APC AFX Series Technical Information download pdf (Page 20)

17Remote Air Cooled Condenser

Example of operation using an FM50 and LNH-S03-

A026 condenser:

The condenser has three fans. The first fan is located

closest to the header, is controlled by a P66 electronic

speed control, and is not discussed here. The second

fan (stage 1) is controlled by an A350A temperature

control module and the third fan (stage 2) is

controlled by an S350A temperature stage module.

Settings are as follows:

• A350A and S350A differential is 3°.

• A350A setpoint is 100°F ambient.

• S350A offset is 10°.

When the ambient temperature is above 90°F (100º

A350A setpoint minus 10º offset), the S350A is

deenergized and the third fan (stage 2) will run

(remember that the normally closed contacts are in

use).

When the ambient temperature falls below 87°F (90º

minus 3º S350A differential), the S350A is energized

and the third fan (stage 2) will stop (the stage 1 fan is still running).

When the ambient temperature goes above 100°F (A350A setpoint) the S350A is de-energized. The

stage 3 fan runs (the stage 1 and 2 fans remain running).

Note: In the case of A350A or S350 failure, the controls fail closed. The fan or fans will run

continuously. This may cause head pressure lower than required or wanted, but the fans will

stay on.

Adjustments to A350A/B

Electrical Hazard: Disconnect power supply to avoid possible electrical shock or

equipment damage. More than one disconnect may be required to completely de-energize

equipment.

1. Remove the stage module cover by loosening the four cover screws.

2. Using the potentiometer on the right, adjust the differential to 3°F.

3. Using the potentiometer on the left, adjust the offset to the desired setting (the difference in

degrees).

4. Replace the cover, fasten in place with screws, and restore power to the system.

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APC AFX Series Technical Information Page 20