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David R
03-13-2007, 05:23 PM
OK, I have been reseaching for a while. My shop has a single phase power factor meter. I am careful to shut off the compressor when I am using my wirematic 250 that draws 30 amps on higher settings. Now I am getting an invertec 350 that draws about 85 amps at 425 output.

I called the electric company and waded through a bunch of menues and finally got a real person. I asked the person how I was charged and she did a terrible job of answering me. I had to do it all over again to get another person. This one was nice and knew what I was talking about.

She told me they charge \$8.85 per Kilowatt. That would be maximum Kw. SO, I read my meter and it said 2.4 Kw. I have run my wirematic 250 at near max spray welding and it draws 30 amps. I may of only reached 25 amps because it wasn't all the way up. By MY figuring, Volts X amps = Watts. 220 volts, 25 amps = 5500 Watts, or 5.5 Kw. Maybe they only use one leg. I dunno.

They charge the \$8.85 per Kw and add that to the bill. I pay 9.2 cents per KilowattHOUR, PLUS the \$8.85 * 2.4 = \$21.24 added to my usage.

If this is right, the Invertec should use tripple that at max output, so that would add another \$42.48 PLUS the actual usage in Kilowatthours.

The lady told me if I don't go over 5 Kw in a year, they will take out my demand meter and put in a regular one. The rate per Kilowatthour would go up to 12.something cents.

Discussion invited
David

enlpck
03-14-2007, 09:02 AM
Do you mean peak demand meter?

What is the timebase for the meter? My shop has (about) a 15 minute cycle on the peak meter.

browny
03-14-2007, 04:32 PM
Although I am in Aus, it sounds like you have similar metering.

First off, volts x amps = total power. Total power x Power Factor = kW. I have no idea what the power factor of a welder is, but a transformer based machine could be quite low.

The way our metering (and probably yours) works is that it totals the energy consumption at time increments (eg 15min, 30min) as enlpck suggests. The demand is actually the average over this period. So if you are only welding for a small proportion of the billing interval, the meter will have a much lower figure than the max instantaneous power you use.

David R
03-14-2007, 10:59 PM
Do you mean peak demand meter?

What is the timebase for the meter? My shop has (about) a 15 minute cycle on the peak meter.

The lady told me its 30 minutes.

Browny, that could explain why the reading is lower than what I expect.

David