Product manual

IOMM ACR/AGR-1 9
9. If the unit is used as a replacement chiller on a previously existing piping system, flush the
system thoroughly before unit installation. Regular water analysis and chemical water treatment
for the evaporator loop is recommended immediately at equipment start-up.
10. The total water volume in the system should be sufficient to prevent frequent “on-off” cycling.
Turnover rate should not be less than 15 minutes for normal variable cooling loads. Turnover rate
for process cooling or a constant load, should not be less than 6 minutes.
11. When glycol is added to the water system for freeze protection, the refrigerant suction pressure
will be lower, cooling performance less, and water side pressure drop greater. If the percentage of
glycol is high, or if propylene is used instead of ethylene glycol, the added pressure drop and
loss of performance could be substantial. Reset the freezestat and low leaving water alarm
temperatures. The freezestat is factory set as follows:
• UNT Control; Low Water Temp=38°F, Low Press=54psig
• MicroTech Control; Low Water Remp=36°F, Low Press=54psig
Reset the freezestat setting to approximately 4 to 5 degrees F (2.3 to 2.8 degrees C) below the
leaving chilled water setpoint temperature. See the section titled “Glycol Solutions” for additional
information concerning glycol.
12. Perform a preliminary leak check before insulating the piping and filling the system.
13. Piping insulation should include a vapor barrier to prevent condensation and possible damage to
the building structure.
Figure 5, Typical Field Evaporator Water Piping
Flow Switch
Mount a water flow switch in either the leaving water line to shut down the unit when water flow is
interrupted. A flow switch is a safety control and should never be used to cycle a unit. The unit
control circuit is provided with a remote start/stop feature.
A flow switch is available from McQuay (part number 017503300). It is a “paddle” type switch and
adaptable to any pipe size from 3” (76mm) to 8” (203mm) nominal. Certain minimum flow rates are
required to close the switch and are listed in Table 5. Installation should be as shown in Figure 6.
Connect the normally open contacts of the flow switch in the unit control center at terminals 5 and 6.
There is also a set of normally closed contacts on the switch that can be used for an indicator light or
an alarm to indicate when a “no flow” condition exists. Freeze protect any flow switch that is installed
outdoors. Differential pressure switches are not recommended for outdoor installation.