Laars Mighty Therm Installation And Operation Instructions Manual

Laars Mighty Therm Installation And Operation Instructions Manual Manual pdf 11 page image

Mighty Therm Lo-Nox Page 113.3.2 Piping System Requirements1. Check piping diagrams with local applicableplumbing, heating and building safety codes.2. All two-temperature systems using temperaturevalves must have forced recirculation in the lowtemperature building loop.3. A check valve installed at the hot water inlet tothe tempering valve will prevent cold water frombeing drawn in reverse through the temperingvalve into the hot water.4. When installing a tempering valve, place atbottom of antithermosyphon loop at least 24"high to prevent excessive hot water fromentering mixed water supply. Bring the coldwater supply up from the floor to the valve (seeFigure 10).3. Install an auxiliary small relief valve set at 25 psiless than the main relief valve. The valve must bepiped to a drain and may require occasionalcleaning. It will bleed off the expanded waterand protect the main pressure relief valve frombecoming fouled.4. Install a properly sized expansion tank.3.3.4 Pump Requirements1. The factory provided pump on PW heaters aresized to provide proper circulation through theheater and heater-to-tank circulation loop (seeFigures 12, 13 and 14). If the heater-to-tankcirculation loop does not contain more than 6elbows and 30 feet of pipe, use pipe fittings inthe loop no smaller than the following:Model Pipe Size500 through 715 2"1010 through 1825 2-1/2"If the heater-to-tank circulating loop containsmore than 6 elbows and 30 feet of pipe, usepipe or fittings in the loop no smaller than thefollowing:Model Pipe Size500 through 715 2-1/2"1010 through 1825 3"2. Model PW heater is not suitable for heatingswimming pools or any other application wheretemperature of the water flowing through theheater remains below the dew point (110°F).In applications requiring the rapid use ofmeasured volumes of water, the recovery of theheater between the time intervals of use mustequal the volume used. See the recovery table inthe current Document 2129 (Submittal Data).3. Pump Sizing: the heater circulating pump issized to provide enough flow to prevent damageFigure 10. Tempering Valve Installation.3.3.3 Water ExpansionWhen cold water is heated the water expands. Ifno water is being used during the heat-up period theexpanded water will normally back up into the citymains.A water pressure reducing valve installed in theincoming cold water line may act as a check valve andprevent the expanded water from moving backward.This will cause pressure to rise in the heater, whichwill be relieved by the pressure relief valve.If the relief valve pops frequently a mineraldeposit may build up on the valve seat, causing it toleak.The following suggestions may solve theproblem:1. Replace the installed water pressure reducingvalve with a suitable valve having a back flowport. These valves have a back flow port whichallows water to flow backwards when thepressure in the system exceeds the pressure in themains.2. Install a check valve around the pressurereducing valve to permit reverse flow. This willallow the expanded water to back flow into themains (see Figure 11).Figure 11. Check Valve/Pressure Reducing ValveInstallation.