Tempstar 40VA Transformer for THB09R50RTA — 277V to 24V Control | Ships Today

Overview

This is the genuine OEM 40VA control transformer for the Tempstar THB09R50RTA, stepping 277V line voltage down to the 24V required by the unit's control circuit (OEM 1091226, TRANS 277>24 40VA S). This listing also covers the related 24V control relays used in this chassis — 1053004 (RELAY 24V X) and 1060940 (RELAY 24V DPST X). The transformer powers the thermostat, relays, and control board; when it fails, the entire low-voltage side goes dead. A 40VA rating provides ample headroom for the unit's control loads. A burned-out or shorted transformer is a common cause of a completely unresponsive unit even when high-voltage power is present.

Specifications

Compatibility

Direct-fit replacement for the Tempstar THB09R50RTA PTAC chassis configured for 277V service. The same 40VA 277V-to-24V transformer is used across matching ICP, Heil, and Comfortmaker PTAC units. Verify your supply voltage is 277V before ordering.

Installation Guide

1. Safety First — Disconnect 277V power at the breaker and verify zero voltage with a multimeter.
2. Access — Remove the control-area service panel.
3. Document — Photograph the primary (line) and secondary (24V) wiring before disconnecting.
4. Remove — Unbolt the transformer from its bracket and disconnect both windings.
5. Install — Mount the new transformer, land the 277V primary and 24V secondary leads per your photo.
6. Test — Restore power and confirm 24V across the secondary with a multimeter.

Signs You Need a Replacement

• No 24V control voltage at the thermostat or relays
• Unit completely dead despite line power present
• Burnt smell or visibly scorched transformer
• Tripping breaker on a shorted secondary

Shipping & Returns

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