Hydronic Heating Boilers and Domestic Water Heaters
CLEANING AND MAINTENANCE CONTINUED
A faulty hot surface igniter or ignition module must be replaced with an identical part. A specification igniter and ignition module for this specific unit is available from your local distributor. Do not use general purpose field
replacement ignition modules or igniters.
Ignition System Checkout
1.Turn off gas supply to unit.
2.Turn electric power on.
3.Adjust the set point on the temperature control to a setting above water temperature or to the highest safe setting.
4.The igniter will cycle on trial for ignition.
5.The ignition module will lock out and turn the alarm light on.
6.Adjust the Set Point Differential and
7.Turn on gas supply.
8.Press the module reset button to reset the ignition module. This is a red button beside the ignition module or on the diagnostic panel on the
9.If ignition system fails to operate properly, repair work must be performed by a qualified service person or installer.
SEQUENCE OF OPERATION
OVERVIEW
This sequence of operation can be considered the order of events in sequential order that occur after the appliance has received a call for heat. The process begins with 120VAC power entering the appliance and ends with the appliance going into an idle state after completion of a successful call for heat.
Note: The following descriptions do not include remotely connected devices that may be connected to the appliance. Refer to the wiring diagram for actual point to point wiring connections that show power delivery.
1.The POWER switch is placed in the “ON” position.
2.120VAC power is supplied to the control transformer along with L1 and F1 on the ignition module.
3.24VAC is supplied to the electronic temperature control, the ignition module and the adjustable high limit control.
4.24VAC is then supplied to the auxiliary limit control (if equipped).
5.If equipped, 24VAC is supplied to a low water
6.24VAC is supplied to the continuous alarm terminals A1 and A2 and then to the remote stage one terminal strip, 1C and 1NO.
7.24VAC is supplied to the electronic temperature control.
8.The electronic temperature control then calls for heat.
9.24VAC is supplied to the intermittent alarm field safety contacts, B1 and B2.
10.24VAC is supplied to the water flow switch (if equipped).
11.24VAC is supplied to the TH terminals on the ignition module.
12.As power is applied to the TH terminals on the ignition module, 120VAC is switched from the F2 terminal to start the combustion air fan at full speed on the 495,000 - 745,000 Btu/hr models and at low speed on the 985,000 - 2,065,000 Btu/hr models.
13.24VAC is supplied to the C terminal of the air pressure switch. As the low air switch makes, power is supplied to the ignition module.
14.24VAC is then supplied to the PS terminals on the ignition module as the air pressure switch makes to prove fan operation..
15.The combustion air fan operates for the
16.At the end of the
17.The hot surface igniter proves 1800 F (982 C) ignition temperature by current draw through the ignition module.
18.The ignition module supplies voltage to the MV terminals on to the gas valve(s).
F9 SINGLE STAGE FIRING
19.All gas valves on the 495,000 - 745,000 Btu/hr models and approximately half of the valves on the 985,000 - 2,065,000 Btu/hr models open, supplying gas to the orifice and burner inlet to
20.The gas/air mixture is forced into the burner and out of the burner ports under pressure.
21.The hot surface igniter lights the gas/air mixture and then serves as a flame sensor to prove main burner flame by rectification.
22.After a time delay of 10 seconds, the remaining gas valves on the 985,000 - 2,065,000 Btu/hr models open, supplying gas to the remaining burners.
23.The gas/air mixture is forced out of the burners and out of the burner ports under pressure.
24.The burners light by carryover from the burners currently firing.
25.The heater is now firing at full rated input.
M9 MODULE FIRING
26.The first stage gas valve(s) opens and supplies gas to the orifice and burner inlet to
27.The gas/air mixture is forced into the burner and out of the burner ports under pressure.
28.The hot surface igniter lights the gas/air mixture and then serves as a flame sensor to prove main burner flame by rectification.
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