constant superheat at
the coil outlet regardless of l oad conditions.
2.6 WATER-COOLED CONDENSER
Thewater-cooledcondenserisusedwhencoolingwater
is available and heating the surrounding air i s
objectionable, such as in a ship’s hold.
Thewater-cooledcondenserisoftheshellandcoiltype,
with water circulating through the cupro-nickel coil.
Therefrigerantvaporisadmittedtotheshellsideandis
condensed on the outer surface of the coil.
2.6.1 Water--Cooled Condenser with Water
Pressure Switch (WP)
For operation of t he refrigeration unit with the
water-cooled condenser, perform the follow i ng:
a. Connect the water supply line to the inlet side of
condenserandthedischargelinetotheoutletsideof
the condenser.
b. Maintain a flowrate of11to26 litersperminute(3
to 7gallons perminute). Thewaterpressureswitch
will open to de-energize the condenser fan relay,
unless overridden by the out-of-range lockout
feature (if so equipped). The condenser fan motor
will stop and will remain stopped until the water
pressure switch closes, or it is overridden by the
out-of-range lockout feature (if so equipped).
The refrigeration unit operating with the water-cooled
condenserwillperformasoutlinedinsection4.4except
that the condenser fan motor may be stopped in all
modes.
Toshift toair-cooledcondenseroperation, performthe
following:
Disconnect the water supply and the discharge line to
the water-cooled condenser. The refrigeration unit will
shift to air-cooled condenser operation when the water
pressure switch closes. (Refer to section 2.2.)
2.6.2 Water-Cooled Condenser with Condenser
Fan Switch (CFS) -- Optional
For operation of t he refrigeration unit with the
water-cooled condenser with (CFS), perform the
following:
a. Connect the water supply line to the inlet side of
condenserandthedischargelinetotheoutletsideof
the condenser.
b. Maintain a flow rate of 11 to 26 l pm (3 to 7 gpm).
c. Set CFS switch to position ”O” when water is
supplied to the water-cooled condenser. This will
de-energizethecondenserfanrelay. Thecondenser
fan motor will stop and will remain stopped until
the CFS switch is set to position ”1.”
The refrigeration unit operating with the water-cooled
condenser and the CFS switch in position ”O,” will
perform as outlined in section 4.4 except that the
condenser fan motor is stopped in all modes.
WARNING
Whenwater flowis below11 lpm(3 gpm)or
when water-cooled operation is not in use,
the CFS switch MUST be setto position ”1”
or the unit will not operate properly.
Toshifttoair-cooledcondenseroperation,performthe
following:
Turn the unit OFF and set the CFS switch to position
”1.”Disconnectthewatersupplyandthe dischargeline
to the water-cooled condenser. The unit should now
perform as outlined in section 4. 4.