Heatcraft Refrigeration Products II - Manual (Page 24)

24
Beacon II Controller
Evaporator Fans Shut Off
In some installations, it is desirable to shut off the evaporator fans periodically. This is easily accomplished on
Beacon II by wiring a single pole, single throw switch (SPST) between the terminals marked “SERVICE” and
“COM” on the Beacon II board. Closing this switch will cause the system to pumpdown and shut off. Air
defrost fan motors must be wired through the fan relay on the Beacon II board for this to be effective on air
defrost systems. The entire system will be shut off and remain off until the SPST switch is opened.
Air defrost evaporator fans are setup to run constantly. If there is a need to shut down the evaporator fans on
an air defrost system, it can be accomplished by wiring the evaporator fan motor or evaporator fan motor
contactor through the fan relay on the Beacon II board. When this is done and the air defrost system is placed
in “SERVICE” the evaporator fans will shut off when the system is in pumpdown.
Power Failures
In the event of a power failure, Beacon II will automatically close the expansion valve to prevent refrigerant
from migrating throughout the system. After power returns, with 24 VAC at the board, the system will restart in
the cooling mode after the 4-minute hold off period.
Spare Sensor Terminals
Beacon II provides a set of input terminals for customers who may want to monitor an additional temperature
or items such as Product Temperature. This input terminal requires a signal from a thermistor which meets the
temperature/resistance values in Table 4 below.
If a product temperature simulator is used, it must meet the resistance/temperature specification listed in
Table 4 below. The temperature range for this input is -30°F to 140°F. Sensors on the Beacon II system, as
supplied, will not simulate product temperature.
This input can be monitored on the LED display by using the “MONITOR” button and scrolling the SPt . The
values displayed will be the temperature of the spare sensor.
Checking Sensors
DO NOT REMOVE SENSORS FROM EVAPORATOR FOR CHECKING.
Use the monitor button to display the value the sensors are reading on the LED (suction temp. SCt, defrost
temp. dFt or room temp.). Compare this value to the measured value with a thermometer at each of these
points. If they do not match, change the sensor.
or
The sensors can be checked for their proper operation by placing it in a cup of ice water. Stir the ice water
and measure the resistance of the sensor. At 32°F the resistance should be 32,650 ohms. If it is higher or
lower by 5,000 ohms approximately, the sensor should be replaced.
Resistance of sensors at various temperatures.
Table 4. Resistance / Temperature Specification
Temperature ° F Ohms Temperature ° F Ohms
104 5,320 32 32,650
86 8,060 23 42,330
77 10,000 14 55,330
68 12,490 5 72,950
59 15,710 -4 97,070
50 19,900 -13 130,410
41 25,400 -22 176,960