EngA DJM3

A DJM3
IOM-17 18 of 27 Mar 99 R3
5. CurveMatchingProcedure
TurnServicePottohighfire(approximately3450RPMor57.5Hz)for1minute.Adjustthe
ServicePotdownveryslowlyuntilthecombustionmotorspeedisabout3060RPM(51Hz).
Ifthepotisadjustedbelow51Hzreturntohighfireandattempttolowerwithoutpassing
51Hz.Lettheburnerstabilizefor2minutes,thenre‐checkO
2
reading.IfO
2
hasdroppedto
lessthantheoriginalhighfireO
2
 reading, adjust the CurveMatching pot. Adjusting CCW
increasestheO
2
readingbyreducingthevoltagetotheMaxitrolmodulatinggasvalve.The
CurveMatchingpotonlychangesthevoltagetothegasvalve;itdoesnotaffectfanspeed.
IfthecurvematchingpotisadjustedtothefullyCCWpositionandtheO
2
readingisstillnot
within 10% ofthe originalhigh fire O
2
 reading, adda 180‐ohm2 watt resistor across the
modulatinggasvalveterminals;repeatabovetestuntilpropercurvematchingisachieved.
(A150‐ohm,2‐wattresistormayhavetobeusedifO
2
levelstilldoesnotrisetowithin10%
oforiginalhighfireO
2
reading.)
Switch burner to low fire again and re‐check low fire, both at 0 VDC and 2.25 VDC. (An
additionofaresistorabovemayhavechangedthelowfiresetting,ifitwasneeded.)
 Lockthelockingringonthespringactivatedlowfireadjustmentscrew(fromstep1).Failure
tolockitmaycausethescrewtovibratelooseallowinglowfire gaspressuretoincrease.
Thiscancreatesootingofburnerpartsandtheheatexchanger.Ifthelockingringismissing,
droponedropofLoctitethreadlockerontothebrassscrewthreads.

Series50/M550,M650ANDES350(HighTurndownBurner)
Thesevalveshaveonly1lowfireadjustment(springactivatedlowfire).
1. Thecombustionsetupissimilartotheaboveexceptthereisnolowfirebypassadjustment
onthebottomofthesevalves.Thereforesimplysetuplowfirebyturningthemanualfiring
PotResetRatiotothelowfireposition‐1250RPM10RPM20.8Hz.(15:1turndownsetat
1195RPM,19.91Hz.)Voltagetotheseries50valveshouldbenear0voltsDC.Adjustthe
springactivatedlowfireadjustmentatthetopofthemodulatinggasvalve(smallscrew)
untilanO
2
readingof16.8%to17.5%isachieved.
2. Lockthelowfireadjustmentscrewasdescribedinpoint7aboveandthenadjustthecurve
matchingpotasinpoint5above.

TypeES345D‐L(HighTurndownBurner)
Asthisvalvehas2lowfireadjustmentsthefollowingprocedureshouldbeapplied.
1. BringtheunittolowfireusingtheservicefiringpotfullyCCW.AdjustPotLowFireuntilthe
combustionfanisturning1250RPM10RPM(20.8Hz).(15:1turndownis1195RPM,19.91
Hz.)VoltagetotheESvalveshouldbenear0voltsDC.Thelowfirebypassadjustmenton
thisvalveisunderthetopcoveronthelargeportandtheadjustmentinsideitismarked:
IncreaseDecrease
Afterremovingthecover,loosenthelockingscrewfirstbefore making adjustment. This
shouldbedoneat0VDCtothemodulatinggasvalveterminalsandthespringactivatedlow
firebrassscrewturnedfullyCCWandthelockingringloosenedoff.
