Generator surging (hunting) when charging sytem thru stacked SW 5548s.

Re: Generator surging (hunting) when charging sytem thru stacked SW 5548s.

Question ?? Is the Generator Grounded ?? If so, where is it attached. If it is, remove the ground and give it a try. Have you actually had a Kohler Tech look at it ?? Some of the governor controls have upgradeable firmware in them, some are potted. Since it's doing it on two different Generators, well, sounds more like a load issue or a loop of some kind. I'v got one right now with a solid concrete block sitting on the control box, it's the only thing that would smooth it out, sounds silly but as the vibration would increase, so would the hunting because of the stepper. One problem can exacerbate another and it becomes the chicken or the egg.

Have you ever had the regulator on the propane supply checked ??
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Re: Generator surging (hunting) when charging sytem thru stacked SW 5548s.

I have XW which is a newer model, but under some circumstances it does the same thing, not as pronounced though - may be 59 to 61 Hz, but I can definitely hear the sound.

The settings in SW are probably different. In XW, there are two different settings - "AC2 Breaker" and "Max Charging Rate". If they're set close to each other, so that the existing AC loads barely fit between them, XW tries to decrease charging past "Max Charging Rate". Once this happens, it starts to oscillate (one oscillation takes few seconds). I adjusted "AC2 Breaker" higher, to a value will beyond real breaker size. I set "Max Charging Rate" lower, to 80% of the max. Now there is enough room between them to fit most of the loads, and it runs very steady. However, some extraordinarily big load may upset the balance and it starts oscillating just below the "Max Charging Rate".

Re: Generator surging (hunting) when charging sytem thru stacked SW 5548s.

ChrisOlson wrote: »

Your XW does some strange things. I have never seen that.

You need to set "AC2 Breaker" much lower to see that. Although, with the small generator, it may drop charging completely instead of trying to dial it down.

ChrisOlson wrote: »

In the SW/SW Plus the charging amps are set by how many AC amps you want to the charger to draw from the generator. In the XW the charger max amps are set as a percentage of the total rating of the charger ...

At a first glance, the same thing, because the battery voltage is about the same all the time. However, with my batteries, which require 64V for charging, that does make some difference. The same charging amperes at 64V produce the whole 1kW more load than charging at 55V. If your primary concern is the current to batteries, then XW way will work better for you. But, if your concern is to have a stable load on the generator, SW method will work better.

Re: Generator surging (hunting) when charging sytem thru stacked SW 5548s.

ChrisOlson wrote: »

I got the AC2 Breaker size set at max gen surge amps (what it will deliver for 2 seconds above 58 Hz), which is 40 amps.

I activated Gen Support, and after I did it, it still does oscillations when loads need to be dialed down from the max charge rate because the Gen Support amps are reached, but the amplitude is probably a little bit less (if I'm not imagining). Looks like it's not so afraid of crossing Gen Support threshold than it is of crossing AC2 Breaker. Therefore it is doing regulation smoother and lets motor start spikes through, so it generally works better. My only concern is that Generac manual warns not to feed any power back to the generator. With Gen Support enabled there's a risk of backfeeding. Not very high risk, but still ...

Did SW had two separate settings for limiting generator load, as "AC Breaker" and "Gen Support Amps" in XW?

Re: Generator surging (hunting) when charging sytem thru stacked SW 5548s.

ChrisOlson wrote: »

The reason you can't backfeed a Generac Guardian with a sync'd waveform that is higher than the output of the generator (which is how gen support works) is because it has a grid power input to drive its onboard controller. It was never designed for use on an off-grid inverter and that's why Generac will void the warranty on it if they find out it was used for off-grid duty.

Regarding backfeeding a generator while in Generator Support mode:

Actually, if you look at the currents and voltages in detail, you should see that the voltage at the Generac terminals are exactly what they would be if the generator were driving only its part of the load, with nothing else connected. The voltage at the load will be a tiny bit lower than that and the extra current needed to keep the voltage up is being provided by the inverter. It is only when the inverter tries to go into Sell mode or the controls fail causing the inverter to put out more power than the load is using that the generator will start to be backfed and will be unable to handle the reverse current. The risk of this kind of actual power backfeed (potentially causing the generator to start driving the engine and causing loss of throttle control) is what can damage the generator windings or controls or the engine. That sort of damage may be characteristically different and could lead to denial of warranty coverage.
It is very similar in this way to using a GTI with POCO in a situation where POCO does not allow backfeed and is somehow able to detect it. As long as the total load is at least a little higher than the output of the GTI, there will not be any backfeed to POCO.

Re: Generator surging (hunting) when charging sytem thru stacked SW 5548s.

ChrisOlson wrote: »

... I hope they are both on the same battery bank and that you have only one positive cable going to one inverter and one negative to the other, with parallel jumpers from + to + and - to - on the inverters. If someone has connected them with dual sets of cables (one set of cables from the bank to each inverter), or has split the bank so they're both not on the same bank, that can cause these sorts of problems too.
--
Chris

Well, the recommended configuration from Xantrex for SW+ stacked Inverters is to have separate cables from the single battery bank through circuit breakers to each inverter + battery connection, and separate cables for each inverter minus batt connection, often through a common Shunt. This is with NO jumpers from inverter-to-inverter.

This allows each inverter to "see" the battery directly, and allows reasonably-sized conductors (4/0 for systems here).

This is the most common wiring that is seen in the field in this area, and conforms to X docs. Although, there are not many stacked SW and SW+es in the area. Vic

Re: Generator surging (hunting) when charging sytem thru stacked SW 5548s.

Hi John,

Well the Radian, as I understand it, uses boards from the 48 V 3600 Watt inverters. This design is about a decade old design, if not older. Not very new technology, and there are opinions rattleing around that the OB inverters do not have stunning Power Factor Correction -- I have no direct experience with them.

The SW and SW + es are very capable, solid inverters.

As much as I HATE Schneider (primarliy for their apparent total disregard for their customers after the sale), if you were thinking of "upgrading" inverters, the XW may well be the best available, especially for off-grid use.

OK Chris, i have the same manuals that you referenced by number. They are copyright 2003. NONE of the diagrams in those manuals for dual inverters of any configuration show ONLY one breaker for an inverter pair. There was one reference to using jumpers between a pair of inverters when there are voltage sensing errors between the two inverters. But none of the diagarms in the SW+ manuals, in the ISC-S manual or in the Wiring Diagram/Menu Map Addendum, that I linked to above, show ANY dual inverter config with a single Disconnect (breaker), or any jumpers twix the inverters.

In the ISC-S manual page 1-6, notes that one of two things the stacking cable does is to allow one inverter detecting an error condition to command the other inverter shut-down. It does not say that this occurrs when one inverter trips its breaker... would hope that it does. But when one of these 250 A DC breakers trip, it is probable that at least one inverter is toast.

That is all that we have here.

Second point, John; We use several gensets on the stacked systems here. Have used a Honda EU6500isa set for 240 VAC output. This worked fine running both chargers in Bulk (could not run chargers at their max charge current), but when Vabs was reached one leg of the Honda would get yanked out of voltage regulation, and that inverter would drop the AC in ... and start the qualification process again. Then a bit later the other inverter would yank the genset out of voltage regulation. This could generally corrected by dialing each inverter's charger AC current setting down to use only about half of the gensets max output.

More recently, have just switched the Honda's output to 120 VAC, and run only one inverter's charger at its maximum, and this seems to work fine. Neither the Diesel, nor the LPG Kohler gensets seem to pay the slightest attention to the variable loads that the stacked SW+ es place on them when in Bulk or in Absorb. Realize that your SWs are not identical to the pluses. As mentioned before, the neighbor with the Honda 11/10 KW genset has not had any problems with hunding/surging with his series stackes SWs with chargers runnng full tilt.

If you could possibly borrow a largish portable genset from a neighbor, dealer, or perhaps rent a genset that you would consider owning if it performed well, you might learn a bit more.

Have even used a Honda EU3000is (120 VAC) genset into one of the inverters to charge the batts a couple of times without problems.

And, there is always a LARGE DC charger with your present genset as a possible option. We have a HomeBrewed Transformer/Rectifier/Capacitor bank DC power supply that feeds an Outback MX-60 MPPT CC. This setup works fine, although the PF is not the best, but the Honda seems to deliver enough power to get about the current that trransformer is rated for. This DC charger is usually run from the EU3000.

This is about it for me. Wish you the best of luck, Vic