140.010-IOM (NOV 2019)
Page 27
IDSC EVAPORATIVE CONDENSERS
OPERATION
NOTICE
Immersion basin heaters do not prevent the residual
water in the pump and recirculated water piping from
freezing. These components must be heat traced and
insulated.
EXTENDED SHUTDOWN
When a unit needs to be shut down for an extended pe
-
riod of time, perform the following steps:
•
Disconnect, lock out, and tag any electrical motors for
fans and pumps
•
Drain the cold water basin and ensure that the make-
up water line is shut off
•
Draining all water from the units minimizes the possible
risk of biological contamination during the shut-down
period
•
Flush cold water basin and clean, with strainers in
place
•
Clean and replace the strainers
• Drain all exposed water piping
•
Leave cold water basin drain line open
•
Heat trace and insulate all exposed piping, water distri
-
bution pump, and piping up to overflow level
•
Clean all dirt and debris from the exterior and interior
of the units
•
Clean and replace inlet louvers
•
It is recommended to cover the fan discharge outlets to
prevent the ingress of dirt and debris
• During periods of extended shutdown or prolonged
storage all impellers must be rotated each month at
least 10 revolutions
CAPACITY CONTROL
NORMAL OPERATION
The EC motor option incorporates fan speed control within
the motor’s electronic controller without the need for any
external VFDs. Fan cycling requires the use of contactors,
controlled through a feed from either the PLC or a pres
-
sure/temperature sensor. Fan cycling is not recommended
for evaporative units due to the elevated power input
requirements associated with fan cycling versus variable
fan speed technology. When cycling individuals fan off and
on there is the possibility that moist air could condense
and freeze on the impellers or fan orifices of the motors
which are not running. As such, during these low ambi
-
ent conditions all fan motors must be cycled to prevent
extended idle times for each motor. The fan cycling option
not recommended by FRICK.
Automatic control of the motors using an internal set point
on the GMM, external analogue input (0 VDC to 10 VDC)
or external communication protocol (Modbus, Profibus)
is the most energy efficient option available, and is the
methodology recommended by FRICK.
COLD WEATHER OPERATION
When operating the IDSC unit at low ambient tempera
-
tures above freezing, the control logic matches that of
the summer operation. The water distribution pump runs
continuously during operation, and as the condensing
temperature for evaporative condensers decreases or
increases, you must increase or decrease the fan motor
speed respectively.
However, when ambient conditions drop below freezing,
additional precautionary measures are required to pre
-
vent the potential for damage to the equipment from ice
formation.
NOTICE
While spring and fall daytime ambient temperatures
may be above freezing there is always the possibility
that night time temperatures can drop below freez-
ing. Operators of this equipment must take this into
consideration.
The IDSC EC (Electronically Commutated) motors offer the
best solution for fan motor speed control. All EC motors
are provided with a GMM controller which modulate the
motor speeds dependent on the leaving fluid temperature
or condensation temperature setpoint. It is also possible to
provide a 0 V to 10 V or 4 mA to 20 mA feed to the con
-
troller to regulate motor speed. With this controller, one
every cell, all motors change speed collectively.
NOTICE
Varying the recirculated water flow rate across the
heat exchange coil is not suggested as a means of
capacity control in low load or low ambient condi-
tions, because this may increase scale buildup on the
coil surface.