Adjustment
There must be sufficient load to operate the boiler at high fire to perform the following adjustments. Start the boiler and observe proper operating parameters for the system.
Required Tools:
TORX® T40 or 5mm hex wrench 3mm or 7/64in hex wrench Combustion analyzer
The VF 500, 750, and 1000 boilers are equipped with a Honeywell combined gas/air control and gas safety shut off control valves. The valve functions in parallel with the variable speed combustion blower to supply the correct gas air ratio for optimum performance and efficiency. The combustion blower speed is controlled automatically and determines the amount of negative pressure experienced by the gas safety shut off/ control valves.The gas/air regulator adjusts gas flow to maintain the proper pressure at the outlet nozzle of the associated valve.
Setting of the Test Mode
On UIM go to main menu, scroll down to user settings and press select. Scroll down to MOD mode, press select. Use the up and down keys to select options: MIN (MINIMUM FIRING RATE). MAX (MAXIMUM FIRING RATE). MOD (FOR AUTOMATIC MODULATION MODE). Press select for the desired option. For checking the combustion setup on MIN or MAX the boiler will remain in this state for ten minutes before defaulting to the MOD (modulation) mode.
TABLE 11. - HIGH FIRE SETTING
NATURAL GAS | 8.5 | - 9.0% CO2 |
PROPANE | 9.5 | - 10.5% CO2 |
Set boiler to the “Test Mode High,” as described above, to achieve maximum firing rate of the boiler. Check combustion readings using a combustion analyzer. If combustion readings are not in accordance with the chart above adjust as follows: remove the flat, round, blue plastic cap from the cover. Using a 3mm (7/64”) hex wrench, turn the adjustment screw counterclockwise to increase or clockwise to decrease gas flow and achieve the desired CO2 level. See Table referenced above for correct settings. There will be a slight time delay between the adjustment and the response of the CO2 measuring instrument. Adjust the settings in small increments and allow the combustion readings to stabilize before readjusting. When desired adjustments are complete, reinstall the blue plastic cap on the cover. Combustion samples shall be taken within two feet of the boiler. IMPROPER ADJUSTMENT CAN CAUSE
INCOMPLETE COMBUSTION RESULTING IN DEATH.
TABLE 12. - LOW FIRE SETTING
NATURAL | 6.5 - 7.5% CO2 |
PROPANE | 7.5 - 8.5% CO2 |
Set boiler to the “Test Mode Low,” as described above, to achieve minimum firing rate of the boiler. Check combustion readings using a combustion analyzer. If combustion readings are not in accordance with the chart shown above adjust as follows: remove the cap on the gas regulator using a slotted screwdriver. This will expose the offset adjustment screw. Using a TORX® T40 or a 5mm hex wrench, carefully adjust the low fire gas setting to achieve the CO2 level prescribed in above reference table. Note: The rotation of the Low
Fire adjustment is opposite of the High Fire as follows: Clockwise rotation increases gas flow, counterclockwise rotation decreases gas flow.
Adjustments to the offset pressure regulators should not exceed 1/4 turn at a time before allowing the readings to respond and stabilize.
After proper low fire offset adjustment is made, reinstall the slotted cap on the regulator.
Following all gas valve adjustments, check for proper light-off and verify correct fuel/air mix and combustion quality throughout the entire firing range (from lowest to highest fan speed).
Control System
The EMC modulation control system is a fully integrated, state of the art electronic control system. It consists of sensors, output devices, a power switch, a 24VAC transformer, wiring, and the following printed circuit boards:
•Modulation Control Board (MCB), see Figure 2.
•Power Distribution Board (PDB), see Figure 2.
•User Interface Module (UIM), see Figure 20.
The MCB contains circuitry for both master control and flame control. Dip switches on the MCB are used to configure the system. The User Interface Module (UIM) communicates with the user through a set of touch pads and a 4-line, 20-character LCD display. The PDB provides connection points for input power, the water pump, and the transformer. It also distributes power to the system and contains the system fuses.
The MCB also contains an external communications system to allow for connection to a PC, a modem, an EMS system, or something similar. Through this connection, multiple boilers can also be linked together. CAUTION: The internal communications cables should never be connected to the external communications connectors, and vice- versa.
There are several microcontrollers used on the boards. These control the temperature and ignition control functions for the boiler. Inherent in the design are the normal operating sequences and safety features associated with a gas ignition control system. The system continuously performs various diagnostic tests to verify proper appliance and control operation. Should an unsafe condition occur, the control will shut down the burner and display a red service light as well as indicate the cause of the error on the display. The operating programs for the system are stored in permanent memory inside the microcontrollers. User-selectable operating parameters and a history of detected faults are stored in rewritable memory in the microcontrollers. A loss of power does not affect either of the memories.
