Metering a Sub Panel, Please Help

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Old 09-18-13, 12:46 AM
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Lightbulb Metering a Sub Panel, Please Help

I am installing a new sub panel in my garage and I would like to track the amount of the kilowatt-hours I use. I was planning on using a Square D combination unit (SC1624M100S) and putting a meter on it (Itron of ebay), like the ones the electric company uses, just its for my own records. Is there any safety problem with doing this???

I know that the neutral needs to be isolated in the subpanel, and my major concern is that the addition of the meter would somehow bond the neutral and ground and create a dangerous situation. I dont really know how the meter itself works, so maybe I am just overthinking it. At first I thought it would be very straight forward, but the lack of information concerns and confuses me.

I would think there would be more people wanting to do this, whether its so they can accurately charge a tenant or see how much their shop, pool, ect is using compared to their home use. But I have spent several hours online and haven't found any good info on it, besides these very expensive E-mon devises. Id really just like a simple meter right on panel... Help would be greatly appreciated.



I dont think it really matters: But the plan is to put the panel on a 60 amp breaker, use 2-2-2-4 Aluminum wire, 220v, the run is about 50 feet. I want to monitor the electricity usage for the panel, because the circiuts it powers will be used for business and would like to track the amount of KWH for tax purposes.
 
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Old 09-18-13, 01:22 AM
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Welcome to the forums.

I install a lot of those e-mon d-mons in commercial applications. You're right..... they are very expensive. Many of the ones I'm putting in now have remote monitoring.

That Itron meter looks like a real bargain. Those meters are four wire devices. Two hot leg lines (240v) in and two hot legs (240v)


That Square D panel you were looking at may work ok. I didn't look up the specs. on it.



Thanks for the catch Furd
 

Last edited by PJmax; 09-18-13 at 02:50 AM. Reason: corrected incorrect info
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Old 09-18-13, 02:09 AM
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All of the single-phase 240 volt 3-wire watt-hour meters I have seen have four connections, two in and two out. Look at any single-phase watt-hour meter and you see four connection jaws. So to answer your question simply run the insulated neutral wire through the meter socket without making any connections.
 
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Old 09-18-13, 08:45 AM
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Furd, will a KWHR meter register the power-consumption of 120 volt loads without a Neutral connection?.

It's interesting to note that a KWHR meter in a "integrating" meter : to integrate is to calculate the area under a curve or irregular line.

Let's presume a continually fluctuating load with any number of instantaneous power-values from 100 Watts to 1000 Watts operates from Time Zero Hours to Time 24 Hours. A graph of the instantaneous power-values would be an irregular curve .At Time 24 Hours, the KWHR meter has registered 12 KWHR's.

12 KWHR's = 24 X .5 KW's , so the power consumed = a constant load of 500 Watts for 24 hours.
 
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Old 09-18-13, 10:12 AM
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Thanks for the help everyone, forums like this can be so helpful

Ok great, it should work fine then... I just started to get concerned because of the lack of information about using normal electric meters as a submeter; Im suprised there aren't more people using them.

So, 2 hots in, 2 hots out. Neutral bypasses the meter and goes straight to panel. What about the ground? will I bring the ground in the 2-2-2-4 straight to the panel and then run a wire from the ground bus back to the meter?

In any panel even this combination unit, I should still be able to isolate the neutral, correct? I haven't seen this particular model panel, but the ones ive done in the past (without meter) have just had a little bar you unscrew connecting the two buses


PAT: Im not sure if your saying that it wont work if its 110, but I am planning to use the meter for a 60amp - 220v two hots, neutral, and ground circuit
 
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Old 09-18-13, 10:54 AM
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With a 240/120 volt 3-wire supply, you'll need to meter any 120 volt loads, such loads having a Neutral connection .
 
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Old 09-18-13, 01:01 PM
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With a 240/120 volt 3-wire supply, you'll need to meter any 120 volt loads, such loads having a Neutral connection .
Furd is correct, the typical single phase utility meter does not need a neutral connection to register useage.
 
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