Summary: The following procedure is to be used for setting up modulating gas heat on Trane Creative Solutions modified Precedent units only. See standard product literature for unmodified/standard units with modulating gas heat. The article below can be used to identify if a unit has been modified.
Getting Started:
1. Turn off power to unit
2. Confirm entering gas pressure is a minimum of 4.5”w.c. (6" w.c. 400,000 BTU/Hr model burners) and maximum is 14” w.c.
3. Remove plug from manifold pressure tap and connect a manometer. (See Fig.1)
4. Locate the White Rodgers 2-stage gas valve. Hi and low stages have been wired together so the valve functions as an on/off 1-stage valve, only Hi regulator adjustments will be necessary. Remove the brass cover to gain access to the adjustment screw. Check to see valve switch is in “ON” position (See Fig. 2)
5. Unscrew blue cap on the Maxitrol modulator valve (M520B) covering the low fire adjustment. Two blue caps/low fire adjustments are available. Only one of the two require adjustment, use the one that is most convenient based on the valve orientation in the unit. Turn screw counterclockwise until screw head is flush to the end of fitting. (See Fig. 3)
6. Connect adjustable DC voltage supply capable of 0-10 VDC to terminals 7 and 8 on SC30 control with correct polarity. (See Fig. 4). You may skip this step if you have Tracer TU since you can override the VDC output from the UC controller for staging heat for this procedure.
7. Connect DC voltmeter with range of 0 -30 volts to terminals 3 and 4 on SC30 control. (See Fig. 5)
8. Adjust the VDC voltage to 0 if using a separate power supply or connect your PC to the UC controller and override the Analog Output labeled as Modulating Gas Heat Output to 0%.
9. Turn on power to unit.
10. Initiate a call for heat 1 using the Symbio App or through Tracer TU.
11. Draft fan will start at high speed and run for a 30 second pre-purge period.
12. At the end of pre-purge period, an ignition cycle is initiated opening both White Rodgers 2-stage valve and the M520B modulator valve, and a delay timing sequence in the SC30 control starts. The delay timing depends on the control model and holds the system at mid-fire input to allow heat exchanger warm-up prior to control modulation. Refer to model number on case (see Fig. 5) for delay time:
Model SC30 – 30 seconds
Model SC30-001 – 120 seconds
13. If ignition does not occur, turn Hi fire regulator (See Fig.2) 1 ½ to 2 turns clockwise. Cycle the heat 1 off / on in Symbio App to restart the heating sequence. (Note: If ignition control is 1016-427, unit will not restart until 60 post-purge is complete).
14. During this warm-up period, only the mid-fire manifold pressure can be measured, and the modulator “hold” voltage can be adjusted.
15. The mid-fire manifold pressure should read 1.1 to 1.2” w.c. and the modulator valve voltage should be 12 to 13 VDC.
16. Verify that the modulator valve voltage is 12 -13 VDC. Use the R22 potentiometer on SC30 to adjust the voltage as needed. Clockwise rotation will increase the output and counterclockwise will decrease the output. Adjust the R22 potentiometer as close to 13 VDC as the control will allow. (See Fig. 6) Warning: Do Not force dial screw as this will damage potentiometer. Do Not Adjust above 13.5VDC.
17. With DC supply voltage @ 0 VDC, the draft fan will switch to low speed 20 to 30 seconds after burner ignition with the SC30 or switch to low speed 60-90 seconds after burner ignition with the SC30-001.
18. NO other adjustments can be made during the balance of the warm-up period.
19. At the end of the control timing on the SC30 control, the output to the modulator valve will drop to minimum (0 to 1.0 V).
20. If the SC30 times out in less than 25 seconds or the SC30-001 times out in less than 100 seconds, turn Potentiometer R18 clockwise to increase hold time to desired time. (See Fig. 6)
21. Turn screw on modulator valve (See Fig. 3) clockwise to reduce manifold pressure to 0.4” to 0.5” w.c.
22. Replace blue cap on M520B modulator valve.
23. Adjust the VDC voltage to 5 if using a separate power supply or override the Analog Output labeled as Modulating Gas Heat Output to 50%. Modulator valve voltage should be 9.5 to 10.0 VDC. If voltage is less than 9.5, turn Potentiometer R77 clockwise to increase. If voltage is higher than 10 VDC, turn R77 counterclockwise to decrease. (See Fig. 6)
24. Draft fan will still be operating at low speed.
25. Adjust the VDC voltage to 6 if using a separate power supply or override the Analog Output labeled as Modulating Gas Heat Output to 60%. After a 10 to 30 second delay, inducer fan will switch to high speed. Manifold gas pressure should be less than 3.0” w.c. Adjustments to gas pressure cannot be made.
26. Adjust the VDC voltage to 10 if using a separate power supply or override the Analog Output labeled as Modulating Gas Heat Output to 100%. Manifold pressure should be 3.3 to 3.5 “w.c. If manifold pressure is less than 3.3”w.c., turn Hi regulator (See Fig. 2) adjustment clockwise to increase manifold pressure. If pressure is higher than 3.5”w.c., turn Hi adjustment counterclockwise to reduce pressure to specified range.
27. Release the overrides in TU and disconnect your PC.
28. Turn off power to unit.
29. Remove pressure gage from manifold tap and replace pipe plug.
30. Reinstall the brass cover for the Hi regulator adjustment on the on/off gas valve.
31. Remove voltmeter leads from terminals 3 and 4 on SC30.
32. Turn power on and the system is ready to operate.
WARNING:
Information in this article is intended for use by individuals possessing adequate backgrounds of electrical and mechanical experience and who comply with all federal, state, and local laws, rules, orders, or regulations related to the installation, service, or repair of a heating or central air conditioning product. Any attempt to install, service, or repair a heating or central air conditioning product may result in personal injury and/or property damage. The manufacturer or seller cannot be responsible for the interpretation of the information contained herein, nor can it assume any liability in connection with its use.