Installation and Service Manual
29.Burners are now firing for approximately 50% of the heater’s input.
30.24VAC is supplied from the second stage of the electronic temperature control across the 2C and 2NO terminals on the terminal strip on to a control to a relay.
31.The control relay switches the fan on the 985,000 - 2,065,000 Btu/hr models to high speed and energizes the gas valves for the remaining 50% of burner input.
32.The remaining gas valves open and supply gas to the orifice inlet to
33.The gas/air mixture is forced out of the burner ports and light by carryover from the burners currently firing.
34.The heater is now firing at full rated input.
HEAT TRANSFER PROCESS
35.Heated products of combustion pass over the heat exchanger transferring heat to the water.
36.The rate of flue product movement is controlled by “V” baffles on the heat exchanger to maximize heat transfer.
37.Flue products pass into the flue collector and are exhausted from the unit.
END OF SEQUENCE
38.Set point for the high fire on the electronic temperature control is satisfied.
39.Power to all valves is turned OFF on F9 systems and power to the high fire gas valves is turned OFF on M9 systems.
40.The water temperature continues to rise and the set point for low fire is satisfied (M9).
41.Power to the low fire gas valves is turned OFF (M9).
42.The combustion air fan runs for a 30 second post purge timing and turns OFF.
43.The appliance is now in a Standby Mode waiting for the next “call for heat”.
GLOSSARY
Power Supply
(AC120VAC/60Hz)
120VAC/60Hz/1PH power connects to black (line) and white (neutral) wires located within an electrical wiring box located on the left side of the unit. A green chassis grounding wire is also provided for connection to earth ground.
ON/OFF Rocker Switch
The black line voltage wire runs directly to a single pole, single throw On/Off rocker switch located behind the front cover accessible by a thumb screw. Turning ON the rocker switch delivers line voltage to the low voltage transformer and ignition module.
Note: The On/Off switch does not provide for disconnection of power being supplied to any remotely connected devices that may be connected to the unit (i.e. pumps, louvers, power
venters, etc.,). As such, it may be necessary to locate and turn off power to these items before attempting to service the unit.
Low Voltage Supply Transformer
A 120VAC to 24VAC transformer located within the control panel provides 24VAC/60Hz to many of the components located on the unit. One of its 24VAC outputs (blue) is connected to a circuit breaker and the other (yellow) is connected to chassis ground.
24VAC Circuit Breaker
A circuit breaker is provided on the 985,000 - 2,065,000 Btu/hr models for protection of the low voltage supply transformer from overloads and short circuits. The breaker is located inside the unit on the lower right corner of the control panel. Power from this breaker goes to the electronic temperature controller, ignition module and various other components and/or options on the unit. When tripped, all
Manual Reset High-Limit Thermostat
A manual reset high limit thermostat is provided as backup for the temperature controller. This will either be an adjustable dial or fixed temperature
EMS/Sequencer/Remote Aquastat Terminals
The EMS/sequencer/remote aquastat terminals are provided for connection of the unit to an external energy management system or sequencer and are located along the top edge of the terminal strip located within the electrical wiring box. In addition to providing a means to externally stage fire the unit, these terminals also provide for remote shutdown and override by routing through dry contacts from external devices. Connection of the external dry contacts to these terminals requires the removal of one or more factory installed jumpers located on the terminal strip.
Safety Device Terminals
The safety device terminals ensure that no power can be delivered to the ignition module unless
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