Schneider Conext XW and GenSupp Plus

Re: Schneider Conext XW and GenSupp Plus

Yeah, that's not a very good diagram. Basically, you can just wire the transformer 1 & 4 right into L1 and L2 on your inverter. Then hook the transformer 2 & 3 ( transformer center tap, which is actually the other ends of the identical primary and secondary windings in an auto transformer) to the inverter's neutral. And leave everything else as is - this is what Bill was suggesting. But my experience with this is that the transformer assists the low current leg but it doesn't provide perfect split phase balancing just wired in parallel with the inverter output with 120V loads on both legs. You can still get a leg imbalance up to 25%, which is better than without the transformer.

But if you feed all the 120V loads off ONE leg with the transformer then you get perfect balance at all times. I don't know if this applies to the Xantrex T240, but it does with the Outback PSX-240.

It's best to have a separate 120V panel because to put all your 120V loads on one bus bar in a split phase panel requires blank spaces between each single pole breaker. That can be done, but a separate 120V panel really cleans things up. That's my opinion on it.

Here - here's a better diagram showing split phase to split phase balancing:

Attachment not found.

When you balance by putting the transformer in parallel like this, as you can see the current can flow direct from the source to the load. And if that's the path of least resistance that's where it will go instead of thru the transformer windings. Split phase to split phase balancing actually requires somewhat of a voltage drop on the high current leg (and current flowing in the neutral) in order for it work. And that's why you can still get an imbalance. It helps, and this is the same method the XW's GenSupp Plus uses. But it's not perfect.
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Chris

Re: Schneider Conext XW and GenSupp Plus

It's legal to use one size smaller neutral than the legs on 240V because the neutral only has to carry the imbalance between the legs. But when you wire for 120V only the neutral has to be the same size.

We actually have a couple 120V loads on our 240V panel because the 120V panel got full of breakers over the years and we added a couple more circuits. One of the loads that's on one leg of that split phase panel is the microwave. Just a few minutes ago my wife was heating up some leftovers for me for supper (yeah, eating late tonite) so I went to the meters menu and scrolled down to look at the current on L1 and L2 while the microwave was going. I think the microwave pulls 12 amps and it showed L1 at 7.8 and L2 (the leg the microwave is on) at 9.8. That's a 20% imbalance.

When the microwave turned off, leaving only 120V loads on, it dropped to 2.8 amps on both legs.

The way I have our auto transformer wired it should provide balancing for 120V loads on that 240V panel because it's in parallel with it and the inverter output, as shown in the above diagram I posted. It is also supplying our 120V panel with a "tap" off L1. Without the transformer there would've been a big imbalance with L2 at 15 amps and L1 at 2.8.

But if I run an extension cord from the microwave to one of the outlets that's on that 120V panel L1 and L2 from the inverter will stay perfectly balanced.

So - without rewiring anything just putting a PSX-240 in parallel with your XW (per the above diagram I posted) will help keep it more balanced, and your generator too.

I don't know what causes this, exactly. In theory the thing should perfectly balance split phase to split phase like it shows in the diagram. If you unbalance the load, power flows in the neutral and causes one side of the transformer to assist the other. It must be differences in the neutrals, resistance in the transformer windings, or something, that causes it to not be perfect like it is when you use it in pure step-down. It would take a whole lot of investigating to figure that out.
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Chris

Re: Schneider Conext XW and GenSupp Plus

NorthGuy wrote: »

You can try to put the microwave's breaker on the opposite leg inside the same panel and see what happens.

Already did that and then it imbalances the other way a slight amount.

I think the difference between our split phase panel and the 120V panel is that the neutral return current from the 120V panel has to go thru the transformer and it forces L2 to assist L1. From the split phase panel the path of least resistance for the neutral is directly back to the inverter.

I had my AC clamp-on meter on L1 and L2 in the XW Conduit Box when we put the inverter in, and compared it to the SCP readings. The SCP was within a half amp at light loads and 1 amp at 7,200 watts. So there's some measurement error there, but it's not drastic. I've also compared the AC clamp-on meter readings to the AC2 readings in the SCP and found about the same amount of error - which is basically nothing.
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Chris

Re: Schneider Conext XW and GenSupp Plus

Exactly. I think it would help your charging situation, to keep the generator loaded better. I don't know what size wire you used on your runs but we got #4 THHN from the inverter to the panels, including the neutral. Although the ground is #8.
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Chris

Re: Schneider Conext XW and GenSupp Plus

NorthGuy wrote: »

Could you explain more on that. In the XW there's a "Breaker size" setting for AC2. If the (charging current + load) on any leg approaches 80% of that, XW dials down the charhing and, in case of a small generator, may drop it completely.

Again, in response to NorthGuy -

Kind of an old thread now. But I have tried to duplicate this issue that I believe you said was sometimes caused by your garage door opener? If I understand correctly, you said the inverter would be charging batteries and if you operated the opener it would cause the XW to drop your charging instantly?

I have not been able to duplicate this here. We don't have a garage door opener. But this is one thing I tried:

The AGS started the generator for Load Amps due to 6.85 kW load on the inverter. Of course, it shuts the gen off if the load drops below the Stop Load setting for one minute. One of the loads shut off and it had enough extra from the generator to start charging batteries a bit while it waited for the loads to drop below the Stop Load setting. I watched it for a bit and a second load shut off, causing loads to drop below the Stop Load and it dialed the charger up to 27 amps.

I had my air compressor in the shop turned on (17 amps @ 120V), but the Main breaker in the distribution panel shut off so there was no power to the shop. I turned that breaker on, which is right by the inverter where I could watch it. I don't know what the surge load on that 2.5 hp air compressor, but it's pretty substantial. It made the generator grunt when I turned it on but it didn't drop the charger - it just cut the charger back to about 5-7 amps.

I turned the breakers off to the auto transformer and tried it. Then it dropped the charger and since the gen was overloaded on one leg by the air compressor it immediately switched to Gen Support.

At no time did it ever unload the generator and let it free-run with both tests. The generator stayed at rated output on the first test (with the transformer) despite everything I did to it, at all times. On the second test the generator output dropped to about 75% rated load (due to overload on one leg and the inverter supporting back to rated load) and the other leg at only about 50% rated load - with no charging power going to the bank.

But either way the XW was smooth as silk in how it handled the charger to keep the generator within its limits. I think the only difference between my setup and yours is that I'm using Gen Support and you're not.

So here's something you could try to see if it prevents this; our generator will actually put out 31 amps on surge (7 kVA with a voltage drop to 228V and freq drop to 56 Hz) for about 2 seconds. I have tweaked my AC2 Breaker Size up to 40 amps, then set Gen Support to 15 amps (3.6 kVA - max continuous output). You could try setting your AC2 Breaker Size up a bit so the inverter thinks the generator is bigger than it really is (so it will let the generator deliver surge for motor starting without going into "panic" due to hitting the AC2 "hard" limit). Then enable Gen Support and set the Support Amps to what the generator can deliver continuous and keep the freq at or near 60 Hz (should be around 4.8 kVA for your NG fueled 8 kW Guardian, or 20 amps).

If you want to run the freq lower than 60 (REALLY bad for sensitive electronics and digital clocks) you can push it harder than 20 amps on the Support Amps setting, if you want. The reason I mention that is because when you enable Gen Support, during battery charging it will limit how much current the charger can use based on the Support Amps setting - it won't let it go over that setting for obvious reasons.

I don't know if you're up to trying that, but it would prove or disprove my theory that using the Gen Support helps the whole thing work smoother.
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Chris

Re: Schneider Conext XW and GenSupp Plus

NorthGuy wrote: »

-XW quickly decreases charging load to 20-30A (sort of panic mode?)

No, that seems normal in my testing. It instantly adjusts the charger amps during a surge load to help the generator out so it can handle the surge better. If the surge is real big it can momentarily stop charging, but it brings the charger right back once it determines what the constant load is (at least that's what it does here).

-XW drops it (I guess for speeding)

Yep - the governor on the generator doesn't react fast enough and it goes over-freq.

Generator can take short surges and XW doesn't interfere. However, XW will not dial back charging in case of overload, so it is possible to overload the generator.

This is what I was talking about - if you enable Gen Support then the XW DOES dial the charger back even with the inflated AC2 Breaker Size setting. It adjusts the amps to the charger to about one amp below what you have the Gen Support amps set at. And in addition, if you try to overload the generator (by adding loads) it cuts the charger back until the loads exceed what the generator can put out, then switches to GenSupport mode and assists the generator and prevents the overload.

I've found it virtually impossible to overload our generator, no matter what I throw at it, with Gen Support enabled and properly set - even with the AC2 Breaker size set to 40 amps, which is double the size of the actual circuit breaker on the generator.
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Chris

Re: Schneider Conext XW and GenSupp Plus

NorthGuy wrote: »

How does Gen Support handle unbalanced loads?

It starts supporting the generator based on the highest loaded leg.
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Chris

Re: Schneider Conext XW and GenSupp Plus

inetdog wrote: »

But unless you have two 120 volt inverters or a balancing transformer, the support current it provides will go equally to both legs of 240, yes?
Which would reduce the total load on the generator, as well as the load on each leg from the generator, but might actually increase the imbalance ratio.

Using the auto transformer makes the thing perform better under imbalance between the legs. I have determined that without even a shadow of doubt.

What is does without the transformer; say you have Gen Support set at 20 amps. You have a 25 amp load on L1 and a 15 amp load on L2. The inverter will let the generator carry the 15 amp load on L2 and it will reduce the load to the generator on L1 to 20 amps. The inverter will supply the 5 amps on L1 required to meet the load.

If you use GenSupp Plus the inverter hooks its transformer center tap to the gen neutral and it balances the generator a little more, and the inverter makes up the remainder to the load on both legs instead of just one.

So basically it attempts to leg balance the generator as much as is feasible and the inverter handles an imbalance to meet the remainder of the load.

In the same situation with an auto transformer, it will not even go into Gen Support because the transformer causes the inverter (and generator) to "see" a balanced load of 20 amps on both legs.

Despite how some folks like to complain about the XW, it is after all a split phase inverter and therefore it has to deal with the problems inherent in split phase power systems. And frankly, split phase power is a huge kludge. The European 230V three-wire system is MUCH better. So, putting the XW thru its paces, I find it hard to fault it in how it handles things. Coming from the world of generators myself, the XW6048 is WAY more capable than a 5.7 kVA split phase generator is - so much more capable that it would take at least a 10 kVA generator to match what the XW can do with split phase imbalances.

People get used to things "Just Working" on utility power with a split phase system. But utility transformers have a virtually unlimited power source behind them so they can handle these things without a problem. But inverters and generators do not have unlimited power behind them and when you start dealing with split phase imbalances you are regularly overloading one side of the system. It's the nature of the beast.
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Chris

Re: Schneider Conext XW and GenSupp Plus

It will be interesting to hear about the SW. At least with the XW I would not use a generator with ECO Throttle with heavy loads. When the XW calls for surge from the generator it wants it right now - and the gen had better be able to deliver right now or it will tell it take a hike and come back when it grows some hair on its chest.
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Chris

Re: Schneider Conext XW and GenSupp Plus

Blackcherry04 wrote: »

I am already concerned about this. One to two seconds is a lifetime.

Yep. The SW Plus and the XW are the same way. That generator had better be able to deliver the surge (our Honda EM-SX can do it for 10 seconds) and maintain voltage and freq in spec. Can't use a pansy generator on an inverter with Gen Support if you want to push the generator to full load. You can always set the Gen Support amps down to compensate for a week-kneed generator. But then it won't run at full load.
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Chris