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.. PRESSURE CONTROLLERS PR
Trang 1controllers afe com~nly usaa' on steam boilers and hoi
PflESSUFi"E CONTROLLERS USED ON STEAM BOILERS AND HOT WATER HEATING S Y S T E M S - - -
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 con
troller 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 con
troller 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 pres
sure 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
.& 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 pro vided 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 information, 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.)
Trang 2FIG 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 is at Uforunison q:)(lralibn, at S for sequence cpera·
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: en
tirely 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
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 be10re 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 conlinues 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
Trang 3PRESSURE 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 propor
tioning 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
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
Trang 4RATE
SSOV CONTROL
VENT 'RV
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
c Negative prflSSUre - Connect the low pressure side
~AS ~~tsSV~E: SWITCH
- - IAT RIGHT ~GLE:S TO
THE: M.'~ ~I'E: L'~E)
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
Trang 5onfice 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 accor
dance 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
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 information, reler to the instruction sheats for the controllers
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 mer
cury 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 cOnnecting 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
Trang 6RECIRCULATING CONTROL
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 pre
vent the controller from operating prcperly
When used with preheated oil, a siphon 10ClP must al
ways 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 di
rectly 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 di
rectly 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 se
ries 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
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 presenl, and to shut Gbwn the system if the atomi2inQ pressura 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 instruclions 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)
Trang 7, /Oll PJtU,5UR£ ~ONTFlQLlE~
., (Ar "'G"r ANGLES TO THE "' ".E UNE)
.'.fTEE (lU"" TO U\I[L
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-_-CR "'-=GC"H::T"AH :cC"O:cC"WC"R"O"NC"G= =M"O"U-N='::N"G-O"F"A" -CT
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
AN INTEGRAL OIL PUMP
FIG 22- HOOKUP OF AN Oil PRESSURE
CONTROLLER USED ON A SINGLE BURNER OR MULTIBURNER 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
Trang 8(pounds per SQJareinch), or In oz./in (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
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 gradu-TABLE
,p,
kg/em 20'
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.)
WIPER AR"'ISI
FROPORT'ONIN(; RANGE
SC LHLATE
'"
FIG 25-SETIING A TYPICAL PROPORTIONING
PRESSURE CONTROLLER
Trang 9TABLE II-SUMMARY OF HONEYWELL PRESSURE CONTROLLERS
SySTEM APPLICATIONS TYPE PRESSURE RANGES MODELS SWITCHING ACTION
PRESSURE RANGES AVAILABLE
NO LOWEST HIGHEST
On-Ofl Cootrollerf limit
High
Law (Vapor Heating Systems)
Vacuuml Prl$Swe
l404
U,,,,
PA404A High LSnit PA404B Fan Control L4079 (High Limits only) l408 l508
l411
1 spst mercury a
1 spdt mercury
1 spst snap-acting
1 Of 2 lfpat
!tllap-acling
1 spst mercury
1 spdl mercury
1 spst
-"'"
, ,
2 \:115 psi 0.5 \:I 9 pSI
2 \:I 15 psi
o to '8 ozlsq in (0 to ,
p!t~
22 ill Hgl:!
vacuum b
35 psi pressure
35 psi pressure
o b 15 psi
Gas/Air Pressure
0637
C645A B C645C.O (Air only)
1 spst mercury
1 spdt mercUl)' 1or2spm mercury
1 spdt mercury
1 spst snap-acting
1 spdt snap-acting
In wee
10 \:I 100 psi
1 \:I 10
" ,."in wee
Co",,,, ,
On·Ort
limit
(Air Of Sloom)
-l404T W l404V, Y
otm potentiometer ftlr proportionirJ9 control
e Inches at water column; 1 in we 0.036 psi = 0.249 koPEI
231
Trang 10A temperature contrOller is 8 device which acts indi
rectly 10 regulate the temperature 01 air or liquids A sens
ing elame"U responds 10 temperature changes and
1hrOl./ttl a diaphragm or bellows and mechanical linkage,
actuates a switch or potentiometer 10 keep the lempera
ture within predetermined limits
Temperature controllers we commonly used In flame safeguard systems to reQJlale the temperature 011iquids
in toilers ()( lOtorage tanks, and for fuel chanceoV9I (switching from crle luello another when the temperature rises or falls)
TEMPERATURE SENSING E L E M E N T S : - - -
applicatiOl'l$ 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 liq
uid 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 relalionship 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~aluree/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
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
Trang 11perature at the bulb, the liQUid surface will shift to the cold
spot outside the bulb and Il'1e bulb will lose control
As not much liQUid is required, (he bulb is small-1/2
loC:h112.7 milllmetres, or mm] diameter by 4 inches [102
mmllong is a common size The elevation 01 the bulb with
rasped 10 lhe bellows is not critical; the prassure head (j&
veloped by the weight 01 Il'1e vapor in the capillary and bel
lOWS Is negligible
Typl~le ranges tor low temperature elements are
minus 130 F 10 minus 70 F [minus 90 C (0 minus 57 q at
one eJ(lreme~ar1dplus 65 F 10 plus 95 F [plus 18.5 Ctoplus
35-C] al the'other.'Themaximumsafe temperature,l.e., the
pressure is reached, is generally much higher than the op
erallng range of lhe controller This is beCause fadeout oc
curs Just above Ihe maximum operallng temperature, so
~~~'LJ!QS (see the gas curve in Fig 25)
HIGH TEMPERATURE ELEMENT (FIG 28)
Ahigh temperature element is desigIed to q:.erate with
lhe bulb always warmer than the bellows and capillary
This system contains enough liquid so that, at the highest
operating temperature, the bellows and capillary will al
ways be tWed with liquid and the bulb wlll contain some liq
uid As the temperature at the bulb rises, more vapor will
be produced In the bulb, il]creasing the pressure on the
liqUid surface and also at the bellows As the temperature
As the bulb must cOnlaln only enough liquid to ensure
that there will be a small vapor space present at the lowest
operating temperature and a little liqJid present at the
hil1'esl q:.erating temperature, the bulb Is small-1f2 inch
(12.7 mm] diameter by 4 Inches j1021TVTl]long is a com
mon size Preferably, the bulb shOlJId be at about the
same elevaliooasthe bellows It there is a large difference
in elevation, the pressure head developed by the weight 01
;/?::::t-l,.Imlts><C·oot,ollers
:;{;:'::K,:<:::'~ij#'~llh't'~'r1(,)Cks
the liquid In the capillary and bellows would be ad:Iad \0 or subtracted tram the vapor pressure and might cause Imprc:per calibration at the controller,
Typical extreme scale ranges tor high temperature ala
menls are plus 75 F 10 200 F [plus 24 C to 93 CJ and plus
510 F to 700 F [plus 266 C to 371 C] The maximum safe bulb temperature, Which at high temperatures also in· cludes the safe temperature of the metal or the melling point of the solder, Is generally not much higher than the top of the c:perating range ot the contrOller
CROSS-AMBIENT ELEMENT (FIG 29)
A cross-ambient element is so-called because It Is (j&
signed to operate with the bulb temperalure either higler
or lower than the aJrt)ient temperature (at the controller and capillary) The system contains enou~ liqJid so that
at a temperature somewhal higher than the hig,est oper ating temperature, the liq.Jid will 1111 the bellows and c:apll· lary wilh a litlle ll!ttJl'£S,l: tor the bulb
When the temperature at the bulb rises aoove the arrbient temperature, more IlqJid will condense In the colder bellows and capillary More vapor will be present in the bulb, increasing the pressure on lhe liqJid surface and also at the bellows When the lamperature at the bulb falls below the ambient tempera!ure, more liquid will condense
in the colder bUlb and the vapor pressure will decrease Bolh ot these conditions are shown in Fig 29
at the bulb falls, more liquid Will condense in the bulb and
the vapor pressure will decrease
The bulb must always be warmer than the bellows and
capillary It the temperature at any point along the capillary
or at the bellows rises higher than the temperature ot the
bulb, the liQUid surface will form OIJtslde the bulb and the
bulb will lose control
FIG 28-DIAGRAM OF A HIGH TEMPERATURE
(uS> VAPO" ''* BULB)
FIG 29-DIAGRAM OF A CROSS-AMBIENT,
VAPOR-PRESSURE TEMPERATURE SENSING ELEMENT
The terrperalure relationship between the bulb and the bellows is not crillc:al as ills for the low and hi~ t~rature elements Even if part of the system is wanner than the bulb and filled with vapor • while the remainder is colder
71-97558-1
Trang 12than the bulb andtilled with liquid, there will slill be a liquid
surface in the bulb and the bulb will continue to conHol
As there Is enoug-t liquid in lhesystem to fill the bellows
and ~Ill;:l.ry, and lhebulb must contain all of this liquid at
the towest ~raling lemperalure, the bulO must be
large-11/l6 inch 117.5 mm] diameter by 14-1/2 inches
{368 mm]long Is a common size lflhe bulb temperalure
will sometimes be warmer than the ani:lient temperature
causing the bellows ani::! capillary to be filled with liquid,
the bulb should be at aboulthe same elevation as the bel·
lows Olherwise,' the grassure !:!~d devel~ by !he
weight of the liquid in lhe capillary and bellows would be
added to or subtracted from lhe vap:::l( pressure This
would make the device unslable dJe to shifting of the con
Irol p:>int, and would cause irT';:lr~r calibration of lhe con
- troller If it is known thatlhe bulb will always be colder than
the ambient temperature, the elevation is not critical
Typical scale ranges for cross-ambient elements are
minus 25 F to 0 F [minus 32 C to minus 18 C] at one ex
treme, and plus 40 F to 210 F !plus 4.5 C to 99 C] at fhe
other The maximum safe bulb temperature is generally
nol much higher than the tcp o1lhe ~rating ral1QEl
L1aUID·FILLED ELEMENTS
The basic IiquicHUed temperature sensinQ elemenl
(Fig 30) consists 01 a remole bulb, a ~werhead consist·
ing of a diaphragm and case, and a connectinQ capillary
The entire element is completely 1iIIed wilh a temperature
expansive liqUid Temperature changes al the bulb are
transferred lhrolJQh the bulb wall (usually cq:per) to the
liqUid The volume of the liquid eilher expands or con·
tracts, causirlQ resultinQ molion 01 the diaphragm Aslhe
oPeration is hydraulic the force at the diaphragm is '!fP~e
ciable This force is transferred by mechanical linkage to a
switch or ~lentiomeler in the controller
FIG 30- DIAGRAM OF A TYPICAL LIQUID
FillED TEMPERATURE SENSING
ELEMENT
The capillary lor a remote bulb element is made of cop
per, monel, or stainless steel, and cantle any length up 10
about 30 feet [9 metres]: the most common lenglhs are 5,
20, and 30 feet [1.5, 6, and 9 metres] Some controllers do
not have remote bulbs In Ihese direct-mounted control·
lers, lhe capillary is very short and internal; only the bulO itself proJecfs OUI trcm the case (Fig 31)
A standard bulb is about 3{8 inch [9.5 mm] or l/Z inch [12.7 mm] in diameler, and from 2106 inches [50 to 150 mm] long It can be used in either air or liquids Fastresponse and averaginQ elements (Fig 32) are also available 10r remote mounhnQ in air ducts
5TANOARO REMOTE BULB
A fasl-response element is in the form of a lightly coiled capillary About 6 feet I 1.8 melres] of capillary is coiled into an elemenl about 1-1/2 inches [38 mm] in diameter by about 5 inches [127 mm]long The surface area 10 volume ratio is about 7 times greater than that or a slandard bulb,
so its response time is about 7 times faster
AA averaginQ element (Fig 33) is althe end of about 10 feet {3 metres] of standard capillary, and Is similar to the capillary except thai it has a larger bore in order to hold the same amount 01 liquid as a standard bulb It is usually
Trang 13about 1/8 inch {3,2 mmj in diameter by about 12to 20 feet
[3.7 to 6 meres] long An averaging elament is usually
wound back and tanh across Ille ducl It is distributed
-evenly over the cross section ollhe duct to oblain the aver
agE! temperature in the duct
~'''KA''E
CA"Ll.A~Y' TY/'£
~VE~AGt"G €UM£N' uOU'o
FIG 33- DIAGRAM OF A lIQUID·FlllED
AVERAGING ElEMENT
The commercial type temperature controllers used in
f,'ame safeguard applications have elements tllat are CaT!
manly filledwilh hydrocarbon liquids, SUCh as toluElfle, sili
cone, or alkazine The ~HiC~!lt of ekpansion of these
liquids resu,lls in a motion-temperalure relationship that is
not too linear, This nonlinear eHect is minimized by selecl
ing a narrow temperature range whiCh awroaches linearity, or by calibrating the set point of the controller 10
match the nonlinear properties of the liquid
Typical operating ranges for coni rollers with li(J.IidIiIled elements are 0 F to 100 F [minus 18 C to plus 38 C] at
one extreme and 160 F to 260 F [71 C to 127 C] al the other The maximum sate bulb temperature ,'s Ihe point at which the diaphragm is extended as fat as it can I):l without taking a permanent sel This lemperature is not much higher than the top of the operating range, and should never be exceeded
Since the liqUid is homogeneoos and fills the capillary and powerhead as weiI' as the bulb, temperature changes
at the capillary or al lhe powerhaad caUSe errors These
errors are minimized by making the volume in the capillary and powerhead as small as possible, by usinga liquid with
a low coefficient of expansion, and by providing arrtlienttemperature compensation This compensation is usually
in the form of a bime(allic device in the powerhead liquid-filled elements provide power and rapid response, and are not aHected by dHerences in elevation between Ihe bulb and Ihe controiler They can be used at any ~, and can control at temperatures above, ba
low, or awroximately the same as Ihe temperature at the case of the controller They we generally less expensive lhan vapor-pressure elements, althOugh they may t'()t be
as precise
LOCATION AND M O U N T I N G - - -
Both the controller case and Ihe sensing element must
be located where the arrt>ient temperature will not ekceed
lhe maximum aiTCIient operating temperature speCified
for each !The specified maximum temperature for the
case is different than that for the sensing element)
The case can be mounted in any convenient posilion
on a flat surface, such as a wall or panel If the mounting
surface is hot or cold, the case should be insulated lrom it
tJy insulation maleria! (such as a wooden bOard), or offset
1.0 allow a spa e for air circulation Mounting hales or lugs
are provided on lhe back at lhe case
The sansing element should be located where it is ell
posed Co the average tf3tl'lP9lalure or the cootrollad me
dium The temperature and elevation rules shOllld be
obse~ed for vapor-plessure elements (see Table 111)
A few temperalure controllers are direcH'nounted, but
most models have long capillaries fO( remote mounting 01
lhe sensing element r remota bulb· models) Depending
on the application of the contrOller, the sensing element
may be mounted in an immersion well, compression fit
ling, capillary holder, bulb holder, or bulb shield AA aver
aging element is usually mOllnled inside an air duct using
perforated strap iron or Clips Usual applications, pur
poses, and limitations of various mounting means are
summarized in Table IV Mounting means are shown in
Figs 34 through 45
Soma controllers have a very short capillary lhal cbes , t'()1 ektend beyond the case; only the sensing elemenl (bulb) sticks out
These models- are for mounting directly to boilers or storage tanks Horizontal models are available for a tap
ping on lhe side of the boiler or lank, and verocaJ mcdels
are available for a lapping on top Some models include an immersion well and Ofhers incll ll:E a compression Ming
REMOTE BULB TEMPERATURE CONTROLLERS
Mosl temperature controllers have long capillaries (~
10 30 feet [9 metresjlongl so the sensing elament can be mounted at a distance from the controller, The !EWlQlh of the capillary may limit the choice of location Sharp bends
or Wnks in the capillary could serious/)' affect th8 operation
or cafibrarton of the controller: ttMy should be cafBfully avoidfU'J All excess capillary shOuld be carefully coiled
and left directly beneath or beside the canlralle(
MOUNTING IN A BOILER OR STORAGE TANK
1lle manufacturer of a boiter or storage tank usually provides a tapping for Insertion 01 the sensing element Follow {he manufacturer's instructions If available If the boiler or tank is fiiled, drain II until the level 01 the fiQ lid Is
Trang 14J{ ·PI'l'lIt~tC:.i:mtroll~lS ::'i:
Rig !:?}'~ctJn\~rlC)!?Il.:~i/" ';,JB;"}
TABLE ill-TEMPERATURE SENSING ELEMENTS
','
ELEMENT TYPE BULBSlZE TYPICAL ELEVATION BULB
TYPICAL SCALE RANGES
MAXIMUM SAFE BULB TEMPERATURE
Vapor·
Pressure
Low Temperature (bUlb co/de!"
ttlan behows) High Temperature (bult wwmer
than bellows)
1/2114 in
112.7 II l02lmll 1t211 4 in
+65to95F {+ 18.5 to 35 CJ
+510 to 700 F [+26Sb37' CJ
MUCh hlgl'oer than operating range, Not much higher than top of operating renge
(bulb can be CrOs.s·Ambient tither
COIdar Of warmer ttlar belb )
11/18 II 14·1/2 In, {17.5K368m-nl
Same as ballo'oYs
iI bL-llb wi" be
WlV/r>er 1t111.n ambienl a: other
wise rot critical
-25bOF [-32 b -18 q [+<4.5 to gg Cj +40to210F
NOI much higher han lop 01 operating range
,
Filled
Liqlid-Standard Bulb Fast-RespoNe
'Ioment
(air ducts) Avel'ag'ng Element
Nol much h'lgher than bp of operating ranga
TABLE IV -METHODS OF MOUNTING TEMPERATURE SENSING ELEMENTS MOUNT1NG
MEANS ELEMENT SENSING FfG{S)
COH·
TPOLLEO MEDIUM
- pro\llCt eltlment from mechanical or chemical damagl;l
- Provid$ llasy ra
moval of element
- More than doubles response time
- Well must be 01 pr6pDr siZ':' to frt snugly
Remote Bulb ,
5 B~'
ComprGSSion Fitting
DirE!ct m::Junled Bulb ,.R.~ Bulb
(wittl II flange)
3
• Liquid
''''' ,,- <,,,,,, ,
Boiler!; or storage tanits
- Form a positive seal
- Form a posi1ivtl seal
at tapping in boiler
or tank
- F~~QbeUlbS with:lut a flan e
- Bulb must be direclly mnersible
Capillary Holder
- Bulb must not be
100 large b support Fast·response
EI9I"I1ent "
"'"
Holder
large Remote Bulb
42
'" ~r ducts
- SBme as capillary IXIlder
- For larger bulbs (such liS c~-amb~
ent, vapor-pressure elements)
- Requires large IXIle in duct wall
Bulb SIieId R8'rote Bulb 45 ", -Dual fuel change0tJnm0r nnmting
"""'
- Au1c:matic reset uSing dual bulb t9mperlllJJre con-
"""",,
- Protect bulb While exposing n to Itle.alr
- Requlrell hole in wall 01 building,
Trang 15below the tawing In the boiler or tank Remove the plug
from the tawing, and screw the spud of the immersion
-WQUor compression lilting Inlo the lapping A redUced tlt
tlng may be necessary to adapt lhe spud 10 the tawing
Make sure lhe well or filUng Is screwed in tightly lopre~ent
leakage Il"IStalied Ihe sensing bulb and controller Then
refill the boiler or lq.nk Do not tIY to tightan the well orfitting
in the tapping by turning the controller
USE OF AN IMMERSION WEll (FIGS 34 AND 35)
- An immersion well (~rable well) is used to protect
Ihe sensing elEll'T'l8nt (in Ihis case, the bulb) from mechani
calor chemical damage, and to permit easy remo~al of the
element from the liquid without haVing to drain the boiler or
tank In addition, it pro~ides a lighter filling than other
rf,'ounlingmethods An immersion walt is very desirable for
mounling the element in an agitated liqUid
The immersion well must be mounted where it is always
exp::lsed to the circulation of the liqUid under control, but it
must never be localed close to a hot or cold inlel or steam
coil
The use of an immersion well more than doubles tMe re
sponse time compared to that for a bare bulb Therefore,
the weI( mustfl! the bulb snugly II may be desirable to !Ill
the space between the bulb and Ihe well with a haat-<::on'
ductive comp::lund The use of a heat-conducti~e grease
will reduce the resp::lnse lime 10 aboul 1-1/2 times Ihat for
a bare bulb
USE OF A BULB COMPRESSION FITTING
(FIGS 36 AND 37)
A bulb compression filling is LJS.8d to form a positi~e
seal althe p::linl where the sensing bulb is inserted into the
controlled liquid It Is Llsed in awlications where lhe bulb
can be immersed directly in the liquid without danger 01
mechanical or chemiCal damage The COOlJression fitling
is Qanerall'( Selected tO,be,the same malerial as the bulb A
remote bulb must have a nange for the filling 10 hold
USE OF A CAPILLARY COMPRESSION FITTING (FIG 38)
If the remote bulb doEl6 not have a flange, a capiilary
~ressJon tilling can be used to form a fXlSlllve seal In awllcallons where the bulb can be Immersed directly In the liquid without danger of mechanical or chemical
damage
RlAO JAW510 "T
O~." COCLAR ON SPUO
Of "'Hl SCREWORIVER
I><SULAno Of 80lcER
WAlLOfaOllEROR STORAGE u
& RlOUClR F,rrl"G MAY 8t NECESSARy TO AO T?VO T<l u ,
FIG 35- MOUNTING A REMOTE BULB IN AN
IMMERSION WELL
CONTROLl.ER CASE
&
IMMERSION l'I'ELL,&
SPUO SCREWS INlO lAPPING IN ~
Trang 16FIG 38- MOUNTING A REMOTE BULB USING A FIG 41- MOUNTING A FAST-RESPONSE
MOUNTING IN AN AIR DUCT
The remote bulb, fasl·response elemenl, or averaging element should be located where air of average lampera
lure.~ circulate freely around it Avoid mounling the ele
ment clOse 10 hot pipes, coolinQ coilS, the combustion charrt:ler, and other places where the air temperature is
6 R'Du~' R ""'Nt > et N~~fS'ARY _0 ADAfT SPuD TO TAPPINt
FIG 31- MOUNTING A REMOTE BULB
(WITH A FLANGE) USING A BULB COMPRESSION FITTING
USE OF A CAPILLARV HOLDER (FIGS 39-41)
A cap1l1ary holder and plale asserrt::Jly 15 used to S4> pen and prolectthe capillary and elBment In lhe wct, ancI
to prevent excessive air leakage The holder should be long enCllV1lo hold the element In freely clrculatinQ air, away from the duCi wall lfl! is too long, it Carl easily be broken on to the proper length
USE OF A BULB HOLDER (FIG 42) For larQEl remole bulbs (SUCh as cross-ambient, VapJr
pressure sensing elements) the capillary holder will rol provide enough ~rt A bulb holder (Pan No 311266)
is available for mounting lhese bulbs This holder has spring clips that G8l'1 be adjusted to hold various sizes of remole bulbs as well as thermometer bulbs Ijt desired)
BE SuRE EXT£NS'ON TUBE IS uNOER BULB HOLOER, AS S"'OWl'<
FIG 39-INSERTING THE CAPILLARY IN A
CAPILLARY HOLOER
~ :"R'''''H "L.'
FIG 40- MOUNTING A REMOTE BULB AND
CAPILLARV HOLDER tN AN AIR DUCT
IItO Duel WAL.L ,'NeH I'" mm, IN IiI I
eA"LL.ARY I'
HOL.O,R
Trang 17- - -
'ERFOR"'TIO~TR"" IRON
oueT
CL
FIG 43- MOUNTING AN AVERAGING
ELEMENT IN AN AIR DUCT USING PERFORATED STRAP IRON
lary tubing The element must be S!.4JPOrted so that it is distributed evenly ?oCfOSS the entire height and width ot the q;ct:
FIG 42- MOUNTING A LARGE REMOTE BULB
AND BULB HOLDER (PART NO
311266) IN AN AIR DUCT;
DIMENSIONS IN INCHES (MILLIMETRES IN BRACKETS)
OUTDOOR MOUNTING USING A BULB
SHIELD (FIG 45)
A bulb shield is usually used 10 mount the remole l;ll lIb outd:;x:lrs for ciJal fuel chal'lQElOver, or for automatic resel using a dual bulb tElrllJerature controller
The b.Jlb should be mounted under the shield in a horizontal posilioo 011 the outside 01 the building where it will
be exp:lsed to r~resentative air temperature, but not 10 direct sunllghl (However, for structures with large glass areas that absorb more radiant haat from the sun, it may
be preferable to mount the bulb where it will be exposed to the same heating effect.) It should be mounted high enough so Ihal it cannof be covered with snow, Ice, leaves,
or olher debris and so it cannot be tampered wllh VenlS Irom the building should be avoided
/:liEhG'NG., NT
c y ',NG,ol'"
CLIP WITH PLIERS SPLIT WOOO PLUG
ll~ If'tCH II' "''''I
HOLE IN WALL
lO
FIG 45- MOUNTING A REMOTE BULB
OUTOOORS USING A BULB SHIelD
71-97558-1
Trang 18Typlcarwlrlng hookups are shown In Figs 3 through 7
in Basic Principles 01 Controllers Special hookups are
shown In Figs 46 and 47 In actual practice ii's wise 10
also consull the burner boiler, or storage lank manufac
turer's Installation and 'l!L'iring diagrams Additional hook
~ are included in Ihe instruction sheets for the
controller'5
AUTOMATIC OUAL FUEL CHANGEOVER
For economy, it is otten desirable 10 switch a dual fuel
burner from one fuel to another (usually from gas to oiQ
when the weather gets cold An SjXIlemperature control·
"'er can be used 10 accompliSh this functlon automalically
Fig.·46 shows an L600aC connected as an automatic
dJal fuel changeover switch lne controller Is mountecl
outside or In an outside air ducl Where il can sample Ihe
outside lEll1l'9rature As long as the outside l~ratule
slays in the normal range, Ihe '9/TC9ralure controller will
be made A 10 W lhe R482F relay will not be pulled in so
the conlacls will be as shown PowB[ will be ~liecl1rom
OEnCTOR I-® r" RA8llOF.I1.0llK £
PRIM Ry CONTItOL &
& PPOV'OE OI~O"'HCT MI NS "'NO lJIfIRIO O ",!lneTIO"''''S
RIOvPRIO
ill T"EII 'STOR OEL n PULL·IN OF IIfl"'Y,
ill""EN IIILAY II ENEIIGIZlO, JK' OPE S BEfORE Jl,
ill ou uo OUTSIDE OR t OUTSIDE "',R DUCT SWITCI1ES FROM G S
TO Oil 1 n PIR"'TURI F"'"l,
& fOil OET"'"EO ","cUIT 'NFORM"'T1~,
ill T""i C'IICU" C"'NNOT BF uno T A PIIOQR"'MMI G CONTROl ",II>
L1 through the limits, temperature controller (R to 'Nl, r90 lay contact 3K1, and the burner controller 10 lerminal6 of the RAB90, which energizes il 11 the burner is running and
a flame is detectecl, internal switching in tha RA890 applies power from terminal 5 in the RA890, through the jumper belwEl9l'llarminals 6 and 7 on tha R482F raJay, and through relay contact 3K5 to the main gas valve
11 the outside temperature falls below a pr9Clelerminecl valua (set on the temperalure controller), the temperature controller will break R to W and make R to a Power will be appliecl from L1 through tha limits and temperatura controller (R to B) to ralay 3K in the R48ZF relay Tha relay will pull in and all the 3K conlactswill switch Contact 3K5 will
close, connecllng (he main oil valve to terminal 5 on the
RA890 Power 10 Ihe RA890 will be interrupted momentarily until 3K2 closes 111he burner is running, it will be shut
c:bwn and raslaf1ed If lhe burner is nol running, it will be staf1ecllater on a call tor heal In either case, lhe pilaillame
T91l\EORf PROPORTIONING
~S6& HMPEIIATURE CONTROLLER
TO n E • _J &=:.~~u_OETEcTOR
FIG 47-TYPICAL HOOKUP OF A PROPORTIONING
TEMPERATURE CONTRDLLER USED TO REGULATE THE FIRING RATE, WITH AN END SWITCH USEe AS A BURNER CONTROLLER