5. Low Ambient Fan Control
Page 17
PRODIGYT M2 UNIT CONTROLLER
5. Low Ambient Fan Control
5.1. High Efficiency A Box Fan Operation
The outdoor fan in a high efficiency A Box unit operates at three distinct speeds; High, Low and Extra−low. At higher outdoor
temperatures, (above 65F), the fan operates at high speed for a high cooling demand and at low speed for a low cooling or
de−humidification demand. At low outdoor temperatures the fan is off until the liquid pressure switch, S11 closes. Then the
fan runs at extra−low speed.
5.2. Low Ambient Fan Cycling − Other Units
During low ambient conditions, various outdoor fans are cycled by liquid line pressure switches; S11, S84, S85 and S94. The
M2 unit controller will also de−energize fans due to low outdoor temperature. See Figure 4, for fan layouts and tables 9
through 14 for low ambient fan operations.
BOX
Size
Fan Layout Models Compr. Fans
A
LCH, LGH 36H,48H,60H 1 (2 step)
1 (vari-
able)
LCH, LGH 36S,48S,60S,72H 1 1
B
BOX
LCH, LGH 090,102,120,150 2 2
C1
BOX
LCH, LGH 156 3
3 (2 out-
puts)
C2
BOX
LCH, LGH 180 3 4
C3
LCH, LGH 210 3 6
BOX
LCH, LGH 240/300S 4 6
E
BOX
LCH, LGH 420,480,540,600 4 6
Figure 4. Number of Compressors/Fans and Fan Layout
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