CAPACITY CONTROLLERS - 101ALAS
OVERVIEW
The 101ALAS works with the System 2000 Heat Pump System Controller
(101AACBHP). The 101ALAS provides leaving air temperature readings
to the System Controller, which allows it to make capacity control decisions.
OPERATION
The 101ACBHP System Controller has four status lights that represent
capacity control. The heat Y1 and Y2 red lights indicate heating opera-
tion and the cool Y1 and Y2 green lights indicate cooling operation. Heat-
ing or cooling will be initiated depending on the position of the revers-
ing valve. When one of the lights turns on, the leaving air temperature in
the duct, sensed by the LAS, has exceeded one of the capacity control set-
points. The light will indicate which stage will be turned off. The sec-
ond stage factory default cut-in temperature for heating is 95 degrees, and
for cooling 60 degrees. If the setpoint is exceeded, a stage light will illu-
minate, the stage will be shut down, and a four-minute time delay will
begin. After the four minute delay, if the leaving air temperature has recov-
ered to an acceptable temperature, the stage which was shut down will
restart. If the temperature has not recovered, the time delay will contin-
ue. If both first and second stage setpoints are exceeded by the leaving
air, then a four-minute time delay per stage will go into effect.
MODIFYING SETPOINT ADJUSTMENT
The Heat Pump Controller is designed so that it is possible to modify the
cut-in setpoints for cooling, heating (and electric heat on the Heat Pump
Controller). If necessary, locate the potentiometer associated with its test
point on the diagram above. “GND” is the common ground test point, TP2
is the cool test point and TP3 is the heat test point. (TP1 is the electric
heat test point on the Heat Pump Controller). Clip the leads of a digital
volt meter, set to 20 volts DC, between the potentiometer test point that
needs to be modified and the ground test point. Rotate the correspond-
ing potentiometer until the meter reads the proper voltage according
to Table 2 below.
WIRING
The 101ALAS is installed as detailed in the Capacity Controllers
Installation Section, page 40. The + or – terminals of the LAS are
wired to the + or – terminal of the 101AACBHP using two
conductor 18 gauge thermostat wire.
101AACBHP
HEAT PUMP
CONTROLLER
REV.
VALVE
Y1
Y2
Y1
Y2
HEAT
COOL
J1
ON
PWR
OFF
COOL
HEAT
OFF
AUTO
OFF
ON
AUTO
FAN
Y1
G
Y2
TB2
W
R
O
BL
/
TC2
Y W
B G
Rd
TR1
TR2
S
TB1
TC1
TEMP
–
+
J2
HEAT ADJ
TP3
COOL ADJ
TP2
ELECTRIC
HEAT ADJ
TP1
GROUND
GND
101ALAS
+
–
1
1
LAS VOLTAGE CONVERSION CHARTS
TABLE 1: CAPACITY CONTROL
TABLE 2: TEMPERATURE TO VOLTAGE
CONVERSION CHART
Deg. F.
DC Volts
Deg. F.
DC Volts
Deg. F.
DC Volts
40
2.775
70
2.942
100
3.109
41
2.781
71
2.948
101
3.114
42
2.787
72
2.953
102
3.120
43
2.792
73
2.959
103
3.125
44
2.798
74
2.964
104
3.131
45
2.803
75
2.970
105
3.137
46
2.809
76
2.975
106
3.142
47
2.814
77
2.981
107
3.148
48
2.820
78
2.987
108
3.153
49
2.825
79
2.992
109
3.159
50
2.831
80
2.998
110
3.164
51
2.837
81
3.003
111
3.170
52
2.842
82
3.009
112
3.175
53
2.848
83
3.014
113
3.181
54
2.853
84
3.020
114
3.187
55
2.859
85
3.025
115
3.192
56
2.864
86
3.031
116
3.198
57
2.870
87
3.037
117
3.203
58
2.875
88
3.042
118
3.209
59
2.881
89
3.048
119
3.214
60
2.887
90
3.053
120
3.220
61
2.892
91
3.059
121
3.225
62
2.898
92
3.064
122
3.231
63
2.903
93
3.070
123
3.237
64
2.909
94
3.075
124
3.242
65
2.914
95
3.081
125
3.248
66
2.920
96
3.087
126
3.253
67
2.925
97
3.092
127
3.259
68
2.931
98
3.098
128
3.264
69
2.937
99
3.103
129
3.270
Deg. F.
DC Volts
130
3.275
131
3.281
132
3.287
133
3.292
134
3.298
135
3.303
136
3.309
137
3.314
138
3.320
139
3.325
140
3.331
141
3.337
Cooling
Second Stage
60
GND & TP2
2.887
Heating
Second Stage
95
GND & TP3
3.081
Electric Heat
85
GND & TP1
3.025
Discharge Duct
Temperature
––
LAS + & –
per table #2
STAGE CUT-IN TEMPERATURES*
*The Y2 cut-out temperature is 10° fixed below the cut-in temperature
in cooling, and 10° above in heating.
The Y1 cut-out temperature is 15° fixed below the cut-in temperature in
cooling, and 25° above in heating.
35
