The Mars 50354 is a foot-mount step-down control transformer designed to power 24-volt control circuits in air conditioning, heating, and refrigeration systems. With color-coded primary and secondary leads, low heat rise construction, and UL5085 listing, it drops right in as a direct replacement for a wide range of OEM and aftermarket transformers.
Control transformers like the Mars 50354 are the backbone of low-voltage thermostat and control circuits in commercial and residential HVAC systems, walk-in coolers, rooftop units, and split systems. The 50354 accepts 120, 208, or 240 volt primary input and delivers a steady 24 volt AC output at up to 40VA -- enough capacity to drive contactors, relays, and thermostat circuits without voltage sag.
The foot-mount design makes installation straightforward: secure the transformer to the equipment chassis or panel, connect color-coded primary leads to the appropriate input voltage tap, and wire the secondary to your 24V control circuit. Secondary terminations include color-coded leads or 1/4-inch male quick-connect terminals, giving you flexibility depending on the control board or wiring harness you are working with.
Accepts 120V, 208V, or 240V input via color-coded primary leads -- one transformer covers the most common single-phase supply voltages.
NEMA Class II construction limits heat buildup, extending transformer life and reducing risk to surrounding components in tight equipment enclosures.
Secondary leads are color-coded for polarity, and 1/4-inch male quick-connect tabs are included for tool-free hookup to compatible harness connectors.
Replaces Honeywell, Packard, SUPCO, Diversitech, Smart Electric, Zettler, and IRP part numbers -- see the compatibility list below.
The 50354 is engineered as a drop-in replacement for a long list of common HVAC control transformers. If you are stocking a service van or repair shop, one Mars 50354 can replace multiple SKUs from different brands.
Mount the transformer to a stable surface inside the equipment enclosure using the foot-mount bracket. Select the correct primary lead pair for your supply voltage (120V, 208V, or 240V) and insulate any unused leads. Connect secondary leads or quick-connect tabs to the 24V control circuit. Verify output voltage with a multimeter before closing the panel.
The 50354 uses color-coded leads for each primary voltage tap. Always identify the correct lead pair for your supply voltage before energizing. Cap and insulate unused leads with appropriately rated wire nuts or tape to prevent accidental contact.
If a control transformer fails repeatedly in the same system, check the 24V circuit for shorts or overloaded secondary loads before installing the replacement. A transformer rated at 40VA should not be loaded beyond approximately 35VA continuously. Oversized secondary loads cause overheating and premature failure.
The Mars 50354 (also listed as NBK Parts 20604) is a verified direct replacement for the following part numbers:
This transformer is sold under multiple catalog numbers. NBK Parts number 20604 is the same unit as Mars 50354. If you are ordering from a distributor catalog, either number will identify this product.