FLAME SAFEGUARn CONTRULS phần 7 potx

, .~ PRESSURE CONTROLLERS A pressure controller is a device thai monitors the pres- waler heating systems, In gas burner systems, and in oil sure of sleam, air, gases. or /iQ.lids. AA internal diaphragm burner systems. Honeywell pressure controllers available or bellows responds 10 pressure changes and, throu;j1 IS for use In these systems wltJ be described In (he following mechanical linkage, acluates a switch or polenllomeler to sections. Installation procedures peculiar to each system keep the pressure within predetermined limits. Pressure will also be diSCUSSed. controllers afe com~nly usaa' on steam boilers and hoi PflESSUFi"E CONTROLLERS USED ON STEAM BOILERS AND HOT WATER HEATING SYSTEMS The pressure controllers discussed in this section can be used with steam, air, noncombtJslib!e gases, or fluid noncorrosive 10 the pressure sensing element. They pro- vi~ operating control or limll protection, depending on the controller model al"d wiring hookup (Figs. 3-7/. LOCATION AND MOUNTING When used with sleam boilers, always mount the. controller above the water fine in the boilEir. A steam trap must always be connected between the controller and the boiler (Fig. 11) to prevent boiler scale and corrosive vapors from atlacking the diaphragm or bellows. The 1<::q:1 on the steam trap must always be perpendicular to the face of the controller. 11lhe f<::q:l is parallel to the contrOller, expansion or contraclion 01 the 1<::q:I will tip the controlier and cause the switch to operate inaccurately. The controlier can be mounted (1) alongside the pressure gauge, (2) in a filling on tile boiter provided by the manufacturer, or (3) at a remote location in case of exces· sive vibration. When making pipe conn&ctions, use pipe compound sparingly to seal tile joinlS. Excess pipe c0m- pound may clOQ Ille small hole in tile fitting al"d prevent the controller 1rom operating properly. ~"E55U"E , ,,,,~/~~O"TROLLER .""~~ • PIlESSOJII(. Zkl S7 10'A. RIGHT , T GAUGE , ."2 TO~"2 (1 a TO aOj WRONG .& l/O-'''C," BLACK 'RO" ~'~E WI'," ,/ ,a NPT [XTER l T f. OS Oil BOTH ENO~. , ,e BOILER FIG. 11- RIGHT AND WRONG MOUNTING OF A STEAM TRAP, WITH APPROXIMATE DIMENSIONS IN INCHES [MILLIMETRES IN BRACKETS]. NOTE: If using tile controller with a CO!T'Pressor, install a dampening device (wch as a needle valve. header, or surge lank) to dampen pulsations which can damage the controller or reduce its life. To mounllhe conlroller alongside the pressure gauge (Fig. 11), remove the gauge. In its place. install a steam trap with a lee on tap. Using elbows and pipe nipples, mount the controller and pressure gauge on the ends of Ihe tee. If it is not convenient to mount lhe controlier alongside the pressure gauge, install a steam trap in the fitting provided by the boiler manufacturer. If there is no 1ilting. mount the steam trap al a location recommended by the boiler manufacturer. Screw Ihe controller directly to Ine steam trap. If there is ex.cessive Vibration at the boiler that mayad- versely affact the operation of the controller, the controller should be mounted' at a remote location. All piping from the boiler must 'os suitable and solidly mounted. The piping must be properlV pitChed to drain all cOndensation back to the boiler. A steam trap must be mountEKl between the remote piping and the controller. HONEYWELL PRESSURE CONTROLLERS AVAILABLE FOR USE ON STEAM BOILERS AND HOT WATER HEA,TING SYSTEMS Honeywell pressU/8 controllers are fistEKl in Table II al the el"d 01 this section. along with their applications, switch types, al"d operating pressure ranges. Fig. 12 shows the mcx:lels IiSIEKl. AlIl'T'\Ode1s operate as desCribed in Basic Principles ot Controllers except the P455. which is a corrtJination prq:;ortioning al"d on-otf controller. lis operation is descri'osd next. For furttel infor- mation, refer to the instruction sheers tor the controllers. OPERATION OF THE P455 COMBINATION CONTROLLER The P455 is a combination prq:;ortioning al"d cn-otf pressure controller. [n addition to a prorortioning potentiometer, it has an spst swilCh with a subHacUve ditferenlial that breaks on pressure rise. Tha main scale is set at the manmum pressure desirEKl. The differential is adjustEKl in- stead of the prcportioning range. Tl"le proportioning tange will automatically be sat 10 approximately 85Percent of the differenlial. (The differential sca[ap1ale is graduated from A to F with a MIN value below A. Refer to the P455 instruction sheet for values 01 the differential and proportioning range.) 223 71-97558-' FIG. 12- HONEYWEll PRESSURE CONTROLLERS AVAILABLE FOR USE ON STEAM BOILERS MID HOT WATER HEATING SYSTEMS. '.' The P455 also has a UNISON/SEQUENCE adjust- ment, which provides a choice 01 firing rale at burner startl.P. The odjusling dial is located just below the wiper armof the potentiometer (Fig. 2?). The dial is turned so Ihe arrow isat Ufor unison q:)(lralibn, at S for sequencecpera· lion, or at one of 3 inlermediale positions, Fig. 13 sh(w,rs the operation at Ihe P455 for each of these p::lSitions. In (he UNISON position, Ihe prcportioning range is: entirely within Ihe differential range, so the on-ott swi'ch and the prClJX)rtloning potentiometer are functioning at the same Ifme. When Ihe pressure falls to the sel point minus the differential, Ihe on-oN switch makes and the burner Is lumacl on. The potentiometer wiper is aU the way over to the Bend, lhe firing rate Controls are a! the high fire jXlSi- tion. and the bUrner starts al high fire, As the burner heats l4=l and the pressure increases, the wiper moves toward the W end of the potentiometer. It the pressure contlnues 10 Increase, the Wiper moves all the way to the Wend and !he firing rate conlrols are at the low tire ~ilion. Ordinar- Ily, modulallon keeps the pressure belW9Eln thess posi- lions within lhe proportioning range. If It prOblem devek:ps or the Iced drops suddenly, and the pressure continues 10 rise, the on~f'I' switch breaks and shuts down lhe bUrner when the pressure reaches lhe main scale sel point. In the SEQUENCE posilion, Ihe prqx>rtionlng range is entirely below Ihe differenlial range, so the on~ff switch and the proportioning potentiomeler are not funclioning al 224 the same time. As in the UNISON position, when the pressure falls 10 lhe sel point minus Ihe differential, Ihe on-off switch makes and the burner is turned on. However, the potentiometer wiper is all the way over to the Wend, the 1iring rale controls are al the low tire position, and the burner starts at low fire, It the pressure continues to fall be- 10re the burner can heat up, the Wiper moves toward the B end at the poten/iometer. If the pressure 1alls far enough, Ihe wiper moves all the way 10 the B end and the firing rate controls at the l1igh fire posilion. As the burner heats l.4) and the pressure increases, the Wiper moves toward the Wend at the potentiomete(. Again, the pressure is ordinar- ily kept within the proportioning range. t1the pressure con- linues to rise, the wiper moves all the way 10 theW end and lhe 1iring rale contrOlS are at the low tire jXlSilian. The burner slays at low 1ire as the pressure increases through the differential range, and is Shut do ·:n when Ihe pressure react'19S the main scale sel point. In an intermecliale jXlSition, the proportioning potentiometer is functioning partly wllhin the differential range of the an~N switch-the amount varies with the ~ilion. This provides a ChOice of lhe firing rale-somewhere between low 1ire and high fire-al burner startl4=l when the on~ff switch makes. As shown In Fig. 13, the pressure range over which the burner will operate at low fjre also varies with the position 011he UNISON/SEQUENCE dial. • ( -"'GH • ,,~t , ,. I "'I.UNG ""ESSURE " ", j U"'SON / OI'ERATlO,", r-_~/ \ \, \ I ~ \ / ~ \ I ( /,," \"'li' 'oJ _ l~" I -"'G a "M I I -H'OH • FIRE I I I I I • ',AE I r iL" I I I I I I I I 'HTrRWW'''rf OHRATlO'l \ -, I I rli l 1'-_ / -, \ ,\J I \ //\, \_~ I I I", 1\.\1 r- , \"""(\1 I I 1 - \ I I I 1'':-:, r\il J I \"5\ '''' . ./ I \-\ '''' I I 1 <; ,,_ I L ____ J L __ :'_J L ____ J \ ",.,loC>NlllOJ<JVICE AOJusr nn I I I U(]UENn O"ERA"<lN , \ I l@) .I FIG. 13-0PERATION OF THE P455 COMBINATION PROPORTIONING AND ON-OFF PRESSURE CONTROLLER. PRESSURE CONTROLLERS (PRESSURE SWITCHES) USED IN GAS BURNER SYSTEMS The pressure controllers used in gas burner systems are commonly called gas pressure swilchas_ They may be used with natural gas, LP gas, or air. (The C64sC and D models can be used only with air.} They provide safety shutoff or diflerential-pressure control, depending on the controllsr model and wiring hookup (Figs. 3-5). No proportioning controllers are available tor use in gas burner systems. LOCATION AND MOUNTING Gas pressure switches in the main burner line should be located downstream from the PRII (pressure rBgJlaling valve). The low gas pressure switch should be localed u(r stream from the safety shutoff valve(s). In a downstream location, there would be zero preSsure when lhe burner Isn'( running and the safely shutoff valve(s) is closed. This could prevent startup or reqUire manual reset every time the burner is started. The high gas pressure switch should 225 be located as near thE! burner as p:;lSSibre. Typical loCa- tions arE! shown In Fig. 14. A pressure switch is t JSllally rrounted dlrectPy on the main pipe by Inserling a tBEI in the pipe lJne, and connecting a pipe nil=flle at appropriate size 10 the tBEI (Fig. 15). Screw the main pressure connection ot Ihe pressure switch to the pipe nil=flle. The main connection is a heJt- agonallilling with 1/4 or 1/2 inch NPT Internal threadS. To avoid leaks and damage to the case. use a parallel jaw wrench on the hexag::mal fitling close 10 lhe pipe ni~le. Make all connections carefully and lest lor leakage. Do not tighten rhe pressure swifch by hand by holding the case. In some cases, it may be more convenient (0 mountlha pressure switch on a nearby wall. using the optia'lal mounting bracket. The braCket should be Installed before connecting the piping from the main line. ContrOllers with mercury swilches (C437. C447, C637, (;647) must be carefully leveled as described In Basic Pri". 71-97558-1 FIRING RATE SSOV CONTROL o MSOV MAIPIl VENT 'RV MSOV i=t~~;E}::;~BUlrER HIGH GASPS BURNER PRESSURE • PILOT LINE TEST TAP MSOY _ MANUAL SHUTOFF VALVE PRY - PRESSURE REGULATING VALVE PS - PRESSURE SWITCH SSOY - SAFETY SHUTOFF VALVE FIG. 14-TVPICAL LOCATIONS OF THE GAS PRESSURE SWITCHES IN THE MAIN BURNER LINE. ciples of Controllers. C645 Pressure Swilches are snap- a. Hazardous (combustible) gas-Install a vent pipe at acting, so they 00 nol have 10 be leveled, The C645A,B, or the venl conneclion so that any gas leakage will be o may be mounted in any position, but they are slighlly vented into the combustion Chamber or to another more accurale when mounled with the diaphragm hOri· safe place in case the diaphragm in the pressure zontal. The C645C (low operating pressure range) must switch fails, be mounted with the diaphragm vertical and (he vent con- b. DifferentjaJ pressure-Connect the high pressure nection (bleed fitllngl at the I:ollom. side at the system to the main pressure connection, A vent connection (1/B inch NPT with inlernal lhreaci5) and the low side to the venl conneclion. This appli- is provided on all pressure switches. This connection must Cation cannot be used with hazaroous gases as no be used in the following awlications: venting is possible. c. Negative prflSSUre - Connect the low pressure side __ ~AS ~~tsSV~E: SWITCH IAT RIGHT .~GLE:S TO THE: M.'~ ~I'E: L'~E) Ii MAI~ ~IPE L1NE ",'EHE [TIJR~ TO LEVEL T"E ~RESSURE SWITCHl FIG. 15- MOUNTING A GAS PRESSURE SWITCH DIRECTLY ON THE MAIN PIPE. to the vent connection. This awlication also cannot be used with hazarcbus gases, When using a pressure switch with a low pressure range, momentary pressure surges or &bumps" can cause the switch to break. Orifices are available for C437 and C637 Pressure Switches to eliminate or reduce chal· lering or nuisance lockouts caused by Ihese -bumps.· An orifice is inserted in the main pressure connection (Fig. 16) [0 reduce the effect at pressure surges. The bushing and ORI FICE TOOl AG. 16-INSTALLING AN ORIFICE IN A C437 OR C637. 226 onfice 1001 shown are used only for installation at the ori- tice, and are removed afterward. PRESSURE SWITCH SETIING Industrial Risk Insurers (formerly F.LA.) recommenc1s that gas pressure switches on the manifold be seln accordance with the turncklwn range of Ihe installation. They recommend thatlhe high gas pressure switch be sal 20 per,cent above Ihe maXimum firino rate pressure, and the low gas pressure switch be set 20 10 50 percent below the minimum firing' rate pressure, wilh the preference being 20 percent. ,,' J.IMllli, C0l'ltrp1lehf ", 'andlntlllrlocks HONEYWELL PRESSURE CONTROLLERS AVAILABLE FOR USE IN GAS BURNER SYSTEMS HoneyweJl pressure conlrollers evailable are listed ;n Table II al the end of Ihis section, along with their awlications, switch types, and operating pressure ranges. Fig. 17 shows the models listed, All models operale as d&- scribed in Basic Principles 01 Controllers. For runher infor- mation, reler to the instruction sheats for the controllers. PRESSURE CONTROLLERS USED IN OIL BURNER SySTEMS Prassure controllers are used in oil burner systems to supervise oil pressure and to supervise the pressure 01 the atomizing medium (if used). OIL PRESSURE SUPERVISION The Oil pressure controllers (also called oil pressure SWitches) discussed in this section can be used with any type of fuel oil, inclUding heavy preheated oils. They have a stainless steel diaphragm to resisl corrosion. The dia· phragm transmits changes in oil pressure to an spst mercury switch Ihrough a mechanical linkage. The L404T and Ware high pressure limits; they break a circuit and st'1ut down the system if the oil pressure gets too high. The L404V and Yare operating controllers and low pressure limits: they preventlhe system from staning untillhe oil pressure is high enough, and they Shut down Ihe system ir lhe oil pressure falls too low. TIle L404T and V have adjustable subtractive differenhals: the L404W and Yare manual reset models. C447.C547 _ LOCATION AND MOUNTING Oil pressure controllers can be mounledat any location in Ihe ojl supply line, dePending on Ihe application. Typical loca/lons are shown in Fig. 18. The low oil pressure switch should be located upsrrfjam from 1M safely shutoff valve{S), In a downstream location, there would be zero pressure when the burner isn't running and the safety Shu10ff valve(s) is closed. This could prevent startup or require manual reset every time the burner is staned. The hiGh oil pressure switCh should be located as near the burner as possible. An oil pressure controller is mounted directly on the main pipe by inserting a tee in tha pipe line. and cOnnect- ing a pipe ,iJ:Ple of appropriate size to lhe tea (FiQ. 19). Screw Ihe he:tagonal fitting (1/4 inch NPT with internal threads) at the pressure controller to lhe pipe niJ:Ple. To avoid leaks and damage to Ihe case, use a paralle! jaw wrench on the hexagonal filling close to the pipe niJ:Ple. Do not tighten rhe pressure contro/ler by hand by holding the caSe. FIG. 17-HONEYWEU PRESSURE SWITCHES AVAILABLE FOR USE IN GAS BURNER SYSTEMS. 227 71·97558-1 MAIN mL UNE • TO OIL )=~~=~==p':I:;!==~=:::t';j.E:J==-::=CJ-=t~:E~BU;NER FIRING SSOV ANO RATE RECIRCULATING CONTROL VALVE LOW A.M.PS ATOMIZING MEDIUM. ====:":===::=J (AIR OR STEAMI " MSOV - MANUAL SHUTOFF VALVE - PRESSURE SWITCH ssov - SAFETY SHUTOFF VALVE A,M, PS - ATOMI21NG MEOIUM PRESSURE SWITCH FIG. 1B-TYPICAL LOCATIONS QFPRESSURE CONTROLLERS (SWITCHES) IN AN OIL BURNER SYSTEM. Make all pipe conneclions in accordance wilh ap- proved 5tandardi. Use only a small amount of pipe com- pourd 10 seal the connection joints. Excess pipe Corrp:lUnd may Clog Ihe small hole in the filling and prevent the controller from operating prcperly. When used with preheated oil, a siphon 10ClP must always be connecteCl between the controller and the main pipe {Fig. 20) to provide thermal buffering. The 10ClP must always be perpendicular to the face of the controller. If the 10ClP is parallel 10 the controller, expansion or contraction of the 10ClP will tip the controller and cause the switch to cperate lnaceuralely. Oil pressure controllers have· mercury switches, so they must be leveled for proper operation. If mounting directly on the main pipe (Fig. 19), install the controller at rIght angles to the pipe; leveling can then be accom- plished by turning the pipe 100. If using a siphon 10ClP with prehealed oil (Ag. 20), leveling can be accorTfJIlshed b)I carefully bending the siphon 10ClP. The controller is level when the leveling indicator hangs freely with lis pointer directly over the Index mark on the back of the case (see Rg.2). WIRING HOOKUPS If the oil burner system is a single burner system with an integral oil pump, connectlhe oil pressure controller In series between the flame safeguard control and the main oil valve solenoid (Fig. 21). If it is a single burner or a multibur- ner system with an external oil pump, connect the oil pres- 228 sure conlroller in series wilh the other controllers, limits ard interlocks (Fig. 22). SUPERVISION OF ATOMIZING MEDIUM PRESSURE (AIR OR STEAM) When air or steam is used as an atomi.ing medium, aulhorities having jurisdictiqn (approval bodies and codes) often require a-rowiimitto prevent openinQ of the main oil valve unlil sufficient atomizing pressure is pre- senl, and to shut Gbwn the system if the atomi2inQ pres- sura falls too low. The L404B Pressure Controller, designed tor use on steam boilers and hot water healing systems, is recommended tor (his appllcallt:rl. It has an spst mercury switch wilh an adjuslable Slblraclive diMerenlial. The switch makes a circuit when the pressure rises to the set jX)int, and breaks when the pressore fcllls to the set point minus the differential (see Fig. 8). The L404B is available in 4 0p- erating pressure ranges, from 2 to 300 psi. LOCATION AND MOUNTING The L404B is mounled in Ihe supply line for the atomizing medium (Fig. 18). Follow the same mounting instruc- lions as for the ofl pressure c?1trollers. WIRING HOOKUPS The cperation of the L404B Is the same as for the L4D4V,Y (makeS on pressure rise to setjX)int). II should be connected In series with lhe oil pressure controller (Fig. 21 or 22). , /Oll PJtU,5UR£ ~ONTFlQLlE~ ., (Ar "'G"r ANGLES TO THE "' ".E UNE) .'.fTEE (lU"" TO U\I[L THE CONrJtOLUlOI L "" FIG. 19- MOUNTING AN OIL PRESSURE CONTROLLER DIRECTLY ON THE MAIN PIPE. , ; 4 2 T051 1114 TO 1401 L 14026 SIPHO"& LOOP • Oil PIlUSWI[ CONHIOllER • PflEI'iE",Tl:O OIL PREl'itATED O'L SUP'PLV LINt SU","L.II 1,.10'[ & (, eli eLACI( IRON "P[ WITH 1/""'"PT [)(TEIlN 1 THREAOS Oil BOTH ENDS. 8tHD TIiE SIPHON LOOP TO LEVEL THECONTIIOLL.ER. I "F'" GC" =2-=O-_-C R :cC"O:cC"WC"R"O"NC"G= =M"O"U- N ='::N"G-O"F"A" "'-=GC"H::T" AH -C T SIPHON LOOP, WITH APPROXIMATE DIMENSIONS IN INCHES [MILLIMETRES IN BRACKETS). HONEYWELL PRESSURE CONTROLLERS AVAILABLE FOR USE IN Oil BURNER SYSTEMS Honeywell pressure controllers allailable are lislad In Tabla II al (he end or this section, along with their awica· !.ions, switch types, and operating pressure ranges. Fig. 23 shows the models listed. For further infonna(ion, refer to the instruction sheets lor lhe con/rollers. OllPAE$SIJAE , .,"vALvE '~""l UoHGUAIIIO CONTIIIO~ U ~ - FIG. 21 - HOOKUP OF AN OIL PRESSURE CONTROLLER USED ON A SINGLE BURNER SYSTEM WITH AN INTEGRAL OIL PUMP. FIG. 22- HOOKUP OF AN Oil PRESSURE CONTROLLER USED ON A SINGLE BURNER OR MUL TIBURNER SYSTEM WITH AN EXTERNAL OIL PUMP. L.O&Oo&T,V,W,Y L __ ('_·_'_·B_"_'_'._'_'_A_._' ~ FIG. 23- HONEYWELL PRESSURE CONTROLLERS AVAILABLE FOR USE IN OIL BURNER SYSTEMS. SETTING PRESSURE CONTROLLERS The operating p:>ints 01 pressure controllers are set by tq::l of the case. as shown in Figs. 24 and 25. Sealeplales turning ild}usting screws or knobs, usually located on the are rnar1<oo in in. we (inches of vwater colLKm), in psi 229 71-97556-1 I (pounds per SQJareinch), or In oz./in. t (ClUl'lCeS per S(JJare inch; 1 oz./ln.' = 0.0625 ps~. Those which extend into a vacuum range (prescurK below atmospheric pressure. Which 15-0 pslg or ~rQ){imalely 14.7 psial are mar1<:ed in In. Hg (inches of mercury; , In. Hg "" 0.4912 psi). Many scaleplales are also marked in metric equivalents, such as mm ,we (milllmelres of water column), mbar (millibars), kll1 cmr (kilograms per squate centimetre). or kPa (kilopas- caIS). SOme international models are marked in kll1CfT11 and kpa. Table I lists conversions befween II18se units. SETIING ON-OFF PRESSURE CONTROLLERS The main scale is SEll at the desired ~raling pressure by turning the main SCale adjus\irQ screw (Fig. 24) or Inter· 081 dial (0447, C647J unlJl the main scale selling indicator is al. thedBslred value. On some models, the differential is fiXed; bJt on ITOSt I'TlOd9ls. it is adjustable by turning lhe differential adjusting screw (Fig. 24) or internal dial (PA4Q4) until the differential tatting indicator Is at the de. sired ~akJe Manual reset models are reset by pushing in and releasing 1he manual reset lever (Fig. 24). SETIING PROPORTIONING PRESSURE CONTROLLERS The main scale Is set allhe desired q?eraling pressure by luming the main scale adjusting sere (Fig. 25) unlillhe main scale se1ting indicator is at the minimum pressure desired (excepl the P455, which 'was d8scribed ~revi. ouslyl. TIle .oroportioning ranoe (also called throWing range) e.:tends above this value, as shown in Fig. 9. The proportioning range may be fixed or adjustable, depending on :he controller model. An adjustable model is sel OJ turning the proportioning range adjusling screw (Fig. 25) untillheproponioning rangesel!ingindicalor is af the dasired val~. "Fha prop::>r1iQlling range scale is gradu- TABLE J-PRESSURE CONVERSION TABLE INCHES mm mllll- ,p, kg/em 2 0' 0' p" brr. b WATER WATER a , 0,249 3 0.036 25.4 .49 0.00254 7.47 0,00762 0,747 0108 75.2 , , .245 10 12.45 0,0127 0,181 127 24.91 0.0254 2.491 0.0533 0.361 254 S.231 0.75 533 .31 2' 68.95 0.0703 6,895 1.000 703 , 7 , -R~ 7 0.7031 2768 10 689.5 68.95 703' , 105~6 1.055 415,2 1C.34 553.6 20 " 14062 1379 1.406 137.9 - 2t13 2.461 24608 24'.3 ,38< 96eB 35 35154 3m 3.515 344.7 7,031 SO 689.5 4152 _ 70309 689' 2'68 '00 10.55 105463 10342 'SO "", 210927 21.09 2068 8304 JOO ""54 5536 2 1406 137, 0.1406 13.79 , .4 , 3516 3447 0 51' 34.47 a,rT'ITI of waler = OOOC1 kg/em' b, millibar ~ J,1 kPa c1 kg/Cm~ = 98.0065 kPa FIG. 24- SETIING A TYPICAL ON-OFF PRESSURE CONTROLLER. ated from A to F with a MIN (minimum) velue below A. TIle value at each division depends on lhe pressure range of the controller. (Refer to the instruction sheet for the controller 10 deleJ:nine the value.) - "' IN ., $C"'LCP~A TE 1 '" 8 ., ~ 'ih lOA IN SC lE 'Ii ;H SETTING ><. 1;~ INO'(ATO~ .: M"r" SCAlE AOJUST'NO SCREW PROPORTIONrNG R"'N(;E ADJUSTING seRE'" PROPORTIONING R NGE StTT'NG INOICATOP WIPER AR"'ISI FROPORT'ONIN(; RANGE SC LHLATE '" FIG. 25-SETIING A TYPICAL PROPORTIONING PRESSURE CONTROLLER. 2]0 TABLE II-SUMMARY OF HONEYWELL PRESSURE CONTROLLERS SySTEM APPLICATIONS TYPE PRESSURE RANGES MODELS SWITCHING ACTION PRESSURE RANGES AVAILABLE NO. LOWEST HIGHEST . , St.om Boilers ,,' Hot Water Heatinl;l 9,'stems OperaUng Coo,,", '" limit Protection On-Ofl Cootrollerf limit High Law (Vapor Heating Systems) Vacuuml Prl$Swe l404 U,,,, PA404A High LSnit PA404B Fan Control L4079 (High Limits only) l408 l508 l411 1 spst mercury a 1 spdt mercury 1 spst snap-acting 1 Of 2 lfpat !tllap-acling 1 spst mercury 1 spdl mercury 1 spst -"'" , , 2 2 2 1 0\:1 15 psi 2 \:115 psi 0.5 \:I 9 pSI. 2 \:I 15 psi o to '8 ozlsq in (0 to , p!t~ 22 ill. Hgl:! vacuum b 35 psi pressure 20 • :lOO ,.1 20. :lOO ,. 31015 ,. 10 b 150 ,,, 0.' psi ~. Operating Control (Regulate Firing Rate or Prenura) Proportioning Controller<! Highll.o / Vacuum 191 P4SS d potentiomemr spst and POterrtiometerd 7 3 22 ill. Hgb vacuum to 35 psi pressure o b 15 psi 10 \:I 300 '" 10 \:I 300 ,'I Goo Burner Systems safety Shutoff safety Shutlrt OfAJr1Iow Switch Gu Prassure Switch Gas/Air Pressure Swi10h High Law Law 0447 0647 C4J7 0637 C645A. B C645C.O (Air only) 1 spst mercury 1 spdt mercUl)' 1or2spm mercury 1 spdt mercury 1 spst snap-acting 1 spdt snap-acting 2 , 2 2 '.30 psi 1/2 to 5-112 in. wee 3 b21 in. wee 0.6 to 5.3 In. wee 10 \:I 100 psi 1 \:I 10 " ,." in. wee 3 \:I 21 In. wee Oil Burner 9,'stems High limit low Limit and Operating Control lDwlimitlof Atanizing Medium Pressure Oil Preseure Co",,,, , On·Ort limit (Air Of Sloom) - - l404T. W l404V, Y l4048 1 _pst "'""'''''' 1 spst -"~ 2 , 10 \:I 50 ,. 2 \:I 15 psi 25 to 150 pO 20. :lOO " 8 Except the l404F hich has an spdt MICRO S'oVITCH snap·acting switl:h, and the L404l, whiCh h&lI2 spst men::ury SYfiIl:has. brnchaa at mercury; 1 in. Hg = 0-'912 psi "" 3.387 )(Pa. c Bellows-operated potentiometer: the L910 Iw.II 2 b allow control at 211"1Ot:lr8 in unison. dThe P455A is a combination proportioning and on-otr controller. It has an spst 5l1ap·acting switl:;h ftlr on-otr control, and a 135 otm potentiometer ftlr proportionirJ9 control e Inches at water column; 1 in. we 0.036 psi = 0.249 koPEI. 231 TEMPERATURE CONTROLLERS A temperature contrOller is 8 device which acts indi- rectly 10 regulate the temperature 01 air or liquids. A sensing elame"U responds 10 temperature changes and. 1hrOl./ttl a diaphragm or bellows and mechanical linkage, actuates a switch or potentiometer 10 keep the lemperature within predetermined limits. Temperature controllers we commonly used In flame safeguard systems to reQJlale the temperature 011iquids in toilers ()( lOtorage tanks, and for fuel chanceoV9I (switching from crle luello another when the temperature rises or falls). TEMPERATURE SENSING ELEMENTS: The temperalure conlrolJels used In flame sakQ;a{d applicatiOl'l$ hSWil silMr vapor-pressure or liquid-filled aenslng elemenls Various types of these elements are s.rnmarized in Table 11/ at the end of lhis discussion. , VAPOR·PRESSURE ELEMENTS A vapor-pressure temperature sensing element c0n- sists 01 a remote bulb connected \0 a ~ in the c0n- troller by a ~jl1alY tubing. These meta! ~ts contain a volatile liquid and the vapor from it When a volatile IQJId is c.Ql1fiQed, a portion of the liQ.Jid is ~.iven offas a vapor (jusl as steam is driven off by boiling wale~ until a limiling pressure is developed. This pressure Is adirect function of the t~rature of the liQ.Jld, particu- larly af thElliqJid SUrface (the dividing lina between the liquid and the VajXlrj. Changes of temperature thus result in corresponding changes ot pressure. This relationship is shown in Fig. 26. T[""l:R~TURE FIG. 26-TEMPERATURE-PRESSUAE RELATION- SHIP IN A TYPICAL VAPOR-PRESSURE TEMPERATURE SENSING ELEMENT, The vapor pressure increas9S wilh 'BI1l'9!alure, as shown by the curve in Fig. 26, until the fadeout tempera, ture Is reached. This is the temperature al which all the liQ- uid has Vl'tpOrized so lllere is no liQUid letl in tile s','Slem. A further rise in temperature prOduces a more gradual rise in pressure conforming to the gas laws. The contro'ler must be desi"n91::fscdhe 1adEloul temperature will be higher lhan the maximum operating temperature. For reliable operation, the liquid surface mLJ!;I always be within the bulb. As long as the liQ.Jid surface occurs in the bulb, the bellows and capillary may be filled with either liq.JJd or vapor wllhout aNecling the control 0' lerrperature al the bulb. Qlangas in bellows or capillary temperature will only cause condensalion or evajXlratlon Of a lillie iiquid in the bulb, with a ~ligi!;!'e change Of pressure in the system. Vapor-pressure lemperature sensing elemems have a very smalltime lag, and temperature variations along the capillary and bellows (within the r9Slrlclions for Jow and high t~ratul'8 elemenls, which will be described late~ cb not affect the plecise control 01 the remote bulb eleme"t There are 3 types or remote bulb vajXlr-pressure elements, ~ng on the bulb-to-bellows tel'Tl;:JElrature re- lalionship. They differ in lhe size of the bultJ and in thai relative amounl 01 liquid contained in the bulb and in the bellows. LOW TEMPERATURE ELEMENT (FIG. 27) A low l~alure e/el"l'l6l1t /also called a "/imiled fill" or "ladeout~ element! is designed to operate with the bu'b always colder than the bellows and capillary. The system contains a limited amounl of liquid so lhat fa,jeoul will 0:' cur al a temperature not much higher than the maximu'T1 operating tefTl)erature. Therefore the bellows and capillary are always filled with vapor. As the lemperature attha bulb rises, a little more vapor will be prOduced in the bUltJ, increasing the p'essure at the bellows. As lhe tefTl)eratu~e falls, a litlle more liQ.Jid will condense in the bulb and the pressure will decrease. ,,~ LWAYl COLDER Ir __ ",.AH '~LLOW< L'QU'D FIG. 27- DIAGRAM OF A lOW TEMPERATURE VAPOR-PRESSURE TEMPERATURE SENSING ELEMENT, Condensalion occurs first al the COldest paint in the system. Therefore, the bulb must always be colder t1-an lhe bellows and capiUal'\'. If lhe lemperalure at any ~inl alone the capillary or al the bellows falls below the lem- 232 [...]... [-1510 +35 C] 160 10 2'50 F [75 10 125 Cj T 675 B pot 1 3010 50 F [-110 +10 CJ - T 678 A Uquid filled 01 070 F (-1810 21 C) T 675 A (lingle bUlb) SW8I"al l.6OO6 • O,.()tl pot 2 spdt, sequence operation 4 Oto1ooF [-15 to +35 Cj 160 10 2'50 F [75 10 125 C] -50 10 +10 F [-45 to -12 C] 160 to 280 F (70 to 140 C] 01 070 F [-1810 +21 C] 160 10 280 F [70 to 140 C) 151090F [-1010 +32 80 10 2&1 F [ 27 to 121 C] T91SA C Vapor·... 248 -301O +70 F 30 10 270 F [-34 10 + 21 Cj [-1 10 + 130 CJ CJ -30to +70 F [-34 10 + 21 C] 160 to 260 F [75 10 125 C] 010100F +38C] 160 10 260 F [71 to 1 27 C] r~1e1O 1 70 10 140 F [2110 60 C) - 1 70 10 140 F [2110 60 CJ - 1 potentiometer T991B T991F 11010290 F 10 143 C) 1. . 7. 47 0,0 076 2 0 ,74 7 0108 75 .2 , , .245 10 12.45 0,01 27 0,181 1 27 24.91 0.0254 2.491 0.0533 0.361 254 S.231 0 .75 533 .31 2' 68.95 0. 070 3 6,895 1.000 70 3 , 7 , -R~ 7 0 .70 31 276 8. main line. ContrOllers with mercury swilches (C4 37. C4 47, C6 37, (;6 47) must be carefully leveled as described In Basic Pri". 71 - 975 58-1 FIRING RATE SSOV CONTROL o MSOV MAIPIl. 0 .70 31 276 8 10 689.5 68.95 70 3' , 105~6 1.055 415,2 1C.34 553.6 20 " 14062 1 379 1.406 1 37. 9 - 2t13 2.461 24608 24'.3 ,38< 96eB 35 35154 3m 3.515 344 .7 7, 031 SO

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