Mueller E-Star OESE 3.5 and 5 HP HFC Condensing Unit
Installation and Operation Manual, Part No. 8828747 Effective April 13, 2020
8.1 LOW-PRESSURE SWITCH WITH AUTOMATIC RESET
The low-pressure switch should be tested during installation to ensure proper operation by following these steps:
IMPORTANT: For brazed-plate chiller applications, ensure the glycol solution temperature is above 50°F
(10°C) to prevent damage to the evaporator by freezing.
1. Attach an accurate low-pressure gauge to the suction service valve (P2).
2. Slowly close the service valve (P6) 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 the service valve (P6) and monitor the suction pressure on the gauge.
5. The low-pressure switch should close and energize the compressor’s control circuit at approximately
30 psig (± 2 psig).
6. The low-pressure switch should be replaced if it does not operate as indicated above.
8.2 HIGH-PRESSURE SWITCH WITH AUTOMATIC RESET
The high-pressure switch should be tested during installation to ensure proper operation by following these steps:
1. Attach an accurate high-pressure gauge to the high-side service valve (P6).
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 405
psig (± 5 psig) on R-22 units and 480 psig (± 10 psig) on R-507 units.
4. Reconnect the fan motor wires at the high-voltage terminal strip; monitor the high-side pressure on the gauge.
5. The high-pressure switch should close and energize the compressor’s control circuit at approximately 305 psig
(± 5 psig) on R-22 units and 350 psig (± 10 psig) on 507 units.
6. The high-pressure switch should be replaced if it does not operate as indicated above.
8.3 RGE ELECTRONIC FAN SPEED CONTROL
E-Star OESE condensing units use 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. The RGE has two modes: minimum
speed and cutoff. The RGE is intended for operation in the cutoff mode. Cutoff mode is selected by the changeover
switch, located inside the encloure. By placing the switch in the cutoff mode when pressure is below the setpoint
value, the fan motor will be turned off and remain off until the pressure increases above the setpoint value.
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Section 8.0 – Pressure Switches and Fan Control
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