Burnham FREEDOM - Method 1: Primary;Secondary Piping

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Method 1: Primary/Secondary Piping
  Thismethodcanbeusedinheat-onlyapplicationsasshowninFigure9.2orwithanindirectwaterheaterasshown
inFigure9.3.Thismethodreliesonprimary/secondarypumpingtoensurethattherequiredowisalwaysmaintained
throughtheboiler.Inthissystem,theowratethroughtheboileriscompletelyindependentoftheowratethroughthe
heatingsystem.UsethefollowingguidelinestoensurethattheboilerwillhavetherequiredowshowninTable9.1
regardlessoftheowintheheatingsystem.
1) PrimaryLoopPiping-Sizetheprimarycirculatorandpipingtoobtainthedesignowratethroughtheheatingsystem
asyouwouldonanyotherheatingsystem.Allpipingbetweentheexpansiontankandsecondaryconnectionteesmust
beatleastaslargeasthatshowninTable9.5,column(a).Inordertokeeptheowratesintheprimaryandsecondary
loopsindependentofeachother,provideatleast8diametersofstraightpipeupstreamoftherstsecondaryteeand4
diametersdownstreamofthesecondsecondarytee.Keepthedistancebetweentheexpansiontankandtherstsecondary
teeasshortaspractical.
2) SecondaryLoop(“BoilerLoop”)Piping–AllpipingmustbethesizeshownfortheboilerinTable9.5,column(a).To
sizethecirculator:
a) SelectoneoftheboilerwaterowratesshowninTable9.5,column(b)fortheboilerbeinginstalled.When
 selectingtherequiredboilerowrate,keepinmindthatiftheowrateintheprimaryloopexceedstheow
 ratethroughtheboiler,itwillnotbepossibletoobtaina180°Fsupplytemperatureintheprimaryloop.Thisis
 becausethesupplywaterexitingtheboilerwillbemixedwithcoolersystemreturnwaterbeforeenteringthe
 radiation.
b)Countallttingsintheplannedsecondaryloop(thesecondaryloopconsistsoftheshadedpipinginFigure 
9.4a).Indoingso,donotcountthesecondaryconnectiontees,unions,orthettingssuppliedwiththeboiler
 (thesehavealreadybeenaccountedfor).
c) UsingTable9.7,ndtheequivalentlengthsofallttingsinthesecondaryloop.Totaltheseequivalentlengths
 andaddthemtothetotallengthofplannedstraightpipeinthesecondaryloop.Theresultisthetotalequivalent
 lengthofthesecondaryloop.
d) UsingTable9.5,ndtheboilersizebeinginstalledandselectaboilersecondarycirculatorthatshowsa 
 “maximumequivalentlength”(columne)inexcessofthetotalequivalentlengthcalculatedinStep2c.
3)
IndirectWaterHeaterLoopPiping(IfIndirectWaterHeaterisUsed)–AllpipingmustbethesizeshowninTable9.6,
column(a).Iftheindirectwaterheaterconnectionsaresmallerthanthepipesizecalledforincolumn(a),reducethe
pipesizeattheindirectwaterheaterconnections.Tosizethecirculator:
a) CountallttingsintheplannedIndirectWaterHeaterLoop(theindirectwaterheaterloopconsistsofthe 
 shadedpipinginFigure9.4b).Indoingso,youwillbecountingsomepipingandttingswhicharecommonto
 theheatingsystemsecondary(“boilerloop”)pipingandwhichwerecountedinStep2aabove.Donotcountthe
 elbowsorttingssuppliedwiththeboiler.
b) UsingTable9.7,ndtheequivalentlengthsofallttingsintheindirectwaterheaterloop.Totaltheseequivalent
lengthsandaddthemtothetotallengthofplannedstraightpipeintheindirectwaterheaterloop.
 Theresultisthetotalequivalentlengthoftheindirectwaterheaterloop.
c) UsingTable9.6,ndtheboilersizebeinginstalledandselectanindirectwaterheaterloopcirculatorthatshows
 a“maximumequivalentlength”(columnf)inexcessofthetotalequivalentlengthcalculatedinStep3b.
Example – Assume that a FCM120 is to be installed in a heating system along with an Alliance indirect water heater.
A total of 15 ft of straight pipe will be installed between the boiler and the primary loop. A total of 20 ft of straight
pipe will be installed between the boiler and the indirect water heater. Fittings are arranged as shown in Figure
9.3. A 9.0 GPM ow is required in the boiler loop. The MS-40 requires a ow rate of 8 GPM and has a head loss
of 3.0 ft.
Total ttings in Secondary loop (“boiler loop”):
6 90 Elbows
2 Runs of Tees
1 Swing Check
2 Isolation Valves
Note: Unions, Secondary Connection Tees, and factory supplied ttings are ignored.
Calculate total equivalent length from Table 9.7:
15ft Straight Pipe + 6 Elbows x 2.75 + 2 Runs of Tees x 1.75 + 1 Swing Check x 7 + 2 valves x 0.6 = 43.2
equivalent feet straight pipe. From Table 9.5, we see that a Taco 0014 will pump 9 GPM through a FCM120 with 61
equivalent feet of pipe, so the Taco 0014 is OK.