TM_s-MEXT_ME28relC_00_12_19_EN
Technical manual
TRANSLATION OF THE ORIGINAL INSTRUCTIONS
94
12.2
SAFETY REDUCTION LOAD (LP) FUNCTION
The main
purpose of the function is to keep the low pressure at a parameter set value, should it decrease below a “setpoint value, to
avoid the activation of the frost-free
function at low temperatures, which would stop the unit due to the possibility of ice forming on the coil.
The function activates if the pressure falls below the setpoint value (P20.86 for circuit 1 and P20.91 for circuit 2), and op
erates on two levels: A less incisive “Alert” level and a
“Protection” level.
INFORMATION
The time between steps is set by parameters P20.76 for circuit 1 and P20.81 for circuit 2.
The number of steps is set by parameter P20.77 for both circuits and its minimum value is fixed at 1.
INFORMATION
The function prevents the compressor from dropping below the minimum frequency, irrespective of the number of steps and Hz value to be scaled for
each step.
If the pressure does not increase again even after all the protection steps have been carried out, the frost-free function trips, turning off the faulty circuit.
If the pressure increases again above the se differential (P20.74 + P20.75 for circuit 1 and P20.79 + P20.80 for circuit 2), irrespective of the level and step at the time,
the unit returns to normal adjustment mode.
INFORMATION
The safety times of the compressors are observed.
The charts in the following pages show the operation described above.
SAFETY REDUCTION LOAD
–
LP
(2
) C
hec
k
(1
) N
or
m
al
F
an
(3
)S
te
p
1
(4
)S
te
p
2
(5
) F
in
is
h
FUNCTION RESTORE
FAN MANAGEMENT
FUNCTION ACTIVATION
Protection not active.
Ventilation Speed: Req. REGULATION
FAN SPEED
Protection activated for C1 or C2.
The logic check the FAN SPEED status:
A- FAN SPEED < MAX SPEED
→
Go to (3) Step1
B- FAN SPEED = MAX SPEED
→
Go to (5) Finish
FAN SPEED
FAN SPEED
WAIT
IF the protection is still activated.
The logic will speed up the fan and wait a timer before going
to (4) Step2
FAN SPEED
WAIT
MAX
If the protection is still activated.
Go to PAC-IF Request Management for SRL LP
FAN SPEED
MAX
SRL
PAC-IF REQUEST
MANAGEMENT
If the protection is still activated.
The logic will speed up to maximum speed the fan and wait a
timer before going to (5) Finish
Protection not active.
Ventilation Speed: Req. REGULATION
IF the protection is still not active
The logic will slow down the fan and wait a timer before
going to (2) Check
If the protection is still not active and the PAC-IF is in Normal
Zone
Go to (4) Step2
If the protection is still not active
The logic will wait a timer before going to (3) Step1
IF the protection is still not active
The logic will slow down the fan to the original regulation
speed before going to (1) Normal Fan
Figure 12-3:
Representation of fan management, reduction load safety function
