Reply to: RE>SAFETY, UL1950 Amd.3, T1 service status Edward,
I have been considering this lately also. Your question is just the prompting I needed to write. TREGgers, Please send corrections. I will collect and post them. Using UL1950 3rd edition I interpreted the following. Also included is consideration of AS/NZ 3260. For T1 or E1 (balanced 120 ohm) the worst case regulation is AS/NZ 3260. This is because Australia's AS/NZ 3260 says that TNV has the same spacing requirements as AC primary. (paragraph 6.3.3) I use this as a basis for choosing a 250v working voltage. 1. Insulation to ground is supplementary. 2. Insulation to ungrounded SELV is basic. 3. Clearance for pollution zone 2 is 2.0 mm (table 5, 250v, pollution 2). This is true for any working voltage below 600 vrms. 4. Creepage for pollution zone 2, with comparative tracking index (CTI) of 100 to 175 (material group IIIb) is 2.5mm (table 6). This result is for a working voltage of 250 vrms based on AS/NZ 3260. For a working voltage of 125 vac, the creepage would be 1.5 mm which is less than the clearance! Therefore default creepage is 2.0 mm based on the clearance requirement. 5. Hipot testing is done to the RATED voltage (250v) (AS/NZ 3260 paragraph 6.3.3), or according to the overvoltage test of UL 1950. Exclusion (UL 1950 paragraph 6.3.3.2): All the above is excluded if; 1. Equipment is pluggable type B (industrial plug). OR 2. Equipment is installed by service personell with instructions for permanent earth in the manual. OR 3. Equipment has provision for permanent earth connection (not the green wire in the AC plug) with instructions for the installation of that conductor. UL 1950 Overvoltage test (3rd Edition) Overvoltage compliance is covered on the flowchart (figure 18d). My T1 system ride the flow chart this way, If, line cord is heavier than 26AWG, And, Spacings are met, or test 5 is met (annex NAC 125v 25A for 30 Min.) (fuse) And, System is in a fire enclosure Then You pass! Note: Exclusion for spacings required in #005##005#6.3.3.2 do not apply for overvoltage test, however test 5 gets around that. Conclusion: 1. Equipment with special grounds, fire enclosure, 26AWG wire, and fuses will pass. 2. Equipment without special grounds need spacings, fire enclosure, and 26AWG wire, will also pass. Michael Royer Senior Agency Compliance Engineer BABT Approvals Liaison Engineer N.E.T. (Network Equipment Technologies) 800 Saginaw Drive Redwood City, CA 94063 Voice: 415-780-4218 Fax: 415-780-5004 [email protected] -------------------------------------- List-Post: [email protected] Date: 8/7/96 2:09 PM To: Michael Royer From: [email protected] Edward, Using UL1950 I interpreted the following. I would like to propose it here in an attempt to prove it. Your question is just the prompting I needed to write. For T1 or E1 (balanced 120 ohm) the worst case regulation is AS/NZ 3260. This is because Australia's AS/NZ 3260 says that TNV has the same spacing requirements as AC primary. (paragraph 6.3.3) I use this as a basis for choosing a 250v working voltage. 2. Insulation to ground is supplementary. 3. Insulation to ungrounded SELV is basic. 4. Clearance for pollution zone 2 is 2.0 mm (table 5, 250v, pollution 2). This is true for any working voltage below 600 vrms. 5. Creepage for pollution zone 2, with comparative tracking index (CTI) of 100 to 175 (material group IIIb) is 2.5mm (table 6). This result is for a working voltage of 250 vrms based on AS/NZ 3260. For a working voltage of 125 vac, the creepage would be 1.5 mm which is less than the clearance! Therefore default creepage is 2.0 mm based on the clearance requirement. 6. Hipot testing is done to the RATED voltage (250v) (AS/NZ 3260 paragraph 6.3.3), or according to the overvoltage test of UL 1950. Exclusion (UL 1950 paragraph 6.3.3.2): All the above is excluded if; 1. Equipment is pluggable type B (industrial plug). OR 2. Equipment is installed by service personell with instructions for permanent earth in the manual. OR 3. Equipment has provision for permanent earth connection (not the green wire in the AC plug) with instructions for the installation of that conductor. UL 1950 Overvoltage test (3rd Edition) Overvoltage compliance is covered on the flowchart (figure 18d). My T1 system ride the flow chart this way, If, line cord is heavier than 26AWG, And, Spacings are met, or test 5 is met (annex NAC 125v 25A for 30 Min.) (fuse) And, System is in a fire enclosure Then You pass! Conclusion: 1. Equipment with special grounds, fire enclosure, 26AWG wire, and fuses will pass. 2. Equipment without special grounds need spacings, fire enclosure, and 26AWG wire, will also pass. Michael Royer Senior Agency Compliance Engineer BABT Approvals Liaison Engineer N.E.T. (Network Equipment Technologies) 800 Saginaw Drive Redwood City, CA 94063 Voice: 415-780-4218 Fax: 415-780-5004 [email protected] --------------------------- Dear Treggers, RE: T1 service safety classification in USA/Canada This is probably an easy question for those of you in the US. I want to confirm the safety status of the T1 service offered in the USA / Canada. Specifically when applying UL 1950 Amd.3 to a piece of Terminal Equipment. Probably because there are now the issues of SELV, TNV-1, TNV-2 and TNV-3 I am trying to understand if the service is either TNV or SELV. To further complicate matters I am anticipating there to be a differnt classifaction for the point of provision, i.e. DSU/CSU scenario ? Am I making a meal of this ? Can someone put me right, please! (or perhaps provide me with the working voltage of the abopve scenarios) Many thanks in advance for your advice. Edward Fitzgerald European Technology Services (UK) ------------------ RFC822 Header Follows ------------------ Received: by Mac2.net.com with SMTP;7 Aug 1996 14:08:43 -0800 Received: from europe.std.com by unet.net.com (SMI-8.6/SMI-SVR4) id OAA21608; Wed, 7 Aug 1996 14:03:03 -0700 Received: by europe.std.com (8.7.5/BZS-8-1.0) id QAA13485; Wed, 7 Aug 1996 16:10:54 -0400 (EDT) X-Authentication-Warning: europe.std.com: daemon set sender to treg-approval using -f Received: from world.std.com by europe.std.com (8.7.5/BZS-8-1.0) id QAA13452; Wed, 7 Aug 1996 16:10:50 -0400 (EDT) Received: from sigma.itu.ch by world.std.com (5.65c/Spike-2.0) id AA01675; Wed, 7 Aug 1996 16:08:26 -0400 Received: from ties.itu.ch by ITU.CH (PMDF V5.0-6 #16074) id <[email protected]> for [email protected]; Wed, 07 Aug 1996 22:06:14 +0200 Received: from localhost by ties.itu.ch; (5.65/1.1.8.2/20Jun94-1231PM) id AA12193; Wed, 07 Aug 1996 22:08:05 +0200 List-Post: [email protected] Date: Wed, 07 Aug 1996 22:08:05 +0200 (MET DST) From: Edward Fitzgerald <[email protected]> Subject: SAFETY, UL1950 Amd.3, T1 service status To: TREG <[email protected]> Message-Id: <[email protected]> Mime-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Content-Transfer-Encoding: 7BIT Sender: [email protected] Precedence: bulk Reply-To: [email protected]
