Allanson 421-557 Transformer

The Allanson 421-557 is a heavy-duty oil burner ignition transformer engineered specifically for Arco and American Standard burners. This iron-core transformer utilizes a 120V primary supply to deliver a consistent 10,000V secondary output at 23mA, ensuring a powerful arc for reliable burner ignition in demanding environments. Designed with a mid-point ground configuration, the 421-557 features a high-silicon steel core and large-gauge copper windings to withstand high ambient temperatures and provide superior heat dissipation. Its vintage-style mounting profile allows for a direct fit on older Arco oil burners, eliminating the need for field modifications or bracket adjustments. For service technicians, this unit provides a stable voltage curve that minimizes electrode wear while preventing nuisance lockouts during cold starts. When replacing an Allanson transformer, verify the secondary voltage and milliamperage match the OEM cabinet specifications to ensure proper combustion cycles and electrical safety within the burner assembly.

• Direct Fit for Arco/American Standard: Precisely matches the mounting footprint and terminal placement for Arco burner ignition systems.
• Durable Iron Core Design: Provides robust thermal stability and longevity compared to lighter electronic ignition modules.
• 10,000V Secondary Output: Ensures a strong, consistent spark to overcome cold oil viscosity and poor draft conditions.
• Mid-Point Grounding: Enhances safety and electrical balance across the secondary circuit, reducing interference.
• Internal Heat Dissipation: Constructed with high-grade insulation to prevent internal arcing and coil failure under high-duty cycles.

Is the Allanson 421-557 compatible with modern solid-state burners?
This is an iron-core transformer specifically designed for legacy Arco and American Standard burners. While it handles 120V input, always check the physical mounting dimensions and secondary terminals before attempting a retrofit on modern electronic plates.

What causes a mid-point ground transformer like the 421-557 to fail?
Failures are typically caused by excessive ignition electrode gap, carbon tracking on the porcelain insulators, or moisture ingress in the burner housing, which forces the transformer to operate at higher voltages than its 10kV rating.

Can I use this as a replacement for other 10,000V 23mA Allanson models?
Electrically, it may be similar to other 23mA models, but the 421-557 is chassis-specific. Using it on a different burner brand may lead to clearance issues or improper electrode alignment.

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.