Way OT electrical question

[Doug Miller]

Yes, except that "correctly" means comparing long-term averages, not two individual days as you suggested originally.

Your sig is still malformed. Just thought you'd like to know.

[Lumpy]

Lump:

Doug Miller:

Again, other factors don't figure in if the only variable is the machine on or off factor.

January or August, night or day. The machines draw XX current. Do the experiment for two days or do it for 90 days and divide back to get single day figures.

Machines draw XX amps when continually running and not used. Machines draw ZZ amps when shut off then back on 59 minutes later.

Only factor at all I can see skewing the results would be if some workers came back early from lunch and turned their machines on. That would probably be mitigated by other workers returning late.

The guy is looking for a reason to suggest that they either leave them on or off during lunch. I don't think he's looking for the ability to guess within 3 cents how much they'll save. It's the general trend that counts.

Lumpy

You Played on Lawrence Welk? Yes but no blue notes. Just blue hairs.

[Rick Frazier]

One of the things only hinted about is the number of these presses (and "other loads") that would be restarted after lunch/break. several lifetimes ago, when I worked in a mill in the early 70's, the mill couldn't start all of it's equipment at the same time or they'd actually drop the main fuses feeding the transformers to the facility.... Sounds really odd, but the startup currents were so great in proportion to the running current it happened more than once while I worked there. Initially, they seemed to rely on the variability of the workers in solving the problem, IE, you'd find the people that worked there the longest tended to take the longest time to "get ready" and finally power up their machines, while the newbies would be hitting the switch nearly as soon as the whistle went off... Many of the big machines had manually operated starting switches, so the operator would pull the lever on the fusebox/starting switch, hold it until the motor spun up most of the way, then slam it to the operating position. Too early and the motor either failed to "catch" or it blew the fuses. It never seemed to hurt to hold it in the start position a few seconds longer, but you'd get some really strange looks from the millwrights if you did...

So, in a nutshell, there are a LOT more variables to stopping and starting larger mill/machine shop operations than you might originally think about... The cost of idling over lunch may be a small cost to pay (even if the electricity costs more than shutting the machines down) compared to the amount of lost work time (labor) if the machines don't all come up right away after the break....

Thanks

--Rick

[Doug Miller]

Trouble is, you don't know what other loads might be in use elsewhere in the building -- suppose one of the two days you decide to conduct your experiment happens to be the same day that the welders are working through lunch on a major rush project. That's certainly going to skew your meter readings. Taking averages over a longer term is the only way to make sure that you've removed normal day-to-day variation from the analysis.

Your sig is still malformed. It should be preceded by two hyphens, a blank, and a newline, so that conforming newsreaders will recognize it and automatically omit it when quoting.

[Larry W]

If you can persuade management to cooperate in an experiment, the simplest method is probably to check the meter while all the motors are idling, then shut them off and check it again. By counting the revolutions of the spinning disk in the meter during a fixed time (one minute should be plenty) and using some arithmetic the power savings can be calculated. Sometimes the necessary info is printed on the meter itself, if not the utility co. can tell you what the conversion factors are.

[Lumpy]

Of course that's a potential factor. So when you do the experiment, or when you interpret the findings, you do as any good experimenter should and try to reduce or eliminate the other variables. When the figures tend to show something you ask "were the welders working on that rush project then?".

My sig is formed exactly the way I want it formed.

Lumpy

You were able to retire by doing all those voices? Yes. You don't see me punching a clock, do you?

[Larry W]

In some places I've seen (of course not MY shop :) ), this setup would leave many employees sitting in the dark!

[Doug Miller]

Which means measuring over a long enough time period to eliminate, or at least reduce to insignificance, the effect of random events on the quantity being measured.

[dave]

why are you giving the employees off for lunch? cant they eat a sandwich while they're working ;-)

[Doug Miller]

Naah, it gets mustard in the punch presses. Corrosive, you know.