- Location
- Placerville, CA, USA
- Occupation
- Retired PV System Designer
But the transformer(s) would waste the least power.
Missing neutral question
- Thread starter ggunn
- Start date
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kwired
Electron manager
- Location
- NE Nebraska
If it were CT metering and all the ungrounded conductors were smaller and had proper OCPD's for conductor size I'd agree.
I myself feel there is no problem with a 14 or 12 AWG neutral for this purpose but NEC does give us minimum size conductor requirement for feeder neutrals.
kwired
Electron manager
- Location
- NE Nebraska
Wouldn't simple inductors (no secondary coils) do the same thing. Even capacitors that are wye connected?
kwired
Electron manager
- Location
- NE Nebraska
What kind of current will be drawn?
In recent years they added requirements for grounded conductors at switch locations for potential occupancy sensors or other automation devices that previously used the EGC to complete a very low draw control circuit.
ggunn
PE (Electrical), NABCEP certified
- Location
- Austin, TX, USA
- Occupation
- Consulting Electrical Engineer - Photovoltaic Systems
Through the neutral? Virtually zero. Within the meter it is literally a #12 or #14 wire that makes the connection to the neutral. That's why it would be stupid to run a #2/0 neutral from the disco nearly 200' away through 50 year old UG conduit to feed it.
wwhitney
Senior Member
- Location
- Berkeley, CA
- Occupation
- Retired
Got a make or model number for the meter?
Cheers, Wayne
Cheers, Wayne
winnie
Senior Member
- Location
- Springfield, MA, USA
- Occupation
- Electric motor research
What happens if this meter is placed at the other end of the feeder, where the neutral is easy to get to?
Presumably voltage drop in the feeder is no longer metered, a question of who gets charged for it.
I would think the POCO would want the meter as close to their lines as possible.
-Jon
Presumably voltage drop in the feeder is no longer metered, a question of who gets charged for it.
I would think the POCO would want the meter as close to their lines as possible.
-Jon
4-20mA
an analog man in a digital world
- Location
- Charleston SC
- Occupation
- Instrumentation & Electrical
But until then, you did what the AHJ wanted to see. Amirite? Is that the AHJ "making up rules"? Just one example to try to get you to see where my statement in the other thread came from. Sorry to interrupt.
Carry on.
wwhitney
Senior Member
- Location
- Berkeley, CA
- Occupation
- Retired
The OP addressed that in post #7, it would require an additional 100' of trenching and PV conductors.
Cheers, Wayne
ggunn
PE (Electrical), NABCEP certified
- Location
- Austin, TX, USA
- Occupation
- Consulting Electrical Engineer - Photovoltaic Systems
Make that 180' under walkways and other concrete. When I posted that I had walked the site but I had not measured it.
electrofelon
Senior Member
- Location
- Cherry Valley NY, Seattle, WA
I assume you exhausted this route, but POCO ha no flexibility on a metering setup that works with what is there? I wonder if the POCO could take care of the neutral by making a connection to the EGC when then install the meter....that scene from the shawshank redemption comes to mind when they give the warden that apple pie with some $100 bills under it
kwired
Electron manager
- Location
- NE Nebraska
My point was they decided that we shouldn't be using the EGC anymore as the neutral for occupancy sensors or other automatic switching devices that also have nearly a zero draw.
synchro
Senior Member
- Location
- Chicago, IL
- Occupation
- EE
I wondering if you could do the following:
1.) Add a single phase 20A fused disconnect or breaker after the service disconnect, say on phase A for example.
2.) Route a pair of at least 12 gauge wires from the L and N outputs of the single phase disconnect, and through your existing conduit. The neutral conductor could be as small as 12 gauge because it's a separate 20A circuit from the main feeder.
3.) At the other end of the conduit feed the primary of a 277 / 277V isolation transformer with the two new wires, and connect the secondary between the A phase on the meter and the "neutral" input wire to the meter. The transformer output would then apply 277V between the A phase and the "neutral" input wire to the meter. It would have the proper phasing such that it subtracts 277V from the A phase and gets back to the same voltage that's on the neutral coming from the service (but without any direct connection to it). Overcurrent protection would likely be needed on the secondary of the transformer.
It would add a couple of "current carrying conductors" in case that matters.
1.) Add a single phase 20A fused disconnect or breaker after the service disconnect, say on phase A for example.
2.) Route a pair of at least 12 gauge wires from the L and N outputs of the single phase disconnect, and through your existing conduit. The neutral conductor could be as small as 12 gauge because it's a separate 20A circuit from the main feeder.
3.) At the other end of the conduit feed the primary of a 277 / 277V isolation transformer with the two new wires, and connect the secondary between the A phase on the meter and the "neutral" input wire to the meter. The transformer output would then apply 277V between the A phase and the "neutral" input wire to the meter. It would have the proper phasing such that it subtracts 277V from the A phase and gets back to the same voltage that's on the neutral coming from the service (but without any direct connection to it). Overcurrent protection would likely be needed on the secondary of the transformer.
It would add a couple of "current carrying conductors" in case that matters.
ggunn
PE (Electrical), NABCEP certified
- Location
- Austin, TX, USA
- Occupation
- Consulting Electrical Engineer - Photovoltaic Systems
Quick question if we have to pull a neutral: The existing conductors are (2) sets of 500kcmil copper in separate conduits. The neutral would only be for instrumentation and the AHJ is operating under the 2020 NEC, so the minimum size neutral (from Table 250.102) is 2/0 copper. Here's the question: can I pull that neutral through just one of the conduits? The conduits are different sizes; there is room in one but not the other.
I think you need a noodle in both pipes 300.3(B)(1)
electrofelon
Senior Member
- Location
- Cherry Valley NY, Seattle, WA
Any way to break it up from 2 parallel runs to 2 separate feeders?
ggunn
PE (Electrical), NABCEP certified
- Location
- Austin, TX, USA
- Occupation
- Consulting Electrical Engineer - Photovoltaic Systems
I don't know but that is a really good question; thanks!
ggunn
PE (Electrical), NABCEP certified
- Location
- Austin, TX, USA
- Occupation
- Consulting Electrical Engineer - Photovoltaic Systems
What about the exception to 300.3(B)(1)? The conductors are run UG in nonmetallic conduits in close proximity to each other.
ggunn
PE (Electrical), NABCEP certified
- Location
- Austin, TX, USA
- Occupation
- Consulting Electrical Engineer - Photovoltaic Systems
Upon reflection, I don't think we can do that without unconnecting both ends of the parallel sets and feeding them with two reduced OCPDs. We don't want to have to deal with the ancient switchgear.
kwired
Electron manager
- Location
- NE Nebraska
lost track of if it was mentioned what this is, but it would still be do-able if outdoors as you have no length limit on feeder taps.
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