Heatcraft Refrigeration Products 25001501 - Manual (Page 10)

BEACON CONTROLLER
10
PUMP-DOWN
At the end of each cooling cycle, when the box temperature is met, the system will pumpdown and shut off.
To pumpdown, the EEV closes and the compressor pumps down until the low pressure switch trips the unit
off, or two minutes have elapsed. While in the off cycle the system will initiate a short pump-down at four
minute intervals, if the low pressure switch is closed, to ensure that any refrigerant leakage, will not cause a
problem.
To Manually Pump-Down System
The system can be pumped down for service by closing the liquid line service valve in the condensing unit,
then closing the suction line service valve when the system trips on the low pressure switch.
or
Install a switch that will interrupt the circuit to one wire of the room sensor to the Beacon board. This will
cause the system to pump down and shut off. The system will not restart until the switch has re-made the
circuit to the room sensor.
Systems with Optional Pump-Down Switch on the Condensing Unit
The low pressure switch time delay relay will have to be adjusted from the factory set 2 minutes to 0 minutes
before flipping the pump-down switch. After normal operation of the system is restored, the low pres-
sure switch time delay relay must be adjusted back to the 2 minute setting.
CHECKING OPERATION OF EXPANSION VALVE (EEV)
The expansion valve position is indicated by a 0 to 5 volts DC signal. At 0 Volt the valve is closed and at 5
volts the valve is fully open. At values between 0 and 5 Volt, the valve will be opened proportionately. By
using a volt meter to measure the DC volts across the pins marked “EXV TEST” (bare pins near LED) on the
Beacon board, a determination can be made if the valve is open or closed. This must be measured while the
unit is cooling.
ELECTRIC DEFROST MODE
If elapsed time has been selected (this works just like a time clock), the number of defrosts per day will
depend on the number selected on the controller (i.e. 1, 2, 4 or 6). If run time has been selected, the number
of defrosts per day will vary depending on the compressor run time (i.e. 2, 3, 6 or 12 hr.).
When a defrost is initiated, the EEV valve closes, the compressor is allowed to pump-down (see pump-down
description), the evaporator fans are cycled off and the defrost heaters are energized. The master and all
slave controllers must terminate their defrost, either on temperature or time, before the master controller will
end the defrost cycle. There is a 60 second condensate drain-down time before the compressor is started,
followed by a 60 second evaporator fan hold-off time (fan delay). After this sequence, the controller(s) are
back in the refrigerating mode and the EEV(s) open to the position prior to defrost.
AIR DEFROST MODE
Usually the cycling on the thermostat will suffice to defrost the coil(s) when operating at room temps between
35
°
& 45
°
F. However, it will be necessary to set certain parameters. Recommended values when operating
near the 35
°
F range are as follows: select elapsed time, 2 defrost per day, 40 min. fail-safe & 50
°
F defrost
end temp. When operating near the 45
°
F range, it is advisable to minimize the effect of the defrost by
changing to a 10 min. fail-safe & 50
°
F defrost end temp. Note: These are only recommended settings.
Other settings are available on the Beacon board.