1、Electrical Guide forControl CentersApproved 28 June 1978ISARP60.81978RECOMMENDED PRACTICEISA The Instrumentation,Systems, andAutomation Society TMCopyright 1978by the Instrument Society of America. All rights reserved. Printed in the UnitedStates of America. No part of this publication may be reprod
2、uced, stored in a retrieval system, ortransmitted in any form or by any means (electronic, mechanical, photocopying, recording, orotherwise), without the prior written permission of the publisher.ISA67 Alexander DriveP.O. Box 12277Research Triangle Park, North Carolina 27709ISARP60.81978, Electrical
3、 Guide for Control CentersISBN 0-87664-444-2ISA-RP60.8-1978 3PrefaceThis Preface is included for information purposes and is not part of ISA-RP60.8-1978.This Standard has been prepared as a part of the service of ISA toward a goal of uniformity in the field of instrumentation. To be of real value, t
4、his document should not be static, but should be subject to periodic review. Toward this end, the Society welcomes all comments and criticisms, and asks that they be addressed to the Secretary, Standards and Practices Board, ISA, 67 Alexander Drive, P.O. Box 12277, Research Triangle Park, North Caro
5、lina 27709, Telephone (919) 549-8411, e-mail: standardsisa.org.The ISA Standards and Practices Department is aware of the growing need for attention to the metric system of units in general, and the International System of Units (SI) in particular, in the preparation of instrumentation standards. Th
6、e Department is further aware of the benefits to USA users of ISA Standards of incorporating suitable references to the SI (and the metric system) in their business and professional dealings with other countries. Towards this end this Department will endeavor to introduce SI and SI-acceptable metric
7、 units in all new and revised standards to the greatest extent possible. The Metric Practice Guide, which has been published by the American Society for Testing and Materials as ANSI designation Z210.1 (ASTM E380-76, IEEE Std. 268-1975), and future revisions, will be the reference guide for definiti
8、ons, symbols, abbreviations, and conversion factors. ISA S60 is an overall set of recommended practices being compiled by the ISA Control Centers Committee. RP60.8 is the first of this series to be issued.SECTION TITLERP60.1 Control Center (C.C.) FacilitiesRP60.2 C.C. Design Guide and TerminologyRP6
9、0.3 Human Engineering for Control CentersRP60.4 Documentation for Control CentersRP60.5 Control Center Graphic DisplaysRP60.6 Nameplates, Labels, Tags and Terminal IdentificationRP60.7 Control Center ConstructionsRP60.8 Electrical Guide for Control CentersRP60.9 Piping Guide for Control CentersRP60.
10、10 Control Center Inspection and TestingRP60.11 Crating, Shipping and Handling for C.C.The persons listed below served as active members of the ISA Control Centers Committee for the major share of its working period.NAME COMPANYH. R. Solk, Chairman Comsip Customline Corp.C. S. Lisser Oak Ridge Natio
11、nal LabR. W. Borut M. W. Kellogg Co.J. M. Fertitta, Secretary The Foxboro Co.A. R. Alworth Shell Oil Co.M. Arevalo Fischer it is also intended to comply with the provisions of the National Electrical Code. What follows are the practices normally used by architects, engineers, user organizations and
12、control center manufacturers. Special considerations which may apply to particular devices or circuits are not taken into account in this section.2 General2.1 ApplicationThis Section of ISA-RP60 applies to the inter-connection wiring between devices within a control center, or between control center
13、s. It does not apply to the internal wiring of an instrument or device, nor to the wiring between the control center and field-mounted instruments.2.2 ComplianceAll wiring recommendations in this Standard are intended to comply with the National Electrical Code. Compliance with other applicable loca
14、l or industry codes requires specific reference in the control center specification. General references to these codes should be avoided.2.3 Wiring2.3.1 Power wiringEach device requiring control center power shall be wired so that when wires are removed from any one device, power will not be disrupt
15、ed to any other device. It is recommended that no voltages greater than 125 Vdc or 120 Vac be used. If higher voltages are required, refer to color coding below. Provisions should be made for power wire segregation and identification to insure personnel safety.The recommended minimum size for power
16、wiring up to 15 A is #14 stranded copper conductor, 600 V, 60 C with thermo-plastic insulation. Different insulation material should be considered if the insulation has to be self-extinguishing or nontoxic. Refer to Table 310-13 “Conductor Application and Insulations“ of the National Electrical Code
17、, latest revision for particular provisions. Where power is 150 W or less and run to each instrument through a separate fuse or circuit breaker, the wire size can be reduced to #16 or #18. Refer to Article 310 “Conductors for General Wiring“ in the National Electrical Code, latest revision for curre
18、nts greater than 15A.2.3.1.1 Color coding of ac power wiring1) 120 Vac, 2 wire, single phase: Phase1 or L1, black NeutralN or L2, white2) 120/240 Vac or 120/208 Vac, 3 wire, single phase with neutral:Phase 11 or L1, black10 ISA-RP60.8-1978Phase 22 or L2, redNeutralN, white3) 240 Vac, 2 wire, single
19、phase: 1 or L1, black2 or L2, red4) Any 3-phase circuit regardless of voltage: Phase 11 or L1, black Phase 22 or L2, red Phase 33 or L3, blue Neutral in 4-wire systemN, white5) Interlock control circuits wired from an external power source:yellow6) Case ground wire, if insulatedgreen or green with o
20、ne or more yellow stripes.2.3.1.2 Color coding of dc power wiringDue to numerous voltage levels and existing standards, it is recommended that distinctive colors be used which do not conflict with other colors being used.2.3.1.3 Circuit protectionIn addition to circuit protection requirements of the
21、 National Electrical Code, special circuit considerations must be given. In particular, the solution to the problem of the failure of any device in a system which will cause loss of power for that system or other systems.2.3.2 GroundingEach device requiring power should be grounded to the control ce
22、nter by mounting to effect a conducting path or by a ground wire. Ground wire size should be no less than the supply conductor wire size. To determine wire size for grounding of control center to earth ground, refer to Table 250-95 “Size of Equipment Grounding Conductors for Grounding Raceway and Eq
23、uipment“ of the National Electrical Code, latest revision.2.3.3 Control wiringControl wiring is considered distinct from power or signal wiring. This type involves wiring of push buttons, pilot lights, selector switches, relay logic, timers and programming devices. Recommendations for wire sizes, fu
24、sing and color codes may be found in the Joint Industrial Council Electrical Standards for General Purpose Machine Tools EGP-1-67.2.3.4 Signal wiringNormal usage for signal wiring is #18 AWG stranded copper conductor. The recommended minimum wire size is #24 AWG, which should be used in a multicondu
25、ctor cable or be twisted pair. For Class 1, 2 or 3 wiring, refer to Article 725 “Class 1, 2 and 3 Remote-Control, Signalling, and Power Limited Circuits“ of the National Electrical Code, latest revision. Pulse type or low level signals may require twisted pair, shielded, or twisted pair and shieldin
26、g wiring.Wire type, signal grounding requirements, and shield requirements should be based on instrument manufacturers recommendations. Wire carrying measurement signals associated with thermocouples, resistance thermometers, pH instruments and other low level signals are ISA-RP60.8-1978 11best run
27、directly to the instrument without intermediate terminations. Isolated routing should be provided in the control center for running these wires.To avoid inductive pickup, power wiring or control wiring should have maximum possible separation from signal wiring. A practical distance is not less than
28、150 mm (6 in.). If the power wiring has to cross the signal wiring, the crossing should be as close to a right angle as possible.For intrinsically safe signal wiring, refer to ANSI/ISA RP12.6 “Installation of Intrinsically Safe Instrument Systems in Class I Hazardous Locations.“2.3.5 Wire identifica
29、tionAll wiring is normally identified at both ends by suitable wire markers or color codes in accordance with the users design documentation. See ISA-RP60.6 “Nameplates, Labels, Tags and Terminal Identification“ for marker materials and other details.2.4 Terminations2.4.1 Terminal blocksEach termina
30、l block and its terminals should be identified, as suggested in ISA-RP60.6 “Nameplates, Labels, Tags and Terminal Identification.“ Provisions should be made for spare terminations; the recommended minimum is ten percent. Normal practice is twenty percent.Recommendations for minimum terminal block sp
31、acing are as follows:(See Figure 1)Depth of terminal box if used, 100 mm (4 in.). For control center wiring, 65 mm (2.5 in.) between terminal block and sidewall, 90 mm (3.5 in.) between parallel terminal blocks. For field wiring, 100 mm (4 in.) between terminal block and sidewall, 130 mm (5 in.) bet
32、ween terminal blocks.If terminals are mounted on standoffs, wires can be routed behind the terminal blocks which make connections and wire markers more accessible.Typical wire connections used at screw type terminal blocks are spade and ring lugs. Another type of terminal block utilizes compression
33、fittings which accept striped wire. The ring lug and compression fitting terminal block are recommended for applications involving vibration.Preferably, not more than two conductors should be terminated at each terminal connection. If two wire sizes must be terminated in a single compression type fi
34、tting, refer to terminal block manufacturer for the maximum difference between wire sizes.2.4.2 Wiring between control centersInterconnection between control center sections, which will be separated for shipment, should be adequately prepared for convenient reassembly. Wire of adequate length for fi
35、nal connection should be disconnected, and pulled back in sections for shipment.Possible ways of handling the interconnecting wiring are:1) Wiring of each section brought to terminal blocks in that section. Jumper wires used between terminal blocks of both sections.2) Wiring in one section, say sect
36、ion B, brought to terminal blocks in the section. Wires from other sections, say A and C, are brought directly to section B terminal blocks. For shipping, wires from A and C are removed from the terminal blocks in B and coiled back to their respective sections.3) As in (1) and (2) but use multi-wire
37、 connectors instead of terminal blocks.12 ISA-RP60.8-19782.4.3 Cable connectorsCables with multi-pin connectors are an acceptable form of interwiring control centers. The connectors can be mounted on special channels made by the connector manufacturer or control center supplier.Suitable wire and cab
38、le identification should be provided as in 2.3.5. Also, the connector should be labeled. Use live female connector whenever circuit voltages could endanger personnel.2.5 Sizing conduit and electrical metallic tubing Consult Chapter 9“Tables and Examples“ of the National Electrical Code, latest revis
39、ion, to determine the maximum number of conductors in conduit or electrical metallic tubing if it is installed for the internal control center wiring.3 General purpose open wiring3.1 General applicationGeneral purpose open wiring wiring carried in raceways, or bundled and open.3.2 RacewayWires shoul
40、d be run in vented non-combustible or self-extinguishing non-metallic raceway. Metallic wireways are also acceptable.3.3 Open wiringWhere the use of raceways is not practical, wires should be run open, bundled and bound with suitable cable ties at regular intervals not exceeding 300 mm (12 in.). All
41、 wires within a bundle should be run parallel to one another. Bundles should have a uniform appearance, a circular cross section, and be securely fastened to the control center framework.3.4 SafetyConsideration should be given to live parts of terminal blocks, pilot lights and switches which may aff
42、ect personnel safety or circuit integrity. If the control center itself does not constitute an acceptable enclosure, these live parts should be covered or enclosed with a housing. Where wires are to be run to a housing from either an open bundle or from raceway, the housing should be fitted with a s
43、uitable insulating bushing or grommet.3.5 Working spaceWhere working space is required within a control center, Article 110-16 “Working Space About Electric Equipment (600 Volts or less, Nominal)“ of the National Electrical Code, latest revision should be observed.ISA-RP60.8-1978 134 General purpose
44、 enclosed wiring4.1 General applicationEnclosed general purpose wiring all wiring and terminals are enclosed.4.2 Enclosed wiringAll wiring should be run enclosed in electrical metallic tubing, flexible conduit with plastic covering or sheet metal wireway. Sharp edges, burrs, rough surfaces, or threa
45、ds with which wire insulation may come in contact should be removed from conduit fitting, wireway, or any other parts.Electrical metallic tubing, flexible conduit or raceway should be securely fastened to the control center. Pull boxes should be provided with pilot holes, plugs or knockouts for cond
46、uits.5 Hazardous location Class I, Division 2 open wiring5.1 General applicationUsed when control center is made of components for which general purpose enclosures are acceptable under Article 501-3 (b-1, 2, 3) of the National Electrical Code, latest revision. In order to comply with the National El
47、ectrical Code, the control center construction must be considered a single general purpose enclosure. An example is a totally enclosed cabinet, including bottom and hinged, non-removable doors with locks.Wiring and terminals need not be in explosion-proof enclosures. Arcing contacts are either herme
48、tically sealed or enclosed in explosion-proof housing with sealed fittings or in circuits which under normal conditions do not release sufficient energy to ignite a specific hazardous atmospheric mixture. Any device operating at auto ignition temperature of flammable material is enclosed in an explo
49、sion-proof housing and provided with seals.5.2 RacewayWires should be run in vented non-combustible or self-extinguishing non-metallic raceway. Metallic wireways are also accepted.5.3 Open wiringWhere the use of raceways is not practical, wires should be run open, bundled and bound with suitable cable ties or equal at regular intervals not to exceed 300 mm (12 in.). All wires within a bundle should be run parallel to one another. Bundles should have a uniform appearance, a circular cross section, and be securely fastened to the control center framewo
