Number: SB0203 (Page 1 of 2)

Date: November 22, 2002

Subject: Water Boiler Installations with Three-Way Valves

Primary/Secondary pumping is the preferred method for system temperature modulation in commercial hydronic heating installations. Three-way valves are also used on many installations for this purpose. Without proper system design and control, three-way valves can cause cold system water to be returned to a hot boiler. This condition could lead to boiler thermal shock, creating a potential for section failure. With minimal equipment investment, thermal shock conditions can be reduced on three-way valve installations. Weil-McLain makes the following design recommendations.

Piping Selection:

1.Use by-pass piping arrangement – See Figure 1 or 2.

2.Follow basic boiler piping instructions in the boiler manual.

Three-Way Valve Selection:

1.Use valves with minimum timing of four minutes from one extreme position to the other.

2.Size to circuit design requirements. Follow manufacturer’s recommendations. Normally valve will be one or two pipe sizes smaller than recommended boiler piping size.

3.Avoid oversizing to prevent poor control of mixed water.

4.Pressure drop across the valve should be high enough to provide accurate control without “hunting”.

Circulator Selection:

1.Size system circulator to circuit flow characteristics. Specify gpm and head requirements.

2.Size each by-pass circulator as follows:

[1/4 to 1/3 flow (gpm) of system circulator] X

1

# of boilers used

 

3. All circulators must run at the same time.

EXAMPLE: Specify equipment to by-pass one 1,000,000 btuh Weil-McLain boiler.

Piping: (1) tee, (1) ell, (1) 45° tee (By-pass size and length will vary on each installation.) Circulator:

System flow rate with 20° ∆T through boiler = 1,000,000 btuh = 100 gpm 10,000 btuh

By-pass flow rate = 1/4 X 100 gpm X

1

= 25 gpm

1 boiler

 

 

In most cases a standard booster pump can provide the necessary flow at by-pass gpm and head requirements.

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Weil-McLain SB0203 manual Subject Water Boiler Installations with Three-Way Valves
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SB0203 specifications

The Weil-McLain SB0203 is a notable entry in the world of residential boilers, known for its efficiency, durability, and innovative technology. As part of the Weil-McLain family of products, the SB0203 stands out for heating solutions that cater to a variety of home sizes and heating demands.

One of the key features of the SB0203 is its robust construction. Made from high-quality cast iron, this boiler ensures long-lasting performance and resilience against the elements. Cast iron is favored not only for its strength but also for its excellent heat retention properties, allowing the boiler to maintain warmth for extended durations, reducing energy costs.

The SB0203 is designed with efficiency in mind, boasting an AFUE (Annual Fuel Utilization Efficiency) rating that meets or exceeds industry standards. This high efficiency translates to lower fuel consumption and reduced greenhouse gas emissions, aligning with modern environmental standards and homeowner expectations for sustainable living.

Equipped with advanced burner technology, the Weil-McLain SB0203 features a multi-functional burner that maximizes combustion efficiency. This feature not only enhances the boiler's performance but also ensures quieter operation, adding to the comfort of a home. The burner is designed to provide a consistent and reliable heat output while minimizing noise levels, which is an important consideration in residential applications.

Another characteristic worth noting is the easy installation and maintenance of the SB0203. The boiler is designed with a user-friendly interface, making it accessible for homeowners and technicians alike. With focus on ease of access for service, routine maintenance becomes streamlined, ultimately contributing to a longer lifespan for the unit and more consistent heating.

The Weil-McLain SB0203 is also compatible with a variety of heating systems, including radiant and baseboard systems, allowing for versatile applications in diverse residential settings. This adaptability is a significant advantage for homeowners looking to integrate a reliable heating source with their existing infrastructure.

In summary, the Weil-McLain SB0203 is a high-quality residential boiler that combines durable materials, advanced efficiency features, and user-friendly design. Its capability to provide effective and reliable heating makes it a top choice for homeowners seeking an economical and environmentally friendly solution for their heating needs.
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