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3-36T-268-07
Compressor
Starting Sequence
Is Ambient
Temperature Less
Than 60 ˚F?
High Speed Start
Has Compressor Run
For 20 Minutes ?
Has Set Point
Been Reached ?
Is The Operating Capacity *
Below Low Speed Capacity ?
Low Speed
Soft Start (See Note B)
Run 20 Minutes
Is Supply 3 ˚FAboveSetPoint
Or Is Operating Capacity *
Greater Than Low Speed Capacity ?
STEP
A
B
C
D
E
F
G
H
I
YES
YES
YES
YES
YES
Low Speed
Soft Start
(See Note A & B)
Run For 2
Minutes
Are High Speed Switch
Over Conditions Satisfied ?
(Refer To Steps “J & L”)
NO
NO
NO
NO
* Operating capacity is the required capacity to maintain
container box temperature.
YES
Continue In
Low Speed
NO
Does High Pressure
Switch (HPS) Trip ?
NO
YES
NO
J
Was Ambient Greater
Than 60 ˚FDuringStart?
Is Supply Voltage
Greater Than
Required Voltage ** ?
Is Supply Voltage
Greater Than
Required Voltage ** ?
** Required voltage is a function of operating capacity and
supply frequency.
NO
YES
L
YES
NO
NO
NOTE B
Low Speed Soft Start is
performed by closing the
SMV to 0% opening for ten
seconds during the start-up
of the compressor. The SMV
opening is then gradually
increased tothedesired value
at the rate of a 3% opening
per second.
NOTE A
During compressor
operation, if at anytime the
High Pressure Switch (HPS)
trips, the logic will switch to
Low Speed Soft Start.
Continue In
Low Speed
YES
Figure 3-6. Two-Speed Compressor Speed Change Logic -- Perishable Range Only