Dear Jeff, I believe the reason for not responding is mainly because you do not specify the category of the equipment. If you had specified the category of the equipment (example: Medical) and the intended use (example: paitient applied part) then I believe you would have received more responses!
In regards to water fittings and associated tubing, if they can withstand 5 x the pressure available at the fittings, they are considered safe; otherwise, you would need to provide splash guards or some form of protecting live parts from becoming wet. Remember that for North America, by designing your circuitry to be suitable for Class 2 wet locations in accordance to the US NEC and the Canadian Code of Regulations can exempt you from providing additional protection. I believe that here we are talking about a voltage of 21.2 V peak. In Europe, this limit is lower. Some research is needed. Regarding supplemental grounding, I believe it is only necessary if your porduct is cord-connected and not permanently wired. This is because for cord-connected products, you cannot always rely on the earth (ground) connection. Silly people are likely to replace plugs and not connect the earthing connection. It looks like you have some interesting questions. Again, know your standard and then apply the requirements. If in doubt, get a good consultant to help you out. If this is an innovative product that does not fall within the scope of some of the international safety standards, I would suggest you look into similar standards. For example, the UL Standard for Spas in the US is an excellent standard to look into. It is one of few safety standards which involves water and elecricity. You bet, I always check if a Hot Tub or Jacuzzi is Listed before I jump in! From: "JENKINS, JEFF" <jeff.jenk...@aei.com> To: "JENKINS, JEFF" <jeff.jenk...@aei.com>, "'emc-pstc'" <emc-p...@ieee.org> Subject: RE: water-cooled electrodes Date sent: Fri, 13 Nov 1998 11:26:54 -0700 Send reply to: "JENKINS, JEFF" <jeff.jenk...@aei.com> > Hi all, > > I have received no responses to the original e-mail copied below. This in > itself is rather interesting and I would like to know why, so if any of you > have opinions on this, I'd like to hear them. My assumption is that there > have been no responses for one or more of the following reasons: > > (1) Such knowledge is considered a market advantage and is proprietary; > > (2) No one in the group has knowledge pertaining to this subject; > > (3) People are queasy about the subject; > > (4) The query was lengthy and people did not have the time to respond (quite > understandable); > > (5) The query was unclear; > > (6) For some mysterious reason, the e-mail didn't reach anyone in the group > but me and my colleague at Advanced Energy. > > Anybody want to take a stab at this? > > Regards, > > Jeff Jenkins > Senior Regulatory Compliance Engineer > Advanced Energy Industries, Inc. > Fort Collins, CO USA 80525 > > Opinions are my own and not necessarily shared by Advanced Energy > Industries, Inc. or its affiliates. > > -----Original Message----- > From: JENKINS, JEFF > Sent: Wednesday, November 04, 1998 2:07 PM > To: 'emc-pstc' > Subject: water-cooled electrodes > > > I would like to know if anyone in the group has been involved with the > AGENCY APPROVAL of a product containing a water-cooled live electrode or > coil, and what had to be done to make this safe in the eyes of the agency. > My company is occasionally involved with this sort of thing, and some feel > that we are being overly conservative and perhaps unnecessarily burdening > our products with extra cost. To date we have only CE-marked such products > and have had no third-party involvement. > > Partial list of concerns: > > (1) Is it considered necessary to completely isolate the water-cooled live > component from circuitry by locating it in a separate chamber? > > (2) Single-fault safety when circuitry is in the same enclosure as the coil > -- if the tube ruptures and the box fills up with water, this is a hazard as > water is rightly considered a conductive element. Drains are sometimes used > to avoid this, but there is still the problem of water spraying. Splash > guards and the like may be used but this involves some expense. Is copper > tubing considered inherently unsafe, i.e. something that is expected to > rupture? > > (3) If we use de-ionized water (and stainless steel tubing to avoid the > copper corrosion problem), can we assume the water acts as a protective > impedance? Could we prove this by filling the chamber with de-ionized > water, applying RF, and measuring the leakage current? How much RF leakage > current is permissible? > > (4) Are water fittings considered inherently unsafe? We have been unable to > find any agency-approved fittings. > > (5) Has anyone considered (or accepted) putting a ferrite around the water > tubing to form an inductor, thus limiting the RF current in the water? Or > coiling the tubing to create an air-core inductor? > > (6) I once received an RF burn from an experimental system with a > water-cooled cathode. This was in a crude garage shop atmosphere (not our > company). The cathode was immersed in water that was sourced from a faucet, > so it was ordinary tap water. The supply was 400kHz, 5kW. The water supply > hose was ordinary garden hose. Between the faucet and the cathode were two > lengths of garden hose with brass fittings. I inadvertently touched the > fitting that connected the two hoses together, about ten feet from the > cathode. The only grounding at the time was whatever was achieved at the > faucet. We later provided some grounding at the fittings and supplementary > grounding at the faucet. All this prompts the question: Is it considered > sufficient protection if the bulkhead fittings are fitted to a grounded > enclosure? Are starwashers or the like required? > > (7) Is it necessary to provide a SUPPLEMENTARY ground for the enclosure > containing the water-cooled coil/electrode? > > (8) What if, instead of running water THROUGH the coil, the entire coil is > IMMERSED in water in a metal enclosure? Would double ground > connections be sufficient, assuming the leakage current is within allowable > limits? > > (9) Is it allowable to connect neoprene hose to the coil? I have some > doubts about neoprene's capacity to withstand RF fields. What hose > materials would be considered safe/reliable? > > (10) Is a drain required? If so, must it be large enough to drain the water > at the maximum rate at which it could accumulate, or is the pressure relief > provided by the drain sufficient? Then there's the question of equipment > orientation . . . must a drain be provided to serve each potential physical > orientation of the installed equipment? > > These are just a few of the questions that have come to mind as I've > considered water-cooled systems in the past. I would appreciate your inputs > on these and other related issues you may think of. > > Thanks for your time, > > Jeff Jenkins > Senior Regulatory Compliance Engineer > Advanced Energy Industries, Inc. > Fort Collins, CO USA 80525 > > Opinions are my own and not necessarily shared by Advanced Energy > Industries, Inc. or its affiliates. > > --------- > This message is coming from the emc-pstc discussion list. > To cancel your subscription, send mail to majord...@ieee.org > with the single line: "unsubscribe emc-pstc" (without the > quotes). For help, send mail to ed.pr...@cubic.com, > j...@gwmail.monarch.com, ri...@sdd.hp.com, or > roger.volgst...@compaq.com (the list administrators). > PETER S. MERGUERIAN MANAGING DIRECTOR PRODUCT TESTING DIVISION I.T.L. (PRODUCT TESTING) LTD. HACHAROSHET 26, P.O.B. 211 OR YEHUDA 60251, ISRAEL TEL: 972-3-5339022 FAX: 972-3-5339019 E-MAIL: pe...@itl.co.il Visit our Website: http://www.itl.co.il --------- This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, j...@gwmail.monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
