Relocate Current Sensors

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Ravenvalor

Ravenvalor

Senior Member
Location
Triad region of NC
Occupation
Electrician
Hello,

I got a call from a homeowner who told me that his new solar installer installed the current sensors below the main breaker. This is causing his system to overlook the HVAC system. Would someone on this forum please recommend a thinner sensor that will fit between the line lugs on the main breaker and the meter can?

Thanks for the assistance. :)

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synchro said:
Can the HVAC conductors also be routed through the CT's so that their current will be added to the total? The direction of these conductors through the CT's would have to be correct so that the curents add instead of subtract.
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That is a great idea Synchro. I will look into it and let you know.
Thanks
 
Ravenvalor said:
That is a great idea Synchro. I will look into it and let you know.
Thanks
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You'd also need to make sure to route Line 1 from the HVAC breaker through the Line 1 CT from the bus. Otherwise it will subtract from the consumption reading rather than add to it.
 
In case it needs to be said...

You can totally run multiple load wires through a single set of CTs, but it's paramount that all wires through each CT are the same phase and same direction, in order to get correct measurements.

Note that if someone comes along and moves a two pole breaker down one space (for example), it screws up the phasing and the measurements.
 
jaggedben said:
In case it needs to be said...

You can totally run multiple load wires through a single set of CTs, but it's paramount that all wires through each CT are the same phase and same direction, in order to get correct measurements.

Note that if someone comes along and moves a two pole breaker down one space (for example), it screws up the phasing and the measurements.
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Good point. Customer needs to be notified of this possibility plus some signage should be in place. Thanks.
 
LarryFine said:
The #10NM cable shouldn't be outside anyway, so you can replace it with longer wires.
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300.9 Raceways in Wet Locations Abovegrade. Where raceways are installed in wet locations abovegrade, the interior of these raceways shall be considered to be a wet location. Insulated conductors and cables installed in raceway in wet locations above grade shall comply with 310.10(C).
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Exception: The raceway shall not be considered a wet location if:
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(1) The section of raceway routed in a wet location above grade does not exceed 1.8 m (6 ft) in length;
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(2) Any fittings or conduit bodies are watertight and listed for use in wet locations; and
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(3) All termination points of the raceway are only open in any of the following: a. A dry location; b. Equipment suitable for outdoor use; or c. Equipment listed for use in a wet location.
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Ravenvalor, where is that exception to 300.9 in the NEC? It's not part of 300.9 or 310.10(C). ​

 
wwhitney said:
In the laws of the state of NC? So you won't find it in CA.

Cheers, Wayne
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Okay, so it's in the NC state electrical code. Got it, thanks.
I wonder why NC added the exception and how they came up with 6ft? It's always interesting to see where some of these local modifications come from.
 
Hello,

The customer posed an interesting question to me today.
He is concerned that if I do not move the 2 - solar taps from the load side of the service disconnect to the line side of the service disconnect that the home will get power from the grid before getting it from his solar panels. Does this sound feasible? Why would the home choose the solar power before the grid power?

I have to admit I am stumped. :)

Thanks.


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LarryFine said:
He's wrong. Parallel is parallel.
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Larry's answer is quite correct. If the customer is still confused, then a different perspective on the same truth:

The two sources are parallel, which means that the house gets its power from _both_ sources at the same time.

Similarly the PV sends its power _both_ to the house and to the grid at the same time.

All that distinguishes things is the metering. The PV production will reduce what the POCO meters, and that is all that matters.

In a deeper sense, there is a real issue: imagine that the PV produces power at one moment and the home consumes power at a different moment. Depending upon how the metering is done the consumer may not be credited for there production, or may be credited at a lower rate then their consumption. If the consumer wants to make sure that their home is truly being powered by the PV system (and not making deposits and withdrawals from the POCO 'energy bank') then they will need some sort of control system that adjusts their home consumption to match the PV production.

-Jon
 
winnie said:
Larry's answer is quite correct. If the customer is still confused, then a different perspective on the same truth:

The two sources are parallel, which means that the house gets its power from _both_ sources at the same time.
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That's not quite correct. The PV is a current source while the grid is a voltage source, and current can only flow in one direction at a time through a conductor. The upshot is that at any point in time if the household load is consuming more than the power the PV is producing, the house takes all of the PV production and the grid makes up the difference. If the load is less than what the PV is making, the PV provides all the power for the load and the excess goes into the grid.

Frankly, that is above the heads of most folks who are not in the biz, so Larry's explanation should suffice.
 
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