Weil Mclain 381-356-578 Transformer

For veteran contractors servicing residential gas boilers, the Weil McLain 381-356-578 Transformer is the dedicated OEM replacement for domestic water and hydronic heating controls. This 120/24 Volt, 40 VA foot-mount control transformer is engineered specifically for the Weil McLain CGa (Series 2 and 3) and GV90+ (Series 2) residential boiler lines. Providing a stable 24V secondary output, it delivers the necessary 1.67 amps required to power critical low-voltage components, including ignition modules, gas valve solenoids, and zone relays.

Field technicians will appreciate the rugged, compact design that allows for clean foot-mount installation within tight control cabinets. Unlike universal multi-tap alternatives, this genuine boiler control transformer maintains factory-specified electrical characteristics, preventing chattering relays or control board resets common with under-powered secondary circuits. When diagnosing Weil McLain boiler parts, ensuring a consistent volt-ampere rating is vital for maintaining the duty cycle of integrated HVAC control systems. Replace failing units with this high-efficiency step-down transformer to restore reliable 24V power to the burner secondary circuit.

Key Benefits

• OEM Compatibility: Specifically designed for Weil McLain CGa and GV90+ series gas boilers.
• Stable Power Delivery: Rated at 40 VA to provide consistent 1.67-amp current for 24V boiler controls.
• Direct Fit: Foot-mount configuration ensures easy mounting and proper alignment with existing wiring harnesses.
• Quiet Operation: High-quality windings reduce magnetic vibration and audible humming during long heating cycles.

Common Questions

What are the symptoms of a failing 40 VA transformer?
Technicians often see chattering contactors, thermostats that constantly reboot, or the gas valve failing to pull in even when the board sends a signal. Measuring the secondary side under load will often show a voltage drop below 18-20V if the internal windings are compromised.

Can I use this for multiple zone valve applications?
A 40 VA transformer can typically handle the boiler’s internal controls and one or two low-draw zone valves. If you are powering more than three Taco zone valves or high-draw WiFi thermostats, verify the total amperage to ensure the 1.67-amp limit is not exceeded.

Is this a multi-tap transformer or dedicated 120V?
This is a dedicated 120/24 Volt transformer. It is designed for a 120V primary input; always verify the primary line voltage at the boiler junction box before installation to prevent damage to the secondary windings.

Disclaimer: While we strive for 100% accuracy, product data and specifications are subject to change. Please contact our team to confirm compatibility or technical details before purchasing.