Will this work? (CT Metering Question)

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iwire

iwire

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I have situation where I have one revenue grade meter unit and three CTs but I need to monitor two separate feeds from the same source.

Kind of like this crude drawing below.


CTDualload.jpg


Will that work as I have drawn it?

I believe it will but before I count on it I want to run it buy you all.

Thanks in advance.
 
The design of electrical systems should only be done by Electrical Engineers, how is this any different than an EE asking about wire sized in thier home?
 
zog said:
The design of electrical systems should only be done by Electrical Engineers,
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That is incorrect, here in MA electricians can do quite a bit of designing.

how is this any different than an EE asking about wire sized in their home?
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Well first off it's me we are talking about and I have a head as big as outdoors so I expect the rules to conform to my own needs. :grin:

Secondly, and most importantly designing electrical systems is part of my job. :cool:


Do-it-yourselfers
This is not a site for do-it-yourselfers.
This Forum is intended to assist professional electricians, inspectors, engineers, and other members of the electrical industry in the performance of their job-related tasks. However, if you are not an electrician or an electrical contractor, then we are not permitted to help you perform your own electrical installation work.
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As for your setup, you said you need to monitor two separate feeds, but I only see one set of CT's encompassing both conductors. Maybe I'm not understanding what you're trying to do here.
 
zog said:
The design of electrical systems should only be done by Electrical Engineers, how is this any different than an EE asking about wire sized in thier home?
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Does that mean an EE is required to design the premises wiring system for a dwelling unit? :roll:
 
peter d said:
As for your setup, you said you need to monitor two separate feeds, but I only see one set of CT's encompassing both conductors. Maybe I'm not understanding what you're trying to do here.
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Picture two 50 amp three pole breakers in the same panel supplying two separate loads but I run both sets of conductors through one set of CTs.
 
iwire said:
Picture two 50 amp three pole breakers in the same panel supplying two separate loads but I run both sets of conductors through one set of CTs.
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Ahh. Ok. It looks good to me. :cool:

Now you need to get this drawn up and sealed by an EE to do the actual work. :roll:
 
As long as you recognize you are reading the combined loads and can't differentiate the loads on each circuit individually, it will work electrically.
 
iwire said:
That is incorrect, here in MA electricians can do quite a bit of designing.



Well first off it's me we are talking about and I have a head as big as outdoors so I expect the rules to conform to my own needs. :grin:

Secondly, and most importantly designing electrical systems is part of my job. :cool:
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Glad you realized I was just yanking your chain, but I think you see my point.

To answer your question, it will "sort of" work but your accuracy will be effected due to the uneven flux distribution, or Gauss' Law.
 
rbalex said:
As long as you recognize you are reading the combined loads and can't differentiate the loads on each circuit individually, it will work electrically.
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Thanks, the customer is only interested in the total KWH not the individual KWH. I am trying to save the cost of buying an entire second meter set up.

It is actually metering for a grid tied PV system and in truth I have two sources and one 'load' but if I drew it that way I think the focus would have been on the two sources to one load and not the metering. :)
 
zog said:
To answer your question, it will "sort of" work but your accuracy will be effected due to the uneven flux distribution, or Gauss' Law.
Click to expand...

How much are we talking here?

This is 'revenue grade' metering and I think I am supposed to be within 2%.
 
zog said:
Not sure, too many other factors involved, but a 2% variance is possible.
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Yeah it's always those darn 'other factors':grin:


I have options, I could install and monitor a 100 amp feeder that supplies two fused disconnects with 50 fuses for each of the loads.
 
I see you said your trying to keep cost down, but why not take one set of conductors through the CT's then polaris off to the two loads after the CT's?
 
chris kennedy said:
I see you said your trying to keep cost down, but why not take one set of conductors through the CT's then polaris off to the two loads after the CT's?
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To do what you describe will add another set of OCPDs and while that is short money I start running into space issues. :)
 
Bob,

Your drawing is how the POCOs meter multiple drops to a customer for a single bill. I'm sure you see this all the time at risers and at the transformer. It should work fine.
 
iwire said:
It is actually metering for a grid tied PV system and in truth I have two sources and one 'load' but if I drew it that way I think the focus would have been on the two sources to one load and not the metering. :)
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You are correct. My curiosity is killing me, but I'll resist the urge to ask questions.
 
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