From there

you maintain the integrity of the internal wiring and safeguard expensive components like blower motors and heating elements from thermal damage

Is the Lennox 87H92 interchangeable with the 20121901

including the 90UGFA

By utilizing a non-porous heating element

Modine 5H0750290000 Transformer Els PW 17895 From thereMaintain the electrical integrity of your unit heater with the Modine 5H0750290000 Transformer, a precision engineered 40VA control transformer designed for reliable stepped down power distribution. This OEM replacement part is the current direct substitute for the legacy Modine 5H75029, ensuring a perfect physical and electrical fit without field modifications. It operates with a 120V primary voltage and delivers a stable 24V secondary output,