In reply to Mr. Costello's CTI question, we asked similar questions directly to UL Santa Clara in July this year. Our questions were concerning UL 1950 (3rd ed.), Cl. 2.9.3 CTI requirements.
Q. Does "IEC 112 Method A" described in UL 1950 (3rd) mean "Solution A"? A. Yes. -------- Q. What are the differences between IEC 112 and ASTM D 3688-85? A. The main differences are the equipment used for conducting the tests and resistivity. UL has conducted comparison testing between IEC 112 Solution A and UL 746A (ASTM D 3688-85) and the result was pretty much the same. The IEC 112 has recently been revised and we are currently evaluating the revision through comparison testing. -------- Q. Does UL accept the CTI value of UL 746A to determine a material group? A. Yes, we accept CTI value according to UL 746A for determining a material group. -------- Q. Can UL test CTI in accordance with IEC 112, method A? A. Yes (prior to the revisions). Currently the test period is basically UL 746A. Currently, the test period is 4-5 weeks. We would require 10 samples (size 4x4) for the test. The RTP office is currently determining what testing would be necessary for the revised version of IEC 112, Method A. -------- Hope this info is of help. We suggest that you confirm this directly with UL, as their requirements may be different in your specific situation. Also, they may have more information about the revisions to the IEC 112, and whether or not it affects the testing comparison between UL 746A and IEC 112. A-Pex International Co., Ltd. [email protected] > Can anyone tell me if the UL CTI ratings/results are the same as the > IEC 112 CTI. Many EN and harmonized standards use CTI for determining > creepage requirements but is the CTI number in the UL Recognized > Component Directory a valid number for this value? > > Thanks, > > Steve Costello > National Instruments > [email protected] >
