# Estimating KWh electicity billing using clamp-on amp meter

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• posted on May 30, 2011, 5:53 pm

@Home Guy:
Get a clue, 100-amp is *NOT* the smallest installable utility service... It is for houses and buildings but it is not the smallest size of electrical service available...
Traffic signal boxes generally have a 30-amp service and there are pole mounted equipment cabinets for cable companies that also have small services in the way of 30-amp/40-amp single phase...
~~ Evan
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<%-name%>
• posted on May 30, 2011, 1:40 pm

Don;t know how it works where you are, but both the cost of the energy and the delivery costs, which are seperated out are significant parts of my bill.
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<%-name%>
• posted on May 28, 2011, 8:21 pm

since the white return wire returns the current from all 3 phases,wouldn't that give you the sum of all the currents? Perhaps a more accurate measurement of total power than the other way.
--
Jim Yanik
jyanik
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<%-name%>
• posted on May 28, 2011, 8:26 pm

It would seem to me that if the one white return wire returned the current from all 3 phases it would have to be one hell of a conductor.
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<%-name%>
• posted on May 28, 2011, 8:38 pm
wrote:

No, the neutral only carries the imbalanced load, which is why it is allowed to be smaller than the ungrounded legs
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<%-name%>
• posted on May 28, 2011, 8:42 pm

no the white wire returns only the UNBALANCED current
I agree the OP should gain access to the real meter so he can read the meter say once a day and find out what is going on.
Mark
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<%-name%>
• posted on May 28, 2011, 9:38 pm

Only the *difference* of the three phases is returned in the neutral. With a balanced load there will be zero current in the neutral.

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<%-name%>
• posted on May 29, 2011, 12:52 pm
On 5/28/2011 4:21 PM, Jim Yanik wrote:

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<%-name%>
• posted on May 28, 2011, 3:09 am

**You need to put 3 clamp on meters on the wires and monitor them continuously over the desired period of time, which still won't be accurate because they won't give you the peak demand. If you have some reason to believe that the utility company equipment is faulty, you can request that the utility company hang a testing meter to verify the accuracy
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<%-name%>
• posted on May 28, 2011, 3:47 am

idea how much they cost to buy or rent.
We took amp measurements on a parallel run of 3-500. I was amazed that supposedly equal lengths of copper varied as much as 25 amps on the same phase.
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<%-name%>
• posted on May 28, 2011, 10:48 am
wrote:

** That's the sort of meter that the utility company hangs on the service to test the accuracy of their equipment
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<%-name%>
• posted on May 28, 2011, 3:22 am

There is no special math, but I'd wonder just how accurate your number is going to be. Don't for get about seasonal changes too, more lighting in winter, AC in summer, etc. At work, I take readings on some of our utilities daily, others, monthly, and can spot a trend when correlated with material used on a given day, etc. This will often tip you off as to problem areas and waste when you see aberrations from the norm.
Have you talked to the utility company? Some will do the work for you and put a recording meter on the line for a week or two to get you want you want. Your approach, of course, is in the interest of energy conservation. They are big on selling you less these days.
Reading the meter on a daily basis would be a help to determine trends also. Perhaps they will allow a window to the meter so you can take readings.
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<%-name%>
• posted on May 28, 2011, 4:08 am
Ed Pawlowski wrote:

Yes, I have contacted the "front-line" customer service people and expect to hear more from someone more technical or in more authority (or at least someone more "male") next week.
Our last bill was for 5,160 kwh, with a billing period from april 5 to May 4. The previous month (March 5 - April 4) was 1915 kwh.
Infact, looking at the last 12 bills I see some very suspicious things:
5162.41 April 1915.26    March 1582.17 Feb (meter changed end of Feb) 1998.53 Jan 2011 1915.26 Dec 2081.8 Nov 2664.7 Oct 1498.9 Sept 3414.15 Aug 3913.78 July 1998.53 June 2248.34 May 1915.26 April 1915.26 March 5162.86 Feb 3247.61 Jan 2010 2331.62 Dec 2009
Our meter is always read on the first business day of each month. The meter was changed at the end of February. The old meter was electronic (it had a digital LCD readout). The new meter *I believe* is different in that it can do time-of-use measuring and it can do RF (wireless) data transmission. Time-of-use billing is not yet being performed in our area, and at least for our new meter a person is still coming around to read it.
I note that I see 1915.26 show up suspiciously 4 times during the past year (what are the odds that we'd use the exact same amount of electricity for any 2 months, let alone 4?).
It was the large jump from 1915 to 5162 that tweaked me on this and I had an assistant enter all previous numbers from other bills in a spreadsheet. The large spike back in Feb 2010 to almost exactly the same number of 5162 is also suspicious.
I would have expected our electricity use to decline from March to April given a reduced furnace on-time in April vs March.
I have no idea what remedy or proceedure my utility company follows in disputes of this nature. I have the vague idea that they circle the wagons and defend their meters to the last drop of their blood, and that the laws or service contracts may favor them and not the customer. We shall see.
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<%-name%>
• posted on May 28, 2011, 5:02 am

You are correct in being suspicious. My findings from tracking electric, July and August are the highest, January is second highest. There will be a curve on the months between. Winter is high because of running heat and more lighting, then it comes down as you approach spring, then goes up again as the AC use kicks in. Then in September, it comes down then back up for winter use.
I can understand with the old meter that you'd possibly get 4 identical readings if the meter was not read and the bill was estimated. Actual readings, I'd say "no way" you'd have that situation at that use. We do have one tenant that uses very little electric and the meter was originally installed for some machines. It has a multiplier Most bills are the same, in increments of \$18. A few a year are \$36. Another has bills in the \$400 to \$800 range and follows the curves a I outlined.
A couple of possibilities I can think of. The meter is incorrect. (yes, it really does happen) A tenant is carelessly leaving on a space heater. a tenant is running both heat and AC out of stupidity, not a maintenance problem. You have some other pump or device that is running all the time.
Good luck and please keep us posted on what happens.
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<%-name%>
• posted on May 28, 2011, 1:03 pm
Smitty Two wrote:

It's a start.

The main disconnect switch before the meter is name-plate rated at 400 amps. It doesn't mean we're going to ever draw that much.

I know exactly what equipment is in the building - I work there.

I talk to them every day.

What-ever.
Another example of a usenet post that starts with a question, and devolves into "why are you asking?".
I have to waste more time explaining why I want to do something or why I want certain information about measurement techniques, and instead I get a bunch of arm-chair blow-hardts that think they know better.
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<%-name%>
• posted on May 28, 2011, 1:23 pm
On 5/28/2011 9:03 AM, Home Guy wrote:

Poor you and that incredible amount of time you wasted reading three posts after you clearly described you already know and presented everything anyone needs to know and everyone didn't catch on that no questions are allowed and no opinions are wanted..
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<%-name%>
• posted on May 28, 2011, 1:49 pm
George wrote:

No. Poor usenet.
Poor every future poster to any newsgroup that asks a simple technical question and gets told by the peanut gallery that it's important to know all the ancilliary circumstances surrounding the question when in reality in the end those circumstances have no bearing on the question or it's answer.
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<%-name%>
• posted on May 28, 2011, 5:41 pm

@Home Guy:
It is a poor craftsman that blames the tools...
Ask a question based in this reality (rather than your fantasy which is filled with gaps in your practical knowledge that someone could drive a box truck through) and you can get an answer...
Ask a fishy question that doesn't sound right to people who *do* know, and they will want to know more about the situation before they chime in with their opinion...
You very poorly defined your "issue" to begin with and then you focused on techno-babble and ill-advised methods to attempt to monitor your power usage... When there are devices that are purpose made and could be bought and installed in any panel whose power consumption you wish to monitor...
~~ Evan
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<%-name%>
• posted on May 29, 2011, 12:49 pm
On 5/28/2011 9:49 AM, Home Guy wrote:

Not at all. If you walked into a room and presented your "novel" ideas to folks who have a clue and understand what could be done and why your ideas make very little practical sense they would respond in the same fashion asking "why" in order to discover if there was something you didn't convey or to offer a better idea.

See above.
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<%-name%>
• posted on May 29, 2011, 4:10 pm

I'd agree with you if you were right, but in all likelihood, you are not. I've been hanging around USENET for about 15+ years now. I've seen too many question asked, answered, and later find that the real answer is something far different because important facts were left out.