ICP Transformer for RH5420423 — 40VA 208/240V to 24V | Ships Today

Overview

This OEM control transformer (part #1540372) steps down line voltage to the 24-volt control circuit that powers the thermostat, contactor coil, gas valve, and control board on your ICP RH5420423 system. Rated at 40VA with a dual 208/240V primary and a 24V secondary, it supplies the low-voltage signal every modern HVAC control depends on. When a transformer fails, the entire control circuit goes dead — the thermostat blanks out, the contactor won't pull in, and the system won't start at all. A buzzing transformer, a tripped low-voltage fuse, or a melted/blackened housing are classic signs the original has shorted and needs replacement.

Specifications

Compatibility

Designed as a direct OEM fit for the ICP / Tempstar / Heil model RH5420423 and other ICP-family systems using the 40VA 208/240V-to-24V control transformer. Always confirm the printed VA and voltage ratings against the unit being serviced before installing.

Installation Guide

1. Safety First — Disconnect power at the breaker and verify zero voltage at the unit with a multimeter before touching any wiring.
2. Access — Remove the service panel to expose the control compartment and existing transformer.
3. Document — Photograph every primary and secondary wire connection before disconnecting anything.
4. Remove — Label and disconnect the primary (line) and secondary (24V) leads, then unbolt the failed transformer from its bracket.
5. Install — Mount the new transformer, reconnect the matching primary tap (208V or 240V) and 24V secondary leads exactly as photographed.
6. Test — Restore power and confirm 24V across the secondary terminals and normal system startup.

Signs You Need a Replacement

• Thermostat display is blank and the system is completely unresponsive.
• Audible buzzing or humming from the transformer.
• Repeated blown low-voltage (3A) control fuses.
• No measurable 24V at the secondary terminals or visible scorching on the housing.

Shipping & Returns

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