BASIC STEAM HEATING SYSTEMS - gogeisel.com

1 HS-901(A) BASIC STEAMHEATINGSYSTEMSnOne-PipenTwo-PipeBas ic SteamHeatingSystems2In a one-pipe, gravity-flowsystem, each HEATING unit has asingle pipe connection throughwhich it receives STEAM andreleases condensate at thesame time. All HEATING units and the end ofthe supply main are sufficientlyabove the boiler water line sothat condensate flows back tothe boiler by a two-pipe system , steamsupply to the HEATING units andcondensate return from heatingunits are through separate accumulation in piping andheating units discharges fromthe system through the openvent on the condensate pumpreceiver. Piping and heatingunits must be installed withproper pitch to provide gravityflow of all condensate to thepump LOOP2ND LOOPHARTFORD LOOPSTEAMSUPPLY MAINEQUALIZERLOOP RISERWATER LINESUPPLYVALVESAFETYFACTORSTATIC HEADPRESSURE DROPDRAIN15"MAINVENTDRIP CONNECTIONWETRETURNVENTVALVEHEATINGUNIT2 "STEAMCONDENSATEBOILERSTEAMSTEAMSUPPLY MAINBOILERWATER LINESUPPLYVALVETHERMOSTATICTRAPSTEAMCOND ENSATEHEATING UNITSPITCH 1" IN20 FEETDRY RETURNF&TTRAP Y STRAINERDIRTPOCKETBOILER HEADERDRIP CONNECTIONOPEN VENTCHECK VALVEGATE VALVECONDENSATE PUMP Y STRAINERGATE VALVEOne-pipe STEAM HEATING systemTwo-pipe STEAM HEATING systemWATER LINEPITCH 1 INCH IN 20 FEETMAIN VENTVENT VALVESUPPLYVALVEDRIP CONNECTIONBOILERA pplications One-PipeSystems3 Dry ReturnDown-FeedMechanical ReturnWATER LINEBOILERWET RETURNVENTMAIN VENTVENT VALVESUPPLYRISERSUPPLYSTEAM MAINDOWN-FEED RISERSUPPLYVALVESTEAM SUPPLY MAINBOILERVENT VALVESUPPLYVALVEDRIPCONNECTIONCHECK VALVEGATE VALVEF&T TRAP Y

2 STRAINERBOILERWATER LINEOPEN AIR VENT Y STRAINERCONDENSATE PUMPP arallel FlowApplications One-PipeSystems4 Parallel FlowWet ReturnUp-FeedWATER LINEBOILERVENT VALVESUPPLYVALVEDRIP CONNECTIONHARTFORD LOOPWET RETURNPITCH 1 INCH IN 20 FEETMAINVENTWATER LINEBOILERWET RETURNMAINVENTSUPPLY VALVEVENT VALVEUP-FEED RISERSUPPLY MAINRISER DRIPPEDDIRT POCKETWATER LINEPITCH 1 INCH IN 10 FEETMAINVENTVENT VALVESUPPLYVALVEDRIP CONNECTIONBOILERMAXIMUM MAIN LENGTH 100 FEETC ounter FlowApplications Two-PipeSystems5 GravityOPEN VENTBOILERWATERLINEPITCH 1" IN20 FEETDOWN-FEEDSUPPLY RISERDOWN-FEEDRETURN RISERSTEAM SUPPLY MAINSUPPLY VALVETHERMOSTATICTRAP Y STRAINERF&TTRAP Y STRAINERCONDENSATE PUMPGATE VALVECHECK VALVE Y STRAINERDown-Feed with Condensate PumpUp-Feed with Condensate PumpApplications Two-PipeSystems6 Y STRAINERF&T TRAPGATE VALVEPITCH 1" IN20 FEETSTEAM SUPPLY MAINVACUUMPUMPEQUALIZEROPEN VENTTODRAINCONTROLLINECHECK VALVEF & T TRAPSUPPLY VALVETHERMOSTATICTRAPVACUUM PUMPVACUUMBREAKERVACUUMSWITCH Y STRAINERBOILERWATERLINEV acuum Y STRAINERF&T TRAPGATE VALVEPITCH 1" IN20 FEETSTEAM SUPPLY MAINVACUUM PUMPEQUALIZEROPENVENTTO DRAINLIFTFITTINGCONTROL LINECHECK VALVE GATE VALVE Y STRAINER VACUUM BREAKERF & T TRAPSUPPLY VALVETHERMOSTATIC TRAPACCUMULATOR TANKVACUUM PUMPBOILERWATERLINEV acuum with Accumulator TankVacuumTypicalInstallationsCorrect pitch forhorizontal supply mainsand dry returns must be1/4" min.

3 In 10' in thedirection of STEAM andcondensate indicate directionof pipe BRANCHECCENTRICREDUCERS team MainsBranching from mainReducing size of mainRISERDrop riser branched frommain top at 45 angleDrop riser branchedfrom main bottomUpfeed branch from main at 45 angle45 ELLMAINRISERDRIP PIPEWETRETURNDIRTPOCKETR iser branched from main bottom and dripped into wet returnTypicalInstallations8 RISERRADIATORBRANCHD ouble radiator branch from riserSteam MainsBCAANCHORRISERO ffset pipe calculation tablePipe expansion joint for riserRETURN RISERSUPPLY RISERHORIZONTALBRANCH PIPES45 ELBOWSDRYRETURNMAINSUPPLY MAINU pfeed riser connections(two-pipe system )BConstant11 1 4 1 2 find C multiply A by constant for angle BTypicalInstallations9 FULL SIZEAT LEAST 1"BOILERWATERLINEBOILER RETURNHEADERPUMP DISCHARGECONDENSATEPUMPRETURNMAINOPENVEN TSTEAM SUPPLY MAINSTEAMSUPPLYHEADERBOILER HEADERDRIP CONNECTION MIN 1" PRESSURE BETWEENSUPPLY HEADER AND THE RETURNHEADER AT THE BOILERL ooping STEAM main around an obstructionBoiler piping to mainAT LEAST1"PLUG FORCLEANOUTL ooping dry return around door(two-pipe SYSTEMS )TypicalInstallations1018" MINIMUM15" WATER LINE WET RETURNMAIN VENT3/4" ELBOWREDUCER3/4" PIPEHIGH PRESSURE VENTSUPPLYMAINMain vent(one-pipe system )Main and high pressure air valve(one-pipe system )DRY RETURNTRAPMINIMUM COOLING LEGS 5'0" LONGSAME SIZE AS TRAPDROP RISER OR END OF MAINS upply main end dripping into dry return(two-pipe system )Drop riser or end of main dripping into dry return (two-pipe system )

4 Glossary11 Accumulator Tank Where returns in a vacuumpump HEATING system are below inlet connectionof vacuum pump receiver, an accumulator tankneeds to be installed. Its location should be suchthat condensate flows by gravity to accumulator,and is lifted to vacuum pump Drip Connection Pipingarrangement that drips STEAM header to returnheader and equalizes pressure between the Valve Valve that controls water flowbetween pump and boiler inlet, so that watercannot flow back from boiler to The water formed when steamcools, as in a radiator or other HEATING unit. Thecapacity of traps, pumps, etc., is sometimesexpressed in lbs. of condensate they will handleper hour. To convert lbs. of condensate or steamper hour, to sq. ft., EDR, multiply by Pump Used to return condensateto the boiler where it cannot be done by must be located so that condensate flowsinto receiver by Leg A length of uninsulated pipe withsufficient cooling surface to dissipate enough heatso that STEAM condenses and the trap can open todischarge condensate from system STEAM and condensateflow in the opposite direction within the samepiping.

5 Piping should be one size larger than in aparallel-flow system to allow sufficient space forfree flow of STEAM and Pressure Difference in pressuremeasured between inlet and outlet of trap orsimilar Feed Riser Piping that carries steamfrom supply main above to HEATING units piping also carries condensate from heatingunits to the system STEAM system for morethan one floor in which STEAM supply main is neartop of structure and down-feed risers carry steamto HEATING units, as well as condensate to wetreturn. Condensate flows to boiler via the Connection This section of piping, at least18" long, is the minimum distance the end of thesupply main must be above boiler water line forgravity flow of condensate back to the Return Return piping above the boiler waterline that carries condensate back to the Piping from top of boiler to maintainpressure balance on water in boiler STEAM Re-evaporation of condensateback into STEAM . It occurs when condensate flowsinto a reduced pressure area where thecondensate s temperature is above boiling pointfor reduced pressure.

6 For example: if hotcondensate is discharged by a trap into a lowpressure return or into atmosphere, a certainpercentage of water will be immediatelytransformed into STEAM . Flash STEAM usually has awhite, puffy and Thermostatic Trap Stops STEAM flowand continuously discharges condensate and airaccumulations into returns. Install trap far enoughfrom condensate pump receiver so flash steamdoes not affect the pump Valve Valve that completely closes off theflow of water out of boiler inlet valve, usually open,can be closed tightly if pump needs repair Loop Actually two loops, this system ofpiping acts as a safety device to prevent the waterfrom draining out of the boiler if a leak develops inreturn piping. First loop surrounds boiler; secondis the balance of the Unit Convectors, cast iron radiators,wall-fin radiation units, and similar Riser Vertical portion of the wet return thatbrings water into the equalizer 2" below water Vent Valve Lets air escape from supplymain quickly so STEAM can circulate and reachheating units for fast warmup.

7 Main Vent shouldbe located at least 15" from the last fitting of thesupply Return STEAM HEATING SYSTEMS inwhich the height between the end of the main andthe boiler water line (drip connection) isinsufficient for gravity return of condensate back tothe boiler A condensate pump provides themechanical means for condensation Pressure Return Actually a dry return belowthe boiler water line. Condensate flows by gravitythrough this return and enters the condensatepump above the high water line of the pump sreceiver. Air in this return is at atmosphericpressure because the receiver has an open airvent that extends above the boiler water Air Vent Open length of piping extendingup from the pump receiver to above the boilerwater line. The vent keeps air pressure in both thepump receiver tank and the no pressure returnequal to atmospheric pressure outside the system Piping arrangement ofsteam system in which both STEAM andcondensate flow together in the same direction inthe supply main and of Mains Pitch is the amount of slopegiven to a pipe.

8 Correct pitch for horizontal supplymains and dry returns must be 1/4" min. in 10' inthe direction of STEAM and condensate Drop Difference between steampressure at top of boiler and pressure at the endof the STEAM supply main. It is caused from frictionwithin piping and the condensing process in mainsand HEATING Factor Additional static head needed tocompensate for higher pressures and greatersteam consumption during warm-up Head Amount of water needed in returnsto build up necessary pressure to force water backinto the boiler in a gravity feed Boiler A closed vessel for conversion ofwater into STEAM . It should be equipped withautomatic controls to maintain water level andsufficient safety devices for proper burning of Foot of HEATING Surface EquivalentDirect Radiation (EDR) the amount of heatingsurface which will give off 240 Btu per hour whenfilled with STEAM at 215 F and surrounded by air at70 F. (Equivalent square foot of HEATING surfacemay have no direct relation to the actual surfacearea.)

9 Strainer Used to protect valve pins, seats, andother parts from dirt and foreign Main Primary piping that carries steamfrom boiler to HEATING units, and, in a one-pipesystem, condensate from HEATING units to Riser Vertical piping that carries steamunder pressure from boiler up to supply main. Ariser carries STEAM up from supply main to Valve One-Pipe system Located at the bottom ofheating unit s inlet connection. Supply Valvecontrols admission of STEAM , and flow out ofcondensate. In a one-pipe system , the supplyvalve should be fully open or closed tightly, since apartially open valve obstructs free flow of STEAM inand condensate system Modulating-type supplyvalves either spring packed or packless admit STEAM to the HEATING unit through its topinlet connection. Selection depends uponconstruction requirements and system STEAM Trap Located at thebottom outlet connection of the HEATING unit,thermostatic trap stops flow-out of live STEAM , butopens to drain condensate and air into the Vacuum system An ordinary two-pipe vacuum system uses a vacuum pump tocreate a subatmospheric pressure, usually 3" to 8" Hg (Mercury), in the return removes air from system piping andheating units to provide quick HEATING and efficientsteam distribution.

10 Condensate flows to the pumpreceiver by system STEAM system for more thanone floor in which the STEAM supply main is in thebasement above the boiler. Risers carry STEAM toheating units. Condensate from each up-feed riseris dripped by gravity into wet return and then flowsvia Hartford Loop to boiler. Supply main is keptfree of condensate accumulation for free flow system A closed HEATING system inwhich a partial vacuum is induced when theheating units and the main cool below the boilingpoint of water at atmospheric pressure. Pressuresin a vacuum system range from belowatmospheric pressure to a higher pre-determinedpressure. Space HEATING is more even, and boilerwater temperatures are usually lower; HEATING ismore economical. Vacuum vent valves andvacuum main vents must be Pump Equalizer Piping arrangementthat equalizes induced vacuum between thesupply header and vacuum pump Valve Installed on a tapping at theopposite end of the supply valve, float andthermostatic vent valves let air escape from theheating unit under pressure, but closes againstthe passage of STEAM and Hammer A wave transmitted through apipe filled, or partially filled, with water.