Quantech
177
Section 8: Unit operation
Form QTC3-NM1
Issue date: 12/19/2023
8
Table 24: QTC3 Standard Condenser Fan Control Using Discharge Pressure Only (2, 3, or 4 Fans per System)
FAN
STAGE
ON* OFF**
IPU I/O OUTPUT
FAN
CONTACTOR
FAN #
SYS 1 SYS 2 SYS 1 SYS 2 SYS 1 SYS 2
1
DP > PROGRAMMED
FAN CONTROL ON
PRESSURE
DP < PROGRAMMED
FAN CONTROL ON
PRESSURE MINUS
PROGRAMMED
DIFFERENTIAL
PRESSURE
7B7-8 TB10-8 1-KF1 2-KF1 1-MF1 2-MF2
2
DP > PROGRAMMED
FAN CONTROL ON
PRESSURE AND
FAN STAGE 1 IS
ENERGIZED
DP < PROGRAMMED
FAN CONTROL ON
PRESSURE MINUS
PROGRAMMED
DIFFERENTIAL
PRESSURE AND
FAN STAGE 1 IS
ENERGIZED
TB7-8
and
TB7-9
TB10-8
and
TB10-9
1-KF1
and
1-KF2
2-KF1
and
2-KF2
1-MF1
and
1-MF2
2-MF1
and
2-MF2
3
DP > PROGRAMMED
FAN CONTROL ON
PRESSURE AND FAN
STAGES 1 AND 2 ARE
ENERGIZED
DP < PROGRAMMED
FAN CONTROL ON
PRESSURE MINUS
PROGRAMMED
DIFFERENTIAL
PRESSURE AND FAN
STAGES 1 AND 2
ARE ENERGIZED
TB7-8
and
TB7-9
and
TB7-10
TB10-
8 and
TB10-9
and
TB10-10
1-KF1
and
1-KF2
and
1-KF3
2-KF1
and
2-KF2
and
2-KF3
3 FAN:
1-MF1
and
1-MF2
and
1-MF3
4 FAN:
1-MF1
and
1-MF2
and
1-MF3
and
1-MF4
3 FAN:
2-MF1
and
2-MF2
and
2-MF3
4 FAN:
2-MF1
and
2-MF2
and
2-MF3
and
2-MF4
* When a fan stage is turned on, the pressure for the next stage is increased 20 PSIG and ramped back to the pro-
grammed on pressure over the next 20 seconds.
** When a fan stage is turned off (Programmed ON pressure minus the differential), the OFF pressure for the next
stage is decreased 20 psig and ramped back to the programmed OFF pressure minus the differential.
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