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Sequence of Operation – 80/20 Manual Potentiometer
1. With the disconnect in the ON position and the Summer-Off-Winter switch (SW-02) in the WINTER position, power is supplied to the damper motor (MT-02), if equipped
2. When the damper motor approaches the OPEN position, the damper-end switch (SW-07) closes, energizing blower-motor starter contactor (ST-01), powering blower motor (MT-01)
3. Power is supplied to the damper motor through the low-temperature limit control (TS-07), if equipped.
After a 5-min timed period, the low-temperature limit control shuts the unit off if discharge temperatures do not reach the minimum set points on the low-temperature limit control
4. The Manual Potentiometer (PO-01) adjusts the return air and fresh air bypass dampers (MT-03) to the desired building pressure
5. The RCS (Re-Circulating Control System) will drive the unit into 100% fresh air if the temperature drops below the Minimum Outdoor Set-Point (TS-10) or the Minimum Indoor Set-Point (TS-09) until the minimum set-points are satisfied. There are several RCS systems see the chart below to see your systems factory settings
6. When the airflow switch (PS-01) is proven, the flame relay (RE-07) is energized through the hightemperature limit control (TS-04), the optional low- and high-gas pressure switches (PS-03 & PS-04), and the burner ON/OFF intake air stat (TS-06), if equipped. The pilot valve (VA-03) opens, and the ignition transformer (TR-03) energizes
7. After the flame rod (SN-02) proves flame, the main valves (VA-01 & VA-02) open, and the ignition transformer de-energizes
8. The temperature control systems amplifier (AM-01), monitors the discharge air sensor (TS-01) and the remote discharge air set-point (TS-08), and modulates DC voltage to the modulating valve (VA-
05) to maintain discharge temperature
RCS
System
RCS5
RCS10
RCS15
RCS20
RCS25
RCS30
RCS35
RCS40
Minimum Outdoor
Air Temperature
(TS-10)
-30 F
-30 F
-25 F
-25 F
-20 F
-15 F
0 F
0 F
Minimum Indoor
Air Temperature
(TS-09)
7 F
25 F
58 F
54 F
55 F
47 F
52 F
35 F
Maximum Re-
Circulation
Percentage
60%
50%
80%
60%
50%
60%
80%
50%
Maximum
Discharge
Temperature
90 F
120 F
90 F
120 F
140 F
120 F
90 F
140 F
17
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