Path: utzoo!news-server.csri.toronto.edu!cs.utexas.edu!yale!cmcl2!phri!news From: roy@alanine.phri.nyu.edu (Roy Smith) Newsgroups: sci.electronics Subject: Need to buy or build 3-phase recording kW meter Message-ID: <1991Mar5.161244.503@phri.nyu.edu> Date: 5 Mar 91 16:12:44 GMT Sender: news@phri.nyu.edu (News System) Organization: Public Health Research Institute, New York City Lines: 30 The building I live in (a 54 unit residential cooperative) is getting whomped by peak usage charges on our electric bill (last month was $650 in kWh charges and $350 in peak usage). Our peak last month was 18.0 kW (our average was about half that). I have been given the task of trying to figure out how to cut our electric bill. A few years ago, we got timers for all the lobby and hallway lights (which are more than half of our power usage) but while that cut our total usage, it didn't lower our peak any. What I'd like to do now is put a recording meter on our main power feeder and watch our power usage during the course of the day for a few weeks. What's the cheapest way to do that? I could go to the board and say "Look, if you front me $2000 for equipment, I'll find a way to save you $300/month in electric and you'll make back your investment in 7 months" but I suspect they won't go for it, so it's got to be something I can do out of pocket. I can probably scrounge up an old chart recorder, but I'm stuck for sensors. Any ideas? It has to be non-invasive (I can't interrupt the wire to insert a series-shunt ammeter) so I'm stuck with clamp-on meters. Are there clamp-on power meters that one can get cheap in these sorts of power ranges? I can get some clamp-on ammeters, and volt meters for each phase, but that I'll only get me kVARS, which isn't very useful for my purposes. Something built around a junk PC with a cheap A/D board might be feasable, if the sensor problem could be solved, but I suspect that if I could solve the sensor problem, a plain old chart recorder would be fine. -- Roy Smith, Public Health Research Institute 455 First Avenue, New York, NY 10016 roy@alanine.phri.nyu.edu -OR- {att,cmcl2,rutgers,hombre}!phri!roy "Arcane? Did you say arcane? It wouldn't be Unix if it wasn't arcane!"