Tempstar 40VA Transformer for TEB12K34RTA — 208/240V to 24V | Ships Today

Overview

This is the genuine OEM 40VA control transformer for the Tempstar TEB12K34RTA (OEM 1056899). It steps line voltage of 208/240V down to the 24V needed to power the unit's thermostat, relays, and control circuit. The transformer is the power supply for the entire low-voltage system — when it fails or its internal fuse opens, nothing on the 24V side will operate even though the unit has line power. Typical failure symptoms are a dead thermostat display, relays that will not pull in, and a system that has power at the disconnect but does nothing when called. This OEM transformer is a direct electrical and mechanical match.

Specifications

Compatibility

Direct-fit replacement for the Tempstar TEB12K34RTA. This 40VA 208/240V-to-24V transformer is common across the ICP/Tempstar/Heil/Comfortmaker TEB12K34 platform; verify your OEM part number matches 1056899 and your primary supply is 208/240V.

Installation Guide

1. Safety First — Disconnect power at the unit and breaker, verify zero voltage with a multimeter.
2. Access — Remove the service panel to reach the control box.
3. Document — Photograph the primary and secondary wire connections before disconnecting.
4. Remove — Unbolt the failed transformer and disconnect both windings.
5. Install — Mount the new transformer, wiring the 208/240V leads to the primary and the 24V leads to the secondary per your photo.
6. Test — Restore power and confirm 24V across the secondary with a multimeter.

Signs You Need a Replacement

• No 24V output measured at the secondary
• Thermostat and controls completely dead with line power present
• Relays and contactor will not energize
• Burnt smell or visibly scorched transformer housing

Shipping & Returns

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