Tempstar 40VA Transformer for T8MPV125J20B1 — 115V to 24V | Ships Today
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Overview
This is a genuine OEM control transformer (part number 1172810) for the Tempstar T8MPV125J20B1 two-stage gas furnace. It converts 115V line voltage to the 24V low-voltage power that runs the thermostat, gas valve, hot surface igniter circuit, and control board. Rated at 40VA, it has the capacity to drive every 24V load on the furnace simultaneously. A failed transformer kills the entire control system — the thermostat may go blank and the furnace will not answer a heat call even though 115V is present at the primary. Buzzing windings, an open internal thermal fuse, or a burnt-insulation smell all indicate it is time to replace the transformer.
Specifications
| Spec | Value |
|---|---|
| Part Number | 1172810 |
| Type | Control Transformer |
| Brand | Tempstar (ICP / Heil) |
| Rating | 40 VA |
| Primary Voltage | 115V |
| Secondary Voltage | 24V |
| Application | Gas Furnace Control Circuit |
Compatibility
Designed for the Tempstar T8MPV125J20B1 furnace and interchangeable across the ICP family (Heil, Comfortmaker, Arcoaire, KeepRite) using the same 40VA 115V-to-24V control transformer. Confirm the part number on your existing transformer before ordering.
Installation Guide
- Safety First — Disconnect power at the furnace switch and breaker, then verify zero voltage with a multimeter on the primary and secondary leads.
- Access — Remove the furnace control/blower compartment service panel.
- Document — Photograph all primary and secondary wiring before disconnecting.
- Remove — Label and disconnect the line-voltage primary leads and 24V secondary leads, then unbolt the failed transformer from its bracket.
- Install — Mount the new transformer, reconnect leads exactly per your photo, and secure every connection.
- Test — Restore power and verify 24V across the secondary and normal furnace operation on a heat call.
Signs You Need a Replacement
- No 24V output while 115V is present on the primary
- Dead thermostat or furnace that ignores the heat call
- Buzzing, humming, or burnt smell from the transformer
- Control fuse on the board repeatedly blows
Shipping & Returns
Ships same day before 3 PM CST. 30-day returns. 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