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  1. #21
    jim rozen is offline Diamond
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    Sean, it sounds to me like the current sensing
    equipment you want to add, will exactly duplicate
    the utility's meter.

    Seems to me you could simply read that meter,
    and learn what you need to know.

    Wouldn't it be better to put current sensing
    devices on the load side of various breakers
    in the panel? You could easily do that with
    minimal effort.

    Jim

  2. #22
    chadillac is offline Hot Rolled
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    Reading the meter is not the same, if he's interested in isolating the critical loads, UNLESS he has the luxury of being able to turn off EVERYTHING in the building except the item in question and leave it that way for an extended period of time, so that the meter reading would correspond to only that load. Very unlikely.

    It sounds like a smart way to prioritize where to spend your money on insulation, equipment upgrades, etc.

    I've been trying to do that on a much smaller scale at my house for some time now. I got one of those "kill-a-watt" meters that you plug your refrigerator or tv into and it tells you how many KwH of energy get used over some period of time - typically leave it on for a couple of days. Cost about $30 IIRC. Nice to see that my refrigerator costs about $6-7/month to run, widow A/C units about $30-40/month during summer. Only downside is that it's only good for 110V outlets. A little bit of a PITA to rig up on an actual circuit, but it can be done. I'd really like to hook it up to my 230V electric furnace for the house heat, but it's beyond the capabilities of my little meter.

    Yes, a DMM can be hooked up and power calculated while the item in question is operating, but unless you have high-tech logging capability, you end up making assumptions about duty cycle in order to estimate cost of operation.

  3. #23
    JST's Avatar
    JST
    JST is offline Diamond
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    The two items of interest about the meter are:

    1) Can it be read to a reasonably small load amount..... i.e can you get a power reading from it in any sensible time.

    2) Is it actually reading right.

    The first may possibly be answered by seeing the meter face in detail.

    The second can be answered by turning on ONE thing that has a decently well known power draw. Then one sees if the meter reading corresponds well enough to it in kwh.

    The one possible advantage to the added meter is a faster feedback of energy useage rate.

    But adding that meter will be a problem. The clip-on type portable meter setup would be lots better.....

    Which brings me to another point.........

    I did this once on a 480v panel that was live... I wore a rain coat, pant, heavy rubber gloves and boots. I wrapped the heck out of my tools with tape and proceeded by standing intentionally off balance.
    Not the smartest thing to admit, but hey... I don't skydive.
    This is best answered by song lyrics.... " don't ask me what I think of you, I might not give the answer that you want me to....."

  4. #24
    Sean S's Avatar
    Sean S is offline Titanium
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    Gary, I know that just turning off the lights seems like the simple answer. I don't know what to say except that I bet if you were here and could experience the wiring, and how many different things are going on, and how many sub panels I have, and how *they* are wired, that you would sympathize a bit more with my dillema and understand why I am trying to get this data from a single source (the mains).

    Jim, the problem with the utility meter is that it only displays accumulated Kwh, not real-time load. It would be difficult to isolate groups of devices and in some cases even an individual device without days of tracing wires and removing dozens of sub panels.
    As an example, I would like to know not only what a heater draws, but how much *all* the heaters draw in total or per section of the building...etc. Many off my heaters are 3ph, some are not. I have baseboard heating in rooms where half of the units are on one circuit, and the other half on another circuit, yet controlled by the same thermostat.
    The time it would take to chase all this down, and do the right math, and figure loads between single and 3ph systems (and single phase systems on different legs) would be monumental compared to installing a real-time power monitoring system.
    With the system installed, I should be able to determine loads downline in any combination I choose and not chase wires.

    In another recent thread, I tried to figure a way to do this with a single clamp meter and some math, but despite everyone's best efforts, it was a complex if not completely futile.

    The result of that thread was that the only good way was to have a meter that can read the volts and amps of each leg at the same time.
    So, I bought one of these meters. A great deal on ebay means that the one I got also will do the math and give real-time Kw load as well as kwh and a host of other functions. In addition, it transmits the data to software via ethernet.
    This entire building was wired to the hilt with ethernet in the 80's computer explosion so that really works well for my application.
    As Chadillac correctly states, I cannot shut down power to the entire building and sit outside with a stopwatch at the utility meter for each load in the building....there are hundreds. Removing dozens of panels and tracing wires over hundreds of feet and 4 floors is also very difficult....especially when I have to do the math for each circuit (device) tested.

    I bought the special meter, which led me to pre-planning the installation...which led me to a wiring mess at my mains...which led me here (as usual).

    I really appreciate everyone's patience and assure you that I would not be doing this if I thought it was frivilous or a luxury, nor if there was a good way to do it with the tools I already owned. We are already only heating a few important rooms and keeping the lights off as best we can...etc., but the bill is still wiping us out.
    On the other hand, I don't want to live in the dark when it might be some other culprit(s) using an exceptional amount of AC.
    At this point I need a much clearer picture of our electrical usage so I can form a plan of action to reduce it in the future.

    Super Thanks for everyone's advice so far. It has really helped.
    Sean

  5. #25
    Sean S's Avatar
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    J Tiers,

    Yeah...the song fits. I was installing basically the same thing (for a different reason) in the last place I lived. I just needed to slip three CT's over a very open and straight set of lines connected to the buss bars. The utility company was going to charge a bundle and take "up to" two weeks to do it. All downline breakers off, plenty of protection and a 1 inch up/slip/back move. I was completely safe, but could have made a mess. Extremely unlikely I could get that shorted but a high risk if I did. Not so different from working under my forklift. Small risk, high penalty if something goes wrong.

    To clarify your other point... I do have several Clamp type meters. It was my original intent to use those but the actual execution got way too complex.

    Sean

  6. #26
    jim rozen is offline Diamond
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    Correct, in principle the utility meter displays
    only KWH however you can of course divide by the
    time to get amperage. The issue of the meter
    not reading to a fine enough resolution within
    a decent time interval is a real one.

    However remember that putting current sensing
    devices on the incoming lines (if you could,
    for example, simply pass the sense transformer
    winding around each of the three main buss bars
    in your panel) will *still* only give you the
    total current draw for the service. So you
    still have to turn on and off each load that
    you want to measure. The CTs you want to
    install really *do* perform exactly the same
    measurement the utility meter is doing.
    (granted you can inteface it to your readout
    software better, and it has better resolution
    of course)

    So you are still in the barrel for juggling the
    loads for various intervals to measure each one
    individually.

    One issue that the software may or may not do
    is give you the power factor for each load, that
    is, the phase angle between current and voltage.
    Can it display true power or only VARs?

    Jim

  7. #27
    Gary E is offline Diamond
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    Sean S
    Gary, I know that just turning off the lights seems like the simple answer. I don't know what to say except that I bet if you were here and could experience the wiring, and how many different things are going on, and how many sub panels I have, and how *they* are wired, that you would sympathize a bit more with my dillema and understand why I am trying to get this data from a single source (the mains).
    Ohh I understand your problem, I just dont see how measuring what ever you will measure on the incoming is going to tell you anything about WHERE and which sub pannel or which room the power use actually is being used.

    Let me draw a parrallel...
    Dam this car really sucks gas... think I'l put a flow gage in the fuel line...

    Never mind the lead foot driving, or the two 4 barrel Carbs and the A/C running all the time...

    But lookeee here... the flow gage sez...
    In this case, it's the Oil Co monthly bill, hey, Exxon needs the money, Lee Raymond's $400,000,000 retirement pay has to be paid for by someone.

    If I were to attempt this, I'd be using meters on every pannel in the building. And I'd be turning a lot of them OFF.

    Lotza luck

  8. #28
    mrennie's Avatar
    mrennie is offline Cast Iron
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    Sorry if I am hijacking, but I would like some more info about the CT transformer being damaged by an open circuit. I built a genset with a single 60A ammeter, and have a 12:1 (60/5A) CT on each line (Single phase) connected through a DPDT switch to feed the ammeter. When I am monitoring 1 line/CT the other is effective open. If this will fry the CT, what is the easiest way to protect it while adding minimal components? The back to back diodes make sense if the CT output at full load is less than the forward breakdown voltage of the diodes, but I would have to check that. What current rating do I need for the diodes? Slightly higher than the 5A output of the CT?

    Thanks

    Michael

  9. #29
    chadillac is offline Hot Rolled
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    The CTs you want to
    install really *do* perform exactly the same
    measurement the utility meter is doing.
    (granted you can inteface it to your readout
    software better, and it has better resolution
    of course)
    Yes, that is true, but his CT's are portable, unlike the main meter, so he can hook it up to one of the branch circuits, yielding a divide-and-conquer approach w/o requiring him to turn off power to the entire facility in order to test any given circuit.

    So you are still in the barrel for juggling the loads for various intervals to measure each one individually
    Yes, and it sounds like it's a bit overwhelming.

    Logically, you would test the circuits you expect to have high draws, and see if adding them together yields the majority of your electric bill. However, I get the distinct impression that the devil is in the details of either FINDING these circuits or the number of circuits is simply overwhelming??

  10. #30
    cdw
    cdw is offline Aluminum
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    Sean S: I have looked at your posted pictures with interest. I would personally request that the power company drop me a new service to the panel. At that time I would put in a disconnect for the incoming service. If my old eyes arn't failing me I think I see 6 ct's at the pole. You have the 3 that are mounted on the pole and it appears there are 3 more mounted on the incoming legs of the 3ph. just in front of the insulators. I can't tell if they are in fact all being used for metering power. I again suggest that you have them, the power provider, clean up their mess. The connections are IMO poor. They all appear to be dirty and possibly corroded. They are using the old split bolt connectors. I strongly feel these should be changed out to a crimp style connector made for outdoor service.

    The other thing that I think I see is the difference in conductor size on the incoming legs. There "must" be a match in circular mils of cable so that each cable carries a balanced portion of the load. If you have a mis-match in cable circular mils the smallest cable will carry the greatest share of the current. This can lead to some of the issues you are speaking of above.

    Post how things turn out. With all the increased costs of doing business today this is one area that we can affect. Good luck, CDW

  11. #31
    jim rozen is offline Diamond
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    Forward breakdown voltage is 0.7 volts. If the
    open ckt voltage is less than that you probably
    don't need to worry.

    Another approach would be to simpsonize the
    meter that reads the current transfomer, and
    switch in a similar resistor when the meter
    is switched out. That actually sounds like
    a good idea, if the switch could be make before
    break.

    Jim

  12. #32
    Sean S's Avatar
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    Ohh I understand your problem, I just dont see how measuring what ever you will measure on the incoming is going to tell you anything about WHERE and which sub pannel or which room the power use actually is being used.
    Gary, if I am reading the mains, I can turn everything off at the switch and switchless known devices at the breaker. This will give me a baseline of what the building draws for things like timers, security system, alarm system and lights that are always on.
    Then, I can plug in the refigerators one by one and subtract the baseline from the new number, then turn the heaters on one by one and subtract the new number....on and on.
    Then I have a kw load for all the important loads in the building without trying to discover which panel they are on.
    After this, I can log an "vacation" condition where only water heaters and refrigeration are running and get a "practical" baseline of what is being used in a 1/12/24hr period.
    When summer rolls around, I can take these readings again without pulling any panels.
    If I change the device, or add insulation, I can again see if it made a significant difference without pulling panels, which may lead me to do the same in other areas...etc.
    Compared to your flow gauge example, it would be like driving a known speed on a known road with the A/C off and while maintaining that speed, turn the A/C on and immediatly know how many MPG that A/C knocks off. It doesn't mean you'll run the A/C every time you drive, but you'll know what the cost is when you do as opposed to just "a little better" or "not as good".
    I hope this makes sense.

    Jim, I don't have the meter yet. I have a similar model from the same company that only does volts/amp. This higher model looks like it does PF and KVA. I only have the brochure which is in PDF and can be read HERE.
    I also have a few Fluke clamp meters (model 337) so I do intend to isolate some of it at known circuits.
    The excercise will be a combination of single clamp load testing and 3CT logging....and yes, it will involve turning on and off loads and recording the results as well.
    Honestly I don't have an exact plan layed out for the procedure but I'm thinking about it.

    Cdw... you have very good eyes. I had to zoom in on my 8megapixel original to see the extra set of CT's. They appear to be disconnected and were probably replaced with the other three but not removed.

    Chadillac wrote:
    Logically, you would test the circuits you expect to have high draws, and see if adding them together yields the majority of your electric bill. However, I get the distinct impression that the devil is in the details of either FINDING these circuits or the number of circuits is simply overwhelming??
    Yes, that is correct again. In addition the resulting data "per* device would be overwhelming. I'm running a small business and when using a certain area of the building, I don't want to have to think about math for individual devices. Using a room entails more than one electrical device, which I could have mapped out and do some calculations but much easier to have an overall.
    For instance. If I spend the day in the shop, I could look at the logging software and decide that it cost me $35 in electricity for a "shop day". If I have a sick day, I could make a note of that.
    All of these readings could be taken at the utility meter if I feel like going out in the rain with a flashlight at 2am, but I probably woudn't.
    The entire shop is on one sub panel, and while I could individually measure the large loads at that panel, I would also like to know the real total without load testing cell phone chargers and my electric stapler.
    Knowing total building Kwh is useful, as is knowing what an area costs per day, as well as knowing what individual items significantly affect each

    In any case, I've spent about as much time explaining why I need this information as I have discussing how to get it.
    I think I understand what I have to do to get this fancy-dancy meter in and I will happily post if it is of any actual use in practice and if I can find that it has saved any money.
    Hopefully this thread has been of interest to others too.

    I'd be lost without the helpfull people who visit this board.

    Sean

  13. #33
    jim rozen is offline Diamond
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    This sounds like a decent plan, could I suggest
    that you modify it a bit, so you don't need to
    go to the main lugs on the panel:

    Turn on the load you are going to measure.

    Check with a quick and dirty amp-clamp to see
    which breaker is supplying that load.

    Put your current transformers on that branch
    circuit, do the measurement.

    Etc.

    Sounds like maybe most of your load is resistive
    in which case an amp-clamp reading on the three
    phases of any branch ckt should give you a
    good measurement of power being drawn.

    Jim

  14. #34
    gar
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    Sean:

    Your idea to look at main service entrance power input does not make good sense as we have previously discussed in various ways. Two factors --- the mechanical difficulty of installing the current transformers, and lower accuracy than looking at sub-areas.

    Your photo of the breakers in the service entrance indicates the easy method is to use a clamp-on ammeter on the outputs of the various breakers, or to put your current transformers on these outputs. This allows you to disable power to the wires that need to be fed thru the current transformers without having to call the power company. Also the wires are smaller here.

    Jim Rozen' last post is a very clear description of this approach.

    .

  15. #35
    JST's Avatar
    JST
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    One other issue......

    I initially thought you had concerns on accuracy of powerco....

    But, if you are Ok with that, but are worried about loads, try reading the nameplates........

    Lights, they are marked..... bulbs and tubes....

    heaters, should have nameplate ratings.....

    Motors, depends on load, so that is a variable, but you can take standard full load draw.......

    It should be "estimable".

    if you REALLY want to, you can check one or two sub-systems to see how your estimate was relative to real draws.

    It would be far easier to check the loads you have, that to go and try to meter things, even by sub-panels. And, without clip-on metering, you will have a lot of work anyway.

    I'd walk around with a clipboard and write down the info. it would probably take far less time than all this scheming about how to do it..... let alone the wiring to install and remove the CTs

    You ought to find out what is controlled by each breaker anyway. It's the first thing I have done in any house etc I have been in.

    Otherwise you will STILL have to find out, but not when you want to, and under far less convenient circumstances..... with a bunch of un-knowns thrown in.

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