51
YORK INTERNATIONAL
FORM 100.50-NOM1 (604)
5
SECTION 5 – SEQUENCE OF OPERATION
COMPRESSOR STAGING
On the Design Level "C" units the Constant Volume
(CV), Variable Air Volume (VAV) and FlesSys units all
use the same compressor staging sequence.
TABLE 11 – FOUR OR SIX COMPRESSOR
LOGIC – STAG ING DOWN
Note that ASCD (anti short cycle delay) and Minimum
Run Time will take priority above Compressor to tal ized
run time. For example, when turning on the
Þ
rst stage,
the con trol will determine which compressor has the
shortest total run time and also read the ASCD tim-
ers for each compressor. If the compressor with the
short est total run time has expired its ASCD, then that
com pres sor will be started. If the compressor with the
short est total run time has not ex pired its ASCD but
the oth er compressor has, then the compressor with the
long er run time will be started.
TABLE 10 – FOUR OR SIX COMPRESSOR
LOGIC – STAG ING UP
5
Stage
Logic
1
Compressor 1A or 1B with shortest
totalized run time and expired ASCD
2
Other compressor from System 1
(Wait for ASCD to expire if not expired)
3
Compressor 2A, 2B, 3A or 3B with
shortest totalized run time and expired ASCD
4
Other compressor from System 2 or 3
with shortest run time and expired ASCD
5
Other compressor from System 2 or 3
with shortest run time and expired ASCD
6
Other compressor from System 2 or 3
with shortest run time and expired ASCD
Stage
Logic
6 to 5
Compressor from System 2 or 3 with longest
run time and expired Min. Run Time.
5 to 4
Other Compressor from Sys. 2 or 3 with
longest run time and expired Min. Run Time.
4 to 3
Other Compressor from Sys. 2 or 3 with
longest run time and expired Min. Run Time.
3 to 2
Other Compressor from Sys. 2 or 3 with
longest run time and expired Min. Run Time.
2 to 1
Compressor from System 1 with longest run
time and expired Min. Run Time.
1 to Off
Last Compressor from System 1 after Min.
Run Time has expired.
