Tempstar 40VA Transformer for THB07R34RTA — 277V to 24V | Ships Today
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Overview
This genuine OEM 40VA control transformer (part 1091226) steps 277V line power down to 24V to energize the low-voltage control circuit on the Tempstar THB07R34RTA packaged terminal air conditioner. The transformer feeds the thermostat, relays, and contactor coils that operate the unit; without a healthy 24V output, the controls go dead and the unit will not run. This listing also covers the unit's companion relays — the 24V relay (1053004) and the 24V DPST relay (1060940) — which switch the compressor and fan loads on command from the control circuit. A failed transformer typically results from a shorted load, age, or a power surge, and is one of the first components to check when a PTAC unit is completely unresponsive but has line voltage present.
Specifications
| Spec | Value |
|---|---|
| Part Number | 1091226 (transformer) |
| Companion Relays | 1053004 (24V), 1060940 (24V DPST) |
| Type | Step-down control transformer |
| Brand | Tempstar |
| Primary Voltage | 277V |
| Secondary Voltage | 24V |
| Rating | 40VA |
| Fit | OEM direct replacement |
Compatibility
Designed as a direct-fit replacement for the 277V Tempstar THB07R34RTA PTAC chassis. Equivalent ICP, Heil, and Comfortmaker THB-series 277V packaged terminal units share this control platform and use the same 40VA transformer and relay hardware. Confirm your line voltage is 277V and match the part number before ordering.
Installation Guide
- Safety First — Disconnect power at the breaker and verify zero voltage with a multimeter; 277V is lethal.
- Access — Remove the front grille and control-panel cover to expose the transformer and relays.
- Document — Photograph the primary and secondary wiring before disconnecting any leads.
- Remove — Unbolt the transformer mounting bracket and disconnect the primary (277V) and secondary (24V) leads.
- Install — Mount the new transformer, wire the 277V primary and 24V secondary per your photo, and confirm tight connections.
- Test — Restore power and verify 24V across the secondary, then confirm the unit's controls and relays energize.
Signs You Need a Replacement
- No 24V output measured on the secondary terminals
- Unit completely unresponsive despite confirmed 277V line voltage
- Burnt smell, discoloration, or a blown inline control fuse
- Buzzing transformer or relays that fail to pull in
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.
Shipping Information
- Orders placed before 3PM CST ship same business day
- Standard delivery: 2-5 business days
- Express shipping available at checkout
- Free shipping on orders over $75
- Tracking number emailed upon shipment
Return Policy
- 30-day returns on unused parts in original packaging
- Electrical parts (capacitors, contactors, control boards) are final sale once installed
- Email info@nationalhvacparts.com to initiate a return
- Refunds processed within 5-7 business days