Reznor UDZ - User Manual

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Questions and Answers

H
Hayley JonesJul 25, 2025
How to troubleshoot a Reznor Heater venter motor that will not start?
- K
  Kathryn McbrideJul 26, 2025
  If the venter motor on your Reznor Heater won't start, begin by ensuring the unit has power and checking the supply fuses or circuit breaker. Next, verify that the thermostat is turned up to supply 24V power to the integrated circuit board. Check the control transformer output. Inspect the integrated circuit board fuse and replace it if blown (3A, type ATC or ATO, 32VDC) after correcting the cause. Tighten connections at the circuit board and/or motor terminals to ensure power is reaching the venter motor. If these steps don't resolve the issue, the integrated circuit board or the venter motor itself may be defective and require replacement.
H
Heather RobertsonJul 30, 2025
What causes the fan or venter motor to not run in my Reznor Heater?
- J
  Jordan MatthewsJul 31, 2025
  If the fan or venter motor on your Reznor Heater will not run, check the wiring and connections for any open circuits. If the wiring is intact, the integrated circuit board or the motor itself may be defective and require replacement.
R
Rachel DeckerAug 9, 2025
Why does my Reznor UDZ burner keep cycling ON and OFF?
- G
  Gail Mccoy MDAug 9, 2025
  If the burner in your Reznor Heater cycles on and off, the gas pressure might be too high or too low; ensure it's at 5–14 IN WC for natural gas or 11–14 IN WC for propane. Check that the burner and circuit board are properly grounded. If 24V power is available to the integrated circuit board and all other causes have been eliminated, replace the board. Make sure the unit is properly vented, removing any obstructions, and replace any faulty tubing to the pressure switch. Replace the pressure switch if it's faulty. Check that the flame sensor lead isn't grounded and that the sensor insulation or ceramic isn't cracked; replace if needed. If the polarity is incorrect, reverse the line volt leads to the integrated circuit board. Finally, replace the wire harness if a pin terminal is loose.
G
Gina HallAug 14, 2025
Why does the fan or venter motor cut out on overload in my Reznor UDZ?
- S
  Sonia NolanAug 15, 2025
  If your Reznor Heater's fan or venter motor cuts out on overload, ensure the electric supply voltage is correct. If the voltage supply is not the issue, the motor may be defective and require replacement. Poor airflow can also cause this issue, so clean the motor, fan, and fan guard.
A
ashleyhuangAug 20, 2025
Why does the fan or venter motor turn ON and OFF while the burner is operating on my Reznor UDZ?
- W
  wilkinsronaldAug 20, 2025
  If the fan or venter motor in your Reznor Heater turns on and off while the burner is operating, the motor overload device might be cycling. Check the motor load against the motor rating plate, and replace the motor if needed.
C
Connie Moore MDNov 3, 2025
What to do if my Reznor Heater burner will not light?
- J
  Jason HoltNov 4, 2025
  To troubleshoot a Reznor Heater burner that won't light, start by opening the manual valve to ensure gas flow. If it's a new installation, bleed the gas line to remove any air. Check that the gas pressure is within the correct range: 5–14 IN WC for natural gas or 11–14 IN WC for propane. Inspect all wire connections for solidity and confirm 24V power is available to the transformer. Ensure the spark gap is 1/8 inch and replace any worn or grounded spark cables or cracked ceramic spark electrodes. Verify the integrated circuit board and the unit itself are properly grounded. If a lockout device is interrupting the control circuit, reset it at the thermostat or main power. Make sure the interlock door switch is closed, and the unit is properly vented with no obstructions. Replace any faulty ...

Summary

Safety and Hazard Warnings

Fire or Explosion Hazard

Critical safety warnings regarding fire and explosion risks.

What to Do If You Smell Gas

Emergency procedures for gas leaks, including evacuation and contacting authorities.

General Information

References

Lists related technical manuals and documentation for installation and operation.

Important Safety Information

Crucial safety warnings, their meanings, and their importance.

Installation Codes

Compliance requirements with national and local building and gas codes.

Unit Location

Guidance on selecting an appropriate and safe location for unit installation.

Heater Throw

Details air throw patterns and distances for optimal heat distribution.

Mounting Height Requirements

Specifies safe and effective minimum and recommended mounting heights.

Hazards of Chlorine

Warns about potential corrosion risks from chlorine vapors affecting the unit.

Dimensions

Refers to figures and tables for detailed unit dimensions.

Combustion Air Requirements

Details air needs for combustion and installation requirements.

Acoustical Considerations

Refers to sound level data for determining unit location based on acoustics.

Technical Data

Refers to tables listing unit technical data for various models.

Installation

Unpacking and Inspection

Procedures for safely unpacking the unit and checking for shipping damage.

Pre-Installation Checklist

Essential steps and checks before beginning the installation process.

Heater Suspension

Instructions and considerations for securely suspending the heater unit.

Piping Connections

Details on connecting gas supply lines, including pressure and testing.

Electrical Connections

Guidance on proper wiring, grounding, and connection of electrical components.

Controls

Pressure Switch

Explains the function and operation of the pressure-sensitive switch.

High Temperature Limit Control

Details the automatic-reset limit control that prevents overheating.

Flame Rollout Switch

Information on the manually-reset switch for detecting flame rollout.

Main Operating Gas Valve

Importance and function of the gas valve as a safety shutoff.

Thermostat Options

Guidance on thermostat installation and connection requirements.

Circuit Board (DSI Control Module)

Explanation of the control module, its display, and fault codes.

Operation

Startup Procedure

Step-by-step instructions for safely starting the heater unit.

Operating Sequences

Details the normal and abnormal operating sequences of the heater.

Vent System Testing

Procedures for testing the vent system's integrity and performance.

Adjustments

Measure and Adjust Manifold (Outlet) Gas Pressure

Instructions for measuring and adjusting gas pressure for optimal performance.

Maintenance

Service Checklist

A minimum annual checklist for servicing and maintaining the equipment.

Burner Maintenance

Procedures for inspecting and cleaning the burner assembly for optimal combustion.

Heat Exchanger Maintenance

Instructions for inspecting the heat exchanger for damage like cracks or holes.

Ignition System Maintenance

Maintenance for the ignition system, including fuse replacement and sensor cleaning.

Maintenance of Fan Motor, Fan Blades, and Fan Guard

Procedures for cleaning and inspecting the fan motor, blades, and guard.

Venter Motor and Wheel Assembly Maintenance

Steps for maintaining the venter motor and wheel assembly.

Operating Gas Valve Maintenance

Instructions for inspecting and testing the gas valve for proper shutoff.

Flame Rollout Switch Maintenance

How to address and reset the flame rollout switch.

Troubleshooting

Unit Troubleshooting Using DSI Control Module

How to use the DSI control module display for diagnosing issues.

General Troubleshooting

Common symptoms, probable causes, and remedies for unit malfunctions.

Reznor UDZ Specifications

General

Type	Unit Heater
Fuel Type	Natural Gas or Propane
Dimensions	Varies by model
Weight	Varies by model
Heat Output	Varies with model
Efficiency	Up to 83%
Control Type	Thermostat
Ventilation	Power Vented
Heating Capacity	30, 000 to 400, 000 BTU/hr