Hello Kevin, That's correct, we do not have 20 different fire detectors (only 5-6), but in addition we have some sounders, manual call point, address units, fire door controllers, etc. And of course the fire alarm panel (control and indicating equipment). The cable screen is connected to earth on the panel, but not to any devices on the detection loop, it just runs through.
I know this 20m requirements, but I wonder how much more induced surge pulse will occur when testing on a 20m cable compared to induce the pulse close up (0.5m) to a device ? Could be possible to increase the voltage to make some sort of correction? During the discussion with the lab today, it seems that I have to bring my wire cutter tomorrow and an extra 20m cable .... Best regards Amund Westin, Oslo / NORWAY > -----Opprinnelig melding----- > Fra: Kevin Harris [mailto:[email protected]] > Sendt: 31. oktober 2002 22:41 > Til: '[email protected]'; [email protected] > Emne: RE: Surge - injection point on screened cable > > > Hi Amund, > > You only require the one piece of 20 meter cable and it has to be attached > to your EUT. Only one thing can be the EUT at a time. I don't know if the > EUT is your control and indicating equipment ( CIE ) or your other devices > on the cable or if it is all of them. Assuming (worst case) that it is all > of them, then you need to select each part in turn as the EUT add the 20 > meter cable to it and isolate all the other devices from the surge. > Trying to surge all 20 devices at the same time is not proper > either. In the > case you state, you have whatever protection scheme you have > implemented in > each device in parallel with 19 others and therefore improperly distribute > the surge energy across all of them. BTW are your devices on the cable > earthed? If they are not, be sure to check that the test house has a 10nF > cap from the screen to earth at the EUT end of the cable as per > Fig 3 in EN > 50130-4 > I may be reading things in to far, but I inferred from your wish to surge > all devices on the cable at the same time that you have 20 > different things > that you want tested and not 20 identical devices. I can't > imagine that you > actually have 20 completely different fire detectors. If you have devices > that have various options test only a fully loaded one and apply > the results > across the whole line. It's a whole lot cheaper testing that way :) > > Best Regards, > > > Kevin Harris > Manager, Approvals and CAD Services > Digital Security Controls > 3301 Langstaff Road > Concord, Ontario > CANADA > L4K 4L2 > > Tel: +1 905 760 3000 Ext. 2378 > Fax +1 905 760 3020 > > Email: [email protected] > > > -----Original Message----- > From: [email protected] [mailto:[email protected]] > Sent: Thursday, October 31, 2002 10:48 AM > To: [email protected] > Subject: Surge - injection point on screened cable [fadr] > > > > According to IEC/EN 61000-4-5, the surge pulse shall be injected onto a > screened cable 20 meters from the DUT. > > We have a fire alarm system with 20 detectors connected on the > same screened > cable, 1.5 meters between each detector. We have been told from the local > test lab that we have to add a 20m cable between each detector in order to > surge test each detector. > > I'm sure our local cable distributor like that idea ... , but do we really > have to do this ? Why is this 20 meters cable needed ? Is it to induce the > surge pulse from the screen into the cable lines? > > The 20 detectors make a total cable distance of 30 meters and the > screen is > continuous. Is it possible to insert a pulse in the beginning of the cable > and test all detectors simultaneous ? > > Regards > Amund > > > > ------------------------------------------- > This message is from the IEEE EMC Society Product Safety > Technical Committee emc-pstc discussion list. > > Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ > > To cancel your subscription, send mail to: > [email protected] > with the single line: > unsubscribe emc-pstc > > For help, send mail to the list administrators: > Ron Pickard: [email protected] > Dave Heald: [email protected] > > For policy questions, send mail to: > Richard Nute: [email protected] > Jim Bacher: [email protected] > > All emc-pstc postings are archived and searchable on the web at: > http://ieeepstc.mindcruiser.com/ > Click on "browse" and then "emc-pstc mailing list" ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: [email protected] with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: [email protected] Dave Heald: [email protected] For policy questions, send mail to: Richard Nute: [email protected] Jim Bacher: [email protected] All emc-pstc postings are archived and searchable on the web at: http://ieeepstc.mindcruiser.com/ Click on "browse" and then "emc-pstc mailing list"
