Tempstar 40VA Transformer for T8DNL100L20B1 — 115V to 24V | Ships Today

Overview

This genuine OEM control transformer (part number 1172810, TRANS 115>24 40VA) supplies 24-volt power to the Tempstar T8DNL100L20B1 furnace control circuit. It steps line voltage 115V down to 24V and delivers 40VA of capacity to drive the control board, gas valve, thermostat, and relays. When the transformer fails, the entire low-voltage system goes dead — no thermostat response, no call for heat, and no blower or ignition. A burnt smell or a popped breaker on the control side usually points straight to the transformer.

Specifications

Compatibility

Direct factory replacement for the Tempstar T8DNL100L20B1 furnace and compatible across many ICP-family furnaces sold under the Heil, Comfortmaker, and Tempstar brands that use a 115V-to-24V 40VA control transformer. Verify primary/secondary voltage and VA rating 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 control compartment service panel.
3. Document — Photograph every primary and secondary lead before disconnecting.
4. Remove — Disconnect the leads and unbolt the failed transformer from its bracket.
5. Install — Mount the new transformer and reconnect each wire exactly per your photo.
6. Test — Restore power and confirm a steady 24V across the secondary and a normal call for heat.

Signs You Need a Replacement

• No 24V at the control board or thermostat.
• Furnace completely unresponsive to thermostat calls.
• Burnt smell or scorched windings on the transformer body.
• Repeatedly blown low-voltage fuse or tripped control circuit.

Shipping & Returns

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