All Reznor units have wiring diagrams either affixed to the unit or accompanying the unit in a separate envelope. Many times the wiring information that is shipped in the separate envelope is lost or destroyed. For such occasions, the wiring diagram number is needed to acquire a replacement copy. Due to the complexity of many of these units, the exact wiring diagram must be used. For this reason, Reznor has attached a plate on the outer jacket of the blower section. This plate contains model, electrical data, horsepower, CFM, ESP and the wiring diagram number which has the prefix letters "WD". If you need a replacement diagram, this number is paramount in obtaining the correct wiring information. Without this number, you should be prepared to describe the unit in total including model number, gas controls, voltage, damper information and sequencing. Very important also is the serial number from the rating plate. However, with the "WD" number, you can be assured that the proper wiring diagram will be supplied. To acquire a replacement wiring diagram, contact your Reznor Representative. Wiring diagrams are also available on the Reznor web site at Reznor's web site.