D-EIMWC00804-14EN
Centrifugal Chillers
17
CAUTION
Freeze Notice: Neither the evaporator nor the condenser is self-draining;
both must be blown out to help avoid damage from freezing.
The piping should also include thermometers at the inlet and outlet connections and air vents at
the high points.
The water heads can be interchanged (end for end) so that the water connections can be made
at either end of the unit. If this is done, new head gaskets must be used and control sensors
relocated.
In cases where the water pump noise can be objectionable, vibration isolation sections are
recommended at both the inlet and outlet of the pump. In most cases, it will not be necessary
to provide vibration eliminator sections in the condenser inlet and outlet water lines. But they
can be required where noise and vibration are critical.
Cooling Towers
The condenser water flow rate must be checked to be sure that it conforms to the system
design. Some form of temperature control is also required if an uncontrolled tower can supply
water below about 65
°
F (18
°
C). If tower fan control is not adequate, a tower bypass valve is
recommended. Unless the system and chiller unit are specifically for condenser bypass or
variable condenser flow is not recommended since low condenser flow rates can cause
unstable operation and excessive tube fouling.
The condenser water pumps must cycle on and off with the unit. See Figure 15, Field Wiring
Diagram on page 33 for wiring details.
Tower water treatment is essential for continued efficient and reliable unit operation. If not
available in-house, competent water treatment specialists can be contracted.
Heat Recovery Chillers
DHSC heat recovery chillers control the chilled water leaving temperature. The cooling load
determines compressor loading and unloading, the same as in a conventional chiller. A heat
recovery chiller’s control algorithms are identical to a conventional cooling-only chiller.
The temperature of the hot water being supplied from the recovery condenser to the heating
load is established by manipulating the cooling tower water temperature. The 3-way cooling
tower bypass valve is controlled by the heating water inlet temperature to the recovery bundle
of the condenser. Based on the signal the 3-way valve gets from the heating hot water sensor,
it will bypass sufficient water around the tower to force the tower condenser water loop high
enough for the recovery bundle to produce the desired hot water temperature.
The chilled water and its control system do not “know” that the condensing pressure and
condenser water temperatures are being regulated in this manner.
