Gas-Fired Unit Heaters
A gas-fired unit heater is designed to operate on either natural or propane gas (see Figure 2-91). These units should be installed in a location where there will be sufficient ventilation for combustion and proper venting under normal conditions of use.
Local codes and regulations should be followed closely when installing a gas-fired unit heater.
The automatic controls used to operate a gas-fired unit heater closely resemble those found on other types of gas heating equipment, such as furnaces, boilers, and water heaters. For example, the unit heater illustrated in Figure 2-92 is equipped with a 24-volt gas valve with a built-in pilot relay, pilot gas adjustment, shutoff device for use with a thermocouple-type pilot for complete gas shutoff operation, and a gas-pressure regulator.
A separate gas-pressure regulator and pilot valve are generally supplied with control systems when the gas valve does not have a built-in gas-pressure regulator. The usual fan and limit controls are used on most gas-fired unit heaters. A wiring diagram for a typical control system is shown in Figure 2-93.