Technical information

Remote Air Cooled Condenser18
Jumper setting: cooling with relay NO
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/B
temperature control module and the third fan (stage
2) is controlled by an S350A/B temperature stage
module.
Settings are as follows:
• A350A/B and S350A/B differential is 3°.
• A350A/B setpoint is 87°F ambient.
• S350A/B offset is 10°.
When the ambient temperature is above 90°F
(A350A/B setpoint plus 3º differential), the A350A/B
is energized, and the second fan (stage 1) will run
(remember that the normally open contacts are in
use).
When the ambient temperature is above 100°F
(A350A/B setpoint plus 10º offset, plus 3º S350A/B differential), the S350A/B is energized and the third
fan (stage 2) will run (the stage 1 fan is still running at this temperature).
When the ambient temperature falls below 97°F (A350A/B setpoint plus 10° offset) the S350A/B is
de-energized. The stage 2 fan will stop, but the stage 1 fan remains running.
When the ambient temperature falls below 87°F (A350A/B setpoint), the A350A/B is de-energized and
the stage 1 fan will stop.
Note: In the case of a A350A/B and /or S350 failure, the controls fail open. Fan or fans will
stop, causing the computer room air conditioner (CRAC) to go high head pressure. The high
pressure cut switch in the CRAC will stop the compressors.
Mode
Fan
Connection
Sensor
Reading Relay
Fan
Status
Standard
Operation
Control
Failure
Cooling NO to C Below
Setpoint
De-energized OFF Will drive
head pressure
toward
setpoint.
Unit will
trip on high
pressure
switch.
Cooling NO to C Above
Setpoint
Energized ON