Sequence Of Operation; Modes Of Operation - Carrier 619FB Service Manual

Compressor Preheating Function
The compressor crankcase heater activates if:
— The outdoor ambient temperature, T4, is lower than 37_F
(3_C) and power has been recently supplied to the machine.
— If T4 < 37_F (3_C) and the compressor has not been
operating for over 3 hours.
During the preheating mode, a weak current flow flows through
the compressor coil from the wiring terminal of the compressor.
The compressor is heated when this is not operating.
The preheating function deactivates if T4 is greater than 41_F
(5_C) or the compressor starts operating.
Condenser temperature protection
The condenser temperature protection function acts as follows:
— If the condenser coil temperature (T3) is between 131_F
and 140_F (55C_<T3<60_C), the compressor frequency
decreases to a lower level until it reaches the lowest
value, F1. It then runs at the F1 frequency. Once
T3<129_F (54_C), the compressor continues running at
the current frequency.
— When the coil temperature reaches a value lower than
126_F (52_C), the compressor will not limit the
frequency and resumes to the required frequency.
— If T3>140_F (60_C) for 5 seconds, the compressor stops
and restarts once the coil temperature reaches a value
lower than 126_F (52_C).
Evaporator Temperature Protection
The evaporator temperature protection function acts as follows:
— If the evaporator coil temperature (T2) is lower than
32_F (0_C), the compressor stops and restarts once T2
≥ 41_F (5_C).
— If 32_F ≤ T2 <39_F (0_C ≤T2 <4_C), the compressor
frequency will be limited and decreased to a lower level.
— Now, if 39_F ≤T2 <45_F (4_C ≤T2 <7_C), the
compressor continue running at the current frequency.
— If T2>45_F (7_C), the compressor frequency will not be
limited, and operation is normal.

SEQUENCE OF OPERATION

Interface
A wireless remote control, supplied with the unit, is the interface
between the fan coil and the user. The wireless remote control has
the following characteristics:
S Capable of displaying _C and _F with _F being the default
setting. To change the default setting, refer to the Owner's
Manual.
S The remote control setpoint range is from 62_F (17_C) to
86_F (30_C) in increments of 1_F (1_C).
S The wireless remote control has an operating range of 25 ft.
(7.62 m).
S The same remote control can be used to control more than one
unit.
S If the remote control is lost, damaged, or the batteries are
exhausted, the system can be operated by using the manual
button (forced Auto) located under the front panel.
Fig. 18 – Manual Button Location on Unit
Manual Button
AUTO/COOL
15

MODES OF OPERATION

COOLING MODE
In this mode, the system cools and dries the room air with the fan
running continuously, either at a selected fan speed or Auto fan
speed. The fan runs even when the compressor cycles off. This
feature enhances room comfort and efficiency of the system.
Compressor operation in cooling mode:
In cooling mode, the maximum operation frequency (Fmax) of the
compressor, after it starts running, depends on the outdoor ambient
temperature (T4).
Once the system starts running, the compressor runs at the Fmax
frequency for 7 minutes at a specific T4. During this time, the
frequency limitation is active, therefore the compressor continues
running even if the set point condition is satisfied. The compressor
running frequency will then be controlled based on the difference
between the room temperature and the temperature set point (T1- -Ts).
Outdoor Fan Operation in Cooling Mode:
When in cooling mode, the outdoor fan motor cycles based on the
outdoor ambient temperature as shown below:
Fig. 19 – Cooling mode
Indoor Fan Operation in Cooling Mode:
When in cooling mode, the indoor fan runs continuously either at
the chosen set speed (high, medium, or low), or in Auto mode,
where the speed is determined by the microprocessor based on the
difference between the room temperature and the temperature set
point as shown below:
4
High
3
1.5
1
Fig. 20 – Cooling mode
Medium
Low