RESIDENTIAL GAS, NON POWER VENTED, WATER HEATER

SERVICE HANDBOOK

TECHNICAL BULLETIN - 45

THERMAL EXPANSION

SYMPTOMS

•Effects are only noticeable after hot water use followed by periods of no water use.

•Relief valve drips during any recovery cycle when no hot or cold water is used.

•Hot water pipes creak while heater is recovering and all valves are closed.

•Tanks or other components of the water supply system fail prematurely.

•A metallic creaking noise might actually be heard in the location of the heater as the pressure is relieved and the stretched tank returns to a natural shape.

•Faucets drips during any recovery cycle when no hot or cold water is used.

Water surges when a valve is first open and then pressure drops.

CAUSE

The water in a water heating system expands when it is heated and has a greater volume. Since water will not compress (like air), system designers must include provisions for thermal expansion. (Water in a closed tank at 50 psi, when heated just 10 degrees, will reach a pressure of 250 psi).

Many water supply systems have check valves at the water meter to prevent any possible contamination of the public water supply by the accidental back-flow of contaminated water into the supply mains. These check valves are often required by code, and some cities are even installing the check valves. They serve a useful purpose. Do not remove them!

The use of pressure reducing valves (PRV) is another cause. PRVs are designed to conserve water and prolong fixture life. Many PRVs also act as very effective check valves. Again, do not remove them!

Water softeners in the system may also act as back-flow preventers.

TEST

Follow these easy steps to diagnose thermal expansion:

•Turn the heater thermostat all the way down, and install a water pressure gauge with dead hand (part #4798) on the drain valve. Open the drain valve, so the gauge reads system pressure.

•Open a hot water tap and allow 15% to 20% of the tanks volume to run out. Shut off the drain valve and make sure that no other fixture in the system, hot or cold, is open. Make sure that outside fixtures, if they are on the same system, are turned off too. Any water leaks or use will make the test meaningless.

•Check the water pressure gauge, and turn the pointer so it lines up with the pressure indicating needle. Turn the thermostat back up to its normal position, so the heater cycles on. Watch the pressure gauge.

•If the system is closed, the pressure will start to climb steadily and rapidly. A small amount of thermal expansion control may be built into the system because of trapped air pockets or a water hammer arrestor. In that case the pressure will increase slightly, hold steady for a short time and then rapidly increase. The temperature and pressure relief valve (T&P) or PRV should open and release water once the pressure reaches the maximum setting on the valve. The valve will close once the pressure falls below the pressure setting of the valve.

State Water Heater

32

Technical Training Department

© 2004

 

Ashland city, TN

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State Industries STC-080 manual Thermal Expansion, Symptoms
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STC-080 specifications

The State Industries STC-080 is a high-efficiency water heater designed to meet the demands of residential and light commercial applications. With its strategic engineering and innovative technology, it offers a reliable solution for those seeking comfort, efficiency, and sustainability in water heating.

One of the main features of the STC-080 is its exceptional efficiency rating. It operates with an impressive Energy Factor (EF) that not only reduces energy consumption but also translates into lower utility bills for users. The unit utilizes a streamlined heat exchanger design, optimizing heat transfer and minimizing energy loss. This design ensures that users can enjoy hot water on demand without the worry of excessive energy expenditure.

The STC-080 is equipped with advanced heating technologies, including a dual-flame burner system. This system ensures rapid heating while providing consistent water temperature, which is essential for residential applications where demand can vary throughout the day. The integration of advanced controls also allows for precise temperature adjustments, giving users full control over their hot water supply.

Durability and reliability are key characteristics of the STC-080. Constructed from high-quality materials, it features a heavy-duty steel tank with a glass-lined interior that provides excellent corrosion resistance. This not only enhances the product's longevity but also ensures consistent performance even in challenging water conditions. Additionally, the unit includes an anode rod that further protects against corrosion, extending service life and reducing maintenance needs.

The STC-080 is designed for easy installation, with flexibility that accommodates various plumbing setups. Its compact design allows for placement in tighter spaces, making it an ideal choice for homes where space is at a premium.

Safety is another priority with the STC-080. It includes multiple safety features such as a temperature and pressure relief valve, ensuring safe operation. The unit also complies with stringent industry standards, providing peace of mind to homeowners and businesses alike.

In summary, the State Industries STC-080 is a standout water heating solution that combines efficiency, reliability, and advanced technology. With its robust construction and user-friendly features, it caters to the evolving needs of both residential and light commercial users, making it an excellent investment for those looking to enhance their water heating systems while being conscious of energy usage.
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