Thermal Expansion - State Water Heaters GPX User Manual

THE FIX The ideal fi x involves the use of a pressure reducing valve if supply pressures are
above 60 to 70 psi, and a properly sized expansion tank. The PRV reduces supply
pressures to 40 to 60 psi allowing an economically priced and sized expansion tank
to be used. The PRV also offers the benefi t of saving water and prolonging the life of
water fl ow valves. The PRV is not required if the system already has one or if high
supply pressures are desired. A supply water pressure of 80 PSI is a maximum set by
many local or state codes.
The PRV is installed between the check valve and the water heating system. The
expansion tank is installed between the PRV and the water heating system. Follow the
manufacturers instructions for installing the expansion tank.
Run the thermal expansion check again. The pressure should increase only slightly
then hold steady throughout the recovery cycle. The expanded water is fl owing back
from the heater and into the pressurized storage bladder of the expansion tank. Air
pressure will force this water out of the expansion tank into the supply once usage
resumes.
DO NOT DEPEND ON THE TEMPERATURE & PRESSURE VALVE (T&P VALVE) TO
HANDLE THERMAL EXPANSION! The T&P valve manufacturers designed the valve
to be an emergency relief device only. The T&P Valve could be subject to reduced
effectiveness or failure.
FIGURE
WARNING Thermal expansion of water, if not compensated for in system design, will lead to the
early failure of components. These failures are not covered by the manufacturer's
warranty, so it is extremely important that everyone be aware of the causes, symptoms
and solutions to thermal expansion in a closed water heating system.

THERMAL EXPANSION

HOT WATER
OUTLET
36
IN A CLOSED SYSTEM USE A
THERMAL EXPANSION TANK
COLD WATER SUPPLY TO FIXTURES
PRESSURE REDUCING VALVE
WITH BYPASS
COLD WATER
INLET
COLD WATER INLET VALVE
(SHUT-OFF VALVE)