Tempstar Control Transformer for T8MPN100F20B2 — 40VA 115V to 24V | Ships Today
OEM Guaranteed
Same-Day Ship
30-Day Returns
Secure Checkout
Overview
This is the OEM 40VA control transformer (part number 1172810) for the Tempstar T8MPN100F20B2 gas furnace. The transformer steps down incoming 115V line voltage to the 24V control voltage that powers the thermostat, gas valve, ignition control, and relays. Without a healthy transformer the entire low-voltage control circuit goes dead — the furnace will not respond to a thermostat call for heat, and the control board may show no power. A failed transformer is one of the most common reasons a furnace appears "completely dead" while line power is still present. Symptoms include a blank thermostat, a humming or buzzing transformer, a burnt smell near the control compartment, or a popped low-voltage fuse that blows again immediately after replacement.
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 | T8MPN100F20B2 |
Compatibility
Engineered as a direct OEM replacement for the Tempstar T8MPN100F20B2 furnace. This transformer is shared across many Tempstar, Heil, Comfortmaker, and ICP-built furnaces that use the same 115V-to-24V 40VA control circuit. Always confirm the 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 mounting bracket.
- Install — Mount the new transformer, 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 thermostat call for heat.
Signs You Need a Replacement
- Blank thermostat and no furnace response despite line power being 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