miller@dg-rtp.dg.com (Mark Miller) (03/03/91)
My house is starting to become littered with varistor equipped power-strips, and now little individual outlet jobbie$, in an attempt to keep some of my equipment from getting fried from AC line spikes. So I just had a thought: could you do something in the "fuse-box" and take care of the whole house in one fell swoop? Would it just be some heavy-duty varistors? How would you configure them, eg, one between the 220 volt line, and then 1 from each side of the 220 to ground? How much would this stuff cost? Thanks for any insight or speculation. Mark M. Mark T. Miller miller@dg-rtp.dg.com ...uunet!xyzzy!miller
whit@milton.u.washington.edu (John Whitmore) (03/05/91)
In article <1991Mar3.132431.22282@dg-rtp.dg.com> miller@dg-rtp.dg.com (Mark Miller) writes: > My house is starting to become littered with varistor equipped > power-strips, and now little individual outlet jobbie$, in an > attempt to keep some of my equipment from getting fried from > AC line spikes. > > So I just had a thought: could you do something in the "fuse-box" > and take care of the whole house in one fell swoop? The short answer is 'yes'. There are some very large surge absorbers available, which I've heard described as 'a grinding wheel with metal plates bolted to the sides'. It's not a joke, either; the silicon carbide in a grinding wheel makes a fairly well-behaved varistor. Some gas-discharge absorbers can also be found with HIGH current capabilities (kiloAmps); these are basically neon lamps with heavy-duty electrodes and high-temperature packaging. And there's at least one company that shows up at computer fairs with their magic box; they had a claim for something large (like 20 kJoules) that their box could absorb. They were quick to explain, however, that you would end up needing a new box after that. Lightning, of course, was the target. You will find, however, that none of these really wants to be in a box with any delicate wiring. If the thing really DOES get a surge, it will likely melt (and take the main fuse/drop wire with it). Also, you will need a good ground path to attach it to; in some locations that means burying a few square meters of copper mesh and pouring CuSO4 solution around it. Is your area plagued by power surges? I've never had much trouble in Seattle. Rural wires have longer runs between transformers (the power transformer is a very good surge barrier), so get more significant surges. Microsecond excursions to 700-2000V are not uncommon. John Whitmore
lrk@k5qwb.UUCP (Lyn R. Kennedy) (03/06/91)
whit@milton.u.washington.edu (John Whitmore) writes: > In article <1991Mar3.132431.22282@dg-rtp.dg.com> miller@dg-rtp.dg.com (Mark M > > > My house is starting to become littered with varistor equipped > > power-strips, and now little individual outlet jobbie$, in an > > attempt to keep some of my equipment from getting fried from > > AC line spikes. > > > Is your area plagued by power surges? I've never had > much trouble in Seattle. Rural wires have longer runs between > transformers (the power transformer is a very good surge > barrier), so get more significant surges. Microsecond excursions > to 700-2000V are not uncommon. > > John Whitmore I was at a friends house once when the air-conditioner came on and the lights went brighter rather than dimmer. He said it always did that, so i went with him to the breaker panel. A short examination and I pulled the main switch. We spent an hour or so repairing the neutral wire which fixed the problem. If your house is wired for 110-220 and some voltages increase when things start up, you may be in big trouble. Problems with the neutral wiring can set the place on fire. Not trying to scare you but play it safe. --------- 73, lrk utacfd.utarl.edu!letni!rwsys!kf5iw!k5qwb!lrk P.O. Box 5133, Ovilla, TX, USA 75154