Tempstar Control Transformer for T8MPN100F20B1 — 40VA 115V to 24V | Ships Today
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Overview
This is the OEM 40VA control transformer (part number 1172810) for the Tempstar T8MPN100F20B1 gas furnace. The transformer steps incoming 115V line voltage down to the 24V control voltage that powers the thermostat, gas valve, ignition control, and relays. If the transformer fails, the entire low-voltage control circuit loses power — the furnace will not respond to a thermostat call for heat, and the control board may show no signs of life even though line power is present. A bad transformer is a leading cause of a furnace that appears completely dead. Common symptoms include a blank thermostat, a buzzing or humming transformer, a burnt smell in the control compartment, or a low-voltage fuse that blows again the moment it is replaced.
Specifications
| Spec | Value |
|---|---|
| OEM Part Number | 1172810 |
| Description | TRANS 115>24 40VA |
| Type | Step-down control transformer |
| Brand | Tempstar (Heil / ICP family) |
| VA Rating | 40 VA |
| Primary Voltage | 115V |
| Secondary Voltage | 24V |
| Fits Model | T8MPN100F20B1 |
Compatibility
Engineered as a direct OEM replacement for the Tempstar T8MPN100F20B1 furnace. The same 40VA 115V-to-24V transformer is used across many Tempstar, Heil, Comfortmaker, and ICP-built furnaces. Always confirm part number 1172810 against your existing transformer before installing.
Installation Guide
- Safety First — Disconnect power at the furnace switch and breaker, then verify zero voltage with a multimeter.
- Access — Remove the furnace service panel to expose the control compartment.
- Document — Photograph all primary and secondary wire connections before disconnecting anything.
- Remove — Disconnect the line-voltage primary leads and the 24V secondary leads, then unbolt the failed transformer from its bracket.
- Install — Mount the new transformer and reconnect the primary and secondary wiring exactly per your photo.
- Test — Restore power, confirm 24V at the secondary, and verify the furnace responds to a call for heat.
Signs You Need a Replacement
- Blank thermostat and no furnace response despite line power present
- Repeatedly blown low-voltage (3A) control fuse
- Audible buzzing, humming, or a burnt smell from the transformer
- No measurable 24V at the secondary terminals
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