Operation Option Switches, Heat Mode | White Rodgers 50A62-820

OPERATION

OPTION SWITCHES

The option switches on the 50A62-820 control are used to determine the length of the heat delay-to-fan-off period. The following table shows the time periods that will result from the various switch positions.

OPTION SWITCH POSITIONS

HEAT delay-	Set switch
to-fan-off:	#1	#2
180 sec.	On	On
120 sec.	On	Off
90 sec.	Off	On
60 sec.*	Off	Off

* Factory setting

HEAT MODE

In a typical system, a call for heat is initiated by closing the thermostat contacts. This starts the 50A62 control’s heat- ing sequence. The inducer blower and humidifier are energized (if there is an optional electronic air cleaner on the system, the humidifier is not energized until the electronic air cleaner is energized). The 768A Silicon Nitride ignitor is powered within one second.

This controller has an adaptive algorithm that reduces the ignitor temperature to slightly greater than the minimum temperature required to ignite gas in each particular application. The control measures the line voltage and determines an initial ignitor temperature setting based on the measurement. After each successful ignition, the control lowers the ignitor temperature slightly for the next ignition attempt. The control continues to lower the ignitor temperature until ignition does not occur, and the control goes into retry mode. For the second attempt to ignite gas within the same call for heat, the control increases the ignitor temperature to the value it was on the third previ- ous successful ignition. After ignition is successful, the control sets the ignition temperature at this value for the next 255 calls for heat, after which the control repeats the adaptive algorithm. The control is constantly making adjustments to the ignitor temperature to compensate for changes in the line voltage.

The 80 VAC Silicon Nitride ignitor manufactured by White-Rodgers must be used. These ignitors are spe- cially designed to operate with the 50A62’s adaptive ignition routine to ensure the most efficient ignitor tem- perature.

At the end of the ignitor warm-up time, both valves in the 36E manifold gas valve are opened. Flame must be detected within 4 seconds.

If flame is detected, the delay-to-fan-on period begins. After the delay-to-fan-on period ends, the circulator fan is energized at heat speed. If there is an optional electronic air cleaner on the system, the electronic air cleaner and the humidifier are energized. When the thermostat is satisfied, the gas valve is de-energized. After proof of

flame loss, the inducer blower remains energized to purge the system for 5 seconds. When the purge is complete, the inducer blower and humidifier are de-energized and the delay-to-fan-off period begins. After the delay-to-fan- off period ends, the circulator fan and electronic air cleaner are de-energized.

If flame is not detected, both valves are de-energized, the ignitor is turned off, and the 50A62 control goes into the “retry” sequence. The “retry” sequence provides a 15- second wait following an unsuccessful ignition attempt (flame not detected). After this wait, the ignition sequence is restarted. If this ignition attempt is unsuccessful, one more retry will be made before the control goes into system lockout.

If flame is detected, then lost, the 50A62 control will repeat the initial ignition sequence for a total of three “recycles”. After three unsuccessful “recycle” attempts, the control will go into system lockout.

If flame is established for more than 10 seconds after ignition, the 50A62 controller will clear the ignition attempt (or retry) counter. If flame is lost after 10 seconds, it will restart the ignition sequence. This can occur a maximum of five times before system lockout.

During burner operation, a momentary loss of power of 50 milliseconds or longer will de-energize the main gas valve. When power is restored, the gas valve will remain de-energized and a restart of the ignition sequence will begin immediately.

A momentary loss of gas supply, flame blowout, or a shorted or open condition in the flame probe circuit will be sensed within 2 seconds. The gas valve will de-energize and the control will restart the ignition sequence. Re- cycles will begin and the burner will operate normally if the gas supply returns, or the fault condition is corrected, before the last ignition attempt. Otherwise, the control will go into system lockout.

If the control has gone into system lockout, it may be possible to reset the control by a momentary power interruption of one second or longer. Refer to PRECAU-

TIONARY, SYSTEM LOCKOUT, AND DIAGNOSTIC FEATURES.

COOL MODE

In a typical system, a call for cool is initiated by closing the thermostat contacts. This starts the 50A62 control’s cool- ing sequence. The compressor is energized and the cool mode delay-to-fan-on period begins. After the delay-to- fan-on period ends, the circulator fan is energized at cool speed. The electronic air cleaner (optional) is also ener- gized. After the thermostat is satisfied, the compressor is de-energized and the cool mode delay-to-fan-off period begins. After the delay-to-fan-off period ends, the circula- tor fan and electronic air cleaner (optional) are de-ener- gized.

50A62-820 specifications

The White Rodgers 50A62-820 is a highly regarded, multi-stage thermostat designed to deliver precision comfort control in various HVAC systems. With its advanced features and reliable performance, it has become a popular choice among both homeowners and HVAC professionals.

One of the primary features of the 50A62-820 is its compatibility with a wide range of heating and cooling systems. This includes gas, oil, and electric furnaces, as well as heat pumps and air conditioning systems. Its versatility makes it suitable for many applications, ensuring that users can maintain optimal climate control in their homes or facilities.

The thermostat utilizes a user-friendly interface that simplifies operation. Its digital display clearly shows the current temperature and system settings, enabling easy monitoring and adjustments. This interface often includes intuitive buttons or touch screen functionality, allowing users to navigate through settings with ease.

A standout characteristic of the White Rodgers 50A62-820 is its programmable capabilities. Users can easily schedule temperature settings for different times of the day or week, which can lead to significant energy savings. For instance, homeowners can program the thermostat to lower temperatures during the night or when the house is unoccupied, contributing to enhanced energy efficiency without sacrificing comfort.

Another technological advantage of the 50A62-820 is its ability to manage multi-stage heating and cooling systems. This allows the thermostat to regulate the temperature more effectively, responding to changes in indoor and outdoor conditions with precision. Multi-stage systems can help to maintain consistent temperatures and improve overall energy efficiency.

The 50A62-820 is also designed with advanced safety features. It includes built-in temperature limit settings, helping to prevent overheating and ensuring that the HVAC system operates within safe parameters. Additionally, many models offer diagnostic capabilities, allowing users to identify issues and perform maintenance more efficiently.

Durability is a notable characteristic of the White Rodgers 50A62-820. Its construction is designed to withstand a variety of environmental conditions, making it a reliable choice for both residential and commercial installations.

In conclusion, the White Rodgers 50A62-820 thermostat is a sophisticated, versatile option for managing climate control in various environments. With its programmable features, compatibility with multi-stage systems, user-friendly design, and advanced safety technologies, it provides homeowners with a practical solution for enhancing comfort while promoting energy efficiency.