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1770-4.1, Industrial Automation Wiring and Grounding ...

Publication February 1998 Industrial Automation Wiring andGrounding GuidelinesThis publication gives you general guidelines for installing anAllen-Bradley Industrial Automation system that may includeprogrammable controllers, Industrial computers, operator-interfaceterminals, display devices, and communication networks. Whilethese guidelines apply to the majority of installations, certainelectrically harsh environments may require these guidelines as a tool for helping avoid potentialelectromagnetic interference (emi) and transient emi that could causeproblems such as adapter faults, rack faults, communication faults, etc. These guidelines are not intended to supersede local publication is organized into the following sections: Raceway layout considerations Mounting, bonding, and Grounding Power distribution Surge-suppression Ferrite beads Enclosure lighting Avoiding unintentional momentary turn-on of outputs Related publicationsApplication DataPurpose Industrial Automation Wiring and Grounding Guidelines2 Publication February 1998 The raceway layout of a system is reflective of where the differenttypes of I/O modules are placed in I/O chassi

Industrial Automation Wiring and Grounding Guidelines 5 Publication 1770-4.1 – February 1998 Mounting and Bonding the Chassis You can mount the chassis with either bolts or welded studs.

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Transcription of 1770-4.1, Industrial Automation Wiring and Grounding ...

1 Publication February 1998 Industrial Automation Wiring andGrounding GuidelinesThis publication gives you general guidelines for installing anAllen-Bradley Industrial Automation system that may includeprogrammable controllers, Industrial computers, operator-interfaceterminals, display devices, and communication networks. Whilethese guidelines apply to the majority of installations, certainelectrically harsh environments may require these guidelines as a tool for helping avoid potentialelectromagnetic interference (emi) and transient emi that could causeproblems such as adapter faults, rack faults, communication faults, etc. These guidelines are not intended to supersede local publication is organized into the following sections: Raceway layout considerations Mounting, bonding, and Grounding Power distribution Surge-suppression Ferrite beads Enclosure lighting Avoiding unintentional momentary turn-on of outputs Related publicationsApplication DataPurpose Industrial Automation Wiring and Grounding Guidelines2 Publication February 1998 The raceway layout of a system is reflective of where the differenttypes of I/O modules are placed in I/O chassis.

2 Therefore, youshould determine I/O-module placement prior to any layout androuting of wires. However, when planning your I/O-moduleplacement, segregate the modules based upon the conductorcategories published for each I/O module so that you can followthese guidelines . Also, all conductors (ac or dc) in the same racewaymust be insulated for the highest voltage applied to any one of theconductors in the raceway. These guidelines coincide with theguidelines for the installation of electrical equipment to minimizeelectrical noise inputs to controllers from external sources in IEEE standard ConductorsSegregate all wires and cables into the following three categories(Table A). Refer to the publication for each specific I/O module orblock for individual conductor-category classification of each AFollow these guidelines for Grouping Conductors withRespect to NoiseGroup conductor cables fitting this descriptionInto thiscategory:Examples:Control & ac Power high-power conductors that aremore tolerant of electrical noise than category 2conductors and may also cause more noise to be pickedup by adjacent conductors corresponds to IEEE levels 3 (low susceptibility) & 4 (power)Category 1 ac power lines for power supplies and I/O circuits.

3 High-power digital ac I/O lines to connect ac I/O modules rated forhigh power and high noise immunity high-power digital dc I/O lines to connect dc I/O modules rated forhigh power or with input circuits with long time-constant filters for highnoise rejection. They typically connect devices such as hard-contactswitches, relays, and & Communication low-power conductors thatare less tolerant of electrical noise than category-1conductors and should also cause less noise to bepicked up by adjacent conductors (they connect tosensors and actuators relatively close to the I/Omodules) corresponds to IEEE levels 1 (high susceptibility) & 2 (medium susceptibility)Category 2 analog I/O lines and dc power lines for analog circuits low-power digital ac/dc I/O lines to connect to I/O modules that arerated for low power such as low-power contact-output modules low-power digital dc I/O lines to connect to dc I/O modules that arerated for low power and have input circuits with short time-constantfilters to detect short pulses.

4 They typically connect to devices such asproximity switches, photo-electric sensors, TTL devices, and encoders communication cables (ControlNett, DeviceNett, Universal remoteI/O, extended-local I/O, DH+ , DH-485, RS-232-C, RS-422, RS-423cables) to connect between processors or to I/O adapter modules,programming terminals, computers, or data terminalsIntra-enclosure interconnect the system componentswithin an enclosure corresponds to IEEE levels 1 (high susceptibility) & 2 (medium susceptibility)Category 3 low-voltage dc power cables provide backplane power to thesystem components communication cables to connect between system componentswithin the same enclosureNOTE: Remote I/O and DH+ cables must be made of catalog number 1770-CD cable or a cable from the approved-vendor list (publication ).

5 DH-485 cables must be made of a cable from the approved-vendor list in publication LayoutConsiderations Industrial Automation Wiring and Grounding Guidelines3 Publication February 1998 Route ConductorsTo guard against coupling noise from one conductor to another,follow these general guidelines (Table B) when routing wires andcables (both inside and outside of an enclosure). Use the spacinggiven in these general guidelines with the following exceptions: where connection points (for conductors of different categories)on a device are closer together than the specified spacing application-specific configurations for which the spacing isdescribed in a publication for that specific applicationThese guidelines are for noise immunity only. Follow all localcodes for safety BFollow these guidelines for Routing Cables to GuardAgainst NoiseRoute this categoryof conductor cables:According to these guidelines :Category 1 These conductors can be routed in the same cable tray or raceway with machine power conductors of up to 600V ac(feeding up to 100 hp devices).

6 Category 2 If it must cross power feed lines, it should do so at right angles. Route at least 5 ft from high-voltage enclosures, or sources of rf/microwave radiation. If the conductor is in a metal wireway or conduit, each segment of that wireway or conduit must be bonded to eachadjacent segment so that it has electrical continuity along its entire length, and must be bonded to the enclosure at theentry point. Properly shield (where applicable) and route in a raceway separate from category-1 conductors. If in a contiguous metallic wireway or conduit, route at least (3 in) from category-1 conductors of less than20A; (6 in) from ac power lines of 20A or more, but only up to 100 kVA; (1 ft) from ac power lines of greaterthan 100 kVA. If not in a contiguous metallic wireway or conduit, route at least (6 in) from category-1 conductors of lessthan 20A; (1 ft) from ac power lines of 20A or more, but only up to 100 kVA; (2 ft) from ac power lines ofgreater than 100 3 Route conductors external to all raceways in the enclosure or in a raceway separate from any category-1 conductors withthe same spacing listed for category-2 conductors, where : These guidelines assume that you follow thesurge-suppression guidelines (page 15).

7 While these guidelinesapply to the majority of installations, certain electrically harshenvironments may require additional use of the guidelines in Table B are illustrated in Figure 1. Industrial Automation Wiring and Grounding Guidelines4 Publication February 1998 Figure 1 Mounting Assembly DetailsCategory-2 ConductorsEnclosure Wall12618-II/O BlockTransformerUse greater spacing withoutconduitTighter spacingallowed with conduitTighter spacing allowed where forced by spacingof connection pointsPlace modules to comply with spacingguidelines if possibleCategory-1 Conductors(ac Power Lines)Category-2 ConductorsConduit1771 I/O ChassisConduitAfter establishing all layouts, you can begin mounting, bonding, andgrounding each chassis. Bonding is the connecting together of metalparts of chassis, assemblies, frames, shields, and enclosures toreduce the effects of emi and ground noise.

8 Grounding is theconnection to the Grounding -electrode system to place equipment atearth ground , Bonding, andGrounding Industrial Automation Wiring and Grounding Guidelines5 Publication February 1998 Mounting and Bonding the ChassisYou can mount the chassis with either bolts or welded 2 shows details for: stud-mounting a ground bus or chassis to the back panel of theenclosure stud-mounting a back panel to the enclosure bolt-mounting a ground bus or chassis to the back panel of theenclosureIf the mounting brackets of a chassis do not lay flat before the nutsare tightened, use additional washers as shims so that the chassisdoes not bend when you tighten the : Do not bend the chassis. Bending the chassis mightdamage the backplane and result in poor 2 Mounting Assembly DetailsIf the mounting bracket is coatedwith a non-conductive material(anodized, painted, etc.)

9 , scrapethe material around the mounting of a ground bus or chassis to the back panelStud mounting of the back panel to the enclosure back wallStud mounting of a ground bus or chassis to the back panelIf the mounting bracket is coatedwith a non-conductive material(anodized, painted, etc.), scrapethe material around themounting PanelGround Bus orMounting BracketBack PanelNut1766417665 NutNutBack PanelWelded StudScrape paint17666 NutIf the mounting bracket is coated witha non-conductive material (anodized,painted, etc.), scrape the materialaround the mounting bolt mounting of chassis to the back panelMounting BracketStarWasherFlatWasherBack PanelScrape paint12342-IBoltTapped HoleUse a wire brush to removepaint from threads to allow aground paint on panel anduse a star paint on paneland use star Wall ofEnclosureMounting Bracketor Ground BusFlatWasherStarWasherStarWasherFlatWas herFlatWasherFlatWasherFlatWasher Industrial Automation Wiring and Grounding Guidelines6 Publication February 1998 Make good electrical connection between each chassis, back-panel,and enclosure through each mounting bolt or stud.

10 Wherever contactis made, remove paint or other non-conductive finish from aroundstuds or tapped and Grounding the ChassisWith solid-state controls, proper bonding and Grounding helpsreduce the effects of emi and ground noise. Also, since bonding andgrounding are important for safety in electrical installations, localcodes and ordinances dictate which bonding and Grounding methodsare example, for installations, the National Electrical Code(NEC) gives you the requirements for safe bonding and Grounding ,such as information about the size and types of conductors andmethods of safely Grounding electrical Conductor In addition to making goodconnections through each bolt or stud, use either 1-inch copper braidor 8 AWG minimum stranded copper wire to connect each chassis,enclosure and central ground bus mounted on the back-panel.


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