Written on: August 5, 2024 by Timmie McElwain
As we continue looking at some of the more advanced electronic controls used on gas heating, and particularly the more advanced high efficiency equipment, it is important to understand how the controls are applied. The majority of new equipment today involves some form of electronics, as well as the principal of electronic flame detection and the use of flame rectification as a safety and flame proving system.
Different equipment manufacturers may have different ways of applying these controls—from intermittent pilot application to direct spark ignition and including hot surface. It is important to understand how the controls operate and not jump to conclusions without going through the operating procedures. This article continues our series on Advanced Controls for Gas Heating.
On a personal note, I want to take this opportunity to let everyone know that after 30 years in business, we have closed the Gas Training Institute. The eight manuals used in our one-week course are still being printed and are available for purchase.
Honeywell ST9160A-C Electronic Fan Timers
The ST9160A-C Electronic Fan Timers integrate control of all circulating fan operations in a gas warm air furnace. This control is the central wiring point for most of the electrical components in the furnace. The ST9160 monitors the thermostat for heat, cool and fan demands, and controls a two-speed circulating fan as required. Communication with the SmartValve System Control initiates appliance light OFF. The ST9160 features a fixed or field-adjustable heat fan ON delay and a fixed or field-adjustable heat fan OFF delay, depending on model. Cooling fan ON and OFF delay is fixed; specific timings vary. See the label or instructions for timings that are available for a specific appliance. Refer to Figure 2 for model specifications.
Electronic air cleaner (EAC) and humidifier (HUM) convenience terminal connections can be provided as an option, as can continuous low speed indoor air circulation. Thermostat connections are screw terminals or quick-connects.
The ST9160A-C Electronic Fan Timers are used exclusively with Generation III SmartValves SV9510/SV9520 and SV9540/SV9640.
Figure 2 covers the settings of the dip switches on the various models. The ST9160A is a fixed setting all the way. The ST9160B has an adjustable OFF delay, giving four different settings. The ST9160C has two adjustable heat ON delays—30 and 60 seconds, set on switch three. The four adjustable OFF settings are 60, 100, 140 and 180 seconds.
Figure 3 shows the component parts of the ST9160 EFT. Of particular interest is the twinning connection shown on the left hand side just below the R12 resistor. There is also a separate connection for the DATA signal from the SmartValve.
The diagram in Figure 4 shows the ST9160 with the SV9540 or SV9640 SmartValves, which use the Q3450 24 volt igniter. The Figure 5 illustration shows the ST9160 with the SV9510 or SV9610 series or the SV9520 or SV9620, which used 120-volt igniters.
Figure 6 shows the connections from the ST9160 to the SmartValve. The red dotted line is the connection that is different for the SV9540 and SV9640 series. ICM
