835965-UIM-A-0112
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Johnson Controls Unitary Products
3. If the coil needs to be cleaned, use clean water to wash dust, dirt,
and debris from outdoor condensing coil.
4. Refer to the furnace or air handler instructions for filter and blower
motor maintenance.
5. The indoor coil and drain pan should be inspected and cleaned reg-
ularly to prevent odors and assure proper drainage.
SECTION VIII: AC CONTROL BOARD
FUNCTIONALITY
ANIT-SHORT CYCLE DELAY
The control includes a five-minute anti-short cycle delay (ASCD) timer
to prevent the compressor from short cycling after a power interruption
or thermostat signal interruption. The ASCD timer is applied when the
control is first powered from the indoor unit thermostat and immediately
following the completion of a compressor run cycle. The compressor
and the outdoor fan will not operate during the five minutes that the
timer is active.
The ASCD timer can be bypassed by connecting the TEST terminals
for three seconds while the thermostat is calling for compressor opera-
tion (Y1 input signal energized).
LOW VOLTAGE DETECTION
The control monitors the transformer secondary (24 VAC) voltage and
provides low voltage protection for the AC unit and its components. In
particular, the control prevents contactor chatter during low voltage con-
ditions. If the voltage drops below approximately 19 VAC, the control
will continue to energize any relays that are already energized but will
not energize any additional relays until the voltage level increases. If
the voltage drops below approximately 16 VAC, the control will immedi-
ately de-energize the relay outputs and will not energize any relays until
the voltage level increases. The control will store and display the appro-
priate fault codes when low voltage conditions occur.
TEST INPUT
The control includes a TEST input connector that can be used for vari-
ous testing functions during installation and service. Table 2 summa-
rizes the behavior of the control when the two TEST pins are
connected.
On 5 Ton unit the outdoor fan motor is a permanent magnet DC
brushless type. The motor requires a separate Electronic Control to
operate. Do not attempt to replace this motor with a typical PSC
type. Damage to Electronic Control may result.
DO NOT use coil cleaners to clean outdoor condensing coil. clean-
ers containing HF-, hydroxides, chlorides, and sulfates can greatly
reduce the lifetime of the aluminum condensing coil.
NOTICE
NOTICE
Do not connect manifold gauges unless trouble is suspected.
Approximately 3/4 ounce of refrigerant will be lost each time a stan-
dard manifold gauge is connected.
IT IS UNLAWFUL TO KNOWINGLY VENT, RELEASE OR DIS-
CHARGE REFRIGERANT INTO THE OPEN AIR DURING
REPAIR, SERVICE, MAINTENANCE OR THE FINAL DISPOSAL
OF THIS UNIT.
WHEN THE SYSTEM IS FUNCTIONING PROPERLY AND THE
OWNER HAS BEEN FULLY INSTRUCTED, SECURE THE
OWNER’S APPROVAL.
TABLE 1:
R-410A Saturation Properties
TEMP.
°
F
PRESSURE
PSIG
TEMP.
°
F
PRESSURE
PSIG
TEMP.
°
F
PRESSURE
PSIG
TEMP.
°
F
PRESSURE
PSIG
TEMP.
°
F
PRESSURE
PSIG
45
129.70
60
169.60
75
217.40
90
274.10
105
340.50
46
132.20
61
172.60
76
220.90
91
278.20
106
345.30
47
134.60
62
175.50
77
224.40
92
282.30
107
350.10
48
137.10
63
178.50
78
228.00
93
286.50
108
355.00
49
139.60
64
181.60
79
231.60
94
290.80
109
360.00
50
142.20
65
184.60
80
235.30
95
295.10
110
365.00
51
144.80
66
187.70
81
239.00
96
299.40
111
370.00
52
147.40
67
190.90
82
242.70
97
303.80
112
375.10
53
150.10
68
194.10
83
246.50
98
308.20
113
380.20
54
152.80
69
197.30
84
250.30
99
312.70
114
385.40
55
155.50
70
200.60
85
254.10
100
317.20
115
390.70
56
158.20
71
203.90
86
258.00
101
321.80
116
396.00
57
161.00
72
207.20
87
262.00
102
326.40
117
401.30
58
163.90
73
210.60
88
266.00
103
331.00
118
406.70
59
166.70
74
214.00
89
270.00
104
335.70
119
412.20
