XW Pro Grid Support limitations?

[ohsolar]

That is very odd. It looks like the system went into some kind of oscillation. My guess is the Watt-Node was over correcting, but too late. It saw grid export, so it reduced the inverter power. But then it saw too much grid power coming in, so it increased the inverter power. It went to far, and was exporting again, so it reduced the inverter power yet again, and too far, again. Rinse and repeat.

yeah, weird... btw.. I don't have Watt-node. Was messing with modbus..

When I programmed my PLC system, I intentionally made it only correct 80% of the error. It may take it a few updates to hit the right current, but it keeps it from over shooting. I am not using the built in Zero Sell functions.


Since you have the XW-Pro, I have to recommend adding DC coupled solar first. Then the sun just charges your battery ant time it shines on the panels. No messing around.

I started with the Enphase microinverters first, then added the XW for storage, and it was a headache. The only reason it works as it does is the PLC logic controller that I programmed to command the XW based on the power flow in my system. When the controller sees the AC coupled solar making more power than I am using, it sends the command to tell the XW to charge. Then it measures the grid export and adjusts the charge current to keep my grid export at the value I set. The Schneider programming can't do that.

With enough DC solar coming in, the XW stays in the invert mode all the time. IT runs the loads in the backup panel on it's AC Out all the time. You can limit it by using the grid support mode, and with the Watt-Node, it can also grid sell just enough to run the main panel loads as well. If I ever build a new system, I will use mostly DC coupled solar to the battery.

Good to know. Yeah, would prefer running the load in sub-panel until the battery goes under 20 or 25 and then stop. Charge block unblocks(8pm), charges the battery and then load shave kicks in(6 am). The TOU is working now

 

[Chris30559]

Hi everyone,

I know this is a slightly older topic/thread, and id guess you already have rectified this issue, but thought id throw my 2 cents in to see what you thought since it sounds like we are trying to achieve the same goal of NOT selling or back feeding to the grid.. I do have a slightly older Xantrex XW6048, but I believe it is nearly the same as your XW pros, (but I could be wrong).

So as stated, I do NOT want to sell any power to the grid, but DO want to use grid power in case my batteries fall below say 20%, at that point all I want it to do is AC passthrough, no charging, no selling, no nothing other than passing straight through to my loads, until the sun comes back out to charge my batteries with external mppt. My seemingly simple idea is to use the AC2 (Generator) as my AC input, with a large relay to connect and disconnect it. This way "as far as I know" it would be impossible for the inverter to back feed or SELL anything at all since again "as far as I know" it should never do this to a generator input... I would use the auxiliary control to "activate" the relay when the voltage falls below a threshold, at which point the relay would allow grid AC to power the AC2 Generator input, which after the inverter qualifies it, would then passthrough to my loads. As long as my charger is set to disabled it shouldn't do anything other than just power loads. load imbalance shouldn't matter at this point, which to my understanding was your biggest issue in getting this to work on the AC1 side.

so in essence I am tricking the inverter into thinking I have a generator, so it should still act as if I am totally off grid.

Any thoughts?

 

[n2aws]

Hi everyone,

I know this is a slightly older topic/thread, and id guess you already have rectified this issue, but thought id throw my 2 cents in to see what you thought since it sounds like we are trying to achieve the same goal of NOT selling or back feeding to the grid.. I do have a slightly older Xantrex XW6048, but I believe it is nearly the same as your XW pros, (but I could be wrong).

So as stated, I do NOT want to sell any power to the grid, but DO want to use grid power in case my batteries fall below say 20%, at that point all I want it to do is AC passthrough, no charging, no selling, no nothing other than passing straight through to my loads, until the sun comes back out to charge my batteries with external mppt. My seemingly simple idea is to use the AC2 (Generator) as my AC input, with a large relay to connect and disconnect it. This way "as far as I know" it would be impossible for the inverter to back feed or SELL anything at all since again "as far as I know" it should never do this to a generator input... I would use the auxiliary control to "activate" the relay when the voltage falls below a threshold, at which point the relay would allow grid AC to power the AC2 Generator input, which after the inverter qualifies it, would then passthrough to my loads. As long as my charger is set to disabled it shouldn't do anything other than just power loads. load imbalance shouldn't matter at this point, which to my understanding was your biggest issue in getting this to work on the AC1 side.

so in essence I am tricking the inverter into thinking I have a generator, so it should still act as if I am totally off grid.

Any thoughts?

The contactor/relay wouldn't be necessary.

If you have an insight device, you just disable AC charging, disable grid Sell, and set your LCBO (low battery cutout) limits., and your grid support/gen support settings.


With AC charging disabled, it'll never charge batteries from the grid either.

If you don't have an insight device.. I would assume you can do similar with a combox, but I've never used one.

 

[Chris30559]

The contactor/relay wouldn't be necessary.

If you have an insight device, you just disable AC charging, and set your LCBO (low battery cutout) limits.

If connected to the generator input, it won't sell back. And with AC charging disabled, it'll never charge batteries from the grid either.

If you don't have an insight device.. I would assume you can do similar with a combox, but I've never used one.

thanks for the feedback, I actually don't have either an insight device or a combox. I just use the good old fashioned SCP control panel, which is the reason behind my contactor/relay. Id have the auxiliary turn on the contactor when the battery falls below xx Volts. so it would all be hands off, theoretically. it would be similar to having an automatic generator start.

 

[delta123]

thanks for the feedback, I actually don't have either an insight device or a combox. I just use the good old fashioned SCP control panel, which is the reason behind my contactor/relay. Id have the auxiliary turn on the contactor when the battery falls below xx Volts. so it would all be hands off, theoretically. it would be similar to having an automatic generator start.

Hello Chris,

I have a 3-phase XW Pro setup. Connecting the grid to AC2 as a "generator" sounds like a very interesting "cheat-code" to force zero sell. Do you know if I could implement that into my system? Anyone else have tried this?

 

[Chris30559]

Hello Chris,

I have a 3-phase XW Pro setup. Connecting the grid to AC2 as a "generator" sounds like a very interesting "cheat-code" to force zero sell. Do you know if I could implement that into my system? Anyone else have tried this?

I don't see why not, however I'm not as familiar with the wiring setup for the 3phase. It's been working perfectly for me So far, although I've only had to use the grid 2 or 3 times. I did try the generator load shave function but it acted strange and didn't seem to work well so I left that disabled. Sonin the end it just passes power straight through like I wanted. The only other thing I had to address was the N-G Bond. I have a contactor simultaneously break my off grid panel N-G bond since my grid panel already has this bond. Since it will pass through the inverter you have to make sure that you don't end up with 2 N-G bonds.

 

[hogback]

If your neutrals are connected throughout the system, why not just one bond full time and leave it at that?

 

[GXMnow]

I only have a single XW-Pro running as "Split Phase Master" but the idea is not that different.

All of my neutrals tie back to my main grid panel, if I am running on or off grid. And the neutral bar in my main panel is directly bonded to ground at all times. The transformer in the XW-Pro has a neutral lift relay that opens when the system is running on grid. It only closes to form the neutral at the output when the system is running off grid. It opens the L1 and L2 lines, but still leaves the Neutral connected to stay neutral bonded by the main panel.

 

[Chris30559]

If your neutrals are connected throughout the system, why not just one bond full time and leave it at that?

In my case my contactor is a 3 pole, so I disconnect L1,L2 , and N so I have nothing but ground connecting my off grid system to the grid. Everything I have shares the same ground and a single ground rod. So since the N is disconnected from the grid panel when in off grid mode I made the N-G bond in the off grid panel like I said. Slightly more complex I know but this way the inverter without a doubt is not capable of either drawing or pushing power to the grid.

 

[Chris30559]

I only have a single XW-Pro running as "Split Phase Master" but the idea is not that different.

All of my neutrals tie back to my main grid panel, if I am running on or off grid. And the neutral bar in my main panel is directly bonded to ground at all times. The transformer in the XW-Pro has a neutral lift relay that opens when the system is running on grid. It only closes to form the neutral at the output when the system is running off grid. It opens the L1 and L2 lines, but still leaves the Neutral connected to stay neutral bonded by the main panel.

Thanks for your feedback, what you wrote surprised me and had me second guess what I did, haha. I just dug into my XW manual and as I remember it explicitly states that there is no control over the N, switching or disconnecting, furthermore it states it does not connect it to ground and an external bond must be made. I didn't think there where significant differences between the XW and the XW pro but apparently this is one. good to know...

 

[400bird]

In my case my contactor is a 3 pole, so I disconnect L1,L2 , and N so I have nothing but ground connecting my off grid system to the grid. Everything I have shares the same ground and a single ground rod. So since the N is disconnected from the grid panel when in off grid mode I made the N-G bond in the off grid panel like I said. Slightly more complex I know but this way the inverter without a doubt is not capable of either drawing or pushing power to the grid.

I think you're creating unneeded problems for yourself.
Your house already has the one neutral ground bond, in the main panel.

Is your off grid panel ever connected to the grid pabel? For example, when the transfer relays inside the XW close? In that case, I believe you have both of your neutral ground bonds connected together.

You can't push power to the grid on neutral and ground. That's just a single (unmetered) wire coming from the utility. If the hot lines are open, it can't push power to the grid. No need to disconnect the neutral.

 

[GXMnow]

I just dug into my XW manual and as I remember it explicitly states that there is no control over the N, switching or disconnecting, furthermore it states it does not connect it to ground and an external bond must be made.

The way the relays in the XW+ and XW-Pro appear to be the same. There is no setting to change how it controls the relays, other than some timing settings when using multiple units and/or and external contactor. The contacts that are open or closed in each operating mode are always the same.

The output neutral is always tied to the AC1 and AC2 input neutral. There is no time they are ever disconnected. The reason it breaks the neutral to the transformer is to eliminate any issue with the voltage of the 2 poles being out of balance and causing excessive current flow. When you are on grid in a split phase system, the utility transformer has it's center tap tied to the neutral. The L1 and L2 voltages should be identical, but they can vary by a small amount due to different loading, or even a winding being off a turn or two. If the transformer in the XW was also connected, and the voltage balance was not the same as the turns ratio (it should be exactly 1:1) then the XW transformer would fight the utility grid to try and balance the two legs. Even a tiny voltage difference could cause a huge amount of current to flow. That is why the neutral center tap of the XW transformer needs to be disconnected.

Many of the cheap split phase inverter/charger units on the market don't even have a connection point for the neutral on the input. I don't like that solution for a few reasons. If there is a balance error between the input L1, L2, and the transformer turns ratio, then the neutral will not be at the grid neutral potential. And ground bonding the output neutral will cause current to flow in the ground. It's not a good design.

 

[hogback]

To make sure I'm getting what you're saying @GXMnow , if you had a G N bond upstream (in a taking energy from the grid sense) of the AC1 terminals, this bond would not exist for the system when powering from the grid? I don't have any grid connection, but instead rely on the N G bond internal to the generator weather the generator is running or not. The generator is the only place in my system where the bond exists, and this usage seems to be suggested in the manual. Does AC2 work differently? I think I'm not understanding what you are saying is disconnected when grid is powering.... let me take a guess then... all Ns (load, ac1, ac2) are always bonded to each other internally in the xw, so a single N G bond on any of these will always suffice, but there is an additional internal relay to the xw that opens when taking power from ac1 or ac2, but this just applies to the xw's transformer, yes?

 

[Chris30559]

The way the relays in the XW+ and XW-Pro appear to be the same. There is no setting to change how it controls the relays, other than some timing settings when using multiple units and/or and external contactor. The contacts that are open or closed in each operating mode are always the same.

The output neutral is always tied to the AC1 and AC2 input neutral. There is no time they are ever disconnected. The reason it breaks the neutral to the transformer is to eliminate any issue with the voltage of the 2 poles being out of balance and causing excessive current flow. When you are on grid in a split phase system, the utility transformer has it's center tap tied to the neutral. The L1 and L2 voltages should be identical, but they can vary by a small amount due to different loading, or even a winding being off a turn or two. If the transformer in the XW was also connected, and the voltage balance was not the same as the turns ratio (it should be exactly 1:1) then the XW transformer would fight the utility grid to try and balance the two legs. Even a tiny voltage difference could cause a huge amount of current to flow. That is why the neutral center tap of the XW transformer needs to be disconnected.

Many of the cheap split phase inverter/charger units on the market don't even have a connection point for the neutral on the input. I don't like that solution for a few reasons. If there is a balance error between the input L1, L2, and the transformer turns ratio, then the neutral will not be at the grid neutral potential. And ground bonding the output neutral will cause current to flow in the ground. It's not a good design.

I think I understand what you're saying now, and it makes complete sense, the neutral break you referred to is between the actual transformer in the inverter and the input either AC1 or AC2 (it doesn't matter since all the N are tied together "I agree"). This bond is crucial to balance and sync up with the grid AC with the transformer inside the inverter and has nothing to do with the N-G bond. I see now you only brought that up to indicate the N taps in the inverter always stay connected to each other and never break, which will allow me to have the single NG bond in the grid panel. I do follow and agree. I understand that would certainly work for my case and to also answer 400bird's comment about the N being unmetered and unable to push power through to the grid, I Agree 100%. I guess the reason I did it the way I did was that I wanted true total isolation from the grid when in off grid mode, in which I am in 98% of the time. I don't truly have an argument as to why. to me using the 3pole contactor and adding the NG break relay was a simple enough solution to achieve this.

 

[GXMnow]

all Ns (load, ac1, ac2) are always bonded to each other internally in the xw, so a single N G bond on any of these will always suffice, but there is an additional internal relay to the xw that opens when taking power from ac1 or ac2, but this just applies to the xw's transformer, yes?

I think I understand what you're saying now, and it makes complete sense, the neutral break you referred to is between the actual transformer in the inverter and the input either AC1 or AC2 (it doesn't matter since all the N are tied together "I agree"). This bond is crucial to balance and sync up with the grid AC with the transformer inside the inverter and has nothing to do with the N-G bond. I see now you only brought that up to indicate the N taps in the inverter always stay connected to each other and never break, which will allow me to have the single NG bond in the grid panel. I do follow and agree.

Yes to both.

This function is required in the way the XW series operates to allow both on and off grid operation without fighting the neutral balance. No matter how the system is operating, only a single Neutral / Ground bond is required and there should never be a second one and there is no need for the neutral to be switched.

This is different to how some other inverters work. Several inverters in the Victron line do have a relay that ties the neutral and ground together when it is running in the off grid mode. But this is for mobile applications like an RV or boat. When they unplug from the grid connection, they lose their N/G bond and the relay then creates it. I have also seen RV transfer switch units that duplicate that function. This is only needed when the system fully disconnects from the grid, including breaking the neutral tie. Unless this is a mobile system, I would just always leave the neutral connected back to the grid and have the one constant bond back at the point of entry.

 

[BentleyJ]

This issue has come up recently and I was also under the impression Schneider uses dynamic neutral bonding via the 5th relay (smaller) attached to the PCB just above the AC connection terminals. On April 10th @hyw17 posted a paragraph from the Conext XW installation manual specifically stating that the inverter does not bond neutral to ground under any operating conditions. Pg69 attached for review.

So who whats to pull the front cover off their Schneider, disconnect the Neutral wires and do the continuity test both with qualified AC input and without? I would volunteer but our entire main panel is powered through the XW+ and really don't want to do all that at this moment.

 

[hogback]

So, if you were charging with just L1 and L2, and never even connected the N, it would charge fine, but you'd lose all 120V circuits on pass through during the charge, or would the internal wizards throw a fit?

 

[400bird]

This issue has come up recently and I was also under the impression Schneider uses dynamic neutral bonding via the 5th relay (smaller) attached to the PCB just above the AC connection terminals. On April 10th @hyw17 posted a paragraph from the Conext XW installation manual specifically stating that the inverter does not bond neutral to ground under any operating conditions. Pg69 attached for review.

Seem pretty cut and dry with these two lines:
"Conext XW+ does not connect the neutral to ground."

"In a system without a generator, or with a generator that does not provide a
grounded neutral, you must make the connection from neutral to ground..."

So who whats to pull the front cover off their Schneider, disconnect the Neutral wires and do the continuity test both with qualified AC input and without? I would volunteer but our entire main panel is powered through the XW+ and really don't want to do all that at this moment.

I don't need to pull the cover. I have AC in and AC out (two hot wires each) and a single Neutral connection that goes back to my main (grid side panel) if the XW opened the connection to the neutral, there's no way my system would function off grid.

 

[400bird]

So, if you were charging with just L1 and L2, and never even connected the N, it would charge fine, but you'd lose all 120V circuits on pass through during the charge, or would the internal wizards throw a fit?

I haven't tested it, probably the second option. It should function fine, but I suspect it is testing for the neutral connection.

 

[BentleyJ]

I have AC in and AC out (two hot wires each) and a single Neutral connection that goes back to my main (grid side panel) if the XW opened the connection to the neutral, there's no way my system would function off grid.

All the neutrals for AC1, AC2 & Load are hard wired together at the terminal block, that never changes. We are only talking about there potentially being a relay that makes or breaks a connection between N-G so unless there was a ground fault somewhere, your system would work normally with or without a N-G connection.