NCU/NEU Wire Barrier Kit

Transcription

1 Metasys Network Technical Manual 636 App. Notes: Network Units Section Technical Bulletin Issue Date 0191 NCU/NEU Wire Barrier Kit Application Note: Wire Barrier Kit Page 3 Introduction 3 When the Wire Barrier is Unnecessary 3 NEC Codes 5 UL Standards Johnson Controls, Inc. 1 Order No

2 2 App. Notes: Network Units NCU/NEU Wire Barrier Kit

3 Application Note: Wire Barrier Kit Introduction When the Wire Barrier is Unnecessary The Wire Barrier Kit provides a mechanism to separate line- and low-voltage wires (Class 1, 2, and 3) in an NCU/NEU when the requirement exists. What does Class 1, 2, and 3 mean? Class 1 is defined by NEC Article , such that: Remote-Control and signaling circuits shall not exceed 600 volts. (725-11, b) Power-limited circuits shall be supplied from a source having a rated output of not more than 30 volts and 1000 volt-amperes. (725-11, a) For NCU/NEU applications, this would typically include starter holding coil circuits (120 VAC), low-limit and fire/smoke detector interlocks. Classes 2 and 3 are defined in NEC Table (a) and (b), which shows that these AC and DC circuits are typically lower in power than Class 1 circuits. These applications would include sensor wiring, transducer circuits, and non-powered binary inputs. Terminal to the NCU/NEU may not require the Wire Barrier. Exception No. 2 to 1990 NEC Article (a)(2) is written for enclosure wiring where electric light, power or Class 1 circuit conductors are introduced solely to connect to the equipment to Class 2 or Class 3 circuits to which the other conductors in the enclosure are connected. The NCU/NEU base frame wiring layout meets these conditions; combined with the modification in the 1990 NEC code listed on the next page, it is unnecessary to apply the Wire Barrier to the left and right hand base frame screw terminals except at the request of a local inspector. A Wire Barrier may also be unnecessary when all wires are maximally insulated, as shown in the third example. App. Notes: Network Units NCU/NEU Wire Barrier Kit 3

4 a) Maintain a 0.25 inch separation (modification to the 1990 NEC code, Article (a)(2)) The electric light, power, and Class 1 circuit conductors shall be routed within the enclosure to maintain a minimum of 0.25 inch (6.35 mm) separation from the conductors of Class 2 and Class 3 circuits. 1/4 in. Figure 1: Maintain a 0.25 Inch Separation b) Secure the wires For segregating insulated conductors, L916 Paragraph 31.2 allows segregation by clamping, routing, or an equivalent means that provides permanent separation from insulated or uninsulated live parts of a different circuit. Ty-Raps Figure 2: Secure the Wires 4 App. Notes: Network Units NCU/NEU Wire Barrier Kit

5 c) Insulate to maximum voltage Common usage, subject to local authority, allows line- and low-voltage wires in the same enclosure or raceway when insulation for all wires is rated at 300 volts and the maximum circuit voltage is Volts Insulation Figure 3: Insulate to Maximum Voltage NEC Codes When wiring Class 2 and 3 circuits next to Class 1 circuits, without use of heavier insulation or quarter-inch spacing, NEC Article (a)(2), Exception No. 1, allows these circuits to be routed adjacently where the conductors of the different circuits are separated by a barrier. The Wire Barrier Kit provides this separation. App. Notes: Network Units NCU/NEU Wire Barrier Kit 5

6 UL Standards In addition, the Wire Barrier Kit satisfies the circuit segregation requirements found in UL916 (Energy Management Equipment). Point by point: a) The Wire Barrier Kit is simple to install, add boots to, and remove. [If] in some applications a barrier is required while in some other applications no barrier is required, a removable barrier or one having openings for the passage of conductors may be employed. (UL916 Paragraph 31.4) Figure 4: Wire Barrier Kit 6 App. Notes: Network Units NCU/NEU Wire Barrier Kit

7 b) The Wire Barrier encloses line-voltage wires from duct to terminal. Field installed conductors may be segregated from each other...so that there is no likelihood that intermingling of the conductors or parts of different circuits can occur. (UL916 Paragraph 31.5) Line Voltage Wires Low Voltage Wires Figure 5: Wire Barrier Encloses Line-Voltage c) The Wire Barrier slides easily over the wires and allows for an adequate range of slack. [Equipment] is to be wired as intended for service with a reasonable amount of slack left in each conductor within the enclosure and not more than average care is to be exercised in stowing the slack into the wiring compartment. (UL916 Paragraph 31.7) Boot T-Block Wires Line Voltage Duct Low Voltage Duct Figure 6: Wire Barrier Over Wires with Adequate Range Slack App. Notes: Network Units NCU/NEU Wire Barrier Kit 7

8 Notes Controls Group FAN E. Michigan Street Metasys Network Technical Manual P.O. Box 423 Revision Date 0191 Milwaukee, WI Printed in U.S.A. 8 App. Notes: Network Units NCU/NEU Wire Barrier Kit