Weil‑McLain EG‑40 – 125 MBH Cast‑Iron Gas Boiler, 84% AFUE (Steam or Water)
The EG‑40 is a heavy-duty, cast‑iron sectional boiler designed for both steam and hydronic heating systems. With a 125 MBH input and net outputs of approximately 106 MBH (water) or 78 MBH (steam), it maintains an 84% AFUE and accommodates an optional tankless coil opening—ideal for indirect domestic hot water integration.
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???? Design Features for Contractors
Rugged Cast-Iron Construction
Rated for 50 PSIG, with integrated air separator and insulated steel casing to reduce standby losses.
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Efficiency-Boosting Auto Vent Damper
Reduces heat loss during idle periods and pairs with intermittent electronic ignition for reliable startup.
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Dual-Service Configuration
Factory-configured for steam (15 PSI relief, LWCO, siphon, gauge cocks) or water (pressure/temperature gauge, relief valve, air eliminator), with plug-and-play wiring harness.
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Service-Friendly Access
Front-mounted inspection panels, plug-in controls, and accessible vent hood streamline maintenance.
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Optional Tankless Coil Integration
Tankless coil opening available in panel for hydronic models—supports indirect hot-water systems without external tank.
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???? Technical Snapshot
Specification Rating / Detail
Input Capacity 125 MBH
Net Output (DOE) ~106 MBH (water), 78 MBH (steam)
AFUE 84%
Pressure Rating 50 PSIG
Vent Size 6″ Inner Diameter x 20′ chimney + draft hood
Ignition Intermittent Electronic
Weight Approximately 505 lb
Available Configuration Knock-down for water or steam, with/without tankless coil
Warranty 20 yr exchanger (water), 10 yr (steam); 2 yr parts
???? Installation & Service Insights
Draft Requirements: Designed for 6″ chimney; auto damper improves fuel consumption.
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Steam vs. Water Setup: Steam versions include necessary gauges and safety controls; water models feature air eliminator and relief valve.
Tankless Coil Prep: Water-version models with coil opening have pre-piped provisions—bolt-on coil accessible from left side.
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✅ Contractor Takeaway
The EG‑40 offers proven cast-iron durability with high performance in both steam and water systems. Its user-friendly service design, automatic damper, and coil integration make it a solid choice for residential or light-commercial projects. Ideal for contractors specifying reliable, long-lasting boilers with flexible installation options.