Gear Drives; Air Inlet And Wdw Dry Coil; Fan System - Capacity Control; Fan Motor Cycling - EVAPCO ATC-E Operation And Maintenance Instruction

Operation and Maintenance Instructions

Gear Drives

Induced draft units with gear drive systems require special maintenance. Please refer to the gear manufacturers recommended
maintenance instructions. These will be enclosed and shipped with the unit.
Air Inlet
Inspect the air inlet louvers (induced draft units) or fan screens (forced draft units) monthly to remove any paper, leaves or other
debris that may be blocking airflow into the unit.
WDW Dry Coil
Depending on outdoor conditions, the dry coil on the WDW should be cleaned at least twice a year. If the unit is located near trees,
construction, etc., the required cleaning may be more frequent. Per our standard unit maintenance guidelines shown on pages 8 &
9, the coil should be visually inspected monthly along with inlet louvers and inlet screens.
The best cleaning solution for the dry coil is plain water. If the coil has been maintained and cleaned at regular intervals, water is
sufficient to remove dirt and debris from the fins. Heavy build up on the exterior of the fins can be removed with a brush. If a
pressure washer is used, make sure the equipment is set to a low pressure setting and that the nozzle is set to the fan spray, not
stream, otherwise damage to the fins could result. The best method of cleaning the coil is from the inside out. Spraying water from
the outside repeatedly can cause a buildup of debris and airflow restriction.
Fan System — Capacity Control
There are several methods for capacity control of the evaporative cooling unit. Methods include: Fan motor cycling, the use of two
speed motors, and the use of variable frequency drives (VFDʼs).
Note: for the eco-ATW with Sage 2 and eco-ATWE with Sage 3 consult the manual.

Fan Motor Cycling

Fan Motor Cycling requires the use of a single stage thermostat which senses the fluid temperature (closed circuit coolers) or
condensing temperature (evaporative condensers). The contacts of the thermostat are wired in series with the fan motorʼs starter
holding coil.

Sequence of Operation for Fan Motor Cycling

Fan Motor Cycling is often found to be inadequate where the load has a wide fluctuation. In this method, there are only two stable
levels of performance: 100% of capacity when the fan is on, and approximately 10% of capacity when the fan is off. Please note
that rapid cycling of the fan motors can cause the fan motor to overheat. Controls should be set to only allow a maximum of six
start/stop cycles per hour. The recirculation pump may not be used as a means of capacity control and should not be cycled
frequently. Excessive cycling can lead to scale build-up, resulting in reduced wet and dry performance.
Two Speed Motors
The use of a two-speed motor provides an additional step of capacity control when used with the fan cycling method. The low
speed of the motor will provide approximately 60% of full speed capacity.
Two-speed capacity control systems require not only a two-speed motor, but also a two-stage thermostat and the proper two-speed
motor starter. The most common two-speed motor is a single winding type. This is also known as a consequent pole design. Two-speed
two-winding motors are also available. All multi-speed motors used in evaporative cooling units should be variable torque design.
It is important to note that when two-speed motors are to be used, the motor starter controls must be equipped with a decelerating
time delay relay. The time delay should be a minimum of 30 seconds when switching from high speed to low speed.
14