4B. Induced-Draft Combustion System

Hi-E2

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Figure 29. Combustion System Diagram.

properly adjusted. Also be sure that the combustion air filter is clean and that there is no blockage of the vent or combustion air inlet. See later section on combustion air filter service.

4B. Induced-Draft Combustion System

The Hi-E2pool heater has an advanced combustion system which makes it highly efficient and reliable. This system is illustrated in Figure 29.

Aspecial corrosion resistant high-speed blower pulls flow through the system and exhausts it to the outdoors. Air is pulled into the system through a combustion air supply duct, when provided, and through an air filter into a venturi. The venturi functions much like an automobile carburetor venturi - i.e. when air is forced through it, a “negative” pressure is created at the venturi throat. This negative pressure pulls gas through a metering orifice, resulting in an optimal mixture of air and fuel gas. The air and gas are thoroughly mixed in the venturi tailpipe, pulled through a special burner and ignited in the combustion chamber. Hot combustion products are then pulled through a highly efficient downward-flow heat exchanger. Combustion products are cooled below their dew point and condensate water is formed and drained away. Flow then enters the blower, where it is forced out of the heater at the vent terminal or through a vent pipe to the outdoors.

4C. Heater Components and Their Operation

1.Gas valve / Regulator - The gas valve controls gas flow into the venturi. It provides flow only when the temperature control require heat and only if all safety controls

enable operation. It is also a negative pressure regulator. It regulates the gas pressure to 0.2” WC less than the air pressure at the venturi inlet. This is necessary for proper operation of the venturi system and cannot be done with common (positive pressure) gas valves.

2.Combustion blower - The combustion blower is a specially designed to handle moist combustion products, having special plastic housing and impeller. It is powered by a brushless DC motor.

3.Temperature Control - The Teledyne Laars Flex Temp control is an electronic control which senses water temperature by means of a thermistor and controls heater operation to bring the water to that selected. It has two temperature setting knobs which are typically used to set pool and spa temperatures. A selector switch determines which setting is chosen.

4.Ignition Control - The ignition control provides energy for ignition of the air/gas mixture, monitors the flame and controls the combustion blower and gas valve. When the temperature control requires heat, the ignition control starts the blower, providing a pre- purge of the combustion chamber. Then it applies electrical power to a “hot surface” igniter. When the igniter is hot enough, it opens the gas valve. It has sophisticated means to sense ignition and flame condition so that unburned gas will not escape. After the burner is shut off, it continues blower operation to provide a post-purge period.