Compliance with the Standard for Automatic Electrical Controls for Household and Similar Use, Part 1: General Requirements, UL 60730-1, and/or the applicable Part 2 standard from the UL 60730 series fulfills these requirements. Electrical instruments are covered by the Standard for Electrical Analog Instruments- Panel Board Types, UL 1437. UL 508A - Sizing of Power. Required size of the field wiring terminal. 28.3.1 The required size of the field wiring terminal shall not be less than 14 AWG (2.1 mm2) and shall be determined by: a) Calculating the required ampacity per 28.3.2 - 28.3.6;.
We are a UL508A and UL698A panel shop located in Sioux Falls, SD with a solid reputation for quality work! We can build panels to your specs or we can design. UL 508A, but is by no means an exhaustive guide, and does not cover all uses and applications associated with UL 508A regulations. This guide is not intended to be used in lieu of UL 508A or other regulatory standards. Always consult all pertinent actual regulatory standards and local standard representatives to ensure full compliance. 3-2018 Standard for Industrial Control Panels. This revision of ANSI/UL 508A dated April 16, 2020 includes the following changes in requirements: - ECBT2 Connectors in Control Circuits - SCCR for EMI Filters in Panels - Sizing of Branch Circuit Protection for Heat Loads - Emergency Stop Panels - Sizing the feeder: same approach for all Panels - SB4.3.3 - Addition of Class CFI.
Required size of the field wiring terminal
28.3.1 The required size of the field wiring terminal shall not be less than 14 AWG (2.1 mm2) and shall be determined by:
a) Calculating the required ampacity per 28.3.2 - 28.3.6; and
b) Determining the minimum field wiring conductor size from Table 28.1 having a corresponding ampacity that is equal to or greater than the required ampacity from (a).
28.3.2 For motors, fixed electrical space heating equipment and lighting loads, the anticipated field wiring shall have an ampacity of 125 percent of the full-Ioad current rating of the load involved.
Exception N.1: A terminal of a component with a marked horsepower rating, such as a motor starter, is determined to be capable of retaining field wiring having an ampacity of 125percent of the full-Ioad current corresponding to the horsepower rating from Table 50.1.
Exception N.2: A terminal for connection of a heater load provided with individuaI branch circuit protection that is greater than 125 percent of the heater current, shall be capable of retaining field wiring having an ampacity not less than the rating of the branch circuit protective de vice.
28.3.3 For terminals intended to carry current from a combination of one or more motors, or one motor and one or more other loads, the field wiring shall have an ampacity of 125 percent of the largest motor full-Ioad amperes of the group plus 100 percent of all remaining loads
28.3.4 For terminals intended to carry current from a dc motor load operating from a rectified single phase power supply (not a variable-speed drive or speed control), the field wiring shall have an ampacity of:
a) 190 percent of the full-Ioad motor current where a rectifier bridge of the single phase halfwave type is used; or
b) 150 percent of the full-Ioad motor current where a rectifier bridge of the single phase fullwave type is used.
28.3.5 For terminals that will carry the input current to power conversion equipment or a solid-state motor speed controller in which the input current is different from the motor full-Ioad current. the field wiring shall have an ampacity of 125 percent of the input current rating of the device.
28.3.6 For terminals intended to carry the load current from a wye-delta starter, the ampacity of the field wiring shall be:
a) In accordance with 28.3.2; and
b) Based on a load current equal to 58 percent of the motor full-Ioad current.
28.3.7 Field wiring terminals intended to carry the current of a part winding motor, where half of the motor winding is energized during starting and the remaining half of the motor winding is subsequently energized for the running condition, the ampacity of the field wiring shall be:
a) In accordance with 28.3.2; and
b) Based upon the FLA from the respective part or half winding being energized instead of the full motor FLA (both halves).
UL 508A certification is an industrial control panel directive, which is sought by electrical inspectors. The UL 508A Listing Mark on an industrial control panel provides evidence of third party certification to the municipal inspection authority and to the purchaser of the panel. A UL 508A Listing Mark shows that the panel complies with an acceptable safety standard.
The official definition of an industrial control panel, according to UL, is 'an assembly incorporating two or more pieces of industrial control equipment or related control circuit devices, provided with interconnecting wiring and terminals for connections in the field. To allow the installer to properly install the panel in accordance to National Electrical Code (NEC) and other codes, electrical ratings and instructions are to be clearly explained on the panel.'
Installation of a control panel can be completed in two ways: in an enclosure as 'enclosed type' equipment, or arranged onto a mounting panel as 'open type' equipment. For 'open type' equipment, the assembly is installed in an enclosure provided by others, or at the installation site. Any of the outdoor enclosures or cabinets manufactured by Purcell Systems that carry the UL 508A Listing Mark would be classified as “enclosed type”, and complies with the applicable requirements for outdoor panels noted in the UL 508A standard.
UL 508A Certified Enclosures
Benefits of selecting an enclosure or cabinet that carry the UL 508A certification include:
- UL 508A certification provides the inspection authority and your customer evidence that the control panel complies with nationally recognized safety standards. These standards ensure public safety, and provide assurances that the electrical control panel is compliant with national and local electrical codes.
- Manufacturers that carry the UL 508A certification are subject to periodic unannounced inspections of their facilities by UL personnel. Through periodic audits of the manufacturers, UL can insure the manufacturer continues to meet the UL requirements for 508A certification.
- For a control panel to carry the UL 508A Listing Mark, the panel must contain only UL recognized and listed components. The UL Mark on a component means that UL has evaluated and tested samples of this component and has concluded that they meet the UL requirements. This protects the quality and integrity of the enclosure and provides guarantee of safe performance.
Ul 508a Book
Outdoor Enclosures and Cabinets
Within the UL 508A standard, there are two sections that are more relevant to outdoor enclosures and cabinets. The GENERAL section addresses requirements for all enclosures, and these requirements include:
- Protection Against Corrosion
- Support and Securement of Live Parts
- Spacings
- Conduit Bushings
- Insulating Barriers
- Insulating Materials
- Grounding - General
- Grounding - Size of Terminal or Bonding Conductor
- Identification of Grounding and Grounded Circuit Conductors and Terminals
The OUTDOOR PANEL section addresses requirements for outdoor enclosures, and these requirements include:
- Enclosure Openings
- Accessibility of Live Parts
- Ventilation Openings
- Bonding
- Enclosure Environmental Control Devices
- Field Wiring
- Internal Wiring
- Disconnect Switches
- Branch Circuit Protection
- Markings
Ul 508a Standard Pdf
More UL 508A Information
Ul 508a Exam
Regulatory Information