UL 508A Frequently Asked Questions

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• Application
  • Can you address bringing a panel to an area with a larger available short circuit by simply inserting an additional fused disconnect (with current limiting fuses) before the panel?
  • Are solid state contactors and SCR power controllers exempt from having an SCCR rating?
  • Can we use current limiting fuses on branch circuits to increase the SCCR of the branch, and if not why
  • For drives (motor controllers) under 50HP, the table offers a rating of 5.0. How can I increase my overall panel SCCR value when I use drives?
  • Do you have to rate 120 VAC control panels?
  • Power distribution blocks are a weak link for control panel SCCRs. Bussmann has addressed this, does Square-D also plan to fix this problem their PDBs?
  • To increase SCCR rating of the panel, why would you ever want to use anything besides a Main fused disconnect?
  • What is the largest size overcurrent protective device that can increase the SCCR of a 5kA contactor?
  • How are wiring methods (busbar and cable bracing) addressed by UL508A for high SCCR panels?
  • When providing SCCR ratings for a 120 VAC PLC panel, will the primary CB rating be enough
  • Would a control panel for a small condensing unit be defined as an "Industrial Control Panel" and need to meet the SCCR labeling requirements?
  • How would you rate the SCCR of a 3 phase (incoming volt) DC power supply (output 24VDC) connected thru fuses?
  • In your combination ratings I don't see any higher SCCR's for NEMA combinations. Is their any testing to improve these equipment combination ratings
  • Enclosures - what is expected impact of UL508 on modifying existing enclosures as used now by panel builders.
  • If I have a 15 Amp fuse feeding a control panel, wouldn't the fuse protect me on a short circuit downstream of a fuse? Why do I need to worry about K Amps if the 15 Amp fuse is my protection?
  • Is there a list of the exceptions...I just added fuses in front of my "Control Circuit" voltage modules (power transformers right?)....power supplies are also except which means I don't need to add fuses in front of that either? All my questions deal inside the scope of the "Control Circuit".
  • Would fuse / fuse block feeding a control circuit be included in the calculations?
  • What is the recommended method to achieve a SCCR of greater than 2KA for a GFCI?
  • Can you have specific combinations of components tested as we do for dead-front apps?
  • If the feeder breaker or fuses are current limiting, the let-through of that device cannot be used to determine the total rating. True or false...
  • Where should a line reactor be placed in the circuits, and how does it's exempt status affect the SSCR calculation?
  • What is the feeder spacing at manual motor controllers ?
  • The paradox concerning the weakest link also applies for the motor controller bus bar systems, etc.As example: a 0-50HP motor controller applied in an industrial control panel with a total power consumption of 300HP as it has several motor outputs. In this case, a minimum short-circuit rating of 18 kA is expected, however, the industrial control panel can have a maximum rating of 5kA.
  • What about Variable Frequency Drives?
  • Does push button stations mounted remote from panel locations need an SCCR rating?
  • For devices such as a disconnect that specifies a short circuit rating based on certain types of fuses installed upstream, does that fuse need to be in the panel or can it be noted on the prints to be supplied by the customer?
  • Does make any difference in when 120VAC control panel is being feed from UPS.
  • We build panels, basically containing: 1) DC power supply for control 2) PLC (with it's power supply 3). Panel mounted lamps 4). Terminal blocks. We have a single point voltage input from our customer (the end user). We have a disconnect and supplementary breaker. Does SCCR apply?
  • Removing terminal blocks seems to add to the possibility of miss wiring at sight since you lose wire marking ease.
  • I'd like to use a distribution block in a panel with a 65KA rating. The panel is a power distribution panel with a Square D main breaker. Does Square D have a solution I can use for this application?
  • Does UL508A cover well pump control panels?
  • If a solid state relay is used in the control circuit (not the power circuit), would it still limit the SCCR to 5K?
  • What is the difference between a MCC rated at 65KA (includes CBs and relays) and a control panel?
  • Would the SCCR rating for a control panel be 10K if the incoming power is terminated to a power distribution block.
  • Re: tested combination ratings - the example was using Schneider devices - what about using combination of components from more than one manufacturer?
  • Do any terminal blocks currently have SCCR markings?
  • Explain how to protect a 200a panel with a 5k rating? What do you use for the feeder protection that will go down to 5k
  • Do control panels, containing PLC's, relays, terminal blocks, power supplies, etc. need an SCCR rating
  • Does Square D / Schneider Elect offer and/or perform coordination studies to determine available Fault Current at a facility?
  • What if you have 20ka current limiting fuse allowing only 5ka pass-through, how is the panel rated?
  • The panel builder has stated the SCCR of their panel is 25 kA as determined by the AIC rating of the main overcurrent protective device (a circuit breaker). Knowing this is incorrect, as the purchaser what should I do or what is my responsibility in this situation? My specification required a minimum SCCR of 25,000 for this panel.
  • Is the primary protection device for the control transformer considered part of the power circuit and does that apply to the total SCCR?
  • Do you need to consider servo drives or VFD's in the SCCR rating?
  • Can Current Limiting Fuses used in a branch circuits raise the panel SCCR rating, example using type J fuses with a 5K rated contactor.
  • As you talk about the difference between Feeder and Branch Circuit. Were do you make this separation? Is the division at the load side of the main over current device of the panel, or can you have multiple current limiting devices after the main overload device?
  • Am I to understand that an isolation transformer installed in the panel can be used to reduce the feed rating to 5ka
  • I have 4 Sq-D Starters Protected by RK5 fuses, The RK5 Fuses are supplied by a power distribution block which is protected by RK5 Main Fuses. Would my SCCR rating be 5KA
  • Do control panels containing start/run capacitors (start kits)in the branch circuits have an automatic low SCCR?
  • What can you do now before any of the terminal blocks are at a higher rating?
  • If the customer needs higher than 10k but we have no terminal blocks tested higher. customer needs his machine. Do we strip out all terminal blocks and put those companies out of business?
  • Consider a panel with circuit breaker, control circuit, and GFCI receptacle. Would this panel require SCCR rating?
  • Since contactors are rated at 5 kA, how can you get a 65 kAIC rating for a panel using contactors
  • Can current-limiting fuses in the feeder circuit be used to achieve a higher rating of the 10kA terminal block when the fuse's Peak let thru current per table SB4.2 is equal to or less than the 10kA block rating?
  • When non-motor circuits are in the power circuit, are there any combinations that have been tested without the overload unit in the circuit (ex. circuit breaker and contactor alone)?
  • How would you handle calculating the SCCR of an electrical outlet off of a control transformer?
  • For solid state relays, can current-limitation of the feeder device increase the SSR rating?
  • If the SCCR for a panel is at 10K are you able to connect to a power system with the capacity of 65K?
  • If control circuits are powered directly from the branch circuits without a transformer, does this lower the SCCR? for instance, 240v/3ph/4w/60hz incoming service and using L1 and the neutral.
  • If there is only 1 power circuit in a panel can the feeder breaker be used as a branch breaker or do you actually need 2 breakers in series
  • Can current limiting fuses be used on a branch before the starter to increase the SCCR rating on that branch. Example contactor rated at 5kair with fuse of CC 100kA.
  • When using a control power transformer (300va) in a control panel @ CC class fuses on the primary and secondary of same.... How does the control circuit reflect on the SCCR of the panel.
  • If a control circuit has Class CC fuses for overcurrent protection, but are placed in unmarked fuseholders, then what is the SCCR?
  • UL Table SB4.1 declares GFI receptacles as 2K rated. If used in a single phase control panel (no stepdown transformer) does the SCCR follow the GFI protective device rating of the 2K rating of the GFI receptacle?
  • My panel has a 10k rating with a 22k Feeder Circuit Breaker.Is it my responsibility to coordinate with the site to ensure the feeder is at least 22k upon installation.
  • If a machine has several panels (modules) but all feed from one source, it the SCCR required for the main panel attached to the facilities or for the whole equipment?
  • What about an SCCR of a specific load such as a 10kW microwave or plasma generator? Is it required?
  • If a Consultant specifies a SCCR rating of 65kA at 480V and the panel receives a surge of 1300V. What impact is there?
  • What is the transformers default SCCR rating per UL508A and SCCR 1 Table?
  • It looks like its impossible to have an SSC rating higher than 10KA as terminal blocks are all rated 10KA or less. Per NFPA 79, customer connections must be run to terminals up to 80A. How do we increase the rating of a panel with this problem?
  • Does NEC Article 409 and UL508A include fire alarm control panels that are mounted into large industrial control panels and power supplies, IO terminals and other devices?
  • Would consider a panel that is integral to an industrial machine, such as a printing press, to be within the scope of this article? What all is included?
  • NEC Article 409 also states that a control current transformer requires a short circuit rating. All suppliers that I know of and have been in contact with have not conducted such testing. This means that all switch boards in the future must be labeled with a short-circuit rating of 0 kA, as it is allowed to label the switch board according to the weakest link. I believe this is not the intention.
  • Solid state relay have a 5Ka short circuit current rating and I have not been able to obtain any combination SCCR information that would allow a higher SCCR value to be applied to a branch circuit with solid state relays. Does anyone have an idea of how to increase the SCRR panel rating when solid state relays are used? Most industrial plants have more than a 5Ka supply to the equipment?
  • If an OEM has designed or constructed a panel with a 10KA rating but the customer's available SCCR is 65KA, what are some possible solutions? What is designed versus whats available.
  • If you use a feeder device with a limiting pass through would that work for 5 kA?
  • How do you determining the rating of a branch motor circuit when the circuit breaker, contactor, and overloads are manufactured by different manufacturers?
  • Most of the discussion has been around components? What about wires and bussing? Does that figure into the equation.
• Code
  • Is there a list of components that do not need to have SCCR ?
  • Is the SCCR rating of the control panel absolutely defined by the nearest branch circuit from feeder..are there any cases where an exception would be allowed.
  • What if there is no SCCR available from the customer?
  • Do older machines have to be updated?
  • Can Type 2 coordination ratings be utilized
  • Is it safe to say that if a panel meets UL508A requirements it will also meet NEC 409 requirements?
  • Do lighting disconnect ( above the main disconnect) need to be factored ?
  • NEC says "two or more components: what if you only have pushbuttons in an enclosure. Is this a control panel under this article?
  • Is there a published list of exempted component types?
  • We require all ICPs to be listed and labeled (NEC 110.3(b), which means either 1)buy a listed ICP or 2) have a UL 508A shop fab the panel. Article 409 appears to allow field fabrication of ICPs and acceptance by the AHJ by demonstrating compliance to Article 409. This Article does not require listing/labeling. Is this a conflict?
  • Do these requirements apply to existing installations or just new / modified installations?
  • So do existing panel installations included. If not does a rewire or mod trigger compliance?
  • Does the SCCR requirement need to meet or exceed the available fault current and what if that is not available
  • With regard to Article 409 and ampacity of conductors, Which NEC table should be utilized for determining the ampacity. Can table 310.17 be used since the wire would be in a ventilated trough?
  • I agree that UL would allow you to not give a rating, but NEC 409 doesn't appear to have that exception, or does it?
  • Do we need to comply with the State that we manufacture from or the state we're sending our panel to?
  • Am I obligated to retrofit all of my existing cabinets to the new standard a.s.a.p.?
  • Does NEC 409/UL508A include fire alarm control panels that are mounted into a large industrial enclosure along with power supplies, I/O terminals, etc.?
  • How does NEC 409 apply when modifying an existing UL labeled panel that does not meet the requirements of 409? Particularly when our modification does not relate to the non-compliance issues.
  • From all presented data it seems that the panel manufacturer shall disclose the SCCR, but it is the facilities engineer responsibility to make the installation per code.
  • If an existing panel does not have an SCCR and I need to modify the panel (e.g. add a relay) such that an inspection is required, will I need to figure the SCCR for the entire panel?
  • When older equipment is being relocated, the SCCR rating of the equipment may not be known (labeled on the equipment). What should a person do?
  • Who wins NFPA 79, 70 or UL 508?
  • Do we need to supply a "SCCR Information Packet" with each panel to include components individual SCCR rating?
  • Are there points in the regulation and standard that are either unclear or radically different than today's standard practices?
  • How can the kAIc facility available current (typical 20-40kAIc) can be reconciled with the kA low values that UL 508A, SB supplement recommends (5-10kA). With this standard it seems that any panel assembly is not compatible with facilities. Testing of panels is not an option due to cost constraints.
  • Is the background information and calculations sufficient documentation for a UL approved panel shop
  • I agree that UL would allow you to not give a rating, but NEC 409 doesn't appear to have that exception, or does it on a PLC Control Enclosure.
  • Please elaborate on the definition of feeder circuits and the use of current limiting devices. It seems there can be multiple feeder circuits within a panel. An example would be if a main feeder was broken down into two branch circuits. If those branch circuit get broken down into several smaller branch circuits, could the line side of this second set of branch circuits now be called a feeder?
  • Is the any enforceable requirement on the part of the plant or the installing electrician to do a SSCR of the location the panel is to be installed in to determine if it's SSCR is lower than the SSCR of the panel?
  • If the panel has ONLY control components -PLC & I/O and other 120VAC or less powered equipment, but the panels has a CB and Transformer to derive power from a 480 VAC circuit - does it need to be marked with SCCR??
  • Does or will NEC 409 and UL 508A apply to motor control centers?
  • How will this apply to control panels that are being moved to another location?
  • What is meant by "General Use" in the scope?
  • Do these new SCCR rules apply to all control panels regardless of (if they are )UL listed or approved?
  • Is a phase monitor considered an across the line device
  • If we have a low-rated panel, can we not just limit the available fault current by inserting appropriate protection upstream?
  • NEC 409 definition states that any arrangement that has two or more components - even pushbuttons and selector switches is considered a control panel, therefore requiring a SCCR, however several times in the presentation today, the speakers have indicated that SSCR doesn't relate to control circuits. If they are correct, how do you properly label the panel then?
  • Is it the responsibility of the panel builder to provide a panel with the appropriate rating or the installing customer provide the appropriate sized feeder?
  • The combination ratings for circuit breakers with contactors & overloads is listed on UL's website. When can we expect to see the combination ratings for FUSES and starters?
  • Please clarify the use of current limiting devices?
  • Before my company sells another panel it is my understanding that we need to get from the customer their available SCC peak let through and then build the panel with a SCCR that is equal to or greater than the available let through of their electrical feeder system.
  • Who is ultimately responsible for complying with this requirement the end user, the consulting engineer, or the control panel builder
  • Can the SCCR be determined using any available commercial software for industrial applications? If cables are simulated current limiting will occur and SCCR will be raised.
  • Do the UL508A and NEC 409 standards harmonize with European standards
  • Is it correct that a control panel built with only control circuit components (no power circuit components) is not required to have a SCCR.
  • If you move all your equipment from one building to another do you have to add the rating or will it fall under the grandfather clause. Does that just apply when you are adding new components?
  • WHAT IS THE DEFINITION OF WHEN CIRCUIT IS A CONTROL CIRCUIT OR A POWER CICUIT?
  • What about legacy control panels? Will they need to have this information installed?
  • How will UL508A be viewed in Canada and Mexico?
  • What about all the machines that come from out side the US. I have seen most Japan machines have no UL labeled components in the control panel right now. What will be done on this new UL508A?
  • How does the relocation of a control panel (with no change in components) effect the SCCR rating of that control panel ?
  • NEC Article 409 states the SCCR must be determined using an "approved method". Aside from UL508A, what are other approved methods?
  • How do you determine the overall plant SCCR
  • If you modify an existing panel without moving the location. Are you responsible to update the panel with an SCCR rating or would that panel be grandfathered?
  • Do these SCCR requirements apply to existing panels? To existing panels when they are modified? What kind of a modification would trigger a requirement to list an SCCR?
  • Do states that haven't adopted NEC 2005 have to comply to this standard?
  • Does a Non-Fused disconnect fit the scope of this spec?
  • Do existing industrial control panels need to be marked with SCCR?
  • Can a control panel include a tap protection device?
  • Is it correct to assume that a control panel correctly built to UL508A and bearing the UL508A listing mark will meet NEC409?
  • When does the control circuit start? At the branch single pole circuit breaker? So the if the panel is rated at 65K and the single pole control circuit breaker is rated at 10K the panel is still rated at 65K.
  • What about equipment going to Canada?
  • Does this article apply to industrial panels that come as part of a machine, the answer was way to quick for me. A simple yes/no would be better. I was confused or didn't understand.
  • If a panel meets the new standard, does it automatically meet the requirements for states that are still following the old standards?
  • Do we need to comply with the State that we manufacture from or the State we manufacture to?
  • When older equipment is being relocated, the SCCR of that equipment may not be known or labeled on the equipment. What needs to be done in this case?
  • Who is responsible for making the determination? Certainly the panel manufacturer has to disclose the SCCR, but is the facility managers responsibility to follow the Code?
  • What is the SCCR suppose to be protect? Humans or Machinery? Will Control Panel Builders (ex Hoffman) have to address this?
  • Will the electrical component manufacturer be required to label their equipment with the SCCR in the future?
• Inspection
  • If an existing panel does not have and SCCR and I need to modify the panel to add a relay, will I need to figure the SCCR for the entire panel to meet the inspection requirements?
• Standard
  • Is the SCCR basically the lowest rated device in the feeder circuit?
  • Can a combination of components approved for a certain SCCR under a UL 508C listing be utilized for doing an SCCR for a UL 508A listing?
  • How do the presence of PLCs, I/O, and other non power components affect the calculation of the SCCR rating?
  • Who is responsible to maintain records of ID Numbers
  • How does this effect low voltage power supplies such as 24 VDC or less?
  • Many HACR vendors still stating UL 508A don't apply to their equipment. Do most UL standards applying to HACR equipment refer to or adopt UL 508A by reference in some form?
  • Do small 24 VDC power supplies have or need a SCCR?
  • Do panels with control circuits only require a SCCR rating?
  • Where can more examples be found for determining the SCCR via the UL SB's?
  • Are AC to DC power supplies also exempt from an SCCR?
  • What is the format for the SCCR label?
  • How do I find the SCCR if I have a panel that has control circuits only, like a PLC panel?
  • Could you please clarify when the UL 508A certification applies? Does it apply to control panels that have only control components? i.e.: PLCs, PBs, timers, lights, etc. Does it only apply to power circuits?
  • Can you discuss an example of a PLC control panel that is fed with 120VAC only. Also, this panel may have multiple 120VAC power sources from the field for I/O (from an MCC for example).
  • Wouldn't be simple to choose the lowest SCCR rated device in your Panel and adopt that as the SCCR rating for the panel?
  • How large of label is required marking the control panel? Can the label be used by a color coded marking with an archive file listing the various panels and their respective SCCR?
  • Does the additional SCCR information have to be located on the data plate or can it be a separate marking?
  • Are lighting circuits considered power circuits?
  • In the absence of SCCR data (for eg. a CB),Can we consider available KAIC rating of CB as SCCR rating of CB?
  • Is a varister based TVSS exempt?
  • I understood that table SA1.1 is example and to be used where manufacturer's information is not available. I have heard it argued that one can and cannot use the manufacturers peak let through graphs to interpret the short circuit current ratings. What is the opinion?
  • UL-508A SB Can we use fuse manufacturer peak let through currents or only table SB4.2?
  • IF you use a feeder device with a limiting pass through ok 5K would that work?
  • Will electrical component manufacturer's be required to label their equipment with the SCCR in the future ?
  • How do you determining the rating of a branch motor circuit when the circuit breaker, contactor, and overloads are manufactured by different manufacturers.
  • In your experiences, what are the most overlooked aspects of these new standards?
  • When is it appropriate to take a design and have it tested by UL versus using a manufacturer approved tested combination? Is it based upon complexity of the design or number of components?
  • Does main circuit breaker in 120VAC control panel has to be UL489 listed.There will be no motor loads connected to this panel.
  • When multiple starter/CB combinations are used in a single panel, must one add together the min. volumes, or just use the largest one?
  • Which rating for SCCR do I use, 1 pole or 3 pole for circuit breakers ?
  • How do you do a short circuit rating for an enclosure that only houses PLC equipment?
  • When the power circuits are all 120 VAC or 24 VDC is SCCR rating required on label?
  • Can we use distribution blocks under the new standard?
  • How do current limiting ratings impact the SCCR?
  • If I put an electronic Meter in a NEMA enclosure will the control power, and metering inputs (voltage and current leads) need to have a separate SCCR label?
  • Power conversion equipment is common tested according UL508C. If the same solid state protection circuitry is used the SCCR may be increased according UL508C. This is however not marked on the device. How do we handle this ?Can we accept it for higher values without additional testing if tested with a JFHR2 fuse ?
  • Why is the terminal block default rating 10 kA?
  • What if you have a device that does not have an SCCR published by the manufacturer and it is not listed on the "assumed" values table?
  • It sounds like you have indicated terminals may be a limiting factor in equipment design. Why is a termination point a concern with SCCR? Does this mean that we cannot use "wire nuts".
  • UL508A, Supplement SB Table SB4.1 does not seem to address many power components..and seems incomplete (e.g. filters, contactors, relays..). Will this table be modified? What can a user of the Standard do when the manufacturer doesn't mark the SCCR rating of a component and the component is not listed in Table SB4.1?
  • Can we use the power cables as limitation for SCCR ?
  • Does a panel that is powered from a 120 VAC source require and SCCR?
  • Do UL698A listed panels have an impact on overall SCCR ratings?
  • SB 4.2-4.4 cover the SCCR ratings based upon let-through values of CL fuses/breakers. Doesn't this attempt to correlate a peak value with a essentially RMS value of the component. No consideration of I2t?
  • Does the UL 508A only apply to OEMs who are making UL Listed Control Panels?
  • I have a question about solid state overload relays. If the relay uses current transformers to sense power current, is it exempt?
  • The defined difference between power circuits and control circuits can be ambiguous sometimes. Would a power supply that produces a voltage used to create, for example, a gas plasma, that is fed from a panel be within scope when assessing a panels SSCR?
  • Is it possible to build a panel used for testing equipment that does not have to meet the codes for Industrial control panels?
  • Spot Weld controls are attached to a "Weld Bus" which typically has 100,000 KA available. Is a weld control impacted by UL508A?
  • What defines a power circuit? Many control panels will include interior lights, condensation heaters and convenience receptacles all fed at 120 Vac. Is this control or power?
  • Power correction- 480v systems reactors are ok but what about capacitors ?are they excluded from the SCCR requirements
  • IF YOU HAVE A CONTROL PANEL THAT ONLY CONTAINS A PLC AND ITS I/O ALONG WITH OTHER CONTROL DEVICES LIKE RELAYS, DC POWER SUPPLIES AND AN OPERATOR INTERFACE, IS THERE ANY NEED FOR A SCCR ON THIS PARTICULAR PANEL?
  • As an OEM, is it sufficient to provide in the schematic and name plate a SCCR of 5kA (which is what we have determined the panel to be) and state over current protection not provided and list max fuse and circuit breaker size? If so, assuming the plant has more than 5kA available, is there a way the customer can limit the pass through current to the equipment?
  • How do we know if a control circuit is exempt? What if the design includes feedback that breaks isolation?
  • Can we put a fuse on the incoming feed to drop the rating?
  • How large (physically)should the panel labels be? Is there a minimum test size? Where should they be located on the panel?
  • So Supplementary breakers under UL1077 feeding a CPT primary must be part of the consideration for the overall SCCR?
  • If the "weakest link" is the bottom line of the overall SCCR of the panel, then what's the point of doing anything else, and why can't one simply put in a higher rated current limiting device to get a higher rating?
  • Can I use one current limit device for several branches within a panel?
  • How does the standard apply to DC power supplies that are feed by power circuits (480 VAC, 3 phase)?
  • What is "High" SCCR?
  • Will Solid State Power Relays Need SCCR Rating?
  • Why power transformer are exempted from the new std.?
  • How does a panel manufacturer determine the SCCR of a component without SCCR, not listed in the list of components in table SB, and the component manufacturer is not able to provide a SCCR for that component?
  • What about a non-UL listed device? Does UL508 still allow a ground-fault circuit breaker to feed this device inside the industrial control panel and still be listed? For example, a meter, monitor or analyzer.
  • Are you saying that the "SCCR" Rating is not required for PLC Panels that do not contain Disconnects or Transformers.
  • So 20KA can be hooked to 20KA or higher?
  • Does it make a PLC panel require SCCR rating if it is powered by a UPS?
  • Would you say again what the spec for cautionary marking is? I caught the 535 but not the lettering.
  • Are lighting circuits excluded from requiring an SCCR?
  • Any examples of what the caution label should look like? And, Where do we find the default rating tables?
  • Do we have to use Table SB4.2 to determine fuse let-through currents or can we use the manufacturer's data?
  • Why can we not use table SB4.2 to limit the available current if fuses (current limiting) are used ?
  • What about SB4.3.1 of UL508A. Can you explain it?
  • Is it required to determine an SCCR for the DC circuits generated within a panel via DC power supplies?
  • How does UL 508A compare with equipment that has a UL 508C equipment rating? Does one supercede the other?
  • WHAT ACTUALLY DETERMINES WHAT A POWER CIRCUIT IS VS. A CONTROL CIRCUIT. I.E. A CONTROL PANEL THAT ONLY USES 120 VAC, IT MAY HAVE AN ENCLOSURE HEATER.
  • Can you elaborate on the short circuit requirement for PLCs and for power supplies.
  • In the absence of SCCR data, can we consider available KAIC rating of a SB as an SCR rating of a circuit breaker?
  • For panel builders or suppliers of panels, do you need to supply an SCCR information packet or documentation with each panel with individual component SCCR ratings?
  • Who wins in cases of conflicting or intersecting standards? Is it NFPA 79, NFPA 70? UL508A? Which ones are to be followed?
• UL
  • Except UL508A/SB what other educational material like HandBook etc.., is available and Is UL planning to do a regional classes or seminars?
  • If UL were to check out a panel on site will they determine an SCCR rating, or just say if it doesn't meet the requirement. And are they then liable for that rating.
  • What is UL doing to provide uniform enforcement from location to location?
  • I was told from my UL person that you can use the fuse let through from the manufacturer. The UL presenter in the Control Engineering webcast said that you can't. Which is correct?
  • If the SCCR of the branch circuit was based on the lowest rated device. This number was assigned to the line side of the branch protection device. If a feeder protective device is place ahead of the branch protective device, does the let-through of that feeder protective device have to be less than the SCCR of the branch protective device or does it have to be less than the assigned SCCR of that branch circuit?
  • If the UL 508A guidelines are followed does the panel have to be UL listed to achieve the SCCR rating?
  • Tim, most times the available fault current is unknown. Will the panel builder be held liable if the equipment is applied improperly to an installation?
  • Are panels without Motor, Heater, Light, or Appliance loads required to have an SCCR marking?
  • What defines a Feeder Circuit?
  • Do UL508A Panels that have only control circuits do not need a SCCR? UL 508A says ALL panels should have an SCCR. Explain, please.
  • What should the precautionary labels for instantaneous trip CB's and self-protected motor controllers indicate? Where should they be placed?
  • Is there a guideline for a cautionary stickers and markings?
  • How does NEC article 409 apply when modifying an existing UL labeled panel that does not meet the requirements of 409 particularly when the modification does not relate to non-compliance issues?
  • Do we have to size for a "worst case"? If all devices are powered at once or only actual use or only when some devices are powered?
  • Can UL508A SB. Can we use the fuse manufacturer peak let through current or does all reference have to go through Table SB4.2?