Weil‑McLain EG‑40 – 125 MBH Cast‑Iron Steam/Water Boiler, 84 % AFUE
The EG‑40 is a versatile, cast-iron boiler engineered for either steampipe or hydronic applications. With a 125 MBH input and net outputs of approximately 106 MBH (water) or 78 MBH (steam), it delivers 84 % AFUE. It arrives in a factory-assembled block with insulated jacket and horizontal-to-vertical draft hood, ready for chimney venting
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???? Contractor-Critical Features
Factory-Assembled Cast-Iron Sections
Boiler rated for 50 PSIG working pressure; includes built-in air separator and extended steel jacket for heat retention
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Auto Vent Damper & Ignition System
Intermittent electronic ignition with stainless burners and automatic damper enhance efficiency and eliminate heat loss during idle
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Steam & Water Versatility
Configurable for steam (with relief valve, LWCO, pressure gauge, siphon) or hydronic use (with combination gauge, air eliminator)
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Service Accessibility
Front-access panels, plug-in wiring harness, and rollout fuse simplify maintenance; chimney connection remains compact
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Tankless Coil Compatibility
Optional left-side coil opening allows integration of on-demand domestic hot water without external tanks
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???? Specification Table
Parameter EG‑40
Input 125 MBH
DOE Output (Steam) ~78 MBH
DOE Output (Water) ~106 MBH
AFUE 84 %
Pressure Rating 50 PSIG
Vent Connection 6″ chimney via draft hood
Ignition System Intermittent electronic
Weight ~505 lb
Warranty (Water/Steam) Heat exchanger: 20 yr / 10 yr; parts: 2 yr
???? Installation & Service Insights
Vent Sizing & Draft: Requires a minimum 20‑ft chimney with a 6″ flue. Auto damper reduces standby heat loss
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Steam Use: Includes pressure gauge, relief valve, LWCO, siphon, and cocks — ready for one-pipe steam or gravity return systems
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Hydronic Use: Equipped with air eliminator, combination gauge & relief valve — applicable for hot water systems including radiant layouts.
???? Contractor Summary
The EG‑40 is a durable, serviceable boiler engineered for reliability in both steam and water applications. Its high-efficiency gas ignitor and auto damper reduce operating costs, while its universal design offers flexibility across project types. Front-access panels and modular wiring reduce service time, making it a solid option for contract installations in multi-family or light commercial settings.