Jeff - This rumor doesn't make much sense as an across-the-board requirement, especially considering UL has a component product category for MOVs and other transient voltage surge suppressors, along with some product standards that allow reductions of over-surface and through-air electrical spacings when transients are known and/or controlled. Presumably, your friend means one specific product category or standard, but even then it makes little sense for US application.
Could it be that this rumor is based on certain EU countries not wanting MOVs in primary circuits, based on the nature of their power systems and UL is enforcing this requirement for CB Scheme evaluations where specific national deviations come into play? I've seen no official mailing from UL on this topic. Such a drastic measure, after accepting MOVs in primary circuits for a long time, would require a formal Industry Review (File Review), with announced schedules for product compliance. If your friend has more information on this, please convince them to pass it along. Regards, Peter L. Tarver Homologation Engineering Dept. 4D02-4 MPK MS: D-2120 V: ESN 655-2453 F: ESN 655-2575 > ---------- > From: colli...@perkin-elmer.com[SMTP:colli...@perkin-elmer.com] > Sent: Monday, April 20, 1998 11:31 AM > > > I recently received an e-mail from a colleague on the east coast > stating that UL has joined TUV Rheinland in NOT accepting the use > of MOV's in primary circuitry. > > The reasoning behind this is due to the unpredictable dielectric > break down of these components which can increase leakage current > beyond acceptable levels. > > > Has anyone heard any truth to these statements ? > If so, what other methods are being used to solve problems > without these devices? > > Your comments are appreciated, > > Jeff Collins EMC/Product Safety Engineer > Perkin-Elmer Applied Biosystems > colli...@perkin-elmer.com > >
