Mueller E-Star OESE 7.5 and 9 HP HFC Condensing Unit
Installation and Operation Manual, Part No. 8828748
Effective June 16, 2020
18
9.1
LOW-PRESSURE SWITCH WITH AUTO RESET
The low-pressure switch should be tested during installation to ensure proper operation. (For brazed-plate chiller
applications, ensure the glycol solution temperature is above 50°F (10°C) to prevent damage to the evaporator by
freezing.) This can be accomplished by completing these steps:
1. Attach an accurate low-pressure gauge to P2, access charging port.
2. Slowly close P6 service valve while monitoring the suction pressure on the gauge.
3. The low-pressure switch should open and de-energize the compressor’s control circuit at approximately 5 psig
(± 2 psig).
4. Slowly open P6 service valve and monitor the suction pressure on the gauge.
5. When the suction pressure reaches approximately 30 psig (± 2 psig), the pressure switch will reset and the
compressor will energize.
6. The low-pressure switch should be replaced if it does not operate as indicated above.
9.2
HIGH-PRESSURE SWITCH WITH AUTO RESET
The high-pressure switch should be tested during installation to ensure proper operation. This can be
accomplished by completing these steps:
1. Attach an accurate high-pressure gauge to P6, high-side service valve.
2. Disconnect the fan motor wires from the high-voltage terminal strip and monitor the high-side pressure on
the gauge.
3. The high-pressure switch should open and de-energize the compressor’s control circuit at
approximately 480 psig (± 10 psig) on R-507 units.
4. Reconnect the fan motor wires and monitor the high-side pressure on the gauge.
5. The pressure switch will reset and the compressor will energize when the high-side pressure reaches
approximately 450 psig on R-507 units.
6. The high-pressure switch should be replaced if it does not operate as indicated above.
9.3
RGE ELECTRONIC FAN PRESSURE CONTROL
The Mueller E-Star OESE condensing unit uses an electromagnetic variable speed fan control to allow the fan
motor to operate at variable speeds at different ambient temperatures.
The RGE fan control must be checked for proper operation upon installation.
Section 9.0 – Pressure Switches and Fan Control