Loss of Power

Modu-Fire®Gas-Fired Boiler

minal 9 of the Combustion Control is energized. This opens the main gas valve and energizes the air gas ratio control. The 15 second "Main Flame Establishing” period begins. If pilot flame has not been established, the unit will lock out on pilot flame failure.

13.After the 15 second “Main Flame Establishing Period” if flame has been established, Terminal 8 of the combustion control is de-energized, closing the pilot valve. Terminal 15 is ener- gized, providing power to the modulating con- trol of the boiler. If main flame has not been es- tablished, the unit will lock out on main flame failure.

14.The unit modulates between the low fire setting and the high fire setting to maintain the desired outlet water temp set point.

15.When the load is below the low fire rating of the boiler the boiler will continue firing and the out- let water temperature will rise until it reaches operating limit setpoint value. At this point the operating control switch opens and the combus- tion control is de-energized at Terminal 6 and the indicator for HEAT is turned off. This ac- tion also de-energizes Terminal 9 thus closing the main gas valve and the air gas ratio control valve. Terminal 14 is energized which applies power to the close terminal of the air damper motor. The air damper closes.

16.When the water temperature is reduced by the load on the system, the operating control switch will close again. The operating sequence will recycle to step 5, provided the limits on water flow, gas pressure and high temperature are all met.

5.6TROUBLESHOOTING

In the event of loss of power, the entire boiler sys- tem is de-energized, closing all automatic valves and halting all boiler operations. When power is restored the sequence of operation will resume at Step 5, provided that all the limits are satisfied.

Maintenance

Loss of Water Flow

When the "Water Flow" indicator is illuminated, there is insufficient water flow to close the switch, and burner operation is interrupted. When water flow is re-established, the sequence returns to Step 2, provided that the other limits are satisfied.

Gas Pressure

When the "Gas Press" indicator is illuminated, there has been either insufficient gas pressure or the gas pressure to the manifold is too high for safe and proper operation of the boiler. The power to the programmer will be interrupted.

If a gas-supply shut-off valve is closed for any rea- son, a low gas condition will result.

When gas pressure is restored, the "Gas Press" indi- cator will remain on and the boiler will remain locked out until the gas pressure switch is manually reset.

In the event of a high gas manifold pressure condi- tion, the “Gas Press” indicator will illuminate indi- cating a potential air gas ratio control failure. This must be corrected by factory-trained personnel be- fore restarting the boiler.

Once the switch is reset, the sequence returns to Step 3, provided that the other limits are satisfied.

High Water Temperature

When the boiler water has exceeded both the operat- ing and high-limit temperature, power to the pro- grammer is interrupted. When the water tempera- ture falls below the high-limit temperature, the boiler will remain locked out until the switch is manually reset. Once the switch is reset, the se- quence returns to Step 4 to await heat demand pro- vided that the other limits are satisfied.

Low Air

If the "Low Air" indicator remains on for longer than 20 seconds, there is insufficient airflow through the burner. An extended low air indication does not mean that the low air switch is defective.