ICP Transformer for RH5420603 — 40VA 208/240V to 24V | Ships Today

Overview

This OEM step-down transformer (part number 1540372) supplies the low-voltage control power for the ICP/Tempstar/Heil RH5420603 system. It converts incoming 208/240-volt line power down to the 24 volts required by the thermostat, control board, contactor coil, and relays. Rated at 40VA, it provides enough capacity to energize the full control circuit reliably. When a transformer fails, the entire control system goes dead — the thermostat is blank, nothing energizes on a call for heating or cooling, and a frequent culprit is a shorted control wire that overloads and burns out the secondary winding.

Specifications

Compatibility

Direct OEM replacement for the ICP/Tempstar/Heil RH5420603 system. The 40VA, 208/240V-to-24V configuration is also a common replacement across many Carrier-family furnaces and air handlers. Confirm the primary voltage, secondary voltage, and VA rating of your existing transformer before installing.

Installation Guide

1. Safety First — Disconnect power at the unit and breaker, then verify zero voltage with a multimeter.
2. Access — Remove the control-compartment service panel.
3. Document — Photograph the primary and secondary wiring before disconnecting.
4. Remove — Disconnect the primary and 24V secondary leads and unbolt the old transformer.
5. Install — Mount the new transformer and reconnect the primary to matching line voltage and the secondary to the 24V circuit per your photo.
6. Test — Restore power and confirm 24V across the secondary and that the control circuit responds.

Signs You Need a Replacement

• Blank thermostat with no display
• No response on a call for heating or cooling
• No measurable 24V at the secondary terminals
• Burnt smell or visibly scorched transformer housing

Shipping & Returns

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