Hello George, I have checked with UL and the following is a summary:
1. Spacings are evaluated UL840 Pollution Degree 3. 2. Input and Output Terminals must be suitable for field wiring to be able to List units. 3. Additional Heating Tests may have to be conducted. 4. Unlike in UL1950 where specialized short-circuit testing is made, reliance of PWB trace for protective earthing may not be acceptable for UL508 Listing. A UL interoffice discussion is needed. Most probably a dedicated earthing terminal will be required. 5. There are additional markings and instructions which must be supplied with UL508 type power supplies. Thanks for your help and Best Regards From: "Sparacino,George" <[email protected]> To: [email protected] Subject: RE: UL1950 vs UL508 for Switching Power Supplies Date sent: Tue, 13 Oct 1998 11:35:01 -0400 > Hello Peter, > > This sounds like a question for Mr.Len Grant at UL in Melville.. His > Phone # is 516-271-6200 ext. 23123.. > > Let me know how you make out. > > George Sparacino > > > -----Original Message----- > > From: [email protected] [SMTP:[email protected]] > > Sent: Friday, October 09, 1998 5:53 PM > > To: [email protected] > > Subject: UL1950 vs UL508 for Switching Power Supplies > > > > > > Dear PSTC Members, > > > > Assuming a manufacturer had UL1950 Third Edition Recognized > > Component Class I (earthed) ITE Power Supplies and they wanted > > to have a Listing (as an open-end device) to the Standard for > > Industrial Control Equipment, UL508. > > > > 1) What additional requirements must be met? I am already aware > > that the input/output terminal blocks must be suitable for field > > wiring. > > > > 2) What about spacings? > > > > 3) What about if the input terminal block design is such that the > > earth goes directly to the PCB trace? Under UL1950 Recognition > > this was OK since the manufacturer decided to add a Condition of > > Acceptability (instead of meeting a 1000 Amp short-circuit test) > > that states that the power supply earthing terminal is not the > > protective earthing terminal and that this terminal should be reliably > > > > bonded to the end-product protective earthing terminal. Since > > manufacturer intends to also List his power supplies to UL508, this > > Condition of Acceptability must be removed and I wonder if the > > UL508 standard has a similar 1000A test as applied to to ITE > > equipment where the trace is relied upon for protective earthing! > > > > 3) Any other considerations for Listing to UL508? > > > > Thank you all, > > > > --------- > > This message is coming from the emc-pstc discussion list. > > To cancel your subscription, send mail to [email protected] > > with the single line: "unsubscribe emc-pstc" (without the > > quotes). For help, send mail to [email protected], > > [email protected], [email protected], or > > [email protected] (the list administrators). --------- This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to [email protected] with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to [email protected], [email protected], [email protected], or [email protected] (the list administrators).
