This quick start document is intended to help with getting the initial unit startup completed, but does not replace the IOM. Please read the IOM for all safety information and precautions before performing any work on the equipment. Complete pre-start checks and blower start-up prior to this procedure.
Pre-Start Information: Unit Control Circuits
To energize the unit control circuits (field-wiring shown on diagram with dashed lines):
- a. Exhaust fan (optional) - Connect terminals R to H
- b. Supply fan - Connect terminals R to G
- c. Heating - Connect terminals R to W1
- d. Cooling (optional) - Connect terminals R to Y1
Step 1: Energize Supply Fan
Energize the supply fan by connecting terminals R to G.
Step 2: Verify Blower Rotation
Verify blower rotation is correct.
- a. To reverse the rotation on three-phase units, disconnect and lock out the power, then interchange any two power leads going to the motor.
- b. Check motor amp draw and compare to motor nameplate FLA – reduce airflow if amp draw is greater than FLA.
Step 3: Check Burner Pressure Differential
Connect manometer to outer sensing probes. (Refer to diagram description for Fig. 1).
- a. Should be between 0.6-0.7 in wg for natural gas and 0.8-0.9 for LP.
- b. To increase the differential pressure, decrease the burner baffle opening evenly or increase airflow.
- c. To decrease the differential pressure, increase the burner baffle opening evenly or decrease airflow.
Diagram Description (Fig. 1): This diagram illustrates the setup for measuring pressure drop, featuring outer sensing probes, a pressure switch, and a U-tube manometer.
Step 4: Verify Unit Inlet Gas Pressure
Inlet gas pressure needs to be equal to or greater than the “minimum for maximum output”, but not to exceed the “maximum gas pressure” listed on the unit gas pressure label.
Step 5: Verify Inlet Air Sensor Setting
Verify inlet air sensor (TS4) setting is set above outside air temp (if equipped). If unit has a microprocessor, verify heating lockout setting.
Step 6: Energize Heating
Energize the heating by connecting terminals R to W1. If unit has a microprocessor, enable heat by setting the heat control to 1%.
Step 7: Check Pilot Flame Signal
Close main hand valve.
- a. LP only: Connect manometer to pilot test port. Energize fan; zero manometer; energize heat; adjust pilot pressure to 0.5 in. wg. Natural gas pilot pressure is preset at factory. (If not using a digital manometer, see IOM for further details on pilot differential for LP).
- b. Measure flame current with pilot valve lit and without main gas flowing.
- c. Set meter to μA DC scale.
- d. Locate flame signal terminals on BASO ignition control, place red lead on [+] terminal and black lead on [-] terminal. (Refer to diagram description for Fig. 4).
- e. Recommended minimum pilot only flame sense current of 1 μA DC.
Diagram Description (Fig. 4): This diagram shows the BASO Ignition Control with indicated terminals for flame signal sensing, specifying the placement of red and black leads.
Step 8: Set Maximum Firing Rate
Open main hand valve and then set maximum firing rate to the design temperature rise located on the direct gas nameplate. (Refer to diagram description for Fig. 3).
- a. Send unit to high fire by removing the wire connected to terminal 3 of the Maxitrol 14/44 amplifier. (If equipped with the SC25 Amplifier, connect terminals T1 and T2).
- b. While measuring temperature rise, adjust the combo valve regulator to achieve the desired temperature rise. (Temp rise = discharge temp - inlet temp).
Diagram Description (Fig. 3): This diagram shows a Combined Modulating Regulator with adjustments for minimum and maximum firing rates. It indicates removing a wire to send the unit to the minimum firing rate.
Step 9: Set Minimum Firing Rate
Set the minimum firing rate to achieve a small ribbon of continuous blue flame across the burner. (Refer to diagram description for Fig. 2).
- a. Disconnect one of the wires going to the modulating valve and isolate it.
- b. Set the minimum firing rate by adjusting the minimum firing rate adjustment on the modulating valve.
- c. Cycle the heat to make sure the burner can light at this low fire setting.
Diagram Description (Fig. 2): This diagram illustrates separate regulator and modulating valves. It points out the Pilot Pressure Adjustment (LP), minimum firing rate adjustment, and how to remove a wire to send the unit to the minimum firing rate.
Step 10: Remove Call for Heat
Remove power to terminal W1 to remove the call for heat. Reconnect wires to the Maxitrol amplifier and modulating valve.
Pilot Ignition ≤ 1200 mbh Quick Start Guide, Rev. 7, April 2022
