Tempstar 40VA Transformer for TEB12R50RTA — 277V to 24V | Ships Today

Overview

This OEM control transformer steps the 277V primary supply down to 24V for the low-voltage control circuit of the Tempstar TEB12R50RTA PTAC unit. Rated at 40VA (OEM 1091226), it powers the thermostat, relays, and contactor coils that orchestrate heating and cooling. The package also includes the unit's 24V control relays — 1053004 (SPST 24V) and 1060940 (DPST 24V) — which the transformer energizes. A failed transformer is one of the most common causes of a completely dead control system: the compressor and fan won't start, and the thermostat goes blank because it has no 24V power.

Specifications

Compatibility

Direct OEM replacement for the Tempstar TEB12R50RTA PTAC unit and related ICP / Tempstar / Heil TEB-series terminal units running a 277V control supply. Confirm your primary voltage is 277V — do not substitute a 240V or 208V primary transformer.

Installation Guide

1. Safety First — Disconnect power at the unit disconnect and verify zero voltage with a multimeter; 277V line voltage is lethal.
2. Access — Remove the PTAC service panel to reach the control box.
3. Document — Photograph all primary and secondary leads and the relay wiring before disconnecting.
4. Remove — Disconnect the transformer primary/secondary leads, unbolt it from the chassis, and unclip the associated 24V relays.
5. Install — Mount the new transformer, land the 277V primary and 24V secondary leads per your photo, and reseat the relays.
6. Test — Restore power, measure 24V across the secondary, and confirm the relays pull in on a call for heat or cool.

Signs You Need a Replacement

• No 24V at the secondary with 277V present on the primary.
• Thermostat is dead and the unit won't start at all.
• Burnt smell, scorched windings, or a melted transformer housing.
• Repeated blown low-voltage fuses or tripped control circuit.

Shipping & Returns

Ships same day before 3 PM CST. 30-day returns. Backed by the National HVAC Parts fitment guarantee.