Weil Mclain WGO & WTGO Gold Oil Boilers

Weil Mclain WGO & WTGO Gold Oil Boilers are cast iron, oil-fired water boilers built for residential and light commercial heating, with the WTGO adding a built-in tankless heater for domestic hot water that the water-only WGO does not include. Both series run in the 86 to 87 percent AFUE range and ship without a burner, so installers pair the boiler section with an approved Beckett or Carlin oil burner sized to the boiler's input rating. Cast iron heat exchanger sections give these boilers a long service life in hydronic heating systems, and select models carry ENERGY STAR certification. Choosing between the two comes down to whether the building already has a separate domestic water heater or needs the boiler to cover both space heating and hot water production. Confirming the specific model number against burner input and net heating capacity keeps a replacement boiler matched to the system's actual heat load.

Subcategories

• WGO Series 4 Water Boilers: WGO Series 4 boilers are water-only cast iron oil-fired boilers built for space heating without a domestic hot water function, running from 86 to 87 percent AFUE depending on model size. Net heating capacity spans roughly 75 to 257 MBH across the WGO lineup, so sizing depends on matching the boiler's output to the building's calculated heat load rather than its physical size alone. The burner ships separately, with approved Beckett and Carlin models covering the input range these boilers are rated for. Buildings that already have a separate water heater are the typical fit for a WGO, since adding domestic hot water production would call for the WTGO instead.
• WTGO Series 4 Boilers with Tankless Coil: WTGO Series 4 boilers add a high capacity tankless heater to the same cast iron oil-fired platform as the WGO, covering both space heating and domestic hot water from one unit. Tankless heater output on the WTGO lineup ranges from 3.25 to 6 gallons per minute of intermittent draw depending on model size, which needs to match the building's peak hot water demand. AFUE efficiency runs 86 to 87 percent, in line with the WGO series, and the burner is likewise sold separately. Homes without a dedicated domestic water heater, or replacing an older combination boiler, are the common candidates for a WTGO installation.
• Approved Burners and Combustion Components: WGO and WTGO boilers ship without a burner, requiring an approved Beckett or Carlin oil burner sized to the boiler's rated input, which runs from 0.7 to 2.55 gallons per hour across the lineup. Matching burner firing rate to the specific boiler model keeps combustion efficiency and AFUE rating in line with the unit's certification. Both series are B100 certified when paired with an approved burner, supporting biodiesel blends up to 100 percent for buildings switching to bio-based heating oil. Replacing a burner on an existing WGO or WTGO installation still requires confirming the approved burner list for that specific boiler model.

Buying Guide

Deciding between the WGO and WTGO starts with whether the building needs the boiler to produce domestic hot water. A property with a separate, adequately sized water heater fits the water-only WGO, while a building without one, or one replacing an aging combination boiler, fits the WTGO's built-in tankless heater better. Sizing either boiler runs on the building's calculated heat load rather than the physical size of the unit being replaced, since net heating capacity across Weil Mclain WGO & WTGO Gold Oil Boilers spans roughly 75 to 257 MBH depending on model. On the WTGO side, tankless heater output needs a separate check against the household's peak hot water draw, since the 3.25 to 6 GPM range across models will not cover every household equally at the higher end. Both series require an approved Beckett or Carlin burner sized to the boiler's rated input, so ordering a replacement boiler without lining up burner compatibility leaves an installation incomplete. AFUE efficiency sits in the 86 to 87 percent range across both series, with select models carrying ENERGY STAR certification at the higher end, which matters for rebate eligibility in some regions. B100 certification opens up compatibility with biodiesel-blended heating oil up to 100 percent, worth confirming with the local fuel supplier before a changeover. Replacement jobs should also check the boiler's net rating against the connected radiation or baseboard load, since undersizing a replacement boiler can leave a system short on heating capacity during peak cold.

Frequently Asked Questions

What's the difference between the WGO and WTGO Weil-McLain oil boilers?

The WGO is a water-only boiler for space heating, while the WTGO adds a built-in tankless heater for domestic hot water on the same cast iron platform. A building without a separate water heater is the typical case for choosing a WTGO over a WGO.

Do WGO and WTGO boilers include a burner?

No. Both series ship without a burner and require an approved Beckett or Carlin oil burner sized to the boiler's rated input, which runs from 0.7 to 2.55 gallons per hour across the lineup.

What AFUE efficiency do these boilers achieve?

WGO and WTGO Series 4 boilers run from 86 to 87 percent AFUE depending on model size, with select models carrying ENERGY STAR certification at the higher end of that range.

Can these boilers run on biodiesel heating oil blends?

Yes. Both the WGO and WTGO series are B100 certified when paired with an approved burner, supporting biodiesel blends up to 100 percent.

How is the tankless heater on a WTGO boiler sized?

Tankless heater output on the WTGO lineup ranges from 3.25 to 6 gallons per minute of intermittent draw depending on model size, and that output needs to be checked against the building's peak hot water demand rather than assumed adequate by default.