Weil-McLain 383600330
Weil-McLain 383600330
Weil-McLain 383600330
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Weil-McLain 383600330
Weil-McLain 383600330

Weil-McLain SlimFit® SF550 - 517K BTU - 93.9% Thermal Efficiency - Hot Water Gas Boiler - Direct Vent



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Weil-McLain SlimFit® SF550 - 517K BTU - 93.9% Thermal Efficiency - Hot Water Gas Boiler - Direct Vent
Weil-McLain SlimFit® SF550 - 517K BTU - 93.9% Thermal Efficiency - Hot Water Gas Boiler - Direct Vent
Model: 383600330
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Expert Recommended Accessories Selected by Ken, our Expert
Required Accessories 9
These accessories are required to properly setup/install this product.
Optional Accessories 10


    Over the last 130 years, Weil-McLain has built the reputation of designing some of the most reliable boilers in the marketplace. Their dedication to producing long-lasting heating solutions is seen in every boiler they make. The SlimFit® is one of the most versatile, powerful, and efficient boilers on the market. Clocking in at 550,000 BTU with a thermal efficiency of 93.9%, the SF550 can bring excellent energy savings to the largest of commercial applications. Designed to be simple to install, maintain, and operate, the SlimFit® represents peace of mind in addition to comfort. Fully packaged and ready to install, the SlimFit's® durable components and easy-to-use controls round out what is one of the most impressive boilers in the marketplace. Ideal for every application from augmenting existing heating systems to headlining new construction, the SlimFit® is one of the best values in heating.
  • Industrial Power, Amazing Efficiency
  • The SlimFit® brings condensing technology and a modulating burner to industrial scale heating. These features bring efficiency gains in the form of reusing heat that escapes traditional boilers and scaling heat production precisely to your needs.
  • Cast-Aluminum Heat Exchanger
  • The Weil-McLain SF550 utilizes a cast-aluminum heat exchanger. The heat transfer properties of cast aluminum are superior to those of stainless steel; it heats faster and transfers that heat very efficiently.
  • Outdoor Reset Control
  • An outdoor reset sensor is included with every SlimFit® boiler. This sensor allows your boiler temperature to be adjusted relative to the temperature outside, eliminating excess energy use and guaranteeing comfort.
  • Installation Versatility
  • A low profile and two venting options mean that the SlimFit® can accommodate nearly any installation requirements. The SlimFit's® compact size can be the perfect solution for installations with difficult access to tight spaces.
  • Perfect for Retrofits
  • The SF550 is designed to be easily integrated with older, non-condensing boilers; a perfect way to increase efficiency by creating a hybrid system. It also comes fully factory-assembled for quick, on-site installation.
  • Advanced Boiler Controls
  • A user-friendly interface, boiler scheduling, warm weather shutdown, frost protection, and maintenance reminders are a few of many features that come standard on the SlimFit®.
  • Ultra Low NOx
  • The SlimFit® series helps keep peace of mind and harmful emissions low by limiting NOx emission to less than 20 ppm.
  • Modbus® Connectivity
  • The SF550 features Modbus® connectivity, allowing for communication and control between up to 8 SlimFit® boilers and 24 circulators.
  • Product Includes:
  • (1) Weil-McLain SlimFit® SF550 Hot Water Boiler
  • (1) Outdoor Temperature Sensor
  • (1) Natural Gas to Propane Conversion Kit
California residents see
WARNING: Cancer and Reproductive Harm - www.P65Warnings.ca.gov.
For more information go to: www.p65Warnings.ca.gov


specs product image PID-79524
Product Category
General Information
Product Line
Product Category
Medium Learn More
Medium refers to the substance that carries heat through the heating system. Systems are either designed to use either Hot Water or Steam as a medium, and components are usually specific to one or the other.
Hot Water
Fuel Type Learn More
Fuel Type
To create heat, some form of fuel is required. Fuel Type specifies what the product uses as an input to create heat.
Natural Gas
Combustion Type Learn More
Combustion Type
Condensing appliances use leftover thermal energy from combustion gases to heat water in a secondary heat exchanger, resulting in higher efficiency and lower exhaust temperature.
Vent Type Learn More
Vent Type
Products that use combustion (burning) of fuel to create heat also create potentially dangerous gasses that need to be exhausted (AKA "Vented"). Depending on the product, venting can be done via a chimney, through a side wall, or use a second vent to provide fresh air to the appliance.
Direct Vent
DHW Production Learn More
DHW Production
DHW (Domestic Hot Water) is potable water for uses other than space heat. Some boilers are able to provide DHW "out of the box", while others can do so with the purchase of optional accessories.
Modulating/Staging Learn More
Stages are unique speeds or levels that equipment can operate at. More stages allow for better fine-tuned control of output, which improves comfort and efficiency. Modulating equipment can operate across a range of levels, giving the highest level of fine-tuned control. Learn More
Mount Type
Assembly Type
Includes Pump
Gas Conversion Kit
AFUE Learn More
AFUE (Annual Fuel Utilization Efficiency) measures the efficiency of combustion equipment over the entire heating season, and is calculated by dividing the amount of energy that is actually heating your home by the total energy contained in the fuel used by the boiler/furnace. Learn More
93 %
Maximum Input Capacity Learn More
Maximum Input Capacity
The Maximum Input Capacity describes how quickly the appliance will use fuel when delivering it's maximum capacity. The units may change depending on the fuel being used.
550000 BTU
Minimum Input Capacity
110000 BTU
DOE Heating Capacity Learn More
DOE Heating Capacity
Also referred to as Gross Output, this is the output of a boiler after accounting for combustion efficiency. We recommend sizing hot water boilers based on the DOE Heating Capacity.
517000 BTU
Net I=B=R Capacity Learn More
Net I=B=R Capacity
I=B=R, also referred to as Net Output or AHRI Capacity, is the rated heat output of a boiler after accounting for combustion efficiency, piping loss, and an extra pickup factor. We recommend sizing steam boilers based on the I=B=R rating.
450000 BTU
Efficiency Type
Thermal Efficiency
Ultra Low NOx Emissions Learn More
Ultra Low NOx Emissions
NOx is a byproduct of the combustion process, and it's output is regulated in some jurisdictions. Many regulators mirror SCAQMD rules, which regulate air quality for some parts of Southern California. Ultra Low NOx appliances emit less than 10-14 ng/J (nanogram per Joule) of NOx. Learn More
Turndown Ratio
Electrical Data
120 Volts
60 Hz
Flue Connection Size
6 Inches
Gas Connection Size
1 1/4 Inches
Supply Connection
2 Inches
Return Connection
2 Inches
Product Height
53 Inches
Product Width
47 1/4 Inches
Product Depth
18 3/16 Inches
Product Weight
478 Pounds
Shipping Weight
505 Pounds
Country of Origin
United States
UL Listed
CSA Listed
ASME Certified
AHRI Certified
AHRI Reference Number
Warranty Information
Parts Warranty Learn More
Parts Warranty
A warranty is a safeguard from defects in manufacturing and can vary in length and terms. Some manufacturers require registration for extended warranty benefits, be sure to check out features and the warranty document. To see the manufacturer's warranty statement, click on the Manuals tab. Learn More
2 Years
Heat Exchanger Warranty
10 Years


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Weil-McLain SlimFit® SF550 - 517K BTU - 93.9% Thermal Efficiency - Hot Water Gas Boiler - Direct Vent
Weil-McLain 383600330
Weil-McLain 383600330
Weil-McLain 383600330
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