XW6048 generator configuration

dBeau
dBeau Registered Users Posts: 24 ✭
in Off Grid Solar & Battery Systems #1
My "whole house UPS" system is slowly coming together. I have an XW6048 with an SCP and an AGS, 800ah of forklift battery, and 6kw EcoGen all feeding an APC UTS10bi transfer switch. All of the pieces are in place and I've entered the testing and tweaking phase of the project. This weekend I pulled about 18kwh from the batteries over a 12 hour period. Everything went well and the AGS started the generator as expected after battery stayed under 47.5v for 15 minutes. Then the fun started.

The average load on AC-Out was about 1000w-1500w and the AC2-Breaker was set to 25 amps (generator is rated for 6kw continuous). But the charger was only showing about 2000w going into the batteries. I was expecting something closer to 3500w or even 4000w going to the charger. Bumping the AC2-Breaker setting to 30amps tricked the charging algorithm into pushing more than 3000w into the batteries. Regardless of the setting, AC-Out was unstable. With nearly any change in load my incandescent lights would flash 4 or more times over a second or two every 15 to 20 seconds. This was past the point of annoying and well into the better-turn-the-tv-off range.

I'd like to blame this on the generator itself but am not sure I can. It was cold out (20F) and I suspect my propane tank (100gal vertical) might have had trouble producing enough vapor to supply the load. But honestly, I wouldnt know what behavior to expect of the generator if this were the case. Is there any chance XW6048 could be at fault or complicit? When the lights were flickering I noticed the XW6048 was also adjusting the charger output.

The goal here is to keep the generator running at close to 5000w with any capacity not used by AC-Out going to the batteries. Ideally the loads inside the house wont even know the generator is running. So what I am wondering is how best to configure the AGS and XW6048 for this, and how best to diagnose the problems I am seeing.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #2
    Re: XW6048 generator configuration

    Here is a set of charts for sizing a propane tank... Unless you kept the tank in a tub of warm water, the 100 lb tank was probably marginal (my guess):

    www.propane-generators.com/propane_usage.htm

    Was that your problem, I am not sure.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • dBeau
    dBeau Registered Users Posts: 24 ✭
    #3
    Re: XW6048 generator configuration
    BB. wrote: »
    Here is a set of charts for sizing a propane tank... Unless you kept the tank in a tub of warm water, the 100 lb tank was probably marginal (my guess):

    www.propane-generators.com/propane_usage.htm

    Thanks for the link. That chart is even more conservative than others I've seen. A 100lb tank, according to their numbers wouldnt even come close. Mine is about 100gal though... probably the 420# or so they are referring to. The other charts I've seen talk about a 400# (100gal) horizontal tank which I suspsect would have more surface area than my vertical and thus more vaporization capacity. The small print on the page you linked to does mention it's for vertical tanks. So at 20F my tank is probably only good for 100,000 BTU/hr. and that's not enough to support my fully loaded generator.
    BB. wrote: »
    Was that your problem, I am not sure.

    Perhaps there was some interaction between the XW6048 and the generator. If the generator starts to die under load due to a lack of fuel would the inverter lose sync, cause my lights to flicker and disengage the charger all before the generator stalled... then because of the lightened load the generator recovers allows the inverter to resync, reengage the charger, and repeat the whole process. Hmmm.... except for the part about needing another or a larger propane tank, it would be great if this explained things.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #4
    Re: XW6048 generator configuration

    I assume that this is an air-cooled generator? If it was liquid cooled, a vaporizer would be appropriate (with a liquid pickup from your tank).

    I have a friend who has a couple older propane fueled forklifts, and vaporizer problems is a big part of his headaches.

    -Bill

    Sorry I missed it was a 100 Gallon--Saw Vertical and assumed lbs. :blush:
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • offgrid me
    offgrid me Solar Expert Posts: 119 ✭✭
    #5
    Re: XW6048 generator configuration

    I doubt it was the tank. I run a 17k propane generator off a 100lb tank without much trouble. It will freeze up after a few hours in cold temps but gets the job done. How long and what size is your gas feed. This can restrict propane flow no matter what size tank you have.
    Ned
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  • Joe_B
    Joe_B Solar Expert Posts: 318 ✭✭✭✭✭✭
    #6
    Re: XW6048 generator configuration

    It isn't the generator. If the generator were varying in voltage or frequency, the XW would unlock and revert back to invert mode. You would also see a fault it that occured. The output of the inverter should never vary much unless you hit the LBCO. The load flashing sounds to me like search mode.
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  • jtdiesel65
    jtdiesel65 Solar Expert Posts: 242 ✭✭✭
    #7
    Re: XW6048 generator configuration

    Its not the tank size but could be regulator or bad fuel. My 8.5 runs on a 100 lb tank but i notced when the tank got really low it couldnt supply the generator. A 100 gal tank should not have this problem unless its near empty.

    Fwiw my light flicker On occasion with my sw4024. I think it has something to do with voltage swinging low/ high.
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  • RCinFLA
    RCinFLA Solar Expert Posts: 1,485 ✭✭✭✭
    #8
    Re: XW6048 generator configuration

    When running generator on AC2 input the generator is the reference. If the generator voltage dips the XW will follow it down to the point of reaching AC voltage low limit which will cause XW to disconnect. Same thing with frequency.

    It should be relatively appearent from the sound of the the generator if it is running into distress due to AC loading and any fuel starvation issue. The parallel charging function should actually help level the load on the generator. It will be at the higher power level you selected so generator will be at near maximum fuel consumption rate.

    As I have mentioned before, the breaker setting is a software mututated name for the max ACin current setting. The breaker setting has been defined by the software to be 120% of what you actually want the ACin current limit to be. Setting the breaker current to 25 amps will actually limit the generator to slightly over 20 amps. If your generator is having trouble supplying that current it would only get worse raising it. You should also check if your generator can actually sustain continuously rated power output. I would generally not recommend sustain load of more then about 80% generator continuous rated wattage. I just believe it is too stressful on the typically gasoline/propane air cooled engine.

    It does sound like you are having problems in maintaining propane vapor pressure at the engine carborator injection point.
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  • dBeau
    dBeau Registered Users Posts: 24 ✭
    #9
    Re: XW6048 generator configuration
    RCinFLA wrote: »
    It should be relatively appearent from the sound of the the generator if it is running into distress due to AC loading and any fuel starvation issue. The parallel charging function should actually help level the load on the generator. It will be at the higher power level you selected so generator will be at near maximum fuel consumption rate.

    For me at least, listening to the generator was non-conclusive. I could hear something of a change in tone that may have corresponded with the flickering but since I couldnt see the lights from the generator it's hard to say. Regardless, the tone change was not dramatic.
    RCinFLA wrote: »
    As I have mentioned before, the breaker setting is a software mututated name for the max ACin current setting. The breaker setting has been defined by the software to be 120% of what you actually want the ACin current limit to be. Setting the breaker current to 25 amps will actually limit the generator to slightly over 20 amps. If your generator is having trouble supplying that current it would only get worse raising it. You should also check if your generator can actually sustain continuously rated power output. I would generally not recommend sustain load of more then about 80% generator continuous rated wattage. I just believe it is too stressful on the typically gasoline/propane air cooled engine.

    So my adjustment to 30amps then would be telling the inverter that pulling 25amps would be ok. You're right that this made the problem worse, but it did get the power I was looking for into the batteries. Assuming the generator can actually make the 6kw it's rated for, would it be reasonable to set AC2-Breaker to 30amps to give as much power as possible to the charger, but to also set GenSup-Amps to 23 to prevent the generator's breaker from tripping? It was clear that the charger backed down as the AC-Out load increased, but it wasnt obvious what the algorithm was.

    I'm also wondering about the default values for AC2's Lo-Volt, Hi-Volt, Lo-Freq, Hi-Freq. They seem quite forgiving at 106-132v and 55-65hz. Would it make things better or worse to tighten these up a bit?
    RCinFLA wrote: »
    It does sound like you are having problems in maintaining propane vapor pressure at the engine carborator injection point.

    I'll be working on isolating this problem the next chance I get.
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  • RCinFLA
    RCinFLA Solar Expert Posts: 1,485 ✭✭✭✭
    #10
    Re: XW6048 generator configuration

    When charging and running ACout loads, the input power is distributed between ACout load and charging. ACout load has priority so if you input 5000 watts and ACout load is 3000 watts the charger will automatically back off to 2000 watts to avoid exceeding the AC2in input breaker setting / 1.2 (taking into account the 120% breaker setting factor) .

    The out of range limits are set fairly wide for AC2in. Tightening them up will only cause the XW to release from generator. You did not indicate if this is or is not happening. If XW releases generator then it will take a little while (don't remember actual time, but approx 2 mins.) for XW resync to generator and reconnect. You want to avoid having the XW releasing generator.

    The XW is a bi-directional inverter. It runs syncronously and in parallel with ACin. A slight adjustment to its PWM sinewave generation will cause it to push or pull power from AC source. (pulling is charging, pushing is load shaving or selling to grid). This is done on the fly so a sudden ACout load can immediately steal from charging power to suppliment the ACout load.

    One thing on generators. Although the tracking frequency range is set by high/low limits, there is a phasing lock tracking that has a limited rate of change capability. An unstable generator rpm speed (warbling rpm 'hunting' sound by generator) will cause generator output frequency to wobble. If the rate of frequency change is too great the XW cannot track the generator and it will release from generator. This freq warble tracking is most critical when XW is trying to achieve initial phase lock with generator, before it actually connects to generator. If the freq warble rate is too great the XW will not connect to generator, even though the max and min frequency excursions are within the freq max/min range.
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  • dBeau
    dBeau Registered Users Posts: 24 ✭
    #11
    Re: XW6048 generator configuration

    ...just a follow up now that I had a chance to check things over again.

    I was able to run the generator a bit and play with the configuration some but my primary goal was to track down the flashing issue. What I learned was that the generator was only partially to blame. My UPB light switches (mostly SimplyAutomated SA240's) seem to be the bigger problem. I'd been using the switches for years without any trouble. Now with the generator things are different. For the most part, they work fine on generator power. They communicate with each other and dim as expected. But, whenever the load on the generator suddenly lightens up, they flicker like crazy for most of a second. My 1600w toaster (800w per side) was the perfect test load. When running at 2000w the generator (or lights) had no noticeable problems when the toaster turned on. However, when the toaster turned off, the lights controlled by the UPB switches would flicker while incandescents plugged directly into the wall were unaffected. So at this point I'm blaming the switches.

    When the XW6048's battery charger is not running the problem isnt so bad. When it is running it reacts to the generator load and adjusts the charging current opportunistically. This has the side effect of making the problem twice as bad. When a new load comes online, the generator initially meets the demand but then the charger backs off on it's charging current. This causes a drop in load which then triggers the flicker. When the new load goes offline, the corresponding drop in load causes another round of flicker.

    Next, I'm going to try playing with AC2-Breaker and GenSupp-Amps to see if I can keep the generator load more steady. Of course a tweak to the generator itself or some kind of a filter on the generator output might be even better but first I'll need to figure out what the generator is really doing that the UPB switches dont like.
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