Control Panel Layout And Wiring Best Practices. ______________________________________________________ __________________________ ________________________________ ____
Large Control Panel Wiring Example. What are some good practices? What could be improved? Click to enlarge The qualit o! the "iring "iring methods used in an industrial industrial control panel can var quite "idel. "idel. This article summari#es "hat this author believes are some best practice "hen it comes to control panel laout and "iring. The goal is to produce a panel that is logicall arranged and eas to maintain !or the li!e o! control panel. $ leave it to the reader to use these suggested %best practices& outlined belo" to evaluate and improve upon the control panel designs that the encounter or are part o! producing.
BASIC WIRING PRACTICES. 1. * Wire: Use all 600V 90 Deg C rated wire. Use stranded wire. Use MTW type wire. Note any exceptions so tese can !e added to te drawings or design notes.
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* Wiring across a hinged door or panel. U loop# as long as possi!le# $acing down ancored on eac side o$ te inge wit screws or !olts %no adesi&e'. (lace slee&e or spiral wrap o&er te wires r)nning o&er te inge !etween te ancor points.
. * Spacing between wired devices and wireway or other obstructions: "+ ,ini,)," 1" / + pre$erred $or 1"0VC and less. + $or 20 &olt %eno)g to insert a closed $ist !etween te de&ice and te wireway or o!str)ction. . * Minimize the use of cable/wire ties if wire duct is used. Tey get c)t o$$ wen tro)!lesooting and are rarely replaced. good wire ,anage,ent syste, so)ld not re3)ire any wire ties. Ma4e it a goal to )se no wire ties except te,porarily wile wiring. 5. Leaving Slack: enerally# lea&e only 7idden8 slac4. ea&e ser&ice loops as te wires lea&e or enter te de&ice or ter,inal. :)n wires in te wireway so tey enter and r)n to te ,iddle or $ar side o$ te wireway or d)ct. Ta4e all corners in a wiring d)ct as wide as possi!le. :)n wires in ori;ontal and &ertical lines. Tis also adds $)rter 7slac48 and i,pro&es te appearance. &oid looping wires in te wireway )nless te wireway is designed $or tis. 6. * eneral Wire !outing< :)n wires in ori;ontal and &ertical lines# no diagonal r)ns. 7Train8 te wire !y !ending it to ,a4e neat &ertical and ori;ontal lines. Delicate wire will re3)ire 7training8 !y !ending and $or,ing te !end grad)ally. Wire in wire d)ct so)ld !e r)n so tey do not cross eac oter excessi&ely. Wire entering or lea&ing a wire d)ct so)ld !e !ro)gt to te $ront o$ te d)ct !e$ore enteringexiting were possi!le. ea&e ser&ice loops and r)n wires in te wireway so tey enter and r)n to te ,iddle or $ar side o$ te wireway or d)ct and ta4e all corners as wide as possi!le. Do not r)n wire o&er oter de&ices# incl)ding te wireway. =le&ate te d)ct and go )nder te d)ct wit wires i$ needed. :e&iew needed exceptions. >. * Wiring "ower #nd Motor Wiring: (lace (ig tail loops !etween de&ices tat are spaced s)c tat it ,a4es it easier to re,o&e wiring i$ te pig tail is added. Consider )sing ?ig @lex power wires s)c as 7:ailroad Wire8 or ig strand co)nt wire. Train te wire !y !ending it in te direction yo) want it to go or lay in te d)ct# rater tan A)st trying to lay it in a wire d)ct and ope it 7stays down8 in te d)ct. Bee also 7eneral Wire :o)ting8. 2. * Wiring Signal and Shielded $ables: Use 12 W sielded# twisted pair %or Triad' type ca!les rated at 600V as te de$a)lt signal wire type. Unless speci$ically re3)ired strip o$$ a genero)s a,o)nt o$ te Aac4et so tat eac cond)ctor can !e easily accessed $or re,o&al# testing# and replace,ent. lso re,o&e te Aac4et as it exits a wire d)ct#
4eeping te twists were te ca!le oterwise creates )nwanted wire congestion. =xa,ples< going to nalog ,od)les# or ro)ting to ele&ated side ter,inals. Ter,inate all sields. Ter,inate all sields close to te signal wires. Consider )sing "# # or e&en ig ter,inal !loc4s wit A),per slots $or signal wiring depending on te wiring needed. Tis allows !)sing te power s)pply &oltages $or a cleaner installation. ption< (lace eat srin4 t)!ing 1" o&er te c)t end o$ te ca!le Aac4et and 1" o&er te exposed wires. 9. * Wiring $ontrol Wires: Use 1 W 600V MTW %stranded' wire $or 1"0VC wire. Use 16 or 12 W 600V MTW %stranded' wire $or "VDC wire $or )p to 10 and 5 a,ps respecti&ely. Use 7eneral Wire :o)ting8 reco,,endations $o)nd elsewere in tis doc),ent. 10. * %erminations: lea&e so,e !are wire sowing to allow &is)al inspection and to a&oid screwing down on te ins)lation. Wires so)ld exit te ter,inal straigt. Do not !end te wire at te point o$ ter,ination. nstead loop or !end wires on te ins)lation tat do not go straigt to te wireway. 11. * %erminals: Bcrew Ter,inals< Use t)!)lar# press)re plate type screw ter,inals tat ,ini,i;e wire distortions or da,age wen ter,inating. (osition Ter,inals to allow &is)al inspection o$ te recessed connections. =le&ate Control Ter,inals to allow wiring )nder te ter,inals i$ needed. Eeep it sti$$ )sing a ea&yFd)ty DN rail or ?o$$,an Ter,inal Btraps or e3)i&alent. ngle and ele&ate ter,inals ,o)nted on te side panel $or wiring ease and to allow &is)al inspection o$ wiring in te ter,inals. 1". * rounding "rinciple: Wire all gro)nds to te inco,ing gro)nd l)g eiter directly or wit a wire to te oter gro)nd !)s !ars. dd a ,ain gro)nd l)g andor a gro)nd !)s !ar $or eac gro)nded power s)pply. n),!er o$ !)s!ars can !e )tili;ed !)t so)ld all !e wired togeter and ten to te inco,ing gro)nd l)g to at least 1 point i$ not two %"'. Tis is in addition to te gro)nd esta!lised tro)g te panel. Use " gro)nd wires $ro, opposite ends o$ te !)s or cain o$ gro)nd !ars i$ te gro)nd is isolated. Wire te gro)nd on all doors and s)!panels and te ca!inet itsel$ to a gro)nd !ar ter,inated at te ,ain gro)nd l)g. Wire all e3)ip,ent and cassis gro)nds to te gro)nd !ar%s' wic is ter,inated at te ,ain gro)nd l)g. @or additional details on gro)nding and !onding see te ro)nding nd Gonding post dedicated to A)st tis s)!Aect. PANEL LAYOUT CONSIDERATIONS:
Example o! good spacing bet"een the terminals and the "ire"a.
1. * &ptimize the Space. (lace (C rac4s in te 7!ay8 created !y te wiring d)ct to allow roo, $or te ig density o$ wires going to te, $ro, te d)ct. DonHt lea&e space were tere is no wiring# typically te top o$ te rac4. (lace si,ilar si;ed de&ices in teir own 7!ay8 were possi!le. Consider te ro)ting o$ all o$ te wires and ow te &ario)s &oltages will !e 4ept separated. ". * Spacing between wired devices and wireway or other obstructions: "+ ,ini,)," 1" / + pre$erred $or 1"0VC and less. + $or 20 &olt %eno)g to insert a closed $ist !etween te de&ice and te wireway# anoter de&ice# or o!str)ction.
Control Panel Design Approaches 'o" are electrical (and pneumatic) control panels !or industr designed and built? $ see that t"o methods are still largel in use. $n this article * approaches are compared to each other noting the strengths and "eaknesses $ see in each o! them. $ leave !or another discussion ho" engineers are adding value to either o! these approaches+ as "ell as "hat $ have been calling a %data driven engineering& approach+ to not ,ust panel design+ but the entire capital equipment intensive design pro,ect. -or no" lets ,ust compare these t"o common approaches to panel designs.
Panel Design Foundations
Traditionall /esigned Control Panel Example A bill of material (BOM) is o$ten te !asis $or eac control panel design. Tis is )s)ally prepared !y an engineer or experienced designer wo can ta4e te a&aila!le design in$or,ation %(IDHs# layo)t drawings# si,ilar e3)ip,ent# e3)ip,ent list%s'#and or oter !asis $or te new design' and con&ert tis into control panel designs needed to o)se all te re3)ired electrical andor pne),atic control co,ponents.
Electrical (and Pneumatic) schematic (elementary) drawings are also needed so the panel shop can "ire up the devices correctl. To sho" "here terminals should be added or other special "iring+ these can be sho"n on the schematic dra"ing as "ell turning a logic dra"ing into a hbrid dra"ing containing "iring in!ormation as "ell.
Panel Design Approaches %raditional approach: Bcaled ayo)t and Bce,atic Drawings )sing a CD tool are prepared $or te panel sop. Te GM is incl)ded %)s)ally and entered' on te CD layo)t drawing# !alloon all te ite,s to ,atc te pysical depiction o$ te layo)t wit te GM.
Pros: Well recogni#ed method. 0er clear to the panel !abricator "hat to do. Cons: labor intensive !rom a design vie"1 requiring manual checking to veri! part in!ormation is entered correctl+ spatial relationships not eas to visuali#e o!ten requiring the ac tual panel to be modi!ied during assembl+ dra"ings di!!icult to maintain. 234 o!ten exists on the dra"ing onl. /ata !rom the dra"ing is o!ten impossible to extract !or analsis or to make part changes across the pro,ect. 5ot kept up to date a!ter initial build.
0alue Engineered Panel (Click to see enlarged vie") 'alue approach: (repare a GM on a spreadseet# ,a4e a s4etc only to &eri$y tat all te parts will $it in te !ox i$ needed. (anel sop ,)st esti,ate te a,o)nt o$ wiring needed $ro, te GM. $ inter,ediate or special wiring is re3)ired descri!e tis in te :e3)est $or J)ote %:@J' or ()rcase rder %('. Bce,atic drawings are s)pplied wen wiring !egins.
Pros: 3ne spreadsheet can be generated !or all the parts !or all the panels and !ield equipment on the entire pro,ect. $ssuing this spreadsheet to a panel shop directl requires onl a da o! prep tpicall since no dra"ings are needed to bid. This allo"s more time to collect in!ormation and6or allo"s panels to be built quicker. Laout dra"ings or sketches could !ollo" later as a guide to assembl once all parts are received.
Changes to the 234 are easier to manage on a spreadsheet then on dra"ings tpicall. Cons: /ra"ings are usuall !iled in a manner that makes them retrievable b anone "ithin the compan. 7preadsheets are tpicall pro,ect speci!ic and are o!ten lost "hen the original engineering team has moved on.
n !ot te a!o&e approaces te 7design8 is ten sent to te (anel Bop%s' to J)ote andor order parts and asse,!le.
Panel Layout Review and Checkout Layout !eview: ptionally te engineerdesigner can sow )p wen all te parts are recei&ed to ,odi$y te layo)t !ased on act)al parts recei&ed and oter canges tat ,igt re3)ire last ,in)te ,odi$ications. lso it is ,)c easier to &is)ali;e wat te $inised control panel will loo4 li4e wen te engineer# designer# and asse,!lers can layo)t te act)al parts to opti,i;e te panel $or spare space# wiring access# to re&iew wire ro)ting# and te li4e. Tere is ,)c ,ore tat can !e said $or te &al)e tis step can add to te $inised prod)ct. n te two approaces disc)ssed ere tis step is o$ten %i$ not )s)ally' o,itted.
$n the traditional approach the designer6engineer do not sho" up at the panel shop till it is time to %checkout& the panel unless called b the panel shop. 7ometimes "hen the schedule demands it+ the panels "ill be shipped and checked a!ter installation in the !ield. This increases the risk o! adding cost to the checkout "hen modi!ications are needed since the resources o! the panel shop are not ver hand and electricians earn signi!icantl more and are usuall not as e!!icient at doing control panel modi!ications6corrections. $t can also add to the checkout time The value approach also places value on using a panel shop that can make reasonable decisions about ho" to laout the panel !or themselves. The value approach also quali!ies panel shops to do all o! the required %checkout& making sure that all the components are !unctional or at least appear to be po"ering up correctl and veri!ing that the "iring is correct per the elementar dra"ings and !unctioning as expected. 7ometimes in both these approaches additional checkout is required and per!ormed. This includes loading programs+ con!iguring drives+ setting up communications as applicable+ testing $63 !rom the programming environment to test operations end to end. $n addition some !unctional testing might occur !or higher risk items such as running a ne" servo drive sstem "hen a motor is available to testing some ne" $63 device. This high risk testing "ill allo" an
problems to be identi!ied as earl as possible allo"ing extra time to address special problems. 8lso "hen success!ul the potential risks can no" be reduced.
Conclusion Many co,panies a&e a!andoned te traditional approac to panel design in $a&or o$ so,e $or, o$ te value approach $or control panel $a!rications. Tis as led to te red)ction o$ CD design s)pport $or tese co,panies.
Those that continue to use the traditional approach to panel design tend to have larger C8/ design groups in house. 2oth approaches require ans"ering the question "hat is the cost6bene!it o! each approach. $ncreasingl companies are reali#ing that the value o! detailed assembl dra"ings+ especiall once alread built+ is continuing to decrease. 2oth approaches do not value keeping the assembl dra"ings up to date. -or ne" pro,ects+ a set o! good digital photos "ith or "ithout a parts list is o!ten all that is needed to check+ modi!+ or add to an existing panel. Earlier in m career about hal! o! the C8/ design e!!ort "as spent "ith the control panel designs. 5o"+ $d estimate that perhaps this is do"n to bet"een 9 : *;< o! the C8/ design e!!ort depending on "hether assembl dra"ings are required at all. What is le!t !or another discussion is ho" to laout panels !or o ptimal space utili#ation+ !or good access+ !or maintainabilit+ !or !ield "iring+ !or cooling or thermal management+ !or arc !lash protection and "orking on a panel %hot&+ !or good po"er and signal "iring separation+ !or good grounding and shielding !or analog signals+ and the like. What is also le!t out is ho" to determine the number and tpe o! panels and the location o! panels in the !irst place.
Grounding And Bonding Best Practice !Wired "tar Grounding# There is a lot that can be said about grounding and bonding and providing an “effective fault current path”. This article describes "hat this author believes is a best practice "hen it comes to establishing a “safety ground”. The safety ground is one that ensures enough ground fault current to quickly trip the circuit breaker connected to the faulted wire.
Tpical 7ervice =rounding62onding >2ack to the 7ource>. Click to enlarge. Technicall "hat this article is !ocusing on is more correctl called %bonding %. $n control panel designs this is normall established b a green or g reen "ith ello" stripped "ire and is part o! "hat is o!ten called the grounding sstem. 'o"ever there is nothing we do that actually ties anything to the earth . $nstead the control panel bonding6grounding point is tied to a green "ire that at some point is tied to the return path o! some po"er source. -or this article the "ord grounding and bonding are used interchangeabl to con!orm "ith tpical usage. The !ocus is also on the sa!et aspects o! the grounding sstem and does not deal "ith the E4$ and shielding aspects associated "ith bonding. 'o"ever in all but the most special cases this method "ill provide good E4$ and equipment shielding unless high !requenc generating devices (such as variable !requenc drives) are located inside the control panel. $n this case+ this method is still likel a best practice+ but additional measures ma need to be taken. _____________________________________________________________________________ _____ 3ver the ears $ have almost un"ittingl developed m o"n !orm o! grounding and bonding best practices as it relates to grounding6bonding o! control panels and components in establishing a clear ground path “back to the source” . ecentl $ started becoming a"are that it does not appear to be a common practice and am tring to get input on "hat people in the !ield think o! this idea. $ll call the idea the %Wired Star Grounding Method %. The practice puts a wire on everything that needs to be grounded and does not ust rely on the cabinet and!or subpanel connections to establish the ground path. $ implement this using ground bus bars (tpicall the kind used in panelboards to connect the neutrals together) bolted to the subpanel o! each panel in a sstem. The main ground "ire that is run "ith the po"er source "ires "ill !eed the !irst ground bar. -rom there+ po"er !ed to other external devices and panels "ill get their o"n ground "ire o! suitable si#e to each panel or device tied to the same ground bar. $n each panel each device requiring a ground "ire+ the subpanel+ the enclosure bod+ the door "ill have separate ground6bonding "ires connected to the panel ground bus bar. The ground bus bars are tied together !rom panel to panel in a star (rather than series) connection as much as possible. $n this "a there "ill be a "ired ground6bond path %back to the source& that does not count on the metal parts o! the panel to provide the !ault current path.
7tar =rounding Example Click To Enlarge The reason $ pre!er this is that it is much easier to inspect !or proper connection. 4etal to metal connections sometimes are not adequate ground !ault paths to trip circuit breakers in the event o! a ground !ault. 7ince "e tpicall cannot test !or this+ it becomes di!!icult to veri! that the ground6bond is solid. We tpicall check the ground "ith an ohm meter+ but that dra"s almost no current so it is not possible to tell ho" %solid& the ground6bond connection is. 8lso o ver time metal to metal connections can !oul. -inall the can ,ust be installed improperl and this is not al"as %inspectable&. 8 "ired connection is easier to inspect "ith a scre"driver or a good tug on the "ire to tell i! the connection is %solid&. 8 couple o! stories "ill help illuminate the problem. @4 thermionicall "elds the building steel together !or all o! its manu!acturing !acilities ,ust to establish the building ground grid because the have had problems "ith the bolted connections in tpical steel building !rames providing a reliable ground6bond at all points in the building. 8nother example is !rom m most recent pro,ect "here due to a communication problem the vendor asked us to make sure the grounds are solidl connected. /uring the !irst check everthing looked good using an ohmeter and a long spool o! "ire to check resistance !rom one panel to each o! the other panels on the site. 2ut "hen the problem persisted the ground6bonding at one panel "as checked again and this time a 9 and then A; ohm impedance "as measure to the subpanel "hen it "as less then * ohms be!ore. $t "as !ound that the ground "ire going back to the source "as connected to a conduit hub ground scre" that "as loose and it could not be tightened. 4 belie! is that "iring the grounds back to the source ground6bond via a %"ired star grounding method& avoids problems+ is easier to inspect and veri!+ and provides another path to ground+ thereb increasing reliabilit.
How to Power Up a Control Panel for te f!r"t t!#e$ without tripping breakers or blowing things up if things are wired wrong
7mall Control Panel Po"ering Bp an $ndustrial Control Panel !or the !irst time either a!ter !abrication or a!ter all the !ield "iring is connected and read !or po"er up veri!ication+ has some risks. The main risk is that there are short circuits in the "iring that "ill cause the breakers to trip or the !uses to blo". 'o"ever there is also a risk that voltages can be mixed up that can cause damage to the control components. This article examines this authors recommendation !or po"ering up control panels or other equipment !or the !irst time a!ter ma,or "iring changes have been made. There are basically three "#$ different ways to power up a panel for the first ti%e& at least that $ have seen1 1. Metod 1. K)st t)rn on te ,ain !rea4er and !egin te cec4o)t. ". Metod ". T)rn on one circ)it at a ti,e and cec4 o)t once circ)it at a ti,e. . Metod . T)rn o$$ te ,ain circ)it !rea4er or disconnecting de&ice# t)rn on all downstrea, circ)it !rea4ers# $)ses# and disconnecting ,eans# and o, cec4 eac pase or te load side o$ te ,ain !rea4er pase to pase and pase to gro)nd.
4ethod A is quickest method but onl i! there are no shorts. 4ethod * is reall no better since no checks are per!ormed till a!ter each circuit is turned on. 8lso this method takes the most time to !ind all o! the shorts. The above * methods are "idel practiced but rel on everthing being "ired reasonabl correctl in the !irst place. 'o"ever "hen a control panel is !irst turned on+ it is !or the purpose o! veri!ing that the "iring and the !unctionalit o! the controls is correct. There!ore some checks should be per!ormed be!ore po"ering up the panel !or the !irst time.
The %ethod ' prefer is Method # . $n this method all the downstrea% circuits e(cept the %ain disconnect or circuit breaker are closed . (0eri! that there are no voltages present on the load side be!ore proceeding and !ollo" lock out procedures as required b our !acilit). $n closing all the do"nstream !uses+ breakers+ and s"itches+ any shorts in %ost if not all of the wiring will reveal itself when using an oh% %eter on the disconnected load side of the %ain disconnecting %eans and checking phase to phase and phase (or circuit) to ground impedance. $! a short is !ound then open A6* o! the s"itches+ !uses+ and breakers in repeated steps until the location o! the short(s) is(are) isolated.
When checking !or impedance to ground+ $m looking !or at least A 4ega 3hm. When looking !or phase to phase shorts $ am o!ten onl looking !or more than * ohms tpicall i! there are coils in the circuit such as !ans+ as these look like near shorts but are per!ectl normal. $! the phase to phase impedance is less than * ohms+ $ll start to disconnect the !ans or other coils !rom the circuit till the number comes up. 3nce its above *@ ohms then $m usuall satis!ied that the panel is read to po"er up. $! there are no coils in the circuit then there should be a higher impedance. 'o"ever the impedance ma not be much more+ depending on the expected loading. -or example i! the panel dra"s *; amps at A*;08C+ thats ,ust D ohms o! impedance. $! the panel is a *;; 8mp F; 08C panel+ then it could be much lo"er. $n this case it might be "orth"hile to check sections o! the load so the Phase to Phase impedance is above * ohms or is other"ise reasonable !or the given connected load. 4ost o! the time motors are turned o!! so this does not end up being in circuit !or the ground6!ault test. There is one %ore thing ho"ever that "ould be good to check prior to po"ering up the panel. $! there are multiple voltages in the panel+ check the i%pedance between each of the different power sources . The $mpedance should be greater than A 4ega 3hm bet"een an * po"er sources such as A*;08C and *0/C or 90/C. 8lso check each po"er suppl to ground+ again making sure the impedance is high.
3nce the phase to phase and ground checks are per!ormed+ then $ close the door (!or arch !lash protection) and turn on the main breaker to turn on everthing all at once. $ have never seen a reason to turn things on one at time. $! the ohm checks are good then all should be good. 8lso+ this method avoids putting on the 8rc -lash 7uit to po"er up the panel as this is perhaps the most likel time that such an event "ill occur. This entire check takes anywhere fro% )* %inutes to %aybe an hour to per!orm depending on the complexit o! the panel i! there are no shorts !ound.
/isclaimer1 While $ consider this a best practice+ $ cannot take responsibilit !or things going "rong. There is inherent risk in per!orming electrical "ork that cannot be completel eliminated.
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+anel ,ayout and -lectrical esign Posted on 5ovember AF+ *;A* b -rank G Comments H
$ had planned on "riting a bit about m meeting "ith the publisher last "eek+ but $ received a comment on a post !rom about a ear and a hal! ago on Controls 7peci!ications. /oug asked me to cover a little more on the panel design process.
$ am using the above picture because it contains a variet o! di!!erent kinds o! components in the same enclosure. 4an larger enclosures allo" the designer to separate similar components (i.e. voltage levels) into di!!erent enclosure bas+ but "hen ou onl have one enclosure to put all o! our stu!! in ou have to be care!ul about "here ou locate components. The !irst step in laing out an enclosure is to complete the electrical design schematics. This accomplishes several thingsI it ensures that all ma,or devices are accounted !or (controller+ disconnect and po"er distribution devices+ po"er supplies+ ethernet s"itches and !uses6circuit breakers+ 0-/s6motor starters6servo drives and controllers+ etc.). $t also allo"s the designer to determine ho" man terminal blocks and other po"er and signal distribution devices "ill be needed. Prior to dra"ing the schematics preliminar steps such as sstem concepting and creating an $63 list must be done. 4uch o! this process "as discussed in a previous post. -rom the electrical schematics a 2ill o! 4aterial (234) is generated listing all o! the components in the sstem. 8dvanced C8/ packages such as 8utoC8/ Electrical "ill create the 234 !or ou. $t requires the designer to account !or ever component in the dra"ings+ giving it a label and part number. $t also looks at all o! the ,unction points (usuall a dot ,oining at least t"o "ires) and assigns terminal blocks to them. -or more in!ormation on C8/ and "ire numbering check out this post. $! a designer is using a more limited design6dra"ing package the "ill have to create the 234 themselves. Large components are easI ,ust put a number b the component and start a list o! labeled components in a spreadsheet. -uses and !useblocks !all into this categor. The a re also eas to account !or i! a good singleline dra"ing o! po"er distribution is created. $63 terminal blocks are also eas to account !or (i! used)I there should be one block !or ever point. $ "ire all spare $63 to terminal blocks. $t is also common to use distributed $63 via communications or %"iring arms&+ "hich bring a cable to the $63 card "ith a breakout board on the other end "ith $63 and po"er terminations on the board. These are more expensive than terminal blocks but save signi!icantl on "iring time and space. Pe rsonall $ JneverJ "ire $63 devices directl to the card. $ have seen panels "ired this "a to reduce the space taken b terminal blocks and the cost+ but it violates K;< o! the speci!ications $ have ever seen. Po"er distribution terminal blocks can be a little trickier to count. $! multilevel terminal blocks are used a /C and /C ro" "ith ,umpers is available to terminate sensor leads into+ but these can be tough to "ire unless !ingers are small. 8 common method is to mount q uickdisconnect $63 blocks on the machine !rameI this onl requires one /C and one /C termination inside the enclosure !or a group o! sensors+ again it costs more but reduces labor. To account !or all o! the other distribution terminal blocks ,ust count the dots on the right hand (tpicall /C6Com) rail o! the electrical dra"ings. The same can be done !or 5eutral "ires in 8C circuits. The /C and /C blocks are tpicall grouped together and ,umpers are used to link the blocks together. /C po"er !eeds are usuall !used "hile /C buses are o!ten grounded in the B7. $ts a good idea to plan !or a !e" extra points than are counted. 8!ter accounting !or all o! the components its time to locate them on an enclosure backplane. $ generall start b placing the components in 8utoC8/ in a rectangle o! some backplane dimensionI i.e. 9MN x @@N !or a D;N x @DN enclosure. 8t this point its a rough guess until all the
components have been placed. /isconnects are usuall some"here to"ard the right o! the enclosure so $ start "ith locating that since its location is usuall not optional. $ts a good idea to segregate devices o! di!!erent voltages "ithin the enclosure. 4ixing *0/C and F;08C "ithin "iring duct can cause noise problems. 7ince the disconnect carries the highest voltage a distribution block is usuall located close to it along "ith branch circuit !using. The panel laout at the top o! this post onl has *vdc and *;08C devices in it+ note that the *;08C devices are all located on the le!t side. Bsuall in a F;08C cabinet a trans!ormer is used to bring A*;08C to components such as the /C po"er supplies+ controller and other devices. These !uses or circuit breakers are generall separated !rom the F;08C po"er and *0/C !using. -or some reason controllers o!ten end up close to the upper le!t corner o! the enclosure. There is no hard and !ast rule !or this + but i! the po"er distribution is on the right and terminal blocks at the bottom this is o!ten "here it ends up. $ generall tr and locate all !ield termination points ("iring arms+ terminal blocks etc.) to"ard the edges o! the en closure. This minimi#es the amount o! "iring inside o! the cabinet "hich as can be seen belo" can be a considerable amount.
$! the "iring arms in the center area o! this panel had been located verticall on the right side or at the bottom the "ire "ould have been much more manageable. The red devices to"ard the bottom o! this enclosure are guard and Estop circuits. 8s sa!et sstems have evolved over the past *; ears or so the have gro"n to take up more space. The guard s"itches+ light curtains and Estops are all brought in as !ield "iring and generall also require their o"n terminal blocks. These %dots& need to be counted and placed on the backplane also. 8!ter all o! the components+ terminal blocks and other devices have been placed in the rectangle items such as "iring duct ("ire"a) and /$5rail can be placed. Wire"a !ill percentage is another speci!ication o!ten included in companies "iring specs along "ith spare $63 and spare backplane space. 8!ter all o! the /$5rail mounted and other components are located the
"ire"a can be placed bet"een the ro"s o! components. E!!icient space utili#ation+ heating6ventilation+ separation o! voltages and access to terminations !or !ield "iring all !actor into panel arrangement. $ also generall place "ire"a all the "a around the edges o! the backplane. 7ome speci!ications require internal separators or even separate runs o! "ire"a !or di!!erent voltages. 4echanical designers usuall "ant the enclosure to be as small as possible and ideall completel hidden !rom sightI tucked up under the machine some"here. Electrical designers "ant enough room !or a lounge chair and mabe a small T0. The result is usuall some"here in bet"een+ mostl due to speci!ication and space requirements. 7ince enclosures onl come in speci!ic si#es it is usuall prett eas to round up to the next si#e. 8!ter laing out a !e" di!!erent si#es o! panel ou "ill have the start o! our o"n %librar& o! laouts. 3!ten similar sstems can use one o! these saved designs as a rough template+ saving time and giving the designer a running start. 'ope this helpsO
