Tempstar 40VA Transformer for TEB12R25RTA — 277V to 24V | Ships Today

Overview

This is the OEM 40VA control transformer (part 1091226) for the Tempstar TEB12R25RTA, stepping 277V line voltage down to the 24V required by the unit's control circuit and relays. Every low-voltage control component — the thermostat, the 24V relays (parts 1053004 and 1060940 in this unit), and the contactor coil — depends on clean, stable 24V power from this transformer. A failed transformer means a completely dead control circuit: no thermostat response, no cooling or heating call, even though line voltage is present. Transformers fail from sustained overload, a shorted secondary, or simple age-related winding breakdown. This genuine OEM unit is rated at 40VA to match the original load.

Specifications

Compatibility

Direct fit for the Tempstar TEB12R25RTA PTAC unit. The 277V-to-24V 40VA specification is common across ICP, Heil, Tempstar, and Comfortmaker TEB12 packaged terminal equipment running on 277V commercial power. Verify your primary voltage is 277V before installing.

Installation Guide

1. Safety First — Disconnect power and verify zero voltage with a multimeter; 277V is lethal.
2. Access — Remove the service panel to reach the control box.
3. Document — Photograph all primary and secondary leads before disconnecting.
4. Remove — Disconnect the leads and unbolt the failed transformer from its bracket.
5. Install — Mount the new transformer, wire the 277V primary and 24V secondary exactly per your photo.
6. Test — Restore power and confirm 24V across the secondary terminals with a multimeter.

Signs You Need a Replacement

• No 24V control power — thermostat and relays completely unresponsive.
• Burnt smell or visibly scorched transformer housing.
• Repeatedly blown low-voltage fuse after replacement.
• Measured secondary voltage well below 24V under load.

Shipping & Returns

Ships same day on orders placed before 3 PM CST. 30-day returns on unused parts. Backed by the National HVAC Parts fitment guarantee.