North American 4725E Radiant Tube Burners Control System, Instructions
Sheet 4725-1 Ref: Bulletin 4725
Figure 1. Suggested Control System
to others burners
MRV
trans.
low gas pressure switch
8697
1518
main gas cock
gas cock
7219SS
gas adjusting valve
blower
4725- -E Burner
low air pressure switch
1122
control motor with end switches
to other burners
INITIAL STARTING INSTRUCTIONS (Based on modulating or high-low-off control system with low-fire start and ignition shut off.)
1. Close all manual gas cocks. Start combustion air blower.
7. Open burner gas adjusting valve 5 turns from full closed (clockwise) position.
2. Set primary air adjustment for 30% (ratio capacity). From the fully closed (clockwise) position, turn adjusting screw out: 4 turns/4725-2-E 6 ½ turns/4725-3-E 3 turns/4725-4 and -5-E 7 turns/4725-6-E
8. Energize the control system including ignition transformer, MRV, 7219SS Regulator Solenoid (but not control motor). Look through observation port to be sure spark is on. For most reliable light- ing, electrode shoud be positioned as shown in Fig. 3.
9. Open the main gas cock and MRV, but leave individual gas cock(s) closed.
3. Adjust low gas and air pressure limit switches for 75% of supply pressures.
10. Open individual gas cock at one burner. If burner dœs not light in a few seconds, first de-energize the ignition, then close cock and purge tube for a few minutes. Back out Gas Adjust- ing Valve ½ to 1 turn further open; open individual gas cock. Repeat once or twice until main flame lights. If burner still dœs not light, check ignition and gas supply.
4. Adjust the control motor’s low fire proof auxiliary switch to make at ½ osi main air (breaks when driving toward high). 5. Adjust the control motor’s fuel permissive auxiliary switch to make at 1 osi main air (makes when driving toward high). 6. Adjust main air butterfly valve linkage for 1⁄3 osi at low fire and for rated capacity at high fire. Characterize linkage to open valve slowly when driving off low fire. See Fig. 2 and Instruc- tions 1230-2.
11. When flame is established, power control motor until air valve is in the high fire position.
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