RESIDENTIAL GAS AND ELECTRIC WATER HEATER

SERVICE HANDBOOK

TECHNICAL BULLETIN

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 (AOS 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.

A.O. Smith Water Products Company

57

Training Department

©2002

Ashland City, Tennessee

 

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A.O. Smith TC-049-R2 manual Thermal Expansion, Follow these easy steps to diagnose thermal expansion
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TC-049-R2 specifications

The A.O. Smith TC-049-R2 is a highly efficient and reliable water heater designed to meet the needs of both residential and light commercial applications. This gas-fired water heater offers a perfect blend of performance, efficiency, and durability, making it a popular choice among homeowners and business owners alike.

One of the standout features of the A.O. Smith TC-049-R2 is its tankless design. Unlike traditional water heaters with storage tanks, the TC-049-R2 heats water on demand, which means you only use energy when you need hot water. This not only results in lower energy bills but also provides an endless supply of hot water, ideal for households with multiple bathrooms or high hot water demands.

The TC-049-R2 is powered by natural gas, which enhances its efficiency and operating costs. With an impressive energy factor, this water heater is designed to conserve energy without compromising on performance. The unit also boasts a high recovery rate, which means it can quickly replenish hot water, ensuring you’re never left waiting.

Another notable technology in the A.O. Smith TC-049-R2 is its advanced electronic ignition system, which provides reliable start-up and reduces the chance of pilot light issues. Additionally, the unit features a scaled-down footprint, making it suitable for installation in tighter spaces, such as closets or utility rooms, without sacrificing performance.

Durability is a key characteristic of the TC-049-R2, as it is constructed with high-quality materials designed to resist corrosion and withstand typical wear and tear. The unit is equipped with a durable heat exchanger that enhances both efficiency and longevity, ensuring many years of reliable service.

Safety features are also prioritized in the A.O. Smith TC-049-R2. It comes equipped with advanced safety controls that prevent overheating and ensure safe operation. This offers peace of mind for users, knowing that the unit has multiple safeguards in place.

Overall, the A.O. Smith TC-049-R2 is an excellent choice for those seeking an efficient, reliable, and safe water heating solution. Its combination of advanced features, innovative technology, and robust construction makes it a leader in the water heater market, providing convenience and comfort to its users for years to come.
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