A Gas Tube Arrestor is better suited to telephone lines and RF coaxial cables than to 120 VAC AC power lines. If used on AC power lines, when fired, they will produce a "bolted short" and cause a great deal of current to flow. This is not a good thing!
Some computer accessory suppliers vigorously market surge arrestors as a must-have accessory, and the American public is being brainwashed. In fact, most computer circuits do not benefit from surge arrestors, and some power strips that include surge arrestors are banned by many large companies as being prone to catch fire. The gray plastic, half-moon-shaped power strip made by APC is known to be a fire hazard, and my employer (Boeing) banned them after the second fire incident. In each incident, the MOV spontaneously overheated and melted the plastic case, which then caught fire. Fortunately, the damage was limited to the wooden shelf it was sitting on in one case, and some scorched carpet in the other. As a result of these two incidents, the CPSC recommended that any power strip be made of metal rather than plastic, and further, that the plug strip containing a surge suppression device always be placed upon a non-combustible surface. A word to the wise... 73, Eric Lemmon WB6FLY -----Original Message----- From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of kq7dx Sent: Wednesday, June 09, 2010 11:43 PM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Re: MOVs for power supply primary Instead of MOVs, how about a gas discharge tube [GDT]. OR Possibly in parallel with the MOV. They are small and metal and the specs say they can take quite a few discharges and not break down.. Anyone use those? Thank you for all the replies and info on my subject!.. 73 --- In Repeater-Builder@yahoogroups.com <mailto:Repeater-Builder%40yahoogroups.com> , "Jeff DePolo" <j...@...> wrote: > > > Hmmm. That's a tougher one. Mostly I use the Polyphasers (PLDO-120US-15A > or -20A) at sites that don't have facility-wide protection. The TrippLite > Isobar Ultra series is another (ISOBAR8ULTRA et al). The Isobars also have > a $50,000 equipment warranty (can't say I've ever had to use it, don't know > how much red tape there is to go through). I like the Polyphasers because > it's designed to mount to a ground panel/bus bar, so I mount it to the bus > bar that has all of my other arrestors (coax, telco, etc.) on it to provide > a common-point ground. The Isobar doesn't have provisions for direct > grounding - it relies only on the equipment grounding conductor in the AC > cord, but the TrippLite has arguably better EMI/RFI filtering than the > Polyphaser. > > --- Jeff WN3A > > > > -----Original Message----- > > From: Repeater-Builder@yahoogroups.com <mailto:Repeater-Builder%40yahoogroups.com> > > [mailto:Repeater-Builder@yahoogroups.com <mailto:Repeater-Builder%40yahoogroups.com> ] On Behalf Of Chuck Kelsey > > Sent: Tuesday, June 08, 2010 4:48 PM > > To: Repeater-Builder@yahoogroups.com <mailto:Repeater-Builder%40yahoogroups.com> > > Subject: Re: [Repeater-Builder] MOVs for power supply primary > > > > > > > > OK, I should have been more specific. What would be a > > reasonable unit for a > > repeater site that may have only a couple thousand dollars worth of > > equipment inside? > > > > Chuck > > WB2EDV > > > > ----- Original Message ----- > > From: "Jeff DePolo" <j...@... <mailto:jd0%40broadsci.com> > > > To: <Repeater-Builder@yahoogroups.com <mailto:Repeater-Builder%40yahoogroups.com> > > <mailto:Repeater-Builder%40yahoogroups.com> > > > Sent: Tuesday, June 08, 2010 4:22 PM > > Subject: RE: [Repeater-Builder] MOVs for power supply primary > > > > > > > > Probably the ones I've had the most luck with are the > > Islatrol series from > > > Control Concepts. I think they have been bought out by > > Emerson or Liebert > > > or one of the other companies that have power divisions. > > Anyway, they > > > call > > > these "active tracking filters". They not only are TVSS's > > but also filter > > > noise, low-amplitude spikes, etc. Right now I'm typing from > > a mountaintop > > > site (broadcast) that we re-built a few years ago. We put > > in an Islator > > > I-2100 (120/240V single-phase). The old equipment shelter > > which had been > > > here since 1990 had the same model unit. In the 15+ years we've been > > > managing and maintaining the site, we've had zero > > surge-related failures, > > > and this site sticks out like a sore thumb as far as > > lightning goes. In > > > the > > > last few years I've used the same series of arrestors for > > new site builds > > > at > > > a dozen sites or so and have had no power-related problems. > > > > > > Others that make comparable-quality products include > > Joslyn, Transtector, > > > and Innovative Technologies. > > > > > > There is one big difference (to me anyway) between TVSS's, > > that being > > > whether they are the series or parallel type. Series type takes the > > > utility > > > service (or transfer switch output if there's a generator > > too) as its > > > input, > > > and provides a protected output to feed the panel(s). > > Parallel type is > > > typically connected to a breaker in the panel, which puts > > it in parallel > > > with all of the loads. I much prefer series. Parallel type > > can be less > > > effective because a) there will always be some inductance > > and resistance > > > in > > > the wiring between the panel and the protector, b) if the > > TVSS conducts, > > > there's a good chance it will trip the breaker in the > > panel, resulting in > > > no > > > protection until the breaker is reset, and c) they are much > > less effective > > > as a noise filter. The upside to parallel type is they can > > easily be > > > added > > > at any time just by popping breakers in the panel and feeding the > > > arrestor. > > > Series, on the other hand, are in-line with the service > > conductors, so if > > > you want to add one (or repair one), you have to take the > > service down. > > > Series tends to also be more expensive, especially for > > three-phase and > > > unlike parallel type, the price goes up as the current > > rating goes up for > > > obvious reasons. > > > > > > A good 200A single-phase arrestor of the ilk I'm talking > > about starts at > > > about $1000 and goes up quite a ways from there. I think these > > > single-phase > > > I-2100's were in the $2000 range. I recently spec'ed a > > 120/208 3-phase > > > Transtector (parallel type) for another site where I'm much > > less concerned > > > about power-wise, and that was about $1800. No cheap, but > > where you're > > > protecting equipment in the 6 and 7 figure range, it's a > > no-brainer. If > > > you're repeater is a Micor mobile and an Astron, it might be hard to > > > justify... :-) > > > > > > --- Jeff > > > > > > > > > > >
