50
APPENDIX C
Low Ambient Option — Factory Installed
Units with the factory installed low ambient option are
equipped with a Motormaster
R
solid--state head pressure
control which regulates fan speed. A temperature sensor,
mounted on either circuit 1 (569J***A/B/G/H units) or
circuit 2 (569J***D/E/F units) of the outdoor coil
controls the speed of approved outdoor fan motors in
order to maintain a constant head pressure in the outdoor
coil (see Fig. 42 And Fig. 43). The control maintains the
appropriate head pressure at low ambient temperatures
down to --20
_
F (--28
_
C).
Wind baffles are required to prevent wind cross currents
from causing abnormally low condensing temperatures.
Use 20--gauge sheet metal to fabricate wind baffles (see
Fig. 44 and Table 16).
Operation —
Fan on/off control in cooling--only units (569J***A/B/G/H,
569J***D/E/F) is provided by an outdoor fan relay (OFR).
In cooling mode, fan motor speed of outdoor motors
OFM1 and OFM3 is regulated by the speed control
temperature sensor on outdoor coil 1 for a minimum coil
condensing temperature of approximately 100
_
F (38
_
C)
at higher outdoor ambient temperature and 80
_
F (27
_
C) at
lower ambient. Additionally, outdoor fan motor OFM2
and OFM4 are turned on/off by the low ambient
temperature switch, LAS, operating the low ambient relay
(LAR). The LAS control temperatures are 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 operation
during service or maintenance, either:
a. remove sensor and place in hot water >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 capacitor
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 +/---1C
Ohms, nominal
---22
---30
88350
---4
---20
48485
14
---10
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
569J
Содержание 569J Series
Страница 34: ...34 C10925 Fig 29 Typical Single Circuit Single Stage 569J A B Wiring Diagram 569J ...
Страница 35: ...35 C150339 Fig 30 Typical Single Circuit Two Stage 569J 07G H Wiring Diagram 569J ...
Страница 36: ...36 C12547 Fig 31 Typical Dual Circuit Two Stage 569J D E F Wiring Diagram 569J ...
Страница 51: ...51 569J 07 08A B 569J 12A B 569J 14A B C11098 Fig 42 569J 07 14A B Motormaster Sensor Locations RTPF 569J ...
Страница 52: ...52 569J 12D E F 569J 14D E C12551 Fig 43 569J 12 14D E F Motormaster Sensor Locations RTPF 569J ...
Страница 53: ...53 D K J H G F E C B A C10800 Fig 44 Wind Baffles 569J ...
