Jason, Please explain to your colleague that for North American requirements (as depicted in the NEC and CEC) there is no risk of electric shock or fire from circuits in wet locations for up to 21.2 V. For higher voltages you should start taking steps to minimize the risk of water ingress and the risk of a person coming in touch with the circuits.
In Europe, I believe the voltage level is somehat lower; if I recall correctly, 15 V. Someone correct me if I am wrong! This e-mail message may contain privileged or confidential information. If you are not the intended recipient, you may not disclose, use, disseminate, distribute, copy or rely upon this message or attachment in any way. If you received this e-mail message in error, please return by forwarding the message and its attachments to the sender. PETER S. MERGUERIAN Technical Director I.T.L. (Product Testing) Ltd. 26 Hacharoshet St., POB 211 Or Yehuda 60251, Israel Tel: + 972-(0)3-5339022 Fax: + 972-(0)3-5339019 Mobile: + 972-(0)54-838175 -----Original Message----- From: jasonxmall...@netscape.net [mailto:jasonxmall...@netscape.net] Sent: Thursday, January 03, 2002 12:57 AM To: emc-p...@majordomo.ieee.org Subject: Electric Shock and Water My apologies if this is just too naive... I am trying to explain to a collegue why there are so many cautions against "mixing" water with electricity. He is not the type to accept "common sense" as an answer. This is what I have reasoned so far... MAL-OPERATION Water is generally conductive. If it enters the area of a chassis that houses control elements such as relays or switches, it can short circuit the control elements and cause the affected device to "operate" unexpectedly, and sometimes in unexpected ways. ENERGIZING SURFACES Water is generally conductive. If it enters a chassis containing hazardous voltages it is possible it may act as a conductor of the voltage to an otherwise un-energized conductive surface. If the conductive surface, for whatever reason, is itself not sufficiently grounded, it can carry hazardous voltage potentials. INCREASED LEAKAGE CURRENTS Water is generally conductive. If you are working on a chassis and accidentally touch an energized contact, you may not experience any shock because there is no current path between you and the voltage source supplying the contact. Let us assume the contact is energized by a local AC mains. There is always SOME leakage current possible from where you are standing back to a grounded point. Usually it is a very small leakage. However, if you are standing in water, the leakage current is likely to be much higher, and you may experience a serious electric shock from your accidental touching of a contact. AVALANCHE EFFECT Water is generally conductive. If it enters a chassis with high power electrical components, it can instigate an avalanche of failure that results in the release of a lot of energy. For example, the water can provide a short circuit between two potentials. As it carries current, the water may heat up quite rapidly, in doing so it creates steam. The effects of the heat and steam may then provide an even lower resistance path for additional current flow...and so an avalanche of conductivity (from less conductive to more conductive) is started... I welcome any comments and additional "generic" scenarios. Regards, Jason Mallory Product Safety Consultant. -- __________________________________________________________________ Your favorite stores, helpful shopping tools and great gift ideas. Experience the convenience of buying online with Shop@Netscape! http://shopnow.netscape.com/ Get your own FREE, personal Netscape Mail account today at http://webmail.netscape.com/ ------------------------------------------- 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: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson: pstc_ad...@garretson.org Dave Heald davehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: No longer online until our new server is brought online and the old messages are imported into the new server. ------------------------------------------- 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: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson: pstc_ad...@garretson.org Dave Heald davehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: No longer online until our new server is brought online and the old messages are imported into the new server.
