Kill-a-Watt meter for 110-220 Volts

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I'm in California, USA.  During the summer, the wall mounted air
conditioner probably consumes around 80 to 90 percent of the electric
power used in my apartment.

This AC unit has a 220 power plug that's plugged into an outlet right next
to it.

Is there a Kill-a-Watt meter that does both 110 and 220 volts AC?  I've
heard of a higher than 110 volts model obtainable in Europe, but I would
need one that works with the USA version of plug style, voltage, and AC
frequency.

Thanks.

BTW, my DMM measures the "110 Volt" AC outlets at 123 to 125 volts.

---  Joe

Re: Kill-a-Watt meter for 110-220 Volts



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Tend to read high on the mains because most are average reading rms
calibrated meters and there's usually some distortion.  Plus, mains
voltage does wander around as local loading varies and regulators
slowly bring it back to standards.

Grant.

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Not to mention it's officially *120* Volts not 110.

Graham

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Welcome back.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal
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Re: Kill-a-Watt meter for 110-220 Volts


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I would hazard a guess that the inline European ones designed for 240v
would also work on a 110v supply without too much trouble (probably less
accurately and maybe needing empirical calibration).

But the other way around the US ones will be made down to a cheap and
nasty price and probably cannot safely be used at 240v. The same seems
to be true of many US wallwarts which are dedicated to 110v whereas in
almost all other countries they are commonly for 100-240v 50-60Hz.

The clip on magnetically coupled devices like OWL are probably your best
bet if the cabling will allow the sensor to be fitted. Accuracy +/-10W
is poor compared to inline ones but for A/C should not matter.

(Amazon.com product link shortened)

I presume smart meters are also available in the USA, but a quick web
search didn't show anything obvious.

It is probably more informative to use this type to monitor the entire
apartments usage - you can deduce the aircons consumption from how much
the thing jumps by when the compressor kicks in. You might need a pair
of magnetic sensors since ISTR US 240 is across antiphase 110v supply.

Regards,
Martin Brown

Re: Kill-a-Watt meter for 110-220 Volts


On Tue, 24 Aug 2010 08:00:01 +0100, Martin Brown

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Kill-A-Watts monitor the neutral current (keeps the innards at a low voltage),
so are useless, as is, for standard US 240V split-phase.  A friend hacked one
to monitor the hot current and it worked just fine on a 240V circuit.  Safe?
Well, it was hacked.  ;-)

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I just used mine on a 300W boost PFC and according to the kill a watt my
boost converter is makeing power. For a measured 130W out the Kill a watt
says my boost is only drawing 115W @ 0.97 PF.

I have seen it get closer on other SMPS's but its off here!


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There are some really cheap and nasty meters of this type that are
hopelessly inaccurate. I suspect you have one.

Graham

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Probably not 'Kill-a-Watt' brandname, no (those are consumer-grade
and made for the lowest price possible).  The meter on your house
does it, though, and lots of other power meters can do it, too.

Your AC 220V unit undoubtedly uses more current than a standard
wall socket 220V Kill-a-Watt is meant for.   On the used  market, the
house-power-meter gizmos go for $50 and up...

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230V 'Kill a Watts' are rated at up to 16A ( approx 3.5 kW ) as this is
the most popular European wall socket.

I use an Efergy brand unit ( UK model ).
http://www.efergy.com/pages/Energy-Monitor-Socket/pgid-20592.aspx

Graham

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There is no such thing as a 110 volt outlet in the US. The standard is
120 volts, so if it reads 123 to 125 you are getting very close to the
desired or specified voltage(s).

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It used to be 110, decades ago and has crept up to a nominal 120.

check any old appliance with a cloth and rubber cord. they'll be maked
110, 115 and even 117 volts and maybe even 60 "cycles".



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The previous poster is correct. The US standard wall socket voltage has
been 120V for many decades. Read the published standards.

Graham

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Mike's metrology question:
What are you gonna do with the information when you get it?

You save money by turning up the thermostat or turning it off.
You don't need any power measurements to do that.

The utility company has a meter on your dwelling.  You can read
the numbers and get gross answers.  By timing how fast the wheel
(real or simulated on an LCD) goes around, you can get short-term
numbers.  The scale factor is written on the meter face although
cryptically.

Put the house in stable power drain.
Time the wheel.
Run the air conditioner full on.
Time the wheel.
Turn off the compressor, leave the fan on.
Time the wheel.
Turn the air conditioner off.
Time the wheel.
If the first reading isn't the same as the last one,
something turned on/off that you didn't expect.  Repeat
the process till both numbers are the same.

One thing that surprised me is that the fan consumes
an appreciable percentage of the total power...and it usually
runs all the time on a window unit.
You know the fan consumption from the measurements above times
the time the unit is on.
Pay attention to how often the compressor runs to get the
other part of the consumption.

Now what?
You can either turn it off or turn up the thermostat.
And you already knew that.

In my case, the 20" box fan that I use to vent the house in the
evenings takes about 15% of the energy used to run the central air.
So, if the air conditioner runs less than 15% of the time at night,
it's cheaper to leave it on than to run the box fan all night.
That's critically dependent on your insulation.
Moving air is expensive, even if you don't try to modify its temperature.

If you have an electric water heater, that can consume significant energy.
Typically, there's nowhere to hook up a kill-a-watt to that.
But timing the meter wheel still works.
And you don't have to worry about power factor.  The wheel tells you
EXACTLY what the utility is billing you for.

Bottom line is that you already have the means to make the measurement
for free.

Having a cool toy that continuously reads consumption is fun
until the new-car-smell wears off, but the payback period
for the purchase can be LONG.
I paid $2 for my KAW at a garage sale.  Don't expect to save
an extra $2 because I have it.  I already had a stopwatch.

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A compare and contrast of the costs of various ways to keep comfortable on
hot days.


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And you don't need to be condescending.


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<snip lots of stuff about watching the meter>


I did mention "my apartment".  I don't have access to my meter.


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See?  Compare and contrast.


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There you go again with the condescension.

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Interesting.  That's the kind of stuff I'd like to measure, too.

 

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Nope.


Who said I want to measure the wattage use ONLY of the A/C?  I did mention
that I would like it for 110-220 V.

Anyways, thanks for the effort.  There is some useful info there.

---  Joe

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But he is basically correct. The big cost is incurred maintaining a huge
temperature differential.

Raising the internal temperature to be closer to the external one is
actually more comfortable too. I have lost count of the number of US
premises where in summer conference rooms are kept so cold that you need
to put on a sweater or jacket to survive. In winter the situation is
reversed with everywhere kept soporiphically warm and stuffy.

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Which they struggle to read correctly. Mine is prehistoric with
alternate dials with opposite handedness and in a most awkward corner.
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However, if you can clip a magnetic sensor onto the mains inlets then
you can measure total power delivered (and most of it will be going to
the aircon and/or and electric cooker or space heaters).
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A realtime display in your living space makes you aware when something
has been left on. The one we fitted to our village hall has saved a
fortune by preventing the main hot water immersion heater being left on
when people leave.

Regards,
Martin Brown

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You're being WAY too sensitive.  Just facts.  No need to take it personally.

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Interesting...there's gotta be a meter somewhere???  Talk to your
landlord.
The point is that you only need to measure stuff once.  From then
on, the meter just sits there doin' nothin'.
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Yep, I learned that and no longer need to measure that.
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Still way too sensitive.
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This is the first time I've seen you mention this.  Was all about the A/C.

BUT, reading the meter works for ANYTHING you use.
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If you find you do have access to the meter.
AND
If you have an old palm pilot or handspring visor with PalmOS 3 or 4, I
can send you a program
that can monitor/graph the newer electric meters with the digital readout
and led that pulses every watt-hour.
Turns out that WalMart sells yummy deserts in a plastic container
that's a press-fit over a utility meter and just the right size to
hold a Palm.  You can log yourself silly.  Problem is that you have
to add bigger batteries to get enough life to run 24 hours..

I just ran around the house with a watch and turned stuff on/off.
Go retrieve the palm and correlate the graph with the times you turned
stuff on/off.
I can tell you exactly how much it costs me to take a shower.
I couldn't have done that with a killawatt.
And I only needed to measure it once.  It's pretty linearly
related to how long you run the hot water.  Shorter showers cost less.
And I already knew that.  And I don't take shorter showers because
I actually measured the number.
YMMV.
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Reminds me of the story about the balloonist and the accountant.


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Calm down.  I said it's inaccessible, not invisible.



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Umm...  perhaps you missed it.  It was stated at least twice, including in
the subject line.


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It won't work for my HPTB.


---  Joe

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Please disambiguate HPTB, the hits i got were all over the place and
none made any sense for this thread.

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Why would you keep rocket propellant in your meter cupboard?

You want one of the magnetically coupled total power sensors with a
transmitter to send the results to the base station in the house.

Regards,
Martin Brown

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