Common Questions Can I use the MARS 44513 to replace a 40VA transformer

When supply air temperatures exceed the safe 125°F threshold

compatibility depends on the specific model and serial number

Is the locking collar included with the bearing

Reznor 123974 Fan Switch 30067439-890 Common Questions Can I useThe Reznor 123974 Fan Switch is a precise thermal control engineered for gas fired unit heaters and duct furnaces. Designed to manage blower cycles based on internal heat exchanger temperatures, this F135 30F fan control ensures the fan engages when the plenum reaches 135F and terminates operation once it cools to 105F (30F differential). As a direct replacement for part 48706, it maintains the critical timing required to prevent heat exchanger stress