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Thermal Expansionand Your Water HeaterBradford WhiteExplains What it is andHow to Protect Yourself andYour Family From it.Ask your representative for more detailsabout the benefits of expansion tanks 2008, Bradford White Corporation. All rights reserved.Printed in U.S.A.ETB 1108-46059
WHAT IS THERMAL EXPANSION?Thermal expansion is the term usedto describe the circumstance of waterexpanding in volume as it is heated.OPENSYSTEMHOW IT“WORKED BEFORE”THERMAL EXPANSIONIN A WATER HEATERBefore major controlswere placed upon citywater supplies, it waspossible for excesswater pressure build-upin a water heater to flowback into the city watersupply. This created asimple and efficientsystem for removingexcess pressure inwater heaters.All water heaters, regardless of heatsource (gas, oil, electric, solar or indirect),can suffer the effects of thermal expansion.In every tank-type water heater, cold wateris heated as it enters the water heater tank.This increases the overall water volume andpressure inside the tank. For safety, theincrease in volume and pressure must berelieved in some way.COLDWATERSUPPLYCHECK VALVETHE CLOSED SYSTEMHowever when a checkvalve, pressure reducingvalve or backflowpreventer is installed,a “closed system” iscreated. A method ofcontrolling thermalexpansion and relievingpressure build-up mustbe installed.23
4THE SAFETYTEMPERATURE &PRESSURE RELIEFVALVE (T&P)THE T&PVALVEOPENSALLOWINGHEATEDWATER TOESCAPE22The T&P valveopens when asufficient level ofpressure is reached.This allows theheated water to spillout of the systemrelieving thepressure andlowering the volume11THE T&P VALVEThe T&P valve is designed for emergencysituations. Its parts are not manufactured for dailyuse. Even if the valve only opens once a day, thevalve can wear quickly.33WATER SYSTEMS UNDER PRESSURESometimes, damage can occur before the safetyrelief valve has a chance to relieve the water heater ofexcess pressure. Fast acting solenoid valves onappliances (washing machines, dish washers) andsome plumbing fixtures can create an instantaneouspressure spike that exceeds the rating of the waterheater tank.A worn out valve could activate unexpectedly,releasing hot water unnecessarily. If this happens,the efficiency of the system is reduced. The waterheater will waste energy and money.4In gas and some oil-powered water heaters, there is aflue in the center of the tank through which combustiongases (fumes) escape. Under constant excesspressure, the flue can collapse (1) restricting the flow ofcombustion gases and possible resulting in unsafecarbon monoxide levels. Excess pressure can alsodistort the tank head (2), the tank base (3), and the hotand cold water lines (4).5
PROTECTION FROM THERMAL EXPANSIONThe installation of a thermal expansion tank in thecold water line of the water heater can protect thesystem from the damaging effects of thermalexpansion and increased pressure.EXPANSION TANKS - HOW A DIAPHRAGMEXPANSION TANK WORKSFROM TANKThe thermal expansion tank controls the increasedpressure generated within the normal operatingtemperature range of the water heater. The small tankwith a sealed, compressible air cushion provides aspace to store and hold the additional expandedwater volume.EXPANDEDWATERCOMPRESSEDAIR CUSHIONCOLDWATERHOTWATERWhen an expansion tank is installed in aclosed system and the temperature andpressure increases, the diaphragm flexesagainst an air cushion (air is compressible). Theexcess volume and pressure created by thermalexpansion enters the pre-pressurized tank.THERMALEXPANSIONTANKTO TANKEXPANDEDWATERCOMPRESSEDAIR CUSHIONWhen hot water is drawn from the tank or thewater cools, the water leaves the expansion tankand returns to the water heater tank.67
12Installing a properly-sized and chargedthermal expansion tank in a water heatingsystem is the recommended way to eliminatethe problems associated with increased volumeand pressure in a closed or restricted plumbingsystem. Consult the thermal expansion tankinstructions for proper installation.34561.Connection Fitting2.Separate Reservoir3.Diaphragm4.Air Charge Chamber/Air Cushion Area5.Welded Steel Pressure Tank6.Air Charging ValveThermal expansion tanks feature adiaphragm that seals in the air cushionand separates air from the hot water. Thetank also has a liner that protects the tankfrom damage that can be caused by thecorrosive effects of hot water.8For more information, please contact yourlocal Bradford White representative or visitwww.bradfordwhite.com to find a professionalinstaller in your area.9
www.bradfordwhite.comAt Bradford White, we engineer all ourproducts with the professional installerin mind. We’re dedicated to providingyou with a steady supply of newproducts, product innovations andindustry related information. It’s ourway of keeping our customers one stepahead of the competition.QUICK REFERENCE SIZING CHARTSizing chart based on: 40 F incoming water temperature. 140 F maximum temperature setting. 150psi T&P valve.Supply Pressure sion Tank Volume (Gallons)108011
EXPANSION TANKS - HOW A DIAPHRAGM EXPANSION TANK WORKS When an expansion tank is installed in a closed system and the temperature and pressure increases, the diaphragm flexes against an air cushion (air is compressible). The excess volume and pressure created by thermal expansion enters the pre-pressurized tank. TO TANK HOT WATER COLD WATER .
