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connecting inverter with bonded neutral to house panel with same ?

connecting inverter with bonded neutral to house panel with same ?

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Old 08-29-13, 02:52 PM
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connecting inverter with bonded neutral to house panel with same ?

Connecting Inverter with Bonded Neutral to house panel with same ?

on: Today at 11:08:08 AM



Hi all, I'm a long-term reader and a first-time poster to this excellent board. I knew I could get good answers here.

I have a Wagan Proline (5000 watt 120 volt 42 amp) inverter on my offgrid solar w/batteries system. I would like to connect via an interlock or manual transfer switch to my house breaker panel (GE Gold Load Center 20 circuit)
The inverter has hardwire connections for house distributed wiring and the manual states "neutral bonded to ground internally per code"
The house main panel has neutral bonded to ground per code.

Knowing that there should only be one place where the neutral and ground are bonded, I was stumped.

So I called Wagan and the lead tech told me "no problem just connect like this"
1. Wire the inverter neutral straight thru/no breaker to the panel neutral
2. Wire the inverter ground straight thru/no breaker to the panel ground
3. Wire the inverter hot to a 50 amp breaker in the panel
4 Ground to earth the inverter chassis (house panel has water pipe ground)
5 For the 20' run use 10/2 with ground romex or marine grade


When I asked about the multiple neutral/ ground bonds he said "No problem, there really is no neutral on 120v single phase inverters we just call it that"

So, does all this add up to good advice ? Just wire into the panel , breaking only the hot wire ? And grounding the inverter chassis to earth ?
I want to believe this guy, he seems very knowledgeable . Just want to make sure I asked the right questions.

I am ready to lose the extension cords and get this wired up. I can handle the connections safely but will use a pro if it gets more complicated
Thanks in advance for your input
 
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Old 08-29-13, 03:24 PM
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It seems pretty much OK except for the conductor size and the connection method.

If your inverter is putting out a steady 42A while the sun shines, then a 50A breaker is a bit small (42 X 1.25 = 52.5). I think you need to size everything for 60A. That would include #6 or #4 AWG wiring.

Now, how are you going to feed this in and what will it supply? Back-feeding a single-pole breaker in a panel that's connected to utility power at the same time isn't a compliant way to do that. In addition, if this is just a 120V supply, it not only won't power any of your 240V loads, it will also only power only every other row of breakers in your panel.

There must be more to it than what you were told by the company.
 

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  #3  
Old 08-29-13, 04:21 PM
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Inverters are not my area of expertise and on-line utility-interactive inverters are quite special in their own so what i am going to write may not be true.

What I read from the original post is that you have an off-line (non-utility interactive) system so I may be slightly confused by what Nash wrote. I will try to take this line-by-line.

The inverter has hardwire connections for house distributed wiring and the manual states "neutral bonded to ground internally per code"
So there are designations on the output terminals for Hot (or Line) and Neutral as well as Equipment Ground? Is there a fourth terminal for earth ground? Are there any overcurrent protective devices (fuses or circuit breakers) prior to the terminals (internal to the inverter)?

When I asked about the multiple neutral/ ground bonds he said "No problem, there really is no neutral on 120v single phase inverters we just call it that"
If this is a single voltage, i.e. 120 volts only, inverter he is technically correct because the term "neutral" refers to the midpoint in a center-tapped winding outputting 240 volts line-to-line. However, if one line is "grounded" (bonded, connected to) the equipment grounding conductor then the output of the inverter DOES have a "grounded conductor" as well as an "ungrounded conductor" plus the equipment grounding conductor. IF there is no overcurrent protective device (OCPD) in the inverter itself then connecting the "neutral" (grounded conductor) exactly as the technician describes IS code compliant. It is no different than the utility connection which is "grounded" at the supply transformer.
2. Wire the inverter [equipment] ground straight thru/no breaker to the panel ground
This is correct.

3. Wire the inverter hot to a 50 amp breaker in the panel
Incorrect! As Nash stated with a 42 ampere output this should be a 60 ampere circuit breaker UNLESS the 42 ampere rating of the inverter is a "peak output" rating rather than a continuous output. ALSO, this circuit breaker MUST be interlocked with the utility main circuit breaker to absolutely preclude the possibility of having both utility and inverter supplying power to the panel. Third "must" is that this circuit breaker must be securely attached to the panel by hod-down device from the panel manufacturer that holds the circuit breaker in place even when the front cover is removed.
NOTE! Some jurisdictions do not allow circuit breaker interlocks, especially interlocks that can be easily defeated by removing the panel cover. If your jurisdiction has such proscriptions against interlocks then the only recourse is a transfer switch or transfer panel. The transfer switch would select either utility or inverter power and route it to a separate sub-panel that would serve the critical loads. A transfer panel is a set of individual transfer switches and auxiliary circuit breakers that are wired between the service (main) panel and the critical loads.

4 Ground to earth the inverter chassis (house panel has water pipe ground)
Incorrect! The inverter is "grounded" (connected to the earth) via the equipment grounding conductor between the inverter and the service panel or transfer switch/panel. Connecting a separate "ground" to the water pipe could set up circulating currents under some conditions.

5 For the 20' run use 10/2 with ground romex or marine grade
Incorrect! AS Nash already stated this should be no less than #8 copper and if in a cable #6 may be a better choice. Do NOT "downsize the equipment ground in this particular situation.

There MAY be some other things that I am forgetting at the moment. If you use a transfer switch or a transfer panel neutral switching may be required.
 
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Old 08-29-13, 04:24 PM
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I thought the Wagan tech's instructions were suspect. That's why I'm asking here.

My main question is how do I safely connect the bonded inverter to the bonded panel without releasing magic smoke from the inverter ?
Do I need a transfer switch that breaks both hot and neutral ?
Do I need to break the bond in the inverter
?

I know that on turnkey offgrid w/battery solar installs the inverters are hardwired into household load centers, how the heck do they do that ?

There must be a way, as this inverter is designed for distributed wiring. Hence the hardwire connections and the paragraph in the manual that talks about using the inverter to power household wiring.

To answer your other questions
Inverter max output is 42 amps.

No 240v devices will be powered, this is a backup for blackouts and alt-power on sunny days when my 700 ah battery bank can stay above 12.5v . I am planning on powering cfl lights, fridge, home entertainment and a window ac unit . According to my kill-a watt (used and logged for a period of 6 months now) this totals 28 amps max. That's adding the max draw from the fridge, the lights, tv and the ac when all the compressors kick in. For the 20' run #10 should be sufficient according to at least 5 calculators I've used. If they are wrong please tell me

The interlock kit sold by GE for the panel is a break to make device that prevents backfeed to the grid, If I can't use this device I'll use a manual transfer switch that provides the same safety . I'm not into hurting linemen
 
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Old 08-29-13, 04:43 PM
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Thanks Fred that helps some.
to your questions
Yes the terminals on the front are labeled ground neutral and hot the chassis ground is a lug on the back currently on a ground rod with the dc side. I plan to move this ground to the same water pipe the panel grounds to before the inverter to house wiring goes live.
No OCPD in the inverter (only the magic smoke release valve)
Peak output for the wagan is 42 amps, continuous is more like 28 according to Mr. Kill-aWatt
I will check with our inspector about interlocks, if I need a manual transfer switch I won't cheap out on that one
 
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Old 08-29-13, 04:51 PM
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I don't know who Fred might be but let me think about this for a day or two.
 
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Old 08-29-13, 05:26 PM
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I think you'll need a transfer panel. Otherwise, how will you set this up so that the loads you want to power with your 120V inverter get the power and the other circuits don't? Remember that if you connect it to your panel you'll have to choose which half of the breakers, by alternating rows, are powered.

I am planning on powering cfl lights, fridge, home entertainment and a window ac unit.
Is the window A/C a 120V unit?

According to my kill-a watt (used and logged for a period of 6 months now) this totals 28 amps max. That's adding the max draw from the fridge, the lights, tv and the ac when all the compressors kick in. For the 20' run #10 should be sufficient according to at least 5 calculators I've used. If they are wrong please tell me
That's interesting but it doesn't get you to installing wiring that can safely handle the inverter's max output and that, AFAIK, is what you have to have. So I'm still going with a 60A breaker and #6 copper conductors, minimum.

The right transfer panel should help resolve many of these issues.
 
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Old 08-29-13, 05:27 PM
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sorry Furd, dyslexia
and you can call me Bret
 
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Old 08-29-13, 05:33 PM
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Thanks Nash, good advice. I'll go with the #6 and 60amp breaker. Looking like a transfer panel is needed unless I can move the right beakers around easily.
Yes the air cond. is 120v
And I'll hire a pro for the actual work, I just wanted a design I could get my head around
 
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Old 08-29-13, 06:27 PM
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It sounds like you've got what you were looking for, Bert. Glad we could help. If you run into more questions just post again.
 
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Old 08-30-13, 04:26 AM
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Nash
I'm sure I'll have more questions, respectfully request that you leave this thread open
Bert
 
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Old 08-30-13, 06:33 AM
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No worries, Bert. We generally do that anyway.

One question for you: You're now looking for a transfer panel that will switch both the hot and the neutral, right?
 
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Old 08-30-13, 07:18 AM
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sorry Furd, dyslexia
and you can call me Bret
ashenash
Nash
I'm sure I'll have more questions, respectfully request that you leave this thread open
Bert
So, is it Bret or Bert?
 
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Old 08-30-13, 12:05 PM
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I would like to use an interlock kit so I can diy
Much more is beyond my pay grade so
if a transfer switch is needed to do this safely, so be it
but
Is switching neutral and hot really needed ? don't know , just askin'
 
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Old 08-30-13, 12:32 PM
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The transfer panel will probably be 240 which means you will only be able to use half of it or convert it to 120 by using a jumpered 60 amp 2-pole breaker in the transfer panel. The feed from the panel to the transfer panel will have to be 12O, one hot, one neutral. I doubt you'll find a 60 amp 120 volt breaker for the main pane so I'm guessing you would have to use one side of a 240 breaker.

Or am I missing something Pros?
 
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Old 08-31-13, 10:27 AM
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Hi, Bret or Bert.

You stated:
Peak output for the wagan is 42 amps, continuous is more like 28
Is that peak figure from the inverter nameplate or the inverter manual or is it just the peak load that you measured with your kill-a-watt meter? If it is the manufacturer's rating then there is no reason whatsoever to go with a 60 ampere circuit breaker UNLESS you plan on installing a much larger inverter in the near future.

I'm still trying to work out a decent and safe system for you.
 
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Old 08-31-13, 05:26 PM
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I may have misquoted the spec, Wagan says 42 amps continuous. They claim 10k watts peak which would be 84 amps. Here's why I never should see 84 amps

My max draw would be 28 counting peak surge for all compressor motors combined with casual uses

While I suppose a catastrophic cascade failure could produce more, breakers should take care of that.

I've run all my anticipated loads off this inverter at once using drop cords with no issues, not even a warm cord.

Draw from the batts is not even 250 amps dc for which I've sized the breakers on the battery hots and they have never tripped ( I have 500 amp safety fuses on each batt negative cable)

No 240 loads in my system. I've already allocated all my 120 loads to breakers on the right side of the panel in hopes of using the GE interlock designed for the panels

Hope this clarifies, thanks for your interest
 
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Old 08-31-13, 05:47 PM
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In most panels both sides use both bus bars so it is not a matter of left and right but alternating spaces.
 
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Old 08-31-13, 07:05 PM
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yes, 4,8,12,16,and 20
all on the right
 
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Old 08-31-13, 09:22 PM
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Those breakers should all be on the same leg of your service and on one of the two buses in your panel. If so, when you power those breakers you will also power 3, 7, 11, 15 and 19. As Ray said, it's alternating rows.

Is 20 the end of your breaker spaces?
 
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Old 09-01-13, 02:33 AM
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After giving this considerable thought and drawing out the circuit I realize I made an error in post#3 with the paragraph that starts: If this is a single voltage...

The first thing for you to do is to ascertain if a panel interlock for your specific panel is approved in your jurisdiction. It must be approved by BOTH the electrical inspection agency AND the serving utility. IF both agencies approve of the interlock then you MUST break the neutral/equipment bond in the inverter or else you WILL have parallel currents on the neutral and equipment ground conductors between the panel and the inverter if you merely connect through an interlocked circuit breaker.

I would really prefer that you install a separate panel with the desired loads on the inverter and use a transfer switch between this panel and the service panel. doing so will also allow you to run the specific loads on the inverter while running any other loads (still in the service panel) via utility power at the same time. Using the interlock forces you to select either utility power OR inverter power with no combination of both. I would suggest a standard 8 space /16 circuit main lug only panel rated at 60 to 125 amperes. The higher rating is only to get the higher number of CB spaces so if you find a panel with sufficient CB or circuit spaces but only 60 amperes that would be fine. You probably won't find a 60 ampere CB in a single pole model (you might but it isn't common) so you might need to use a double pole CB and that will take two spaces in the panel. This 60 ampere CB will be the main and it will need a "hold-down" kit from the panel manufacturer to keep it in place independent of the panel cover. The second pole of the CB, if you have to use a two pole model will remain unused.

You would use a minimum of #6 copper or perhaps #4 depending on the minimum wire size for the main lugs and tie both lugs together. This will allow the use of all CB spaces in the panel. You would also have to use a circuit breaker of adequate size in the service panel to provide the necessary power to the transfer switch and on through to the sub-panel. Easiest would be to just use a single (or 1/2 of a double) pole CB and #6 copper conductors but that would be dependent upon the total connected load on the sub-panel and any demand factors that might apply.

The transfer switch would be a two-pole model with a rating of 60 amperes or more at120 volts or more. This might be available on the surplus market or you might need to go to a more readily available three-pole unit. In any event, this switch must have an intervening OFF position and also the "break before make" construction so that it is absolutely impossible to connect the inverter to the utility for even a split second.

The inverter's "hot" (line) and "neutral" conductors would both be switched by this transfer switch as would the corresponding utility conductors. ALL equipment grounding connections would be bonded throughout both the utility and inverter systems.

Connected this way your inverter system would be considered a "separately derived system" under the National Electrical Code (NEC) and should pass muster on the local level.
 
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Old 09-01-13, 02:28 PM
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thanks food for thought. I will chew on that for awhile and be back when I have intelligent questions

And I must say, this is very friendly board. No snobbery, just the facts. I like that.
 
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Old 09-10-13, 06:26 AM
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To anyone, but especially to Furd.
Having resolved the bonded neutral issue and the circuit allocation issue, I have a couple of new questions.

Furd, you said

The transfer switch would be a two-pole model with a rating of 60 amperes or more at 120 volts or more.

The inverter's "hot" (line) and "neutral" conductors would both be switched by this transfer switch as would the corresponding utility conductors


Questions
1) With a 2 pole switch I would only be able to connect one hot leg of the utility feed plus the utility ground. And the other leg stays connected to the main panel ? Would that not create a problem ?
Seems like I should use a 3 pole switch and disconnect all 3 conductors from the grid. What am I missing here ?
2) Could I leave the subpanel out ? I know I would not be able to power both sides of the same panel nor any 240v loads. Just seems simpler and more affordable to omit the subpanel. It would still be a SDS, right ? When in inverter mode there would be no connection to the grid including ground.
3) In your "plan B" (transfer switch instead of interlock) would I still need to break the neutral/ground bond in the inverter ?

Thanks in advance
Bert
 
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Old 09-10-13, 07:27 AM
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1) With a 2 pole switch I would only be able to connect one hot leg of the utility feed plus the utility ground. And the other leg stays connected to the main panel ? Would that not create a problem ?
Not Furd but I previously wrote:
The transfer panel will probably be 240 which means you will only be able to use half of it or convert it to 120 by using a jumpered 60 amp 2-pole breaker in the transfer panel. The feed from the panel to the transfer panel will have to be 12O, one hot, one neutral. I doubt you'll find a 60 amp 120 volt breaker for the main pane so I'm guessing you would have to use one side of a 240 breaker.
That is why you need a subpanel with the transfer switch or a transfer panel with a two pole switch. Maybe Furd knows a safe way without a transfer panel or a subpanel used as I suggested but I can't think of one. Short of contactors I can't even think of a safe way to use a three pole transfer switch especially without a subpanel. Pros, am I missing something?
 
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Old 09-10-13, 10:26 AM
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Thanks Ray , but let me clarify my dumb question

I'm more likely to ask dumb questions early in the morning.

Yes, I intend to use only 120 and only on one side of the panel and not using the 240v appliances that are (half) powered by opposing breakers.

The issue now is that using a 2 pole switch would allow switching the 2 legs of grid 120 but the ground would remain connected. My layman's reading of the code seems to indicate that it would not qualify as a Separately Derived System
NEC Art. 100 defines a Separately Derived System as A premises wiring system whose
power is derived from a source of electric energy or equipment other than a service. Such
systems have no direct electrical connection
, including a solidly connected grounded
circuit conductor, to supply conductors originating in another system.

My goal is having a Separately Derived System because it Seems my inspector is more lenient with SDS an is primarily concerned about backfeed (which is solved by the double throw)

I'm thinking I need a 3 pole double throw switch to terminate both legs and ground from the utility. Then I have an SDS and hopefully a pass from the inspector.

Just wondering why it would be unsafe to switch between grid and inverter without the subpanel.

Again, I will have a pro proof the design and do the connections, but I can save a bunch of $ by getting the right parts and pulling the wire myself.
 
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Old 09-10-13, 11:19 AM
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And I'm not understanding why you would switch the second leg. 120 consists of one leg and neutral so what would the purpose be of switching a leg that will not be needed?

Does this help explain my thoughts? You have a 120 volt breaker panel with 120 loads.
The 120 for that panel can come either from the inverter or the main panel. In either case it would only be two wires and a ground.

I really don't think an interlock is best but if you used an inter lock you would add a two pole breaker that would be on only if the main breaker was off. But though the added breaker was a two pole breaker only one pole would not be used. Nothing would be connected to the second pole. ....No that would not work because you would have no way to switch the neutral. So I say no to an interlock.
 
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Old 09-10-13, 11:46 AM
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interlock not being used, I want a " separately derived system"

An interlock is not in my plans.
I am planning to use a 3 pole double throw switch so I can terminate/disconnect/eliminate any and all connections to the utility before putting my inverter online.
The purpose is to achieve a separately derived system. This requires that all connections need to be broken
Seems like I could omit the subpanel, right ?
 
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Old 09-10-13, 12:48 PM
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No. The subpanel is necessary. It is powered either by two wires from the inverter or two wires from the main panel. What would the third pole of the switch be for?

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Old 09-10-13, 02:09 PM
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3 poles for 3 conductor disconnects

My main panel is fed from the utility by 3 conductors
1) hot leg A
2) hot leg B
3) grounding conductor (or neutral if you prefer)

I order for my system to be cosidered "separately derived" all 3 conductors must be disconnected from the utility

When the double throw switch is in the inverter position only 2 poles will be used
 
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Old 09-10-13, 02:38 PM
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I order for my system to be considered "separately derived" all 3 conductors must be disconnected from the utility
It would be. There would be no connection to the main panel. If an inspector told you this I suspect he was talking about a 240 setup not a 120 setup.

What purpose would be served by disconnecting something that is not connected. Doesn't separately derived mean the main panel is disconnected from the subpanel? So if you only have two wires connected to the subpanel and both wires are disconnected how could it still be connected? Put another way an ungrounded lamp has two wires and if you cut the two wires would it still be connected? No. Same thing.
 
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Old 09-10-13, 05:02 PM
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Okay, I'm here. I was working on some of my own projects for a change.

Ashenash, you are being confused by the wording of the code.
Such systems have no direct electrical connection, including a solidly connected grounded circuit conductor, to supply conductors originating in another system.
The "solidly connected grounded circuit conductor" referenced IS THE NEUTRAL CONDUCTOR. The term "neutral" ONLY applies to a 3-wire 240/120 volt circuit. Since you will only be using one-half of the 240/120 volt supply you will have two wires only, an UNgrounded, commonly called "hot" and the groundED conductor, commonly called neutral. The equipment groundING conductor MUST be solid throughout the entire system.

I know that it is often confusing to the layperson to understand the difference between groundED and groundING and for that reason I try to always refer to the "ground" wire as an equipment grounding conductor. The equipment grounding conductor is almost 100% limited to providing a low impedance (low AC resistance) path from a fault back to the source of the power and this is to facilitate the actuating of an overcurrent device. To put it plainly, the equipment grounding conductor allows a high current to flow that will trip the circuit breaker or blow a fuse IF the there is a fault from the "hot" wire to something in contact with the equipment grounding conductor. Try this example:

An electric drill motor with a metal case is being used while the operator is standing in a mud puddle in his bare feet. (That part about the puddle and bare feet isn't necessary but it makes it easier to understand.) The "hot" wire inside the drill case somehow comes into contact with the case of the drill. Since the operator is thoroughly "grounded" (bare feet in dirty water) the electricity, which ALWAYS seeks its source, can travel from the "hot" lead, to the case, through the operator's hand/body/feet into the earth BECAUSE all utility electric sources have one line solidly connect to the earth. HOWEVER, if a proper equipment grounding conductor exists the impedance (resistance) to the flow of electricity through the person will be much higher than the flow through the equipment grounding conductor. The high current flow trips the circuit breaker or blows the fuse while protecting the operator from the large current flow that would result if there had been NO equipment grounding conductor.


Since your inverter system is 120 volts only, you do NOT need or use the "other line connection" (the other UNgrounded conductor) and therefore there is no need to have it appear at the transfer switch or be switched in any way, it simply does not enter into the separately derived system configuration. The transfer switch ONLY needs to switch the groundED and the UNgrounded conductors and for this a two-pole switch is all that is needed. The equipment grounding conductor is maintained across BOTH systems

As for using only one-half of the circuit breakers in the new panel...it seems a bit silly to me but if that is what you want then ignore my earlier advice to use a main lugs only panel and connect to only one side of the main circuit breaker. You would not then need the additional 60 ampere circuit breaker and hold-down kit.

Does this help you to understand?
 
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Old 09-12-13, 05:57 AM
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ok, I get it.

So the equipment grounding conductor is not considered a "direct electrical connection"

In the last paragraph of your latest response are you saying that the subpanel can be omitted ?

As I said, it seems superfluous. I can manage my loads by using branch circuit breakers. I've managed to get all of my emergency loads moved to breakers on one side (alternating numbers and not feeding breakers on the other side)

Using a DPDT switch (with or without the subpanel) would the N/G bond still need to be removed from the inverter ?
 
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Old 09-12-13, 06:13 AM
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are you saying that the subpanel can be omitted
No. You must have a subpanel. What he wrote was:
As for using only one-half of the circuit breakers in the new panel...it seems a bit silly
Furd is referring to whether you convert the subpanel to a 120 subpanel so you can use both bus bars or just use half the panel.
 
  #34  
Old 09-12-13, 09:08 AM
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I never intended to use half of the NEW panel. here's a picture

I never said I wanted to use only half of the new panel. That would be silly.

What I said was , I want to use a double throw to switch between utility and inverter. The chosen source would directly feed my main panel.

(See attachment)

If switched to utility it would power both sides as normal.
If switched to inverter power it would feed one side only.

Thats why I see a need for a 3 pole switch, so I can completely disconnect from utility, as in "no direct electrical connection" as it states in the code

Furd's excellent explanation describes why a double pole is all that is needed to use a subpanel. I want to eliminate the subpanel and switch off all 3 utility conductors then switch on the 2 inverter conductors.

Think of it as a main cutoff between the meter and the main panel, with the added of advantage of a 3rd position which connects the inverter to the main panel.

Yes I know it will require pulling the meter, and I know the old insulation on the service conductors might crumble requiring a new cable (ouch) and I know it will take a pro to hook it up (ouch, but worth it)

I have no desire or need to use grid power at the same time as inverter power, which would require a subpanel

I have no desire or need to run 240v loads

I have no desire or need to preselect which 120v loads I will need in a blackout.

Yes, I'm a layman, but I even I can see how this would work safely.

Still not sure if I need to break N/G bond in the inverter, so I'm still listening
 
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Old 09-12-13, 09:49 AM
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What you want to do would work but given the cost* and difficulty doesn't make sense to me so it never occurred to me. Do you have a 100 amp or 200 amp main panel? have you priced a 3 pole 100 amp or 200 amp transfer switch? You do know this is major rewiring of your panel which will require rerouting the power from your meter. Just don't understand why you would want to do it that way.

*Cost includes an electrician since it isn't really a entry level DIY job.
 

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  #36  
Old 09-12-13, 11:04 AM
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In order to use a transfer switch between the utility meter and the currently installed service panel that switch must meet several criteria. First and foremost it must be a "break before make" switch, secondly, it must have a current carrying capacity equal to or exceeding the amperage rating of the service, thirdly, it must meet the voltage requirements and MOST importantly it must be "listed" as being "suitable for use as service equipment" when used before the first overcurrent device (circuit breaker or fuse). Listed means that the manufacturer has submitted the switch to a "Nationally Recognized Testing Laboratory" (NRTL) such as Underwriters Laboratories to be tested (often to destruction) for use in the intended service.

Ray is correct that installing such a switch will be quite expensive and I state it is totally unnecessary. Why would you want to spend more money and yet at the same time limit yourself to a fraction of the power available from the utility? Let me make an assumption and describe a possible scenario.

You have your electrical switched to the inverter and then for whatever reason you decide to take a nap. You only intend on sleeping for an hour or so but in reality you end up sleeping for six hours. You awaken and the sun has gone down and the house is dark as a tomb. How far will you have to stumble around in the dark before you find a flashlight or are able to get to the transfer switch and switch back to utility power?


With a battery system you really want to "float" the batteries as much as possible. By this I mean that the batteries are connected, but all the power being used is supplied by the solar panels. The batteries are only to supply short bursts of power when the solar panels cannot "make the turns" alone and when it is dark. Constant charge-drain-recharge cycles will lessen the life of the batteries compared to float operation. Further, if your utility is anything like mine they have a customer service fee that you pay regardless of the amount of power you use or else they have a minimum daily charge that is averaged over the course of the billing cycle.

I live alone and I am rather frugal in my use of electricity. Since retirement I average around 11 or 12 kilowatt hours daily, prior to retirement it was around 9 kilowatts daily. That calculates to approximately 330 to 360 kWh per month and I think if you do the research that is one-half or less than the national average. I also live in the land of hydro-power and low electricity rates although my particular utility is one of the more expensive in Washington state. My point is that even though my rates are low, compared to national averages, I still consume far less than the average. I HAVE been "hit" with the minimum daily usage fee in the past and it is extremely irritating to be charged for something that you didn't use.

Unless you completely sever your utility connection you WILL still be paying the utility for the right and convenience of being able to access their services. Honestly, I have described the best system for you to maximize the solar installation and minimize the utility cost. The next step would be for you to install and use a utility interactive inverter system and sell excess power back to the utility. This will have a far better economic return than simply switching off the utility completely during whatever periods you may choose.


I have a sub-panel that contains all my critical loads. These include my furnace, refrigerator, kitchen counter top receptacles (microwave oven and toaster oven plus any other small appliances), my computer and Internet equipment, my television and DVD recorders/players and several lights. In case of a power outage I can live quite comfortably with only a 120 volt 2800 watt generator powering all the above, albeit not everything at the same time. To switch between utility and generator I have one switch between the service (main) panel and the sub-panel. Obviously I won't be using any utility power during an outage but having the generator NOT feeding the service panel I can have one light that is connected to only the service panel notify me when the utility power has returned.

The sub-panel actually makes the system easier and less expensive to construct and to use. It makes it less likely to overload the inverter accidentally. I don't understand why you are so dead set against the use of the sub-panel.
 
  #37  
Old 09-12-13, 01:08 PM
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have you priced a 3 pole 100 amp or 200 amp transfer switch?

Well, now that you mention it I have

Here's one by Eaton
Eaton 100 Amp 120/240-Volt 24,000-Watt Non-Fused General-Duty Double-Throw Safety Switch-DT223URH-N at The Home Depot

Single phase
100 amps
120/240 volt
Suitable for service entrance use with neutral kit installed (neutral kit not included)
ANSI certified and UL listed

$173 for the switch
$88 for neutral kit
$? for the pro installer (which I would need for the subpanel setup anyway)

This pdf from Eaton shows the Eaton switch and also shows some interesting applications diagrams on page 6-9. Substitute an inverter for the generator and theres my system

http://www.cpesupply.com/customer/ci...s/DH362URK.PDF


Here's another switch from GE. It doesn't specifically state "good for service entrance" so it may not qualify.

GE 100 Amp 240-Volt Non-Fused Emergency Power Transfer Switch-TC10323R at The Home Depot



$118 for the switch
$? neutral kit required
$? for the pro

$? Adding a subpanel to the budget can only increase the cost

On your other points

I ain't skeered of the dark and will have no problem finding the kitchen where the main panel is. No flashlight needed, I just turn left when I trip over the dog, which I do with the lights on. Besides that I haven't had a nap since I was married 24 years agohttp://images.ibsrv.net/ibsrv/res/src:http://www.doityourself.com/get/foru...es/redface.gif

My 700ah battery bank lasts us 2 days running critical loads. It floats most of the time when the sun shines. I fully expect to replace the batts in 5-6 years

If I were to overload the inverter it would simply shutdown, no magic smoke would escape.

Why would I want to omit the subpanel ?

1) No wallspace for a sub and a switch, but the switch would fit
2) Fewer moving parts and easier for others to understand and operate
3) I don't have to buy a subpanel or wire to connect it or pay the pro for the extra time it would take
4) Because it can be done (again I refer you to http://www.cpesupply.com/customer/ci...s/DH362URK.PDF Page 6-9 upper right picture)

I've made my points. I'll go away now. Thanks for the free advice
 
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