Tempstar 40VA Transformer for THB07K25RTA — 208/240V to 24V | Ships Today

Overview

This OEM 40VA control transformer (part 1056899, TRANS 208/240>24 40VA) steps the high-voltage line down to the 24V control circuit on the Tempstar THB07K25RTA PTAC. This kit also includes the unit's 24V relays — 1053004 (RELAY 24V) and 1060940 (RELAY 24V DPST) — which switch the compressor and heat loads on the low-voltage signal. When the transformer fails, the 24V circuit goes dead: the thermostat won't power up and nothing energizes. A failed relay shows as a contactor or heater that won't pull in even with a good 24V call. These are factory-spec replacements rated to match the original control circuit.

Specifications

Compatibility

Built for the Tempstar / Heil / ICP THB07K25RTA PTAC and related THB07K25 series units using the same 40VA 24V control circuit. Match OEM part numbers 1056899, 1053004, and 1060940 against your failed components before ordering.

Installation Guide

1. Safety First — Disconnect power at the breaker and verify zero voltage with a multimeter.
2. Access — Remove the PTAC grille and control-box service panel.
3. Document — Photograph all primary and secondary wiring before disconnecting.
4. Remove — Disconnect leads and unbolt the old transformer and relay(s) from the bracket.
5. Install — Mount the new transformer and relay, wiring primary to line and secondary to the 24V circuit per your photo.
6. Test — Restore power, confirm 24V at the secondary, and verify the relays pull in on a call.

Signs You Need a Replacement

• No 24V control power — thermostat is dead.
• Blown low-voltage fuse or burnt/buzzing transformer.
• Compressor or heat relay won't energize on a valid call.
• Intermittent operation tied to the control circuit.

Shipping & Returns

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