Tempstar 40VA Transformer for T8MPL100F20B2 — 115V to 24V Control | Ships Today

Overview

This OEM control transformer (part #1172810) supplies low-voltage power to your Tempstar T8MPL100F20B2 gas furnace. It steps 115V line voltage down to the 24V used by the thermostat, gas valve, hot surface igniter circuit, and control board, and is rated at 40VA to carry every 24V load on the furnace simultaneously. A failed transformer kills the entire control system: the thermostat goes blank, the furnace ignores a call for heat, and the unit may have a burnt-electrical odor. A transformer that buzzes or repeatedly blows the low-voltage fuse is degrading and should be replaced before it leaves the furnace dead.

Specifications

Compatibility

Direct OEM fit for the Tempstar T8MPL100F20B2 furnace and shared across many ICP-built Tempstar, Heil, Comfortmaker, and Arcoaire 115V-to-24V 40VA platforms. Verify your existing transformer reads 115V primary and 24V secondary at 40VA before installing.

Installation Guide

1. Safety First — Disconnect power at the furnace switch and breaker, then verify zero voltage at the primary leads with a multimeter.
2. Access — Remove the furnace control-compartment service panel.
3. Document — Photograph all primary and secondary wire connections before disconnecting.
4. Remove — Label and disconnect the line and 24V leads, then unbolt the transformer from its bracket.
5. Install — Mount the new transformer, reconnect the primary and secondary leads per your photo, and secure all connections.
6. Test — Restore power, confirm 24V across the secondary, then call for heat to verify normal operation.

Signs You Need a Replacement

• Blank thermostat and dead low-voltage controls.
• Burnt smell or visible scorching on the transformer.
• No 24V at the secondary with 115V present at the primary.
• Buzzing transformer and a repeatedly blown control fuse.

Shipping & Returns

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