Stulz CeilAir CW - Condenser Fan Cycling (Condenser Model SCS-AA, 0 °F); Condenser Multi-Speed Fan Switch (Model HES-CAA, 0 °F); Head Pressure Controls-Air Cooled Systems; Low;High Pressure Limit Switch

57OCH0006F08/13/2024
CEILAIR
®
CW & DX IOM
2.10.2.2 CONDENSER MULTISPEED FAN SWITCH MODEL HESCAA , 0 °F
2.10 System Settings and Adjustments
2.10.1 Low/High Pressure Limit Switch
Air conditioning systems using DX refrigerant are equipped with hermetically sealed high-pressure and low-
pressure switches. These switches are set by the manufacturer and cannot be adjusted.
2.10.1.1 R407C Pressure Switch Settings
• High-pressure switch opens at 410 psig (2.283 MPa) and has a manual reset.
• Low-pressure switch opens at 10 ± 4 psig (68.9 ± 27.6 kPa), closes at 32 ± 5 psig (220.6 ± 34.5
kPa), and has an automatic reset.
2.10.1.2 R410A Pressure Switch Settings
• High-pressure switch opens at 630 psig (4.34 MPa) and has a manual reset.
• Low-pressure switch opens at 10 ± 10 psig (68.9 ± 68.9 kPa), closes at 32 ± 10 psig (220.6 ± 68.9
kPa), and has an automatic reset.
2.10.2 Head Pressure Controls—Air Cooled Systems
2.10.2.1 Condenser Fan Cycling (Condenser Model SCSAA, 0 °F)
Used for outdoor installations where ambient condenser air inlet temperatures are 0 °F or higher, this method
utilizes a high-pressure differential control switch with SPST (Single Pole, Single Throw) contacts and an
automatic reset. The switch activates the condenser fan contactor when the discharge pressure reaches a
predetermined value to maintain the condensing temperature.
See Table 1 and Table 2 of the STULZ SCS Series Remote Air Cooled Condensers IOM for information about
the fan cycling pressure control settings (cut-in and cut-out pressures) for the supported refrigerants. Note
that the pressure values vary according to both the refrigerant type and the number of fans in the SCS unit.
2.10.2.2 Condenser Multi-Speed Fan Switch (Model HESCAA , 0 °F)
Used for indoor installations where ambient condenser air inlet temperatures are 0 °F or higher, the
condenser fan adjusts its speed to maintain condenser pressure by sensing refrigerant discharge pressure.
The condenser fan speed switch changes the fan from low to high speed when pressure rises and returns the
fan from high speed to low speed when the pressure lowers.
R407C Refrigerant Factory Setting. On pressure rise, the high fan speed contacts close at 320 psig
(2.21 MPa), increasing the condenser fan speed. A pressure drop to 250 psig (1.72 MPa) will close the low
fan speed contacts, reducing the fan speed. The setpoint range is 170400 psig (1.17 2.76 MPa). The
differential is nonadjustable and set at 70 psi (0.48 MPa).
R410A Refrigerant Factory Setting. On pressure rise, the high fan speed contacts close at 440 psig
(3.03 MPa), increasing the condenser fan speed. A pressure drop to 330 psig (2.28 MPa) will close the low
fan speed contacts, reducing the fan speed. The setpoint range is 275620 psig (1.904.27 MPa). The
differential is nonadjustable and set at 110 psi (0.76 MPa).
NOTE Switch Settings Apply at < 277 V
These condenser fan switch settings do not apply to units with a power supply greater than 277 V.