accurate measurement of kwatt/hrs

[mobile_bob]

thought this might be of use or interest to those that want to do some serious testing
and want some reliable information.

one of the biggest issues i had was trying to determine kwatt/hr accurately
i could power a resistive load so that the power factor was near unity
i could then use a good voltmeter, and a good ampmeter, and do the volts x amps = watts
then use a stopwatch to time the test and then do more math to get to kwatt/hours

the problem is the numbers are always shifting, the accuracy of handheld meters is all over the place,
the resistive heaters shift when there is a gust of wind blow threw the shop etc.

so i found these

http://cgi.ebay.com/LOT-4-GE-CL200-METER-WATTHOUR-WATT-HOUR-kv-kvs-KWH_W0QQitemZ260474897799QQcmdZViewItemQQptZLH_DefaultDomain_0?hash=item3ca5838587&_trksid=p3911.c0.m14

they are new digital residential kwatt/hr meters

home depot had a suitable meter box /breaker box combo for a bit over 30 dollars that would handle 8 single or 4 double breakers
so that seemed like a no brainer,, buy the two for about 60 bucks and now i got an accurate measureing tool.

the meter has a memory, so when you shut down and it goes dark, it doesn't lose its mind, thats a plus

with a few minor hacks i was able to get the screen to read out in watt/hrs instead of kwatt/hrs
this picks up the accuracy significantly.

in test mode the meter can measure any generator output up to 200amps so that covers everything we are likely to test.
and will run a test for 1 hour before resetting itself.

so you simply start the gennie, set the rpm to 60 hz, and check the fuel weight, run until 1000 watt/hrs has elapsed
and recheck your fuel weight,, and wallaaaa you got your fuel consumption iin grams per kwatt/hr with very good accuracy.

also the meter can display up to a couple hundred other goodies, such as volts per phase, amps per, hz, 5 different harmonic
distortion parameter, power factor and all sorts of other stuff, as well as keeping track of total kwatt/hrs.

the meter is easily modified so that test mode is available, and when your done if you know what you want the screen to read
there is an outfit that will program in whatever parameter you want to show up on the screen, a total of 6 parameters can be
scrolled through useing the front button.

over the last few years i have seen all sort of claims of efficiency, fuel consumption numbers etc. the question has always been
one of accuracy,, this meter removes several layers of doubt and inaccuracies that seem to work their way into tests no matter
who is doing the testing.

very hard to beat for the money, and have something that is useful when you are done testing. anyone that adopts its use
will find that their reported test results less likely to be scrutinized i would think.

i know i would trust this meters reading over any combination of voltmeter, clamp on amp meter, and stop watch anyday.

bob g

[mobile_bob]

i am not sure what one might be able to do with one of these, however
they do make an options card that plugs into the thing, and allows the meter to trigger an external action
based on a measured event, such as over/under voltage, over/under hz  and i suppose just about anthing.

there is a opto port on the front that the programmer plugs into, perhaps there is a way to get it to communicate
via an external processor to do whatever you want,, just gotta know more than i do to get it done.

bob g

[LincTex]

I use a "Kill-a-Watt" to measure frequency. That is most important to me. After that is exhaust temp.

Everything else doesn't matter as much.

[mobile_bob]

yup to most folks it won't matter much at all, however
for those that are researching max efficiency, accuracy in test equipment
and procedures makes all the difference in the world.

a bit off here, and another bit off there and the next thing you know
your 6/1 puts out 10 kwatts on a pint of beer.



then there is an issue of repeatability, without which your numbers are about as
worthless as a used beer.

but your right to the vast majority of folks getting a good clean 58-62 hz or better
and a stable 120volts or so is good enough, and a killawatt is more than up to the task
to determine that.

bob g

[cschuerm]

Jens,
Conserv builds a panel meter which displays the normal stuff (V,A,F,PF, etc) and it has a standard MODBUS protocol port.  powermeterstore.com had the best prices I've found.  It's what I use on my listeroid generator and I've been very happy with it.  Best part is that it's cheap considering what it does!

Chris S.

[Henry W]

Hello bob,

I just saw this.

Is the CL200 the one?

I might buy some tonight.
Henry

[mobile_bob]

this is the guy i got mine from

http://cgi.ebay.com/LOT-4-GE-CL200-METER-WATTHOUR-WATT-HOUR-kv-kvs-KWH_W0QQitemZ260488886100QQcmdZViewItemQQptZLH_DefaultDomain_0?hash=item3ca658f754

he is selling them in 4 packs but you might contact him to get a single unit unless you want 4 of them

it requires a small hole drilled through the lexan cover to activate the meter into test mode, there
is a small momentary push switch under the cover that the calibration boys use to move it to test mode
i just found it easier to drill a small hole so i could activate it with a small drill bit pushed through.

later it can be filled with a bit of silicone or a small plug if need be

bob g

[mobile_bob]

what i may have mentioned before and can't remember is the following about these meters that make them useful

1. they can monitor over 200 different parameters, voltage per leg, amps per leg, 5 kinds of distortion, phase angles
power factors, kwatt/hr, watt/hrs, cummulative and peak, hz (withing a range) etc etc.

2. they can be reprogrammed by a company in NC or SC i don't remember which, to display 5 or 6 parameters we need most.

3. there is an option card available that can control a power relay to trip out the generator from the panel if the power goes
outside programmed parameters, such as over/under voltage, over under hz, etc.  making these very useful

4. they make a nice hour meter.

5. they are useful in determining the relative health of your generator system,
(a bit of explanation is in order here)

     because of their ability to measure and display watt/hrs accurately, one can at the first installation of his genset
put fuel on a scale and run a load test with a fixed load that is near peak capacity of his genset (~3kw for a 6/1 etc)
then run the genset until the meter displays 1000 or 2000 watt/hrs, and measure the fuel consumed. then write the
grams consumed per 1000watt/hrs (gr/kw/hr)

     periodically thereafter one could rerun the simple test and tell very quickly what is happening with his genset, if the consumption
reduces over time we can assume the engine is breaking in, if on the other hand the consumption starts to increase it might indicate its
time to decarbon or reset valves or check into what might be causeing the issue long before there is serious damage.

     also with good record keeping one could tell when the engine is beginning to decline and need an overhaul.

These meterheads are so cheap, even after reprogram they are probably less than 100 bucks with the shipping, the box to mount them
is also reasonably priced, and there is one at homedepot that has 8 circuits available in a married breaker panel for ~35 bucks or so.

in my thinking i would probably program one to display on the front screen, watt/hrs, kwatt/hrs, hz, volts and amps per leg, cummulative
kw/hrs, and maybe have a few other parameters programmed in for the button shift if possible, and i would have the option card installed
to handle the disconnect relay for over/under voltage, hz out of range, and maybe some other parameter i can not thinking of right now.

that way i could get accurate metering, data logging, and protection all in a single relatively inexpensive package that is reliable, long lived
and weather proof.

bob g