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Weil McLain 381-800-856 EG Series Boiler Base Box

Weil McLain 381-800-856 Base Box

Weil McLain

The Weil McLain 381-800-856 Base Box is the factory replacement base box for Weil-McLain EG series gas-fired cast iron boilers. On an EG boiler the base is the insulated sheet-metal enclosure beneath the cast iron sections. It forms the burner compartment, supports the section stack, and keeps the heat of the burners directed up into the sections instead of out into the boiler room. Weil-McLain's EG parts list identifies the main pieces of the base as the front base panel, the back base panel, a front base access panel with flame rollout switch bracket, the base side rail and the base insulation kit 510-811-660. The 381-800-856 is the larger replacement base box for when the base itself is damaged, not one of those small panels.

Weil-McLain numbers its EG base box and collector hood kits in sequence by boiler size: the 381-800-853 for the EG-35, the 381-800-854 for the EG-40, the 381-800-855 for the EG-45, the 381-800-857 for the EG-55, the 381-800-858 for the EG-65 and the 381-800-859 for the EG-75. The 381-800-856 belongs to this same numbered run, between the EG-45 and EG-55 numbers. Box size scales with the boiler: the EG-45 kit measures about 24-1/2 by 15 inches, the EG-55 kit about 27 by 20 inches, and the EG-65 and EG-75 kits about 35-1/2 by 27 inches. That is why the correct number depends on the exact EG model and series, and why you should confirm the base box number against your boiler's model and serial number and Weil-McLain's parts list for that boiler before you order.

Base box replacement is a major repair, and it is usually driven by one of four problems: corrosion of the base panels from chronic condensation or a leaking section or fitting above, warping or burn-through from flame rollout or overheating, crumbled or saturated base insulation, or a base that has lost its shape and no longer seats the sections squarely. Because the base surrounds the burners and carries the flame rollout switch bracket, plan on disconnecting the gas train, burners and jacket components to reach it. While the base is open, inspect the flame rollout switch, the burner assembly and the base insulation, and correct whatever caused the damage so the new base is not destroyed the same way. Weil-McLain warns that these boilers contain ceramic fiber and fiberglass insulation, so follow the manufacturer's handling instructions and wear a respirator, gloves and eye protection. After reassembly, leak-test every gas connection, confirm a normal flame pattern and verify venting before putting the boiler back in service.

Key Benefits

  • Factory Weil-McLain EG Series Base Box: The OEM 381-800-856 base box, built to the same numbered run as the 381-800-855, 381-800-857, 381-800-858 and 381-800-859 kits.
  • Restores the Burner Compartment: Replaces a corroded, warped or fire-damaged base that can no longer hold insulation, support the sections or contain the burner area properly.
  • Supports Safe Operation: A sound base keeps the flame rollout switch bracket, burner area and insulation where Weil-McLain designed them to be.
  • Documented Sibling Numbers: Every neighboring EG base box number is named above, so you can compare against the number on your boiler's parts list.

Common Questions

  • Which EG boiler does the 381-800-856 fit? It belongs to Weil-McLain's EG series base box numbering run, and the right number depends on the boiler's size and series. Confirm against your EG model and serial number and the Weil-McLain parts list before ordering.
  • Is it the same as the 381-800-855 or 381-800-857? No. Those are separate base box and collector hood kits for the EG-45 and EG-55. Each number is sized to its own boiler.
  • Are the base panels and insulation sold separately? Yes. Weil-McLain lists the front base panel, back base panel, base access panel, base side rail and base insulation kit 510-811-660 as individual EG service parts, which is useful when only one component is damaged.

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.