Troubleshooting Guide

Screen Is Blank

• The 422 receives power from the 24VAC plug on the back. Verify that the zone/power manager connected to the 422 is supplying power.
• If the zone/power manager is supplying voltage, use a meter to check for 24VAC at the plug. This may require stripping a small section of thermostat wire to allow meter probes to connect. Exercise caution to avoid shorting the 24VAC by touching wires together. If the zone/power manager is not providing voltage, it needs to be replaced.

Check Sensors

• Begin by navigating through the view menu and questioning if the displayed numbers are accurate.
• Consider if the readings are reasonable in the context of current environmental conditions. For example, if it's a cold winter day and the outdoor sensor reads 90°F (32°C), this is likely incorrect.
• If sensor readings appear inaccurate, use an ohm meter for measurements. Consult the sensor manual or the 'Sensor Troubleshooting Guide' for specific testing instructions.

Other Sensor Issues

• Sensor errors can also stem from incorrect placement or wiring to the wrong terminals. Examples include mixing supply sensors with boiler supply terminals, or placing outdoor sensors in direct sunlight or too close to boiler exhaust vents. Sensors must be positioned to accurately measure ambient temperature for the designated input on the 422.

Outdoor Sensor Notes

• The 422 requires an outdoor sensor for the outdoor reset function to operate correctly and manage heating calls according to WWSD (Warm Weather Shut Down) settings.
• DHW (Domestic Hot Water) and setpoint calls are not affected by WWSD.
• Refer to the section on bypassing the outdoor sensor if it becomes necessary to enable heating without relying on the outdoor sensor.
• For situations where a wired outdoor sensor is impractical, consider using the 087 wireless outdoor sensor.

Bypassing Outdoor Sensor

• Common reasons for bypassing the outdoor sensor include testing equipment during summer months or when the outdoor sensor is reading high, causing the unit to enter WWSD during winter.
• You can check the current outdoor sensor reading and adjust the WWSD setpoint above it. It is important to record the original setting before making changes to ensure it can be restored later.
• Alternatively, you can bypass the sensor by removing the wire from the 'Out sensor' terminal (terminal 70). This will trigger an 'Outdoor Open' error on the 422, but the unit will operate as if the outdoor temperature is 32°F (0°C). This temporary measure allows the 422 to supply heat until a replacement outdoor sensor can be sourced.

Boiler Not Firing

• Check the 'View' menu to compare the 'Boiler Target' and 'Boiler Supply' temperatures. If the boiler has reached its target temperature, it will not fire.
• Investigate the differential setting. The 422 fires the boiler until it reaches the boiler target plus half the differential. It then waits until the temperature drops to half the differential below the target before firing again. Determine if the boiler is currently in a cool-down cycle.
• Verify if a call for heat is indicated in the 'View' menu.
• Ensure the On-Off/Mod DIP switch is set correctly for the type of boiler being used.
• Check if the 422 'View' screen displays the burner symbol.
• Examine the 422's output signal to the boiler. If the 422 is sending the correct signal, the issue may lie with the field wiring or the boiler itself.

Not Turning on the Mixing

• Check if the unit is in WWSD mode.
• In the 'View' menu, compare the 'Mix Target' and 'Mix Supply' temperatures. Adjusting the mixing is unnecessary if the target temperature has already been reached.
• Verify that the control for the mixing device (e.g., 440/444) is configured correctly. Mixing devices can operate using either a floating action valve or an injection pump.
• If a floating action valve is used, check if the open and close contacts are reversed.
• Identify the type of pump used for the mixing operation. The 422 requires a standard wet rotor, non-ECM pump.

Checking a Floating Action Valve

• Confirm that the open and close contacts are not reversed.
• During the test procedure (accessed via the 'Test' button), the valve should open and close. When the valve opens, verify 24VAC is present between the C and Opn terminals, and 0VAC between C and Cls. The readings should be reversed when the valve closes.
• To isolate the mixing device's output, label and remove the wires connected to the actuator. Rerun the test procedure and check the voltages. If the device is outputting the correct signal, inspect the field wiring or the actuator itself.
• To test the actuator, label and remove its wires. Apply 24VAC directly to the 'open' or 'close' terminal. It is also possible that the valve assembly may be stiff. To test this, remove the actuator from the valve and rerun the test to ensure the actuator moves freely.

Checking a Variable Speed Pump

• The 422 controls a standard wet rotor, non-ECM pump as a variable speed pump by modulating the sine wave of the voltage supplied to it. It is normal to measure the full 120VAC output when operating below 100% mixing output, even at 0% output.
• Confirm that the mixing pump is the correct type; it must be a standard wet rotor, non-ECM pump.
• When running the test, listen and feel for the pump ramping up and down.
• To test the pump directly, wire it to a 120VAC source; it should operate at full speed.

DHW

• DHW calls are not impacted by WWSD.
• DHW calls originate from an aquastat that must provide a voltage ranging from 20-260VAC across the DHW Demand terminals (53 & 54).
• Verify that the DHW mode setting is correct. Review the DHW pump piping in the 'DHW mode diagrams' on page 24 of the Data Brochure (I/O manual). Ensure the correct mode is selected to activate the system pump if necessary.
• DHW calls will be disregarded if the 422 is in 'Away' mode.

Notes on Bus Configuration

• The 422 can accommodate up to two mix temperature buses. Mix 1 zones and connections are managed through the zone/power manager paired with the 422.
• The second bus connects via terminals 59 & 60. These can be designated as either a boiler bus or Mix 2, determined by the Boiler/Mix 2 DIP switch located on the left side of the 422.

Notes

• To access all available settings, navigate to the 'Misc' menu and set the access level to 'Ad' (Advanced).
• Not all menu settings detailed in the manual may be visible on the 422. Some settings are dependent on the bus configuration and may appear hidden.

Sensor Resistance vs Temperature

Contact customer service for assistance with technical details.