On 3/26/2014 12:21 PM, mike wrote:
On 3/26/2014 9:47 AM, amdx wrote:


I put a power meter on my water heater in 2008.
Look on Ebay, they're cheap.

Got a link? I didn't find anything that would work on
a hard-wired water heater.


I used a regular house meter. You need to break the wire insert
meter box and plug the meter into the box.
http://tinyurl.com/mg3s98c




Cheapest water heater power meter is an electric clock
across the element. You'll need a 240V clock or stepdown
transformer or a relay or some such.

Another fun thing to do is to use a 25-cent Palm III PDA
to watch the flashing light on the power company's digital
meter. Graph the power consumption in real time.
Pretty easy to see when the water heater comes on.



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On Fri, 09 May 2014 12:25:12 -0500, amdx wrote:


I used a regular house meter. You need to break the wire insert
meter box and plug the meter into the box.
http://tinyurl.com/mg3s98c

Cheaper here, freshly calibrated and you don't give any money to
sleazebay

http://www.hialeahmeter.com/

Their small sockets

http://www.hialeahmeter.com/metersockets.html

are handier to use than the large ones you get from the big box
stores.

How to set one up for portable use.

http://www.neon-john.com/Misc/Energy_Audit.htm

John
John DeArmond
http://www.neon-john.com
http://www.fluxeon.com
Tellico Plains, Occupied TN
See website for email address

On 5/10/2014 11:27 AM, Neon John wrote:
On Fri, 09 May 2014 12:25:12 -0500, amdx wrote:


I used a regular house meter. You need to break the wire insert
meter box and plug the meter into the box.
http://tinyurl.com/mg3s98c

Cheaper here, freshly calibrated and you don't give any money to
sleazebay

http://www.hialeahmeter.com/

Their small sockets

http://www.hialeahmeter.com/metersockets.html

are handier to use than the large ones you get from the big box
stores.

How to set one up for portable use.

http://www.neon-john.com/Misc/Energy_Audit.htm

John
John DeArmond
http://www.neon-john.com
http://www.fluxeon.com
Tellico Plains, Occupied TN
See website for email address


Hi Neon,
I was slow in reading your response, but it is very good. The prices
on the site you referenced are very reasonable, and the boxes to mount
the meter are also cheap.
I'm perplexed about your use on 120V, I don't see where it
is wired any different, two leads in, two leads out, except on 120V,
one lead is neutral instead of hot.
Maybe you could educate me on why that connection works on 120V.
Thanks, Mikek

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On Wed, 02 Jul 2014 15:05:12 -0500, amdx wrote:


Hi Neon,
I was slow in reading your response, but it is very good. The prices
on the site you referenced are very reasonable, and the boxes to mount
the meter are also cheap.
I'm perplexed about your use on 120V, I don't see where it
is wired any different, two leads in, two leads out, except on 120V,
one lead is neutral instead of hot.
Maybe you could educate me on why that connection works on 120V.

Sure, no problem. The meter responds to volts * amps * cos(theta)
with cos(theta) being the power factor. for this discussion let's
assume a PF of 1 so that part drops out. Now the meter is simply
volts * amps.

So the meter would rotate the same RPM with 120 volts and 2 amps as it
would with 240 volts and 1 amp, because in both cases the power is 240
watts. I exploit that fact in my connection.

With 240 volts the potential coil has 240 volts on it and the current
passes through the current coil only 1 time for 120 volt loads. The
current returns through the neutral.

On 120, the potential coil has only half voltage, 120 volts. BUT, the
current passes through the current coil TWICE, once going out on the
hot lead and once returning on the neutral. Internally, the coils are
arranged so their fields add. So we have 1/2 the voltage but twice
the current and multiplied together they equal 1. No calibration
factor nor adjustment necessary.

The only time this fails is if some of the current returns through
ground - leakage, for example. Thus, this would not be suitable for
revenue metering where people could cheat by using a ground rod but IS
fine for energy surveying.

The connection scheme that Hialeah shows remedies that flaw but at the
cost of having to run a wire from the potential coil's calibration
link to the hot line. The meter is no longer plug'n'play and could
not be removed or installed without killing the power source. Or
working the aux wire hot.

I prefer my method because the meter IS plug'n'play.

John
John DeArmond
http://www.neon-john.com
http://www.fluxeon.com
Tellico Plains, Occupied TN
See website for email address