Industrial control panels FAQ
Below is an assembled list of frequently asked questions as a source of information on how to become a UL panel builder. Also see the devices used in industrial control panels section for more detailed information on construction issues.
What is the official UL definition of a panel?
UL considers an industrial control panel 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 the national electrical code and other codes, electrical ratings and instructions are to be clearly explained on the panel.
Installation 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 or at the installation site.
What are the benefits of UL Listed panels?
The UL 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. It shows that the panel complies with an acceptable safety standard. The Listing Mark may be applied to a wide variety of designs -- ranging from custom built to standardized designs with only minor variations.
What is covered by the UL Listing Mark?
The UL Listing Mark on an enclosed type control panel only covers the enclosure and the components that are installed within the enclosure or to the enclosure at the manufacturer's facility.
The UL Listing Mark on an open type control panel only covers the mounting panel and those components that are mounted to it at the manufacturer's facility.
Please note that the UL Listing Mark does not include coverage for externally connected loads, even if provided by the panel manufacturer. Also, the UL Mark does not include coverage of any components shown on the wiring diagram that are indicated as being customer provided or as not being in the panel. If a complete equipment Listing is required, please contact us regarding our factory automation equipment program.
What requirements must be met to get a UL Listing on a panel?
Industrial control panels rated not more than 600 volts and for installation in ordinary locations are specified in UL 508A, the Standard for Safety of Industrial Control Panels. The requirements in the outline are based on UL 508, the Standard for Safety of Industrial Control Equipment; the national electrical code, NFPA 70; and the standard for industrial machinery, NFPA 79.
An additional document is written for each individual panel builder and is intended to contain additional construction requirements and specific UL Recognized Components that have been found acceptable as a result of an engineering investigation.
What documents are helpful to review before initiating a panel investigation?
The material contained in UL 508A will help to determine if the product conforms to these requirements. Copies can be obtained from comm 2000.
How do I initiate an investigation?
When UL receives the signed application, along with a preliminary deposit check in the amount indicated on the application, we will open an engineering investigation to establish Listing service for your facility. If you wish, we can reference a purchase number on our paperwork. However, we do require a check for the preliminary deposit before we can proceed.
If a representative sample of your panel constructions will not be ready for some time, it would be better to delay returning the application form and preliminary deposit until a week or less before the sample is available for examination.
How long does the investigation take?
Normally the investigation will be completed approximately six weeks after receipt of the signed application form. However, if you require panels to be labeled in less than six weeks, please let us know the date you require Listing on your application form. We will work with you to expedite completion of the investigation. To cover the extra time and effort involved, expedited jobs will require an increase in the engineering cost limit.
What are the costs associated with getting a UL Listing for a panel?
The cost limit, specified on the quote, is established based on the assumption that all the components used in the panel are either UL Listed or Recognized and used as intended within their marked ratings. Additional costs that are not covered in the cost limit include travel expenses and other non-engineering charges.
Follow-Up Services charges for the factory examination program begin after the product becomes authorized to use our Marking. The cost of the type L Follow-Up Service is defrayed by a yearly service charge for each facility. There is also a charge per visit for conducting examinations at the factory and a nominal charge for Listing Marks.
Will UL visit my manufacturing facility for the review?
An engineering visit is made to the manufacturing facility to examine a representative panel design and answer any questions about 508A. After examining the panel, we will provide comments on any features that are not in compliance with our requirements.
It is helpful to have schematics available for review during this visit. In addition, it is a good idea to have a list of only the UL Recognized Components being used in the representative panel you give us for examination during the visit.
Another visit, the initial production examination, is conducted by a local UL field representative before we authorize use of the Listing Mark on the panels. This examination can accommodate your production schedule, so please inform us when the panels are scheduled for production.
What requirements apply to panels with components operating from a source of more than 600 volts?
Panels operating from a source of supply greater than 600 volts will be required to comply with UL 508 (up to 1500V) or UL 347, the Standard for Safety of High Voltage Industrial Control Equipment (2.2-7.2 kV).
Does UL test hazardous location panels?
Panels intended for installation in a hazardous location or having circuits that will extend into a hazardous location are required to comply with different requirements. Please see the hazardous locations section for more information.
What about other special use panels?
Extra requirements are applied to panels intended for elevator control use. Please contact us for additional information on applicable requirements.
The requirements for the following panels are contained in UL 508A:
- Overhead crane control
- Metal working machine tools, plastic injection molding machinery
- Flame safety supervision control
- Power press
- Service equipment use
What kind of Follow-Up Services apply to industrial control panels?
Once it has been determined that the product meets the necessary requirements, we will establish a factory Follow-Up Service examination program to audit the continued compliance of the panels with the specifications developed during this investigation. You will receive a UL procedure document that contains these specifications. The product will then be eligible to bear a UL Listing and/or Classification Mark.
Where do I get labels to put on my Listed panels?
Each U.S. office maintains a stock of standard labels which may be obtained by sending your order and remittance to the nearest office.