On Thursday 05 February 2009, Guy Sotomayor wrote: FWIW, I've seen 120/240V split-phase DEC PDUs, and have them still, but I'm not 100% sure that they weren't modified 120V single phase ones. I think they were used with some systems that had 240V powered Trident disk drives. I don't remember excatly what model, but some model of 861 PDU sounds about right. Pat -- Purdue University Research Computing --- http://www.rcac.purdue.edu/ The Computer Refuge --- http://computer-refuge.org

On Thu, Feb 5, 2009 at 1:37 PM, Mr Ian Primus <ian_primus at yahoo.com> wrote: Thank you! Very informative. Since the machine was described as being about a half-rack and having a CPU module 8-10" high, I don't think it's a 70. John -- "I've tried programming Ruby on Rails, following TechCrunch in my RSS reader, and drinking absinthe. It doesn't work. I'm going back to C, Hunter S. Thompson, and cheap whiskey." -- Ted Dziuba

IIRC, an RA81 disk has an inrush spec of 80 amps for a time period measured in seconds. Ok, so you don't want one of those anyway. :) De

--- On Thu, 2/5/09, Dennis Boone <drb at msu.edu> wrote: Hehe... The RA90 disks I use on my Vax 3900 are somewhat similar. I can only run one at a time on the circuit I've got the thing hooked to. And I have to be real careful when I spin it up, to ensure that the lights and the TV set are both turned off. And even then, sometimes the thing will run for an hour and then *fump* whirrrrr........ as everything in the room is plunged into blackness. But, then again, I've got a lot of other junk on that circuit... -Ian

On Thursday 05 February 2009, Dennis Boone wrote: that, unless it's 80 amps for less than 1/2 second or so... which it could be. I think I measured a maximum of 30-40A off of the RA82, but that was with a digital (clamp-on) current meter, so it's possible or likely that it spiked higher than that. In any case, you can have a fairly high inrush current on a fairly small circuit breaker before it'll trip; just look at the specs for a circuit breaker sometime. Square D for example has these in their online PDF catalog stuff. And, this makes sense because the breaker is designed to trip based on how much the wiring is heating up... 20A ( * 80%) continuous load will warm up the wire a lot more than an 80A inrush for a second or two. Pat -- Purdue University Research Computing --- http://www.rcac.purdue.edu/ The Computer Refuge --- http://computer-refuge.org

On Friday 06 February 2009, Christian Corti wrote: I'm sure that De's specs were for a 120V circuit. With a 200-240V circuit, the draw should be about half. Also, an RL02 and TU56 draw next to no power; i'd be surprised if both of them together draw much more than 1 amp while running, off of ~240V power. Also, I've always wondered if at "16 amp" circuit in Europe isn't really the same as a "20 amp" circuit in the US; here you're supposed to not load a circuit to more than 80% of the rating for a continuous load, which works out to 16 amps for a US 20 amp circuit. Is there anyone here with electrician-type experience outside of North America that can give me an answer to that? Are you allowed to run a "16 amp" circuit with 16 amps of continuous load? (Not surprising though I guess, at least one electrician at work here insists that you are allowed to draw 100% of the fuse/breaker rating continuously, though I've looked it up and it's definitely not allowed by code.) Considering that they're RA81s, their HDA is likely to be in a condition where they're more useful as scrap (or spare parts for other drives) than as an actual RA81. :( At least RA82s in my experience haven't had the same problems that RA81s had. Pat -- Purdue University Research Computing --- http://www.rcac.purdue.edu/ The Computer Refuge --- http://computer-refuge.org

On Friday 06 February 2009, Christian Corti wrote: Nor did you mention that you're in the majority, but I was able to figure it out with a little deductive guesswork. :) Well, here everything is rated for "20 amps" and labelled as such, but there's a difference between continuous load (eg, lights or appliances that are continuously on, such as emergency lighting, or computers in some cases), and intermittent load (eg, a vacuum cleaner, kitchen appliances, etc). You're allowed to use the full rating for intermittent loads, but only 80% of the rating for continuous loads. The theory here is that an intermittent load will have enough off time to keep the wires from heating up as much. Like I said above, there's different kinds of loads. If you have a device that draws 25 amps, but only on 1/2 of the AC cycles (eg, because it uses a half-wave rectifier), it should be able to be safely run off of a 20 amp circuit. Also, most fuses don't instantly pop when the current through them exceeds their rated value, and there's special types of fuses (motor/time delay) that are designed to handle a much higher current than their nameplate rating for a short amount of time. Circuit breakers are generally even more like this, containing an element to instantly trip over a certain value (the "short circuit" threshold), and a time-delay element that trips the breaker when it heats up enough. I guess the best way to describe them is as a "leaky integrator", with a trip point measured in amp-seconds. Things like the 80% rule that I mentioned are there so that electricians have a guideline for what size circuit to put in, without having to do a lot of high-level math (in effect modelling the circuit characteristics) to figure out what rating the circuit needs. They probably are worthwhile to pick up, then. I'm surprised that a dealer hasn't gotten to them by now... I know at least one dealer on this list (but in the "wrong" country for the offer :) that was interested in RA82s at some point within the past year or two. Pat -- Purdue University Research Computing --- http://www.rcac.purdue.edu/ The Computer Refuge --- http://computer-refuge.org