een As S On THERMAL EXPANSION AND CROSS-CONNECTION CONTROL SOLUTIONS Reference Guide
When water is heated... It expands! Reacting to physical law, water expands in volume as its temperature rises. OPEN SYSTEM In the "Good Old" days COLD WATER SUPPLY Before the advent of cross-connection control, expanded water that exceeded the capacity of the water heater flowed back to the city main, where it easily dissipated. It was "open" at the city supply side of the system, even though it was "closed" on the system side.
DANGER! BACK FLOW PREVENTER BFP Water is not compressible Since water completely fills the water heater and system piping before recovery starts, and since it can't be compressed, the expanded volume, even though small, has no place to go. As a result, the expanding water creates a rapid and dangerous pressure increase in the water heater and system piping, much like the action of a hydraulic ram.
Solution Controlled Pressure Rise During Thermal Expansion SAFE RANGE 150 PSIG Even though the relief valve operates during each recovery period, high internal pressures occurring over and over again can accelerate tank leakage and shorten water-heater life, no matter how it is fired. 6 The best solution to thermal expansion is to control the pressure it generates within a safe operating range, well below the emergency setting of a relief valve.
This is easily accomplished by adding an expansion tank with a sealed-in, compressible air cushion, which will compress as thermal expansion occurs, providing the place for the expanded volume of water to go during recovery. 1. System Connection AIR CUSHION 2. Separate, rigid polypropylenelined water reservoir (NSF listed) 3. Heavy-duty butyl diaphragm 4.
The thermal-expansion tank for domestic water heaters, sized right, is the only logical answer to the growing problem of thermal expansion in water heaters protected by BFP, check valves or pressurereducing valves. A simple installation to the supply side on the water heater, this small tank will eliminate the dangerous condition so that the relief valve will not open during normal heating cycles. BACK FLOW PREVENTER BFP Static Supply Pressure (psi)** Water Heater* Size (gals.
AMTROL Canada, Ltd. 275 Shoemaker Street Kitchener, Ontario N2E 3B3 Telephone: 519-478-1138 Fax: 519-748-1138 Corporate Headquarters 1400 Division Road West Warwick, RI 02893 Telephone: 401-884-6300 Fax: 401-884-5276 ® w w w . a m t r o l .
