Carrier 48FK Controls Operation And Troubleshooting page 17

034-048: TB3
054-104: TB4
1
OCCUPIED/UNOCCUPIED
SWITCH
NIGHT SETBACK THERMOSTAT
NOTES:
1. Occ/Unocc switch closes when occupied.
2. Night setback thermostat closes when in night setback heating.
Fig. 23 — Occupied/Unoccupied Switch with
Night Setback Thermostat
034-048: TB3
054-104: TB4
3
4 6
4
7
5
Fig. 24 — Heat Interlock Relay
034-048: TB3
054-104: TB4
T10
12
15
Fig. 25 — Accessory Reset Board
EXAMPLE:
T10 desired set point is 70 F.
T10 from Table 4 for 70 F is 5929 ohms.
R
P7 = 13,084 – 5929
R
P7 = 7155 ohms
R
Using an ohmmeter, set the P7 potentiometer to
7155 ohms to achieve a reset initiation set point of 70 F.
Potentiometer P3 — Reset limit set point (maximum tem-
perature value for modified supply air set point). Maximum
of 70 F, minimum 40 F. Set between leaving air set point
(P1) and 70 F (maximum range permitted by control).
OPERATING SEQUENCE — If space temperature is above
reset set point (T10 > P7), no reset will occur.
If space temperature is equal to or less that reset set point
(T10 P7), the LED will display
034-048: TB3
054-104: TB4
2
FIELD
SUPPLIED
POWER
V
SOURCE
N.O.
SIGNAL
TO ROOM
TERMINALS
N.C.
RESET
P7
BOARD
20
and reset will begin.
17
Control will automatically adjust leaving air temperature by
the following formula:
MSP = SP + [(P3 - SP) / 3] x (P7 − T10)
where:
MSP = Modified Leaving-Air Set Point
SP = Supply-Air Set Point
P3 = Maximum Supply-Air Temperature (reset limit)
P7 = Reset Initiation Temperature (reset set point)
T10 = Actual Space Temperature
3 = Ratio for reset (F) (fixed parameter)
Table 4 — Thermistor Resistance and
Voltage Drop Characteristics
TEMP RESISTANCE
(F) (Ohms)
31.0 16813.8
32.0 16345.7
33.0 15892.2
34.0 15452.7
35.0 15026.7
36.0 14613.9
37.0 14213.6
38.0 13825.5
39.0 13449.2
40.0 13084.2
41.0 12730.1
42.0 12386.6
43.0 12053.3
44.0 11730.0
45.0 11416.1
46.0 11111.5
47.0 10815.8
48.0 10528.7
49.0 10250.0
50.0 9979.3
51.0 9716.5
52.0 9461.3
53.0 9213.4
54.0 8972.6
55.0 8738.6
56.0 8511.4
57.0 8290.6
58.0 8076.1
59.0 7867.7
60.0 7665.1
61.0 7468.3
62.0 7277.1
63.0 7091.2
64.0 6910.6
65.0 6735.1
66.0 6564.4
67.0 6398.6
68.0 6237.5
69.0 6080.8
70.0 5928.6
71.0 5780.6
72.0 5636.8
73.0 5497.0
74.0 5361.2
75.0 5229.1
76.0 5100.8
77.0 4976.0
78.0 4854.8
79.0 4736.9
80.0 4622.4
VOLTAGE
DROP (v)
3.582
3.553
3.523
3.494
3.464
3.434
3.404
3.373
3.343
3.312
3.281
3.250
3.219
3.187
3.156
3.124
3.093
3.061
3.029
2.997
2.965
2.933
2.901
2.869
2.837
2.805
2.772
2.740
2.708
2.676
2.644
2.612
2.581
2.549
2.517
2.486
2.454
2.423
2.391
2.360
2.329
2.299
2.268
2.237
2.207
2.177
2.147
2.117
2.088
2.058