Doug, sounds like you're having a semantics issue with UL. The crux of their argument is that they're claiming that your equipment is powered by PRIMARY power.
Direct your attention to UL 1950, 3rd ed., 3.4.1, which discusses equipment intended to be connected to a centralized dc power system. The note there says: "A dc powered system is considered to be a secondary circuit, but the connections to the system are subject to the requirements for primary circuits." The CONNECTIONS are subject to primary circuit requirements, i.e., grounding, power connections, etc. Everything else falls under the requirements for secondary circuits. We have numerous dc racks UL certified to 3rd edition and all have been treated as secondary circuits. Mark At 2:06 PM -0500 10/28/97, Doug McKean wrote: >I'm having a hell of a time with UL. > >A piece of equipment I'm having tested is >powered with -48vdc from the power grid >in a CO. That power grid takes in AC from >the street, steps it down to 48 VDC rectified, >then passes it across the batteries, finally >distributing it out to the racks in the CO. > >That 48 VDC is SELV for there are fuses all >over the place in the CO right up to where >the equipment in the racks plug into it. > >Under UL1950 3rd Edition, Table 18, page 125, >I'm declaring that the 48vdc is secondary and >I asked to have my equipment tested operationally >at 500V. > >I have had 48vdc equip tested at another >lab and approved to UL1950 3rd Edition >under the same claim above. > >UL says no way. It must be tested under >the PRIMARY heading of Table 18 page 125. > >It is important to note here that I WANT >the hi-pot testing to be done. > >Well, now I'm told that if I demand this >to stay as I originally asked, then I only >get UL1950 2nd Edition until the year 2000. > >I don't understand. I've had this done >before without a problem. > >Also, the power supply people, more than >one, find this to be news to them. Most >of the hockey puck DC-DC converters out >there (that I've dealt with) aren't able >to withstand 1414VDC operational. > >Am I alone here? > >Are other mfrs of 48vdc and 24vdc equipment >intended for COs running into the same thing??? > >Regards, Doug ------------------------------------------------------------------ Mark Ortlieb | Product Safety Engr. | QUALCOMM Incorporated QUALCOMM Incorporated | 6455 Lusk Blvd. Tel: 619-658-3208 | San Diego CA 92121, USA Fax: 619-651-1997 | <mailto:[email protected]> | <http://www.qualcomm.com> ------------------------------------------------------------------
