Major System Components; General; Main Base Board (Mbb); Economizer Control Board (Ecb) - Carrier 48PG20 Controls, Start-Up, Operation, Service And Troubleshooting Instructions

Table 52 — Pressure (psig) vs. Voltage Drop Values for Suction Pressure Transducers
PRESSURE VOLTAGE
(psig) DROP (V)
0 0.465
2 0.485
4 0.505
6 0.524
8 0.544
10 0.564
12 0.583
14 0.603
16 0.623
18 0.642
20 0.662
22 0.682
24 0.702
26 0.721
28 0.741
30 0.761
32 0.780
34 0.800
36 0.820
38 0.839
40 0.859
42 0.879
44 0.898
46 0.918
48 0.938
50 0.958
52 0.977
54 0.997
56 1.017
58 1.036
60 1.056
62 1.076
64 1.095
66 1.115

MAJOR SYSTEM COMPONENTS

The 48/50PG single-package rooftop units con-
General —
tain the ComfortLink™ electronic control system that monitors
all operations of the rooftop. The control system is composed
of several main control components and available factory-
installed options or field-installed accessories as listed in sec-
tions below. See Fig. 14-19 for the control and power schemat-
ics. Figures 20 and 21 show the layout of the control box, unit,
and thermistor and transducer locations.
Main Base Board (MBB) —
The MBB is the center of the ComfortLink control system. It
contains the major portion of the operating software and con-
trols the operation of the unit. The MBB continuously monitors
input/output channel information received from its inputs and
from the Economizer Control Board (ECB). The MBB re-
ceives inputs from thermistors and transducers. The MBB also
receives the Current Sensor inputs for compressors and other
discrete or digital inputs. The MBB reads space temperature
(SPT) from either a T-55, T-56 or T-58 device and space tem-
perature offset (SPTO) from a T-56 device. See Field-Installed
Accessories section on page 82. The MBB controls 9 relays.
NOTE: The Main Base Board (MBB) has a 3-position instance
jumper that is factory set to '1'. Do not change this setting.
Economizer Control Board (ECB) —
trols the economizer actuator. See Fig. 23 and Table 54. The
control signal from the ECB uses either the MFT
(Multi-Function Technology) communication protocol or a 4 to
20 mA output signal as defined by the configuration
PRESSURE VOLTAGE
(psig) DROP (V)
68 1.135
70 1.154
72 1.174
74 1.194
76 1.214
78 1.233
80 1.253
82 1.273
84 1.292
86 1.312
88 1.332
90 1.351
92 1.371
94 1.391
96 1.410
98 1.430
100 1.450
102 1.470
104 1.489
106 1.509
108 1.529
110 1.548
112 1.568
114 1.588
116 1.607
118 1.627
120 1.647
122 1.666
124 1.686
126 1.706
128 1.726
130 1.745
132 1.765
134 1.785
See Fig. 22 and Table 53.
The ECB con-
PRESSURE VOLTAGE
(psig) DROP (V)
136 1.804
138 1.824
140 1.844
142 1.863
144 1.883
146 1.903
148 1.922
150 1.942
152 1.962
154 1.982
156 2.001
158 2.021
160 2.041
162 2.060
164 2.080
166 2.100
168 2.119
170 2.139
172 2.159
174 2.178
176 2.198
178 2.218
180 2.237
182 2.257
184 2.277
186 2.297
188 2.316
190 2.336
192 2.356
194 2.375
196 2.395
198 2.415
200 2.434
202 2.454
→
Configuration ECON
Indoor Air Quality (IAQ), Outdoor Air Quality (OAQ), and
enthalpy. It also controls two power exhaust outputs.
By digitally communicating with the ECB, the economizer
actuator is able to provide the damper position and diagnostic
information to the ComfortLink controller. The damper
position is displayed at Outputs
information is displayed via Alert T414. More information
about these alarms is contained in the Alarms and Alerts
section.
NOTE: The Economizer Control Board (ECB) has a
4-position DIP switch that is factory set to ON (towards the
center of the board). Do not change this setting.
Integrated Gas Control (IGC) Board —
is provided on gas heat units. See Table 55 and Fig. 24. The
IGC controls the direct spark ignition system and monitors the
rollout switch, limit switch, and induced-draft motor Hall
Effect switch. The IGC is equipped with an LED (light-
emitting diode) for diagnostics. See the Troubleshooting
section for more information.
Low Voltage Terminal Strip (TB2) —
board provides a connection point between the major control
boards and a majority of the field-installed accessories. See
Fig. 25 and Table 56. The interface connection for the Carrier
Comfort Network® (CCN) communication and interface con-
nection for the Local Equipment Network (LEN) communica-
tions are also located on the low voltage terminal strip.
67
PRESSURE VOLTAGE
(psig) DROP (V)
204
206
208
210
212
214
216
218
220
222
224
226
228
230
232
234
236
238
240
242
244
246
248
250
252
254
256
258
260
262
264
266
268
270
→
E.CTL. The ECB has inputs for
→ →
ECON EC.AP. Diagnostic
The IGC
This circuit
2.474
2.493
2.513
2.533
2.553
2.572
2.592
2.612
2.631
2.651
2.671
2.690
2.710
2.730
2.749
2.769
2.789
2.809
2.828
2.848
2.868
2.887
2.907
2.927
2.946
2.966
2.986
3.005
3.025
3.045
3.065
3.084
3.104
3.124