Quantech QWC3050T-200T, Installation Operation & Maintenance

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SECTION 4 – INSTALLATION
FORM QWC3-NM1
ISSUE DATE:11/20/2020
QUANTECH
35
4
CONDENSER COOLING LIQUID SYSTEMS
For primary cooling of units, condensers are usually
piped in conjunction with a cooling tower, although in
some cases they can be cooled by well water.
Direct Pressure Control (by others)
With liquid cooled units it is necessary to control
coolant flow and/or temperature into the condenser to
maintain refrigerant pressure as constant as possible to
ensure satisfactory operation of the expansion valves.
The refrigerant pressure can either be used to control
cooling tower/dry cooler effectiveness by controlling
fans or dampers on the tower, or to control condenser
flow using a three way bypass valve.
The aim is to maintain a stable discharge pressure as
low as possible, but at least 100 PSI above suction
pressure. This can be done at a fixed value above the
highest expected suction pressure, or by also measur-
ing suction pressure and using differential control. In
either case condenser cooling liquid flow and tempera-
ture limits must also be observed.
LD12940
FIGURE 10 - DIRECT PRESSURE CONTROL
DIAGRAM
Inlet Temperature Control (by others)
For a cooling tower/dry cooler system, the simplest
forms of control are to use fan cycling, fan speed con-
trol, or air damper control, with the tower having a ther-
mostat in its sump. This will ensure stable condenser
cooling liquid temperature sensing at design conditions
and should be adjusted to ensure a condenser cooling
liquid entering temperature of not lower than 65°F
(18°C).
If these methods are not available, or a cooling tower is
not the source of cooling water, then a three way valve
recirculation system can be used with control based
on condenser inlet liquid temperature. In this case the
objective is to maintain the inlet cooling liquid tem-
perature as low as possible, although still observing the
minimum limit of 65°F (18°C).
LD12941
FIGURE 11 - INLET TEMPERATURE CONTROL
DIAGRAM