Tempstar 40VA Transformer for T8MPL050B12B1 — 115V to 24V | Ships Today

Overview

This OEM 40VA control transformer (part #1172810) steps down 115-volt line power to the 24-volt low-voltage control circuit that operates your Tempstar T8MPL050B12B1 furnace. The thermostat, gas valve, hot surface igniter, and blower relays all draw their control power from this transformer's 24VAC secondary. When it fails, the furnace loses all low-voltage control — the thermostat goes blank and no ignition sequence begins. The 40VA rating supplies enough current to energize multiple relays and the gas valve at once without overheating. Typical failures include an open or shorted winding, a buzzing core, or a secondary short that repeatedly blows the control-board fuse.

Specifications

Compatibility

Direct-fit replacement for the Tempstar T8MPL050B12B1 gas furnace and many ICP-family platforms (Tempstar, Heil, Comfortmaker, Arcoaire) using transformer 1172810. Confirm your existing unit is rated 115V/24V at 40VA before installing.

Installation Guide

1. Safety First — Disconnect power at the furnace switch and breaker, then verify zero voltage with a multimeter.
2. Access — Remove the furnace service panel to expose the control area.
3. Document — Photograph all primary (line) and secondary (24V) wire connections before disconnecting.
4. Remove — Disconnect the line and low-voltage leads, then unbolt the failed transformer from its bracket.
5. Install — Mount the new transformer and reconnect 115V to the primary and 24V to the secondary exactly per your photo.
6. Test — Restore power, verify 24VAC at the secondary, and run a complete heat cycle.

Signs You Need a Replacement

• Blank or unresponsive thermostat with line power confirmed
• No ignition sequence — igniter and gas valve never energize
• Buzzing or humming from the transformer
• Repeatedly blown low-voltage control fuse

Shipping & Returns

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