51
(LAR). The LAS control temperatures a re open 42_F+/--
5_F, close 57_F+/--5_F (open 5.5_C+/--2.8_C, close
13.9_C+/--2.8_C).
To override the speed control for full fan speed operat ion
during service or maintenance, either:
a. remove sensor and place in hot wat er >120_F
(>49_C), or
b. rewire to bypass control by connecting speed
control input and output power wires.
Troubleshooting —
OBSERVATION POSSIBLE REMEDY
Fans won’t start All fans:
Check power & wiring
Check outdoor fan relay (OFR)
OFM1, OFM3 only:
Check speed control sensor location
Check speed sensor resistance
OFM2, OFM4 only:
Check low ambient switch (LAS)
Check low ambient relay (LAR)
Cooling --- Center outdoor
fans (OFM2, OFM4) off
below approximately 60_F
(16_C) outdoor ambient.
Normal operation
Cooling --- Center outdoor
fans (OFM2, OFM4) not on
above approximately 60_F
(16_C) outdoor ambient
Check low ambient switch (LAS)
Check low ambient relay (LAR)
Cooling --- Slow fan speed
for outer fans (OFM1,
OFM3) at start or during
low outdoor ambient
Normal operation
Cooling --- Slow fan speed
for outer fans (OFM1,
OFM3) above 85_F(29_F)
outdoor ambient (should
be full speed)
Check speed control sensor location
Check speed control sensor
resistance
Check fan motor capaci tor
Cooling --- motor current
into speed control is
greater than motor name-
plate FLA
Normal operation
Up to 30% higher A at partial speed
at low ambient
Speed Control Sensor Resistance —
TEMPERATURE RESISTANCE
_F + / --- 2 _F _C + / --- 1 _C Ohms, nominal
--- 2 2 --- 3 0 88350
--- 4 --- 2 0 48485
14 --- 1 0 27650
32 0 16325
50 10 9950
68 20 6245
77 25 5000
86 30 4028
104 40 2663
122 50 1801
140 60 1244
158 70 876
Motormaster
Sensor -
Attach to
Circuit 1 coil only.
508 mm (20 in)
for Single Circuit
254 mm (10 in)
for Dual Circuit
C10093
Fig. 48 -- Motormaster Sensor Location:
38AUZ*16 & 38AUD*16 (Novation)
38AU
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