Rheem P-M406 Operating Instructions - Page 23

INTERNAL AUTOMATIC BYPASS VALVE PRESSURE RELIEF VALVE INSTALLATION In addition to the Unitherm Governor, a built-in automatic bypass valve is provided in the in/out header. While the Unitherm Governor responds to the changes in water temperature in the heater, the internal bypass valve automatically responds to changes in water pressure in the piping system. Proper amount of water flow is maintained through the heater under varying pressures dictated by the conditions of the pump and filter. Bypass Disc To conform to local building codes, it may be necessary to install a pressure relief valve. A 3/4" pressure relief valve, having a capacity equal to the BTUH output of the model to be installed, is recommended for this heater. The maximum acceptable pressure relief valve setting is 125 psi. A 3/4" NPT connection is provided in the Polymer header for installation of a pressure relief valve. The valve shall be installed in a vertical position. Do not overtighten. Install pressure relief valve hand tight plus 1/2 turn. Spring Bypass Body POLYMER HEADER (STANDARD MODELS) Pressure Relief Valve PRV Discharge Connection EXTERNAL AUXILIARY BYPASS VALVE (Where Required) An auxiliary bypass valve should be used when flow rates exceed 125 GPM. Usually a high-performance pump size larger than two horsepower will exceed this flow rate. This valve is required to complement the function of the automatic bypass valve, particularly when starting the heater in winter or early spring when the spa or pool temperature is below 50°F. It also serves to eliminate needless pressure drop through the heater and accompanying reduction in the flow rate to the spa jets, etc. In/Out Header Fig. #2004 A 3/4" NPT connection is provided in the header for installation of a pressure relief valve. The valve shall be installed in a vertical position. From Heater To Heater CAST IRON HEADER PRV (ASME MODELS) To Pool/ Spa From Pool/ Spa AUXILIARY BYPASS VALVE (DO NOT USE GATE VALVE) AUXILIARY BYPASS VALVE ADJUSTMENT To set bypass: With clean filter, adjustment is made by feeling the inlet and outlet pipes at the heater. Outlet pipes should be slightly warmer than inlet and comfortable to the touch. If pipe is hot, close bypass; if cold, open bypass. NOTE: To avoid water damage or scalding due to valve operation, drain pipe must be connected to valve outlet and run to a safe place of discharge. Drain pipe must be the same size as the valve discharge connection throughout its entire length and must pitch downward from the valve. No shut-off valve shall be installed between the relief valve and the drain line. Valve lever should be tripped at least once a year to ensure that waterways are clear. 23