A meter reader always pays a visit to the building either on the first or second work-day of the month. He reads both the electric and water meter (both are inside the building and can't be read from the outside). I know that because we have to escort the reader to the utility room, and I'm the one that does it about 1/2 the time, and when someone else does it they tell me they did it.
There is never a month that goes by without someone coming to read the meter.
A volt-amp is a watt, when the load is resistive.
If I perform high-speed sampling of both the voltage and current, and if I multiply each reading together to get VA for each sample, and if integrate those VA samples over time, I will get the actual watts or KWh that I should be billed for. That would correctly take into account reative / inductive loads (like motors, light ballasts, computer power supplies, etc).
If I simply calculate watts as equal to VA based on the current measurement from a clamp-on meter, then I'm over-estimating what the billing meter is "seeing" because I'd be assuming that all my loads are resistive. In other words, my calculation of watts = VA can't help but assume that current and voltage are in phase with each other.
The billing meter knows how to calculate wattage correctly when the current and voltage is out of phase.
I guess a clamp-on amp meter that also had a couple of voltage probes so that it could simultaneously measure the voltage could measure true wattage would be needed.
As long as the watt-hour meter is working correctly.
Which seems highly suspect given all the info I've been posting here.
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.
...
Far too little real data to infer that (at least yet)... :)
I'd figure it's likely a combination of estimated or leveled billing w/ a catchup period annually and some tenant or group of tenants w/ loads you're unaware of.
Not that there aren't errors both in manual reading and that the meter can fault but generally those get caught in routine maintenance checks and if the meter were, as you say, replaced recently it's not a high probability.
Hmmm, You know what? You ought to monitor frequency. Usually it is not 60Hz, the lower it shows power factor is getting worse. Ideally load should be pure resistive which does not exist in real world. They are mostly inductive load. There is such a thing called Pf correcting device to improve efficiency. My SIL owns/operates mechanical moulding business based on CAD/CAM. His average monthly bill is pretty constant. The amount of monthly bill is pretty predictable. Other source of energy his plant use is NG, mainly for heating.
BOTH
I agree the billing usage numbers look very suspicious.. I would contact the power company, bypassing the regular customer service, by calling the chairman's office and working from there. You can usually get that sort of information from the investor information section of the stock listing for the company.
You're pushing a very big rock up a hill to nowhere. Your meter will give you little useful information. You need to KNOW the phase. Sticking your finger in your favorite orifice and pulling out a power factor number is just that...a useless number. You don't even want to think about the orifices you find here.
Why do you care? A decision tree is often helpful. If you think the equipment is faulty, you should enlist the power company. I've found 'em to be very knowledgeable and helpful. They have the equipment to determine whether your meter is faulty. A friendly conversation with customer service should get you a call from a real engineer. If it turns out to be faulty, make sure you get calibration numbers off the old system so you can negotiate a refund.
If you think they're intentionally screwing you, you need to hire an electrician with the equipment to measure WATTS. That's what you pay for. Measuring VA is an exercise in futility. Your "finger" ain't gonna hold up in court anyway.
You might be able to get some advice from the local electrical inspector.
If you think one of the tenants is charging their electric car when you're not looking, your amp meter can point you in the right direction.
I've used current clamps into a computer to log AMPS. Useful for determining relative consumption from the same load...in my case it was a water heater. RMS amps is better than peak or average amps, but still not a short path to WATTS...well, in the case of a water heater, it is, but that's a special case of resistive load.
Depending on how the power meter's made, you can get cheap wireless monitors that you might get the utility to let you clamp on the meter...but that will have the same systematic errors that the meter has. But it might help you find any clandestine loads at odd hours.
Newer digital readout meters have an infrared light that blinks in concert with the load. Mine is one blink per watt-hour. I programmed a pda to read out and log consumption in real time. Again, for my relative use. It has same systematic errors as the meter. But you still gotta be able to "see" the meter...or put a fiber optic cable to the outside.
You can buy clamp-on current transformers that also hook to the volts and measure REAL power accurately. But it's much easier to pick up the phone and have the power company help you.
The question about the 5% adder is one for customer service.
Did I mention...rock..hill...futility?
That error should be no higher than 10%. The billing meter is measuring power (watts) that is phase-corrected. My method (of just measuring current) is not phase corrected. So my calculation of watts will always be higher by 5 or 10%. If all the loads in the building were purely resistive, then my method should exactly match the billing meter.
The variability or error in actual device or appliance usage is (I would think) quite low, given that this is an office environment where the duty cycle (ie the on/off power cycle pattern) of all of the 15 or so computers is very regular and known, as are the lights.
The lights and computers probably account for 50 to 75% of the electricity usage, the rest being fixed electronic infrastructure (networking routers / switches / DSL modem, multi-function printer-fax, multi-line phone system) a few low-power exit lights, a couple out-door
75 watt out-door mercury vapor lights (on a mechanical timer), an 18 CF refrigerator, small microwave, a small capacity water distiller / chiller (instead of bottled water), a toaster, a couple of small bathroom ventillation fans wired to the bathroom light switches, the furnace fan (granted it's a large motor, 220 VAC and probably 1 hp) but it's not running all the time, a couple of radios.
Then I'd have a conversation with the electric company and ask them to explain how 4 months in a year can have the exact same usage, down to the hundreth of a kwh. And how there are two other month pairs where the usage is exactly the same down to less than 1 kwh. It's possible but the probablities are clearly very low. Even if you had a truly fixed load that never varied, you'd expect more variation than that due to some months having more days. possible and we could calcu
mike used improper usenet message composition style by unnecessarily full-quoting:
I should not see a huge spike in monthly usage during a month when our hvac usage is practically zero. Investigating the reasons for this spike is not path to nowhere.
An unnecessarily dramatic statement.
To say that a clamp-on amp meter can't give useful information is hyperbole.
To the extent that my aggregate power factor is less than .95 or .9, yes, then I need to know the phase.
Are you suggesting that my effective power factor is likely to be less than .9?
What is the power factor of 10 to 20 year-old florescent lamp ballasts? Or a 1 hp, 220 VAC fan motor? Or a 10 year old refridgerator? Or a typical desktop PC power supply?
Those are the largest (and probably only) non-resistive loads in question here.
Because I pay the bills. What a stupid ass question that was.
I've already stated that I've contacted them, and that I expect to encounter difficulty in having them ever admit that their metering equipment could be faulty or even undertake a process to evaluate the meter, but I will pursue every course of action and give them every chance to determine that.
In the pages and pages of materials and contracts that exist for this utility, describing all manner of service obligation and liability, billing, etc, I find nothing in print that defines a process whereby a billing meter is tested or what is done if a meter is found to be defective.
There is absolutely nothing I can find in writing even contemplating the possibility of a meter that does not measure correctly.
I believe that issue is a political "hot potatoe" for all municipal electricity suppliers, something they'd rather not have to deal with and hence they largely remain silent about it.
I believe that they never "intentionally" screw anyone, but that instead they put up a front that their meters are always correct, all the time, and reinforce that by not mentioning the possibility of erroneous meter operation anywhere in any printed material they make available, let alone define in writing a process or methods to test a meter that the client believes is suspect.
The worst I can do by measuring VA is to OVER-ESTIMATE my watts used by
5 or 10% - unless you think it's likely that my aggregate power factor is less than 90%.Making my own measurements would be a first-step. I never said I'd use those measurement in court (that is your hyperbole again).
If indeed it got that far, then I would investigate my options have having an acredited third-party measurement performed, and that would only happen if my local utility did not perform their own tests that I was satisfied was unbiased and accurate.
Jibe.
I know I sound pedantic, but I want you to look your best when complaining to the electric company, should it come to that point.
You should ask for a refund
Just for the heck of it go after hours and turn off your main breaker with friends watching building.
I had a customewr at a local shopping mall they had electrical troubles and found a connection from their meter powering public spaces in the mall, seemingly left over from the malls construction in the 60s. Tenants on that meter had been paying a big chunk of the malls electric bill..
This was identified one night when the customer had a fire. The fire department pulled the meter blacking out a big piece of the mall.
The mall claimed no knowledge:( I believe there was a lawsuit,,,,,,
@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
@Home Guy:
Ah, the true picture emerges -- an accounts payable rep who thinks that because they pay the bills they understand how everything works...
You clearly lack the technical expertise to do anything about this on YOUR side of the meter...
You seem to not understand the regulations which protect consumers and control how power is sold in your state -- therefore you are unaware of your potential remedies in this "situation" if one really exists...
Instead of spending your time researching something actually useful which might shed some light on what is actually going on (if anything really is at all) you have chosen to ask stupid questions which are clearly not on the proper wavelength to make any sense to someone who actually understands electrical issues AND you are chasing after something *YOU* can do which would support *YOUR* claim that your electrical meter is not functioning correctly when there may in fact be a procedure to follow which has already been defined by the public utilities commission (or equivalent in your state) which would almost always involve bringing in an uninterested third party with the proper credentials and equipment to assess what if anything is happening in this whole convoluted story...
It seems whenever you get some sound advise that would make sense in the real world, you attack the contributor because the person didn't respond with the specific answer you were looking for in your especially preferred format... So you critique based on newsgroup etiquette and posting format rather than the supplied content -- keep doing that and you will be properly labeled as a troll and written off as such...
~~ Evan
@bob haller:
That doesn't sound like it was a professionally managed "mall"...
Sounds more like it was being run by people like Home Guy...
All the malls I have seen inside of have entirely separate switchgear to power tenant versus house circuits...
~~ Evan
@Home Guy:
You are the one being the UseNet douche here guy...
Commercial electricity is metered based on peak demand I don't care where you are in the US, it is the way federal laws on the buying and selling of energy are written...
That first given established, you totally blew off the source of the *most* qualified electrical advice on this newsgroup supplied by RBM because you didn't like the 'format' of his posting method and so called 'etiquette' violations when your postings actual content is way out in orbit of some other planet...
Now let us address the specific issues you seem to be experiencing:
-- Your electrical meter is locked within a cabinet enclosure where *you* the consumer are unable to observe the cumulative readings on it at various points during the billing period to determine any abnormal usage issues...
That is *highly* abnormal for a meter to be locked inside a cabinet like that where the indicator of the amount of electricity you are going to be billed for is concealed from you... I would place a call to the local public utilities official and explain your situation and that your meter is hidden away from you where you can not read it but once a month when the power company unlocks its cabinet, that install does not sound kosher -- at the very least an observation hole can be made in the cabinet so you can see your meter...
-- Is there only *one* tenant in this "building" as it sounds like there is only one meter... That is an abnormal way to pay for electricity in a commercial building if there are multiple tenants irregardless of whether the lease terms are gross or net (NN) (NNN)...
With one meter all you would be able to do legally without some sort of sub-metering involved (the emon demon that RBM mentioned) is divide the total cost by the square footage of the building and apportion it to the tenants based on the tenant's square footage...
-- You are so caught up in the minutiae of how you can home brew a way to calculate your power use by simply calculating all the wattage of all the devices and appliances used in your occupancy that you seem blissfully unaware that many things require a "starting current" like your furnace motor and the ballasts for those exterior light fixtures on the mechanical timer -- with a commercial electrical service you get billed for the highest simultaneous demand for current as well as the simple kWh of usage...
It sounds to me like you have a lot to learn before you even attempt to dispute anything with anyone...
It is also waaaay to late to dispute charges for electricity billed like over a year ago -- there is usually a time limitation which covers when you can challenge a utility bill, I have never heard of one that let you go more than 60-90 days after the billing date to initiate a complaint...
Good luck man -- hope you can return safely to earth since you are clearly in orbit somewhere with all of this...
~~ Evan
That's a *BIG* assumption.
Yes, or you could just use the kWH meter the power company gave you.
That's what everyone has been telling you, yes. Did you actually read any of this thread?
...and it ignores harmonics. It's a smart little thing.
Nope. You're still reading VA, not watts.
Have them calibrate it (they're replace it with one that is calibrated).
Maybe *you* suspect it. They're really pretty good.
They can often get a limited refund from the power company, who will then add it back into the mall's bill. If not, a suit is certainly in order.
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