Category: Thermostats and Humidistats

Troubleshooting the Oil Burner Primary Control

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Table 5-4 lists possible remedies to a number of different operating problems associated with oil burner primary controls. Before checking the primary control, examine the following parts of the oil burner and ignition systems: • Main power supply and burner motor fuse • Ignition transformer • Electrode gap and position • Contacts between ignition transformer …

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Combination Primary Control and Aquastat

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Combination Primary Control and Aquastat

The combination primary control and aquastat is designed for use with a constant-ignition oil burner in a hydronic heating system. The purpose of this unit is to supervise the operation of the oil burner and provide both water temperature and circulator control. A remote sensor (cadmium detection cell) is used to detect any irregularities in …

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Stack Detector Primary Control

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Stack Detector Primary Control

Stack-mounted oil burner primary controls employ thermal sensors to detect ignition or flame failure. A typical stack detectorthermal sensor (see Figure 5-87) consists of a bimetal element inserted into the stack (see Figure 5-88). The thermal sensor (combustionthermostat) is usually located on the stack where the elementwill be exposed to the most rapid temperature changes. …

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Cadmium Cell Primary Controls

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Cadmium Cell Primary Controls

A cadmium cell primary control consists of a primary control assembly operating in conjunction with a cadmium detection cell. The cadmium detection cell is considered the most effective sensor used to monitor the burner flame. It consists of a light-sensitive photocell, a holder, and a cord assembly (see Figure 5-80). The surface of the detection …

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Oil Valves

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Oil Valves

Oil valves are used to provide on-off control of the flow of oil to the oil burner. These are normally closed solenoid valves that open when energized and close immediately when deenergized. They are variously referred to as solenoid oil valves, magnetic oil valves, or oil burner valves and are available in either immediate-discharge or …

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Oil Controls

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The principal functions of the oil controls are (1) to turn the oil burner on and off in response to temperature changes in the space or spaces being heated and (2) to stop the system if an unsafe condition develops. The following controls are necessary to perform these functions: • Thermostat • Limit controls • …

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Mercury Flame Sensors

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Many people frequently confuse mercury flame sensors (MFS) with thermocouples because each has a similar sensor that extends into the pilot flame and a tube connecting the device to the gas valve. Moreover, they have the same function in the control system of a gas-fired appliance, but there are significant differences. The principal components of …

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Igniters

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Igniters

An igniter produces the spark for direct ignition of the main gas burner in various heating applications (gas furnaces, gas boilers,gas water heaters, etc.). The Honeywell Q347 igniter shown in Figure 5-71 consists of an internal electrode with a ceramic insulator, bracket, and ground strap. The flame-sensing rod is separate from the hot-surface igniter in …

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Hot-Surface Ignition Module

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Hot-Surface Ignition Module

The principal components of a hot-surface ignition system are the hot-surface ignition module, a line voltage silicon carbide igniter (also sometimes called a glow stick or glow plug), a remote flame sensor, a 24-volt AC ignition-detection control, and a 24-volt (AC) redundant gas valve (see Figure 5-69). The flame sensor is designed to detect the …

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Direct-Spark Ignition Module

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Direct-Spark Ignition Module

The direct-spark ignition (DSI) module illustrated in Figure 5-67 is a low-voltage, solid-state unit that controls the gas valve, monitors the burner flame, and generates a high-voltage spark for ignition. DSI modules are available with or without a purge timer and with separate or combined igniters and flame sensors. Typical wiring connections for a direct-spark …

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