Do I Need 2 Neutral Wires

MrM1

I have a Schneider SW 4024 inverter/charger.  I am not using a generator but instead use Grid power to power the charger of the SW when solar is not available.    The SW has an L1/L2/Neutral Input AND an L1/L2Neutral Output.   At the Inverter I bring all this together with a Midnite Solar E-Panel.  In the  E-Panel both the Input and Output Neutral connect to the same bus bar. 

I am getting power (Input) for the SW Inverter/charger from my main grid panel using 8/3 NM-B with ground.   

My inverter sends power out (Output) to a Reliance Controls 510C ProTran 2 Toggle Transfer Switch Inverter Load Panel also using 8/3 NM-B with ground.  This allows the Inverter Output on L1/L2 to be toggled between the Inverter power and the grid power.

BUT all the Neutral wires coming and going ultimately connect at the Main Load Panel Neutral Bus Bar inside the Main Load Panel.  And all loads, both Inverter Powered Loads and Grid Powered Loads ALL connect to the same Neutral Bus Bar in the Main Load Panel.    This same Neutral Bus Bar is also connect to the Grid Neutral.   This is the way Reliance Controls wires the 510C transfer switch according to their manual.  The only difference I am doing with the 510c is using an Inverter instead of a generator (which is the 510c's typical usage). And obviously,  generators have no need to have Grid Power Input like the SW Inverter/Charger does.

Questions. 

1. Do I need the Neutral both coming and going  (Input and Output) run from the Midnite Solar E-Panel to the Main Load Panel? 

2. Or can I just use a single Neutral (assuming correct size - I am using #8 for L1/L2 and Neutral) for both Input and Output after the Neutral Leaves the E-Panel? 

3. Would it cause problems to use both a neutral for the power to the SW and power from the SW like in the case of an Input and output using 8/3 NM-B with ground?   (or effectively 2 Neutral wires from/to the same busbar in the Main Grid Load panel and from/to the Midnite Solar E-Panel)

4. Is it best to only use 1 neutral wire,  or include both in the run between the E-Panel and the Main Load Panel?

Note that the Neutral that goes to the 510c Transfer switch does not connect to the 510c it merely passes thru the box via a wire nut connection and does not touch or interact with the 510c transfer switch at all.

See Diagram for how I have it connected now. 

mcgivor

Not sure exactly what you are trying to achieve, the MNE175SW has a inverter bypass to disconnect the inverter output to allow grid to power loads independant of the CSW . What is the purpose of the transfer toggle switch? Generally the essential loads would be on the inverter panel, when grid power drops out, only loads connected to it would be powered by the CSW, so if the load represented by the receptacle were on the essential panel, then there would be no need for the toggle, unless I'm missing something. The CSW would pass through grid AC to support loads even whilst charging the batteries in normal operating conditions.
Attached pdf shows the wiring using Schneider AC switchgear, which essentially is the same as MNE175SW.  , the transfer switch would only be required if a generator were used. Just trying to understand your question.

MrM1

The Reliance Controls Pro Tran Panel allows you to take up to 10 circuits from the main panel, and designate them as critical loads.  To  re-wire the individual circuit,  You disconnect the Black or Red Load wire from the breaker and connect it to the ProTran 510 with a wire nut inside the main panel.  That Load wire goes thru the 510's 3 position toggle switch.  The hot from the breaker in the main panel also wires over to the 510c 3 position toggle switch.    So one side of the 3 position toggle switch is grid,  one position is off,  and one is inverter which is feed into the main alternate power source of the 510c.   That way at any time you can select from those 10 designated circuits, what is inverter and what is grid.  (see wiring below)

I have a separate generator 240v back feed plug going to the main panel with a manual lockout for the main whole house breaker.  That way if power is down I can toggle my 10 critical loads that are routed thru the 510 panel either generator or inverter.

I have critical loads such as Fridge, Well pump, Fans, important Receptacles going thru the 510.  If grid is down,  and charge is down with no solar.  I can connect a genny,  toggle those loads to the grid/genny side,  and ALSO charge the batteries thru the SW as the SW would receive grid power.  Charging can be done with no loads on the battery.  Critical loads are running off Genny.  Once charging is complete,  I can toggle the loads back to the inverter,  turn off genny and run on inverter.

Could this have been done thru the SW alone?  Yes,  as the SW manual diagram you posted suggests it is done that way ... BUT ... it would require a complete separate load panel for inverter loads AND the rewiring of the whole house moving the wiring of the critical loads to the new panel.  Using the 510c all the branch circuit wiring stays in the main panel and gets re-routed over to the 510c panel passing thru the 3 position toggle transfer switch and back to the main panel.  If I sell the house,  I simply remove the 510c,  and re-connect all the critical loads back to their original breakers. 

The difference is ...

1. I do not have to have all my critical loads on the inverter at the same time.  there is not an independent inverter load panel.

2. I can pick and chose, what individual critical circuits are running inverter or grid/generator from inside the house at any time

3. But ... the 2 neutral wires,  the one from the main panel supplying power to the SW for the Charger,  and the one from the SW supplying inverter power to the critical loads ends up at the same Neutral Buss bar inside the main panel

I am thinking I only need to have 1 properly sized Neutral from the MidNite Solar E-Panel to the Main bus bar.  In this system,  All Neutrals are bonded together.  (and actually if you use the MidNite Solar E-Panel that they make for the SW ... All Neutrals coming off the SW Bond inside the E-Panel as shown above.).    What I am asking, is in the E-Panel setup, as the Neutral leaves the E-Panel,  Is it a problem to have 2 neutrals (they are there in the NM-B) or should i disconnect 1 and only have 1 Neutral from the E-Panel to the Main Panel busbar?

Here is a diagram of the wiring of the 501c showing the connection of 2 circuits,  the fridge at 120v and a pump at 240v.  The loads get disconnected from the original breakers and routed thru the 510c  The original breaker hots go to the 510c 3 position toggle switch.  Alternate power (from and inverter) goes directly to the 510 3 position toggle switch, and can be toggled from there either grid / Off / or inverter.  The Neutrals of the circuits stay connected to the main neutral busbar.   (for whatever reason,  in their manual they are not showing the neutrals from the circuits, but you never remove them,  they stay on the main busbar.)

mcgivor

There are rules and regulations involved in electrical installations, which manufacturers must follow in order to comply, hense the Schneider diagram. My experience is with Canadian code rules, which are very similar to US code rules, if research were conducted, into local rules, you would find there are fundemental errors with the proposed design. Firstly there can be no splices within a panel, unless for the purpose of control for energy automation/conservation, an amendment to an existing rule , additionally there can only be one source within a raceway, the panel is considered a raceway, so feeding from a different source within a raceway , the inverter in this case, is not permitted. Granted I'm not currently practicing as an electrican, but fundemental rules rarely change, I would highly recommend reading the appropriate code rules applicable to your location before proceeding with your proposed configuration, or at very least consult an electrican for assistance. No insult intended.

MrM1

Non taken.   But I must be missing something as these panels are sold for this intended purpose by electrical contractor supplies and home centers.   The panel as described is also UL approved.  More research is in order.  Thanks

MrM1

Looking at  the Reliance controls web site (which is where I am also getting the wiring diagram above for installing the Pro/Tran series 2 transfer switch panel) indicates that it is ... "UL Listed to UL Standard 1008 and is suitable for use in accordance with Article 702 of the National Electrical Code ANSI/NFPA 70."   I need to write them with the specific questions about why they are installing these panels by wire nutting load wires within the main panel / raceway. 

Mcgivor,  in the diagram you linked,   Schneider does not even show the connection of a neutral to the Input Side of the Connection to the SW.   AS I look closely at the drawing,  there is No wire at all connected to the Neutral of the Input side,  Only the Output side.  So I wonder if the Neutral for Input and Output on the SW is actually bonded inside the Inverter?    That would answer my question.  According to that drawing,  I don't even need a neutral connection for the input at all. 

MrM1

Mcgivor,  also note I am not using the MNEAC50-2P bypass breaker that I drew in my original post.  Sorry I did not realize that was in there that way.     It should look like this

Estragon

I may well be misunderstanding this, but it looks to me like a problem is the main panel looks a lot like any other main panel. If I was an electrician (I'm not), I would check the main breaker (labelled "live from utility") to be sure the panel was de-energized before working further on the panel. From my understanding of the wiring in your main panel, assuming the panel is de-energized would be an unsafe assumption in your case.

I have a panel for "critical" loads with multiple source feeds, but it's immediately apparent there are multiple sources because each has a separate breaker and a mechanical lockout preventing both breakers being closed at the same time. Both breakers are at the top of the panel, where someone working on the panel would expect input source breakers to be. Opening both makes the panel safe to work on, even if one is a klutz (which I am).

The box may be code compliant as far as the box itself is concerned, but I'm not sure it's safe in the overall context.

mcgivor

MrM1 said:

Looking at  the Reliance controls web site (which is where I am also getting the wiring diagram above for installing the Pro/Tran series 2 transfer switch panel) indicates that it is ... "UL Listed to UL Standard 1008 and is suitable for use in accordance with Article 702 of the National Electrical Code ANSI/NFPA 70."   I need to write them with the specific questions about why they are installing these panels by wire nutting load wires within the main panel / raceway. 

Mcgivor,  in the diagram you linked,   Schneider does not even show the connection of a neutral to the Input Side of the Connection to the SW.   AS I look closely at the drawing,  there is No wire at all connected to the Neutral of the Input side,  Only the Output side.  So I wonder if the Neutral for Input and Output on the SW is actually bonded inside the Inverter?    That would answer my question.  According to that drawing,  I don't even need a neutral connection for the input at all. 

Quoting code rules is generally not a wise decision, especially without the latest code book on hand. All electrical code rules are open to interpretation as well as appearing contradictory in some cases, it's therefore best to  say something is not good practice. For example article 404 of the NEC states no splices within a panel but refers to article 318 which permits splices given certain criteria regarding fill volume. There were changes made to accommodate automation, power monitoring devices etcetera, this is where the confusion comes in, so my comments are what I personally consider bad practice and are my opinions.

The AC input of the CSW  would not require a neutral with a 240V supply, the output is split via a center tap of the transformer to provide the neutral, but there would be no ground bonding internally, that would be done in the main panel.

The absence of the bypass breakers makes the use of the toggle/transfer clearer 

MrM1

mcgivor said:

The AC input of the CSW  would not require a neutral with a 240V supply, the output is split via a center tap of the transformer to provide the neutral, but there would be no ground bonding internally, that would be done in the main panel.

The absence of the bypass breakers makes the use of the toggle/transfer clearer 

That is what I was looking for and thinking.  The input really does not need a neutral. 

And I see what you mean about "practice".  Please forgive me if I appeared to be "quoting" code.  I am not qualified.  I was simply stating that this is what the manufacture is claiming.  They may or may not have a right or wrong interpretation of the code.  And it may be possible they are designing off of their interpretation of code or old code regs.

MrM1

Estragon said:

I may well be misunderstanding this, but it looks to me like a problem is the main panel looks a lot like any other main panel.

You are correct in my "drawing"  I was just trying to show the Neutral and how it "flows".   The pic I posted up in Post #3 is the actual look of Transfer switch panel and main panel.

If I was an electrician (I'm not), I would check the main breaker (labelled "live from utility") to be sure the panel was de-energized before working further on the panel. From my understanding of the wiring in your main panel, assuming the panel is de-energized would be an unsafe assumption in your case.

The box may be code compliant as far as the box itself is concerned, but I'm not sure it's safe in the overall context.

I think you are correct.  And I will probably need to address this with some kind of disconnect at the Transfer Switch Panel.  The 510c is designed  for generator input.  There is no disconnect for the generator main feed into the 510c Transfer Switch panel.  BUT... I think the assumption is, "who would work in either panel if  a generator is running"  

But in my case with an inverter,  who would know (besides me) it was Inverter fed.  There would be no noise and no obvious reason for alternative power.  

I have actually done exactly what you are saying.  Standing in the electrical closet,  Closet light on,  Turn off the main power,  light stays on  ... and just for a second think "What?  Why is this light still on ... Yikes !!!... Oh yeah,  it's being fed from the inverter."  freaked me out, and I knew why.   

Dave Angelini

Frankly I do not see why one would go thru all of this work. An electrician would build a sub-panel for critical loads. It is not a big deal to take the inverter with you when you leave. You just power the sub panel from the main panel with wiring appropriate for the 30A double pole in a CSW.  Seven feet of # 10 and it is done.

MrM1

Dave Angelini said:

Frankly I do not see why one would go thru all of this work. An electrician would build a sub-panel for critical loads. It is not a big deal to take the inverter with you when you leave. You just power the sub panel from the main panel with wiring appropriate for the 30A double pole in a CSW.  Seven feet of # 10 and it is done.

Individual control - Grid or Generator or Inverter - for every circuit in the Inverter / Critical Load  system.   At any time I can toggle any single circuit (Fridge, Well pump,  fan, etc)  between Grid-Genny / Off / OR Inverter.  Something a stand alone critical load panel cannot do.  With a stand alone,  you can turn individual circuits off, but you cannot turn 1 of the multiple circuits back to grid.  In a stand alone it is all inverter or nothing.  (unless you by-pass the inverter all together with a by pass or the internal SW transfer switch where it pass AC grid thru the SW).  

Because my Generator is connected to the Grid side of my system into the main panel using a lockout (so as to never back feed the grid) ... In a grid down situation I can toggle off grid loads between inverter / off / and Generator depending on my SOC.  If my generator was connected thru the SW I could not do this.  The critical load system would be all inverter OR all generator.  Sometimes you have enough SOC to power lights and fans,  but not pumps and Fridges 24/7.  This allows me to turn off the large loads,  or power them with a generator,  while at the same time power the smaller loads  with battery OR charge with the Generator thru the SW charger, until I have enough solar to recharge.    It offers way more flexibility than a separate stand alone critical power/load panel.

Maybe it makes sense ... maybe it doesn't.    But I hope you understand what I mean.

Question is about the need for 2 Neutral wires Both coming and going from the same Neutral Busbar in the main panel and going to the the same Neutral busbar in the MidNite Solar E-Panel and from there 1 to the Neutral Input and 1 to the Neutral Output of the SW.   If what i see and understand from Mcgivor is correct.  2 Neutral runs is not necessary.   1 appropriately sized Neutral is all that is needed. 

MrM1

@mcgivor @Estragon @Dave Angelini

My apologies for my bad drawings.  I inserted a "generic" load panel to represent my Transfer Switch Panel.  Hopefully this clears up my confusing drawings just a little bit.  Thanks so much for all you guys help and challenging me to draw better.  You have no idea how much you have helped me from your many posts.  (most of which I read in threads I did not start and never comment on)

  (Note:  the panel in the drawing is actually the ProTran 2 506 which is a 6 circuit panel,  I am using the 510 which is a 10 circuit panel.)

Dave Angelini

I guess I sort of understand but for anyone else contemplating a strategy for the CSW. The manual shows a very simple set-up. You can feed the whole panel or substitute a critical load panel and the grid input will be your existing load panel. It is very easy to take the equipment with you if you sell the place. The new owner gets a pre-wired critical load panel and adds value to the sale of the home.
You could also expand the AC switchgear panel breakers for your critical loads if you have too many.

Raj174

@MrM1
My understanding is that the Reliance transfer switch is made for connecting a generator to supply specific loads in case of power failure. Many generators bond neutral to ground so the transfer switch also switches or lifts the neutral so that it's not connected to the houses neutral circuit which is bonded in the main panel under normal conditions. In light of the way you're using the transfer switch, I agree, the neutral line in question is redundant since the loads have a neutral connection on the common buss.

Rick  

MrM1

Thanks that is what I was thinking as well  

t00ls

to the original question
1. Do I need the Neutral both coming and going  (Input and Output) run from the Midnite Solar E-Panel to the Main Load Panel? 

my concern is if you just use 1, you lower the overall amperage rating , even if it is a common neutral on the inverter

would be better to use 2if it has a spot for 2