Schneider Conext SW4048 - Remote Solar Generator/Charger Setup and Neutral-Ground Bond

Hello,

I am setting up a Remote Solar Generator/Charger using the Schneider Conext SW4048 product, along with the associated Schneider A/C and D/C boxes manufactured by Schneider for combination with the SW Product Line. I have a technical/wiring question I need some assistance with.

For reference, this system will be housed in an enclosed trailer and be used in Ontario, Canada to run our installation equipment while on-site doing Solar Installations for my PV company (Electric Ladder Equipment Lift, Power Tools, etc.) I will be using PV Panels mounted on the Enclosed Trailer to charge my 280Ah 48V LifePo battery bank predominantly via the Schneider 60 150 Charge Controller, however I would also like to be able to charge from Grid power (120V) using the SW Built-In Charger (I will be using only L1-120V for charger effectively limiting charging power to 50% but I'm ok with this). The issue I have is determining how to complete the system wiring, specifically with respect to the Neutral-Ground Bond and how to wire this.

I plan to connect the Inverter A/C Out L1-L2 to a Inverter Load(s) Distribution Panel that will be used to distribute power to a number of 120V/240V A/C circuits I am installing. When completely operating the system off-grid (most of the time), the Neutral-Ground Bond should exist in the Inverter Load Distribution Panel I will install (as I understand it) as it will be operating as the defacto Main Distribution Panel. However, when I connect the SW charger to Grid power a second Neutral-Ground Bond will exist in the Grid Tie system that I am connecting to. How is this typically handled in a system like this and what would be the best way to complete my wiring? When investigating this online all of the systems I have found have the Inverter connected to Grid full time which provides this Neutral-Ground Bond. In this instance my Inverter Load Distribution panel would be classified as a Sub Panel and I would not connect the Neutral-Ground, however my situation is different with intermittent Grid Connection only when required.

Can someone shed some light on how to complete my set-up? This is my first attempt to set up a system like this and I am not an Electrician so don't want to make any silly mistakes.

Thanks in advance for your input and information.
Pete

Pete B said:

Hello,

I am setting up a Remote Solar Generator/Charger using the Schneider Conext SW4048 product, along with the associated Schneider A/C and D/C boxes manufactured by Schneider for combination with the SW Product Line. I have a technical/wiring question I need some assistance with.

For reference, this system will be housed in an enclosed trailer and be used in Ontario, Canada to run our installation equipment while on-site doing Solar Installations for my PV company (Electric Ladder Equipment Lift, Power Tools, etc.) I will be using PV Panels mounted on the Enclosed Trailer to charge my 280Ah 48V LifePo battery bank predominantly via the Schneider 60 150 Charge Controller, however I would also like to be able to charge from Grid power (120V) using the SW Built-In Charger (I will be using only L1-120V for charger effectively limiting charging power to 50% but I'm ok with this). The issue I have is determining how to complete the system wiring, specifically with respect to the Neutral-Ground Bond and how to wire this.

I plan to connect the Inverter A/C Out L1-L2 to a Inverter Load(s) Distribution Panel that will be used to distribute power to a number of 120V/240V A/C circuits I am installing. When completely operating the system off-grid (most of the time), the Neutral-Ground Bond should exist in the Inverter Load Distribution Panel I will install (as I understand it) as it will be operating as the defacto Main Distribution Panel. However, when I connect the SW charger to Grid power a second Neutral-Ground Bond will exist in the Grid Tie system that I am connecting to. How is this typically handled in a system like this and what would be the best way to complete my wiring? When investigating this online all of the systems I have found have the Inverter connected to Grid full time which provides this Neutral-Ground Bond. In this instance my Inverter Load Distribution panel would be classified as a Sub Panel and I would not connect the Neutral-Ground, however my situation is different with intermittent Grid Connection only when required.

Can someone shed some light on how to complete my set-up? This is my first attempt to set up a system like this and I am not an Electrician so don't want to make any silly mistakes.

Thanks in advance for your input and information.
Pete

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I looked up a SW4048 manual and there is almost no information in it that would help answer your questions.

I do not have experience with the Conext line of inverters, but it sounds like you do.

Pete B said:

When investigating this online all of the systems I have found have the Inverter connected to Grid full time which provides this Neutral-Ground Bond.

Click to expand...

That is a critical statement. If I read it correctly, the inverter presents the grids N-G bond to the output even when the output is powered by the battery (The inverter is not in pass-through mode).

If you can confirm that then this should be an easy problem to solve.

Here is a very good explanation on Neutral options from the manual for the larger inverter (6848)
Might have some info not in the 4048 manual?
(see page-63)

My barely-educated guess is that when the system is operating stand-alone, the neutral/ground bond is as you describe, as it is developed locally only.

When connected to the grid, the inverter neutral should be bonded to the grid neutral.
I would expect that the neutral bond with the ground should be removed in the inverter when grid connected.

I have the xn 6848 with the big panel. I ran for 2 years off grid ( no grid connection). I ran generator through a 3 pole contactor and used 1 pole to bond N to G. Now I sell to grid but disconnect the system from the grid when thunderstorms move in. I have a relay that is controlled from grid input and bonds N to G through the normal closed.

IF the 4048 is the same as the 6848 then this is the key information:



Since Neutral is not switched, the 'only' requirement is that there be an N-G bond upstream from the inverter. I would recommend you contact Schnieder and confirm this is true for the 4048. (Edit)

The way I would approach this is to have a relay that handles switching the N-G bond.


Since you plan on sometimes powering with only 120V to charge the battery, make sure the relay is on the 'charge' leg.

A less sophisticated method would be a manual N-G bond. It could be done with a switch, but there is too high of a chance the switch will be left on when on shore power or left off when not on shore power.. Perhaps a better way to do it manually is to have a dummy receptical that gets plugged onto shore power whenever shore power is not used.


Edit: Updated pic for clarity.

If someone forgets to put the dummy receptacle on, the system would be floating. This would not be good, but it is not the end of the world.

Since the system will be used in a commercial environment with potentially a lot of different operators, I would advise doing the relay... that way it will be a lot harder for the new guy on the crew to screw things up.

acdoctor said:

I have the xn 6848 with the big panel. I ran for 2 years off grid ( no grid connection). I ran generator through a 3 pole contactor and used 1 pole to bond N to G. Now I sell to grid but disconnect the system from the grid when thunderstorms move in. I have a relay that is controlled from grid input and bonds N to G through the normal closed.

Click to expand...

I need to clarify when I disconnect from the grid I unplug a 4 wire 50 amp Range cord( 3 foot air gap from lighting). This disconnects the N to G bond at the utility.

Pete B said:

I would also like to be able to charge from Grid power (120V) using the SW Built-In Charger (I will be using only L1-120V for charger effectively limiting charging power to 50% but I'm ok with this).

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I was scanning through the manual and did not see documentation on how to make this work. It appears that in needs both legs and at least 170V on the input.

Single transformer low frequency inverters often do not allow AC split phase grid or generator neutral to be connected to ACout neutral, which is center tap of secondary side of large inverter transformer. The problem is AC input L1-N and L2-N voltages may not exactly match the inverter transformer center tap L1-N, L2-N voltages as output is set by transformer turns ratio and its loading on each phase side.

The problem with 240/120v source with neutral connected in common is the parallel connected inverter transformer may try to balance the AC input L1-N-L2 which eats up some of the power handling capability of the transformer just pushing power from one half to opposite half of transformer secondary in attempt to rebalance any mismatch.

What this means is grid or generator neutral is not connected, only the input L1 and L2 240vac is connected when 240 vac is provided. Additionally, this means any 120 vac output branches are being supplied by inverter transformer, perhaps limiting maximum 120 vac loads when external AC input pass-thru grid or generator is used.

The SW4048 has a special connection that allows 120vac generator to be fed between L1 (via sync connect relay) and neutral of inverter transformer. Again, the inverter transformer is providing the opposite phase other half 120vac loads and any 240vac output loads in this case. It always provide 240/120 vac split phase AC output regardless if AC input is 240vac or only 120vac.

I believe the SW4048 AC input neutral is only used when only 120 vac input is provided to L1 side to input neutral and normally with 240 vac input the AC input neutral carries no current and is essentially disconnected.

@RCinFLA great explanation.

Now I'm not certain, but perhaps the Midnite Solar ePanel for the Conext SW manual and wiring diagram shed some light. I used Midnites diagram to wire my sw.

I highly recommend providing inverter bypass switching from main to aux panel to cover an inverter failure.

I learned the lesson hard when away on a business trip with family at home when a grid lightning strike surge took out one of the inverter's small AC input voltage sense transformers so there was no grid pass-thru on inverter to aux panel. Only battery powered AC to aux panel esssential loads until I got back from my trip. Luckily my battery capacity was enough to hold out for almost two days until I got home and I was able to fix the inverter. I added an inverter bypass transfer switch a couple of months later.

RCinFLA said:

Single transformer low frequency inverters often do not allow AC split phase grid or generator neutral to be connected to ACout neutral, which is center tap of secondary side of large inverter transformer.

Click to expand...

MrM1 said:

@RCinFLA great explanation.

Now I'm not certain, but perhaps the Midnite Solar ePanel for the Conext SW manual and wiring diagram shed some light. I used Midnites diagram to wire my sw.

Click to expand...

INTERESTING: The Midnight document shows a configuration that ties the Neutral-in to the Neutral-out on the SW4048. (Shown by the brown dotted line in the diagram below)




If tieing the Input and output neutral together is allowed, then whatever NG bond that is upstream from the inverter will be seen downstream of the inverter.

So, if the Midnite document is correct, then this should work just fine:


(Notice the jumper from Neutral-in to Neutral-out. With that in place the downstream circuit will always 'see' the upstream N-G bond)


Also, are we sure the SW4048 is a low-frequency inverter? The documentation talks about 2x surge capability. Normally high-frequency inverters are rated for 2x surge and low-frequency inverters are rated at 3x surge capability.

RCinFLA said:

The SW4048 has a special connection that allows 120vac generator to be fed between L1 (via sync connect relay) and neutral of inverter transformer. Again, the inverter transformer is providing the opposite phase other half 120vac loads and any 240vac output loads in this case. It always provide 240/120 vac split phase AC output regardless if AC input is 240vac or only 120vac.

Click to expand...

Good!! I did not see that discussed in the manual..... but I did not read the whole manual either.

For the Conext SW4048, I believe the management of neutral AC input connection is done within the inverter. The Conext SW4048 120 vac input option between L1-N does require AC input neutral connection so the unit must include the input neutral connection on its terminal strip. The six terminal AC connection strip puts two neutral connections with each one between their respective AC input and AC output L1-N-L2 connections,. Installation manual also refers to their names as 'input neutral' and 'output neutral'.

AIMS, Sunpower, etc., split phase inverters have only 240 vac input L1-L2 with only neutral connection for their split-phase output. If you tie the inverter's neutral terminal connection to an actual split phase AC input source neutral (like a 240/120vac generator) the inverter generates an error and refuses to connect to source.

Other things about Conext SW series, the pass through relay only supports 30 amps with fine print caveat of "a.Limited by SCP to 24 A due to CEC/NEC regulatory requirements.", and I have heard complaints from customers that customer service treats Conext SW as a dark step child, treating it as a low cost throw away unit if you have trouble, suggesting you should buy a real XW inverter to replace it,.

@FilterGuy

Also, are we sure the SW4048 is a low-frequency inverter?

Click to expand...

Yes. It is.

RCinFLA said:

For the Conext SW4048, I believe the management of neutral AC input connection is done within the inverter. The Conext SW4048 120 vac input option between L1-N does require AC input neutral connection so the unit must include the input neutral connection on its terminal strip.

AIMS, Sunpower, etc., split phase inverters have only 240 vac input L1-L2 with only neutral connection for their split-phase output. If you tie the inverter's neutral terminal connection to an actual split phase AC input source neutral (like a 240/120vac generator) the inverter generates an error and refuses to connect to source.

Click to expand...

Again I'm not knowledgeable enough to know, but anecdotally does this help?

I know from experience (because I've done it) that even if you have 120v only on the input side, the SW will "convert" that to 240v ac on the output side even in pass thru mode. That is, 120v in and both 120v outputs are still hot.

I have a 240v double pole breaker and generator interlock on my mainly panel. My 240v that feeds the input to my SW is also on that panel. If I turn off and lock out the main grid input to the main panel and connect only a 120v generator to the L1 side of my main panel, I am then only supplying 120v L1 power to my SW via a 3000w harbor freight inverter generator. Yet I still get 240v ac split phase out of the SW.

Everything works fine on both legs of the SW out, EXCEPT ... my 240v 3/4 hp well pump gets real wonky and won't start correctly. It just surges on/off or something. (it's been a few years. I only did it once. It did not seem to be a good thing.)

But I can still change the batteries as the ac charger in the SW works, it just gets reduced to 50% charge output.

When you use the 120 vac only input, the inverter transformer acts as an auto-transformer. This gives you the 240vac split phase output but only half the maximum power from AC input source that you would get from 240vac input.

You are getting all the input AC current through L1 side pass through relay contact meaning you are limited to half the input power you can get from 240vac input.

Inverter battery power supplimental load shaving still applies.

This is roughly how I think the Conext SW block diagram looks:

RCinFLA said:

When you use the 120 vac only input, the inverter transformer acts as an auto-transformer. This gives you the 240vac split phase output but only half the maximum power from AC input source that you would get from 240vac input.

You are getting all the input AC current through L1 side pass through relay contact meaning you are limited to half the input power you can get from 240vac input.

Inverter battery power supplimental load shaving still applies.

This is roughly how I think the Conext SW block diagram looks:
View attachment 76722

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Very Nice.

So here's one for you. I have a second exterior Autotransformer installed on my SW to balance loads so that the AC Support Mode (schneider term - but basiclly is a grid assist mode for the SW that pulls loads off battery/solar unless the load is under 2amps). This Mode works BUT it does not work well unless the loads are nearly perfectly balanced ... or unless you add an autotransformer, so I did. But what effect does this external AT have on the internal transformer of the SW, especially when the internal transformer is functioning as an AT. So basically at times it would seem I have an AT "going into" an AT.

Assume you mean mean you put an external autotransformer across the Conext SW 240 AC output. You should not be doing this unless you only want to converter 240 vac from inverter to 120 vac only output with higher current capability than inverter's 120 vac output. Inverter's neutral should not be used in this arrangement.

Using an autotransformer to balance the phases of a center tapped output transformer will not work very well and can cause damage.

RCinFLA said:

Assume you mean mean you put an external autotransformer across the Conext SW 240 AC output. You should not be doing this unless you only want to converter 240 vac from inverter to 120 vac only output with higher current capability than inverter's 120 vac output. Inverter's neutral should not be used in this arrangement.

Using an autotransformer to balance the phases of a center tapped output transformer will not work very well and can cause damage.

Click to expand...

I guess the difference mightbe I have it wired like this? I am using the external AT in a bit of a different config. I wired it according to the way Outback suggests it for load balancing with dual 120v Outback inverters

2 Outback inverters per their instructions


My SW as I copied their diagram for the L1 and L2 of the SW

@Pete B The thread has wandered some..... did you get your questions answered?

Soooo, first off WOW lol. I am only just getting back to this thread and the input provided is impressive! I just signed up to this forum however I will definitely be active here, this is fantastic.

I'm somewhat of a newbie so a lot of the details provided here are over my head to be completely honest. I am a Mechanical Engineer but have spent the majority of my career in Powertrain Engineering/Design so am not completely versed in all of the Electrical jargon. My capabilities are certainly growing as I challenge myself with items like this and my Solar Installation Business (we typically only install Grid Tie Net Meter systems and my electrical grid connection work is subbed out to a licensed electrician).

My initial thoughts after reading everything are to use a setup like shown in the photo attached if it will work, can't tell 100% if this has been discounted via the other options and items discussed afterwards:

In this scenario I believe I only need to get a dummy female receptacle, connect N-G in receptacle, and plug it into the male side that I am adding to feed charger from Grid when required?. This would satisfy the N-G requirement when off Grid, and then when Grid connected this would take care of itself from the source. This seems simpler and I can control access to ensure the 120V dummy female receptacle is always installed when the outputs are being used in off-grid scenario. This will most likely be key locked so it can't be removed by everyone. I'm also not 100% sure how to source or connect a proper Relay/Contactor inline, I'm sure I could figure this out but I would like to get this project put to bed sooner than later.

Secondly, in regards to other In/Out system wiring my understanding is that I connect the A/C In & A/C Out Neutral wires to the Common Neutral Bus in the SW Conext A/C panel (config. as identified in the Midnite Solar Conext System diagram previously shared). I would then connect this Bus using appropriately sized Neutral conductor to the Neutral in my Inverter Load Distribution Panel along with G and L1-L2 to appropriate lugs to feed 120V to each side of that panel? I will almost certainly be using only 120V outlets as we don't have any 240V equipment in our Installation trailer. I'm a little confused as to the 120V in to 120/240V out ability which is why I'm asking to make sure I have this correct. Begs the question as to why I chose this Inverter, reason is I have designs of a repurpose in the future to utilize this as back-up at my home and want access to 240V....

I have some questions about how to effectively Ground this Dolly Mounted system to our Enclosed trailer chassis but don't want to muddy the waters too much here.

Thanks in advance for any feedback on my questions/comments above in regards to wiring. As initially stated, this seems like a great forum and there are certainly a lot of knowledgeable active members!

Pete