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SECTION 3
3-37 T-268-07
Compressor
Starting Sequence
Is Ambient
Temperature Less
Than 60 ˚F?
High Speed Start
Has Set Point
Been Reached ?
STEP
A
B
C
D
E
YES
YES
YES
Low Speed
Soft Start
(See Note A & B)
Run For 2
Minutes
NO
NO
Continue In
High Speed
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.
NO
Has Set Point
Been Reached ?
Compressor Cycles OFF
NOTE A
During compressor
operation, if at anytime the
High Pressure Switch (HPS)
trips, the logic will switch to
Low Speed Soft Start.
Figure 3-7. Two-Speed Compressor Speed Change Logic -- Frozen Range Only