American Power Conversion FM, DX manual Cool Deadband Compressor Allocation, Two-ModuleSystem

The following graphic is an example of a two-Module System (with four compressors). The setpoint is 21.1°C (70°F) and the deadband is 2.2°C (4°F). Each compressor engages as the return air temperature reaches its assigned segment of the deadband above the setpoint. When the return air temperature drops back below the temperature assigned to a compressor, that compressor disengages.

Cool Deadband Compressor Allocation

Two-Module System

Compressor	Compressor	Compressor	Compressor
# 1	# 2	# 3	# 4

21°	21.6°	22.2°	22.7°	23.3°
(70°)	(71°)	(72°)	(73°)	(74°)

Return air temperature

na0437a

Caution: If the deadband setting is too narrow, it will cause the System to engage the compressors in response to a small temperature change. Since the compressors must run for a minimum period to avoid damage, this could over-cool the room.

Caution: If the deadband setting is too wide, the System will not engage all of its cooling capacity until the return air temperature is significantly above the setpoint.

NetworkAIR FM DX 60 Hz Operation, Maintenance, and Troubleshooting 35