Installing the water heater.
Thermal Expansion
Determine if a check valve exists in the inlet water line. It may have been installed in the cold water line as a separate back flow preventer, or it may be part of a pressure reducing valve, water meter or water softerner. A check valve located in the cold water inlet line can cause what is referred to as a “closed water system”. A cold water inlet line with no check valve or back flow prevention device is referred to as an
“open water system”.
As water is heated, it expands in volume and creates an increase in the pressure within the water system. This action is referred to as “thermal expansion”.
In an “open water system”, expanding water which exceeds the capacity of the water heater flows back into the city main where the pressure is easily dissipated.
A “closed water system”, however, prevents the expanding water from flowing back into the main supply line, and the result of “thermal expansion” can create a rapid and dangerous pressure increase in
the water heater and system piping. This rapid pressure increase can quickly reach the safety setting of the relief valve, causing it to operate during each heating cycle. Thermal expansion, and the resulting rapid and repeated expansion and contraction of components in the water heater and piping system can cause premature failure of the relief valve, and possibly the heater itself. Replacing the relief valve will not correct the problem.
The suggested method of controlling thermal expansion is to install an expansion tank in the cold water line between the water heater and the check valve. The expansion tank is designed with an air cushion built in that compresses as the system pressure increases, thereby relieving the over pressure condition and eliminating the repeated operation of the relief valve. Other methods of controlling thermal expansion are also available. Contact your installing contractor, water supplier or plumbing inspector for addition information regarding this subject.
NOTICE: Do not apply heat to the HOT or COLD water connections. If sweat connections are used, sweat tubing to adapter before fitting adapter to the water connections on heater. Any heat applied to the water supply fittings will permanently damage the dip tube and/or heat traps.
Water Supply Connections
Refer to the illustrations on pages 8 and 9 for suggested typical installations. The installation of unions or flexible copper connectors is recommended on the hot and cold water connections so that the water heater may be easily disconnected for servicing if necessary.
The HOT and COLD water connections are clearly marked and are 3/4″ NPT on all models. Install a
CAUTION: SIDE CONNECT MODELS are equipped with a special Hot Outlet Tube Assembly. Do not rotate the Hot Outlet Nipple when making water connections. The nipple MUST remain in a position with the indicating mark facing up.
6