Heatcraft Refrigeration Products BEACON II H-IM-79E, Installation And Operation Manual

21

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 four-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 1 on page 22. 

If a product temperature simulator is used it must meet 
the resistance/temperature specification listed in Table 
1. The temperature range for this input is –30°F to 140°F. 
Sensors on the Beacon system, as supplied, will not 
simulate product temperature.

This input can be monitored on the LED display by using 
the “

MONITOR

” button and scrolling to 

SPt

. The values 

displayed will be the temperature of the spare sensor.

Power Failures

Measuring resistance between locations A and C or B 
and D will always show “Open” because these locations 
are between the motor windings.

When the valve is opening or closing, the voltage 
measured between A and B or C and D should be 
between 20 to 22 VAC.

Continued from Page 20

Measuring the DC volt of the EXV TEST pins, on the 
board, will also indicate if the expansion valve is open 
or close. 0 volts DC indicates the valve is closed. 5 volts 
DC indicates the valve is fully open. A value between 
0 and 5 volts indicates how much the valve is open or 
close.

Checking Sensors

DO NOT REMOVE SENSORS FROM EVAPORATORS 

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.