Emerson 2 - Manual (Page 20)

Operation
14
T-pack1 package
Includes a low pressure switch, low pressure bypass timer (described above) and fan cycle control.
Fan Cycle Control—Condenser Fan Cycling Control; allows the InteleCool2 unit to provide cooling
to the space when the outdoor ambient temperature is lower than 50°F (10°C) and down to -20°F
(-28.9°C). The control uses a reverse acting pressure switch mounted on the discharge line that cycles
the condenser fan in response to the discharge pressure. On a call for cooling, when the discharge
pressure increases to 250 PSIG (1723 kPa), the switch will close and start the condenser fan. When
the pressure drips below 170 PSIG (1172 kPa) the switch will open and stop the condenser fan. Dur-
ing low outdoor temperatures, the pressure switch cycles the condenser fan to maintain discharge
pressure that will allow the system to function.
T-pack2 package
Includes a low pressure switch, low pressure bypass timer and an adjustable fan cycle control. See
descriptions above.
5.4.4 Anti-Short Cycle Timer - Standard
The anti-short cycle timer protects the compressor from continuous ON-OFF operation and restarts
after momentary power failures. The timer used is adjustable and is set to a minimum of 3 minutes.
On start-up, or any call for cooling after an off cycle of more than 3 minutes, the compressor will start
immediately.
5.4.5 Heater Protection - With Optional Heat
On units supplied with resistance heating, an auto reset heater safety and a one time (replaceable)
thermal link protects the unit wiring and prevents excessive heat conditions caused by a dirty air fil-
ter or fan failure.
5.4.6 Lockout Relay - Optional
The lockout relay latches the detection of a high-pressure condition in the refrigeration circuit and
prohibits operation of the compressor until the abnormal pressure conditions are acknowledged. The
lockout relay is reset by cycling the unit main power or by changing the setpoint on the thermostat to
temporarily eliminate a call for cooling. A normally open set of contacts is provided to terminals 2 and
3 of the customer terminal strip for monitoring the status of the lock out relay when this option is sup-
plied without the Common Alarm option.
5.4.7 Common Alarm - Optional
Alarm components are an evaporator air sail switch, evaporator high temperature switch, control
relays and an adjustable time delay relay with two normally open and two normally closed alarm con-
tacts. The alarm contacts will activate in the event of a loss of airflow across the evaporator blower,
high evaporator temperature or in the event that the compressor is not functioning due to an abnor-
mal pressure condition. The adjustable time delay relay can be adjusted for a delay of up to 90 sec-
onds to eliminate nuisance tripping of the alarm contacts. To detect low pressure, the optional low
pressure switch with bypass, T-pack1 or T-pack2 must also be selected.
NOTE
During normal operation in low ambient conditions, the condenser fan will cycle frequently.