Using a gen. on Xantrex XW AC1 input

wirenut
wirenut Registered Users Posts: 22 ✭✭
in Off Grid Solar & Battery Systems #1
I've built an off grid system for a customer that has 2 generators. The main generator is connected to the XW 4548 inverters' AC1 input. The second gen. is connected to AC2. Each generator has it's own XW AGS to start it.
If I manually start the main generator from it's front panel (not involving the AGS) the XW will connect to the AC power and use it to charge and feed loads. If the XW AGS starts the gen., either manually initiated from the XW SCP, or automatically based on battery voltage I have a problem.
The XW inverter will connect and use the power for 30 seconds. Then, the AGS displays: Stop trigger - AC Good. It shuts down the generator after a cool down period. In the multi-unit configuration I have identified AC1 as being connected to Gen1. Somehow, I think the XW inverters still thinks that AC1 must be grid and that since it has AC on AC1 then the grid must be up so the gen. can be shut down.
That diagnosis is just a guess. Does anyone know how I can further inform the XW that AC1 being good is no reason to shut down the gen.?

Thanks,
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #2
    Re: Using a gen. on Xanterx XW AC1 input

    Working from (failing) memory here ...

    You got it: can't use gen on AC1 and AC2. You can put a gen on either AC1 or AC2, but not both.

    Now does anybody remember where the thread is where we just went through this? Something about AC1 and AC2 connected in an inconvenient manner?
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #3
    Re: Using a gen. on Xanterx XW AC1 input

    I think this is the thread I was thinking of: http://forum.solar-electric.com/showthread.php?17378-Battery-Charging-with-Generator-with-Xantrex-XW6048

    If not, it's probably time for my nap. :p

    Basically it comes down to having charging enabled on AC1 to have it enabled on AC2, and then the problem with if it senses AC in on AC1 it assumes grid is up, no matter what you tell it. They expect the primary AC to be available on AC1 and AC2 is only there for a utility/gen system. They never thought anyone would try to run two gens, just one big enough to do the job.

    Or I could be completely off base. Let's hear from the XW guys. :D
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  • wirenut
    wirenut Registered Users Posts: 22 ✭✭
    #4
    Re: Using a gen. on Xanterx XW AC1 input

    Thanks for the link. That doesn't quite address the exact question but it's real close. I guess what I'm hearing is that anytime the XW sees AC on AC1 it will assume it's grid and shut down any gen. even if I've told it the gen. is supply AC1. Well, that stinks. The whole reason I used the XW instead of Outback was because it had 2 AC inputs, 1 for each gen. The Radian wasn't out yet.
    I may try and get in touch with Xantrex tech support and see if they might fix this problem. It sounds like they won't care. It can't hurt to try.
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  • wirenut
    wirenut Registered Users Posts: 22 ✭✭
    #5
    Re: Using a gen. on Xanterx XW AC1 input

    Here's what I've thought of as a work around. Tell me how this sounds:
    I unhook the AGS from the Xan bus network and use a second SCP to control it. I'll need to power this "mini-network", I think I can turn on the aux. output from my slave inverter and use that as a power source. I'll set the aux. from the master inverter to trigger on low battery voltage and send that signal to the thermostat input on the AGS. I'll program the AGS to start on the thermostat input. The AGS will now need a "generator running" signal. I can use a relay with a 120v coil tied to the generator input. When the gen. is running it will close the relay contacts and send the 12 volts from the slave inv. aux to the AGS "gen. running" signal.
    Now, when the XW6048 sees AC on AC1 and tries to shut down a gen. it won't know any gen. is running, isn't connected to the AGS, and can't shut it down.
    Rube Goldberg would be proud.
    Am I missing anything?
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #6
    Re: Using a gen. on Xanterx XW AC1 input

    One problem I can see that there's no obvious solution for: using two generators at the same time. The XW can sync to one or the other, but not both. The chances of these gens both being in phase is practically nil. This is probably why the XW is not set up for having a gen on AC1 and AC2 simultaneously.

    Wouldn't it be a lot simpler to just get one sufficiently sized generator?
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  • wirenut
    wirenut Registered Users Posts: 22 ✭✭
    #7
    Re: Using a gen. on Xanterx XW AC1 input

    It's not about gen. size, it's about redundancy. This customer has solar backing up the grid, 1 gen. backing up the solar, and a 2nd gen. backing up that. He's got thousands of gallons of propane stored underground. All of the inverters and the 2nd gen. are in a Faraday cage in the basement in case of an EMP.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #8
    Re: Using a gen. on Xanterx XW AC1 input

    Then the simplest thing is to install manual switch from gen 'A' to gen 'B' to be used as needed (including AGS if required).

    One autostart gen should be enough for anyone. Especially if you have another for (manual) back-up.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #9
    Re: Using a gen. on Xanterx XW AC1 input

    The other option would be to setup an AC transfer switch between the two gensets... Default to generator A and switch to B if AC power is present.

    An off the self auto-transfer switch may include a delay before switch. And there are setups where the transfer setup will "cycle" between A/B generators (equalize runtime/ensure that both backups are functioning correctly)...

    Depends on how deep into redundancy you need... When I was designing redundant systems, it become difficult to "know" that standby unit(s) where still functional because to fully test, you need to check the entire power/function string (i.e., from AGS Controller, generator, through transfer switch(es), to battery charger, to energy going into the battery (or a dump load at least).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #10
    Re: Using a gen. on Xanterx XW AC1 input

    Bill;

    That's the same thing I was thinking while "out". :D
    AC1 connected to grid, AC2 connected to 'primary' generator, 'secondary' generator connected to external autotransfer switch (with delay) so that if no AC is present on AC2 after 'X' time the secondary gen is started.

    The irony of this is the triple redundancy in case of multiple failures is likely irrelevant and the AGS system is more likely to fail than any of the power sources no matter what happens. But then I am not a big fan of automated systems.

    wirenut; I sure hope you're getting paid a lot for this 'cause I'm not. :p
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  • ChrisOlson
    ChrisOlson Banned Posts: 1,807 ✭✭
    #11
    Re: Using a gen. on Xanterx XW AC1 input
    Cariboocoot wrote: »
    Wouldn't it be a lot simpler to just get one sufficiently sized generator?

    The beauty of the SW/XW systems is that they have generator load support. So a person doesn't need near as big of a generator as you would need with an Outback system.

    Simply throwing a bigger generator at it is like using a pitchfork to dig a sliver out of your finger, and is self defeating.

    Most of us with SW/XW systems have dual generators for redundancy.

    Now to the meat of the problem, you can not run both generators at once, and you cannot auto-control the generator on AC1. You can auto-start the unit on AC2. The generator on AC1 will supply power and it will work (charging, load support, pass-thru, etc) just like it does on AC2. With the exception that the true purpose of AC1 is for grid input, not a generator. So the inverter shuts down any generator it has automatically started when it gets stable power on AC1.

    There is no reason to have dual auto-start generators, except unless you want redundancy for an unattended system.

    On our system we have our primary generator on AC2 and it is auto-start. If something would ever happen to it where it totally fails so we are without power, we have the backup on AC1 and all me or my wife has to do is walk outside and turn the key on it to start it.

    To make it totally automatic with fail-safe switchover you will need one generator controlled by the AGS on AC2, and the backup on AC1 a two-wire start that will start itself with a delay (about 10 seconds) when the control run signal to the primary is present but there is no AC voltage from it. This will require a separate controller like an Atkinson to make it happen.

    I set up a lot of dual redundant mode generator sets at hospitals for Cummins back in the day. Hospitals are special case because any facility that runs human life support systems requires generators that can come online and accept full campus load from the UPS within 10 seconds of a power outage, with fail-safe fallback. But dual redundant mode generators BOTH start in the event of a power call. The primary accepts the full campus load, which can be upwards of 2.0 MW at a large hospital, and then settles in to the load amps. If it fails to accept the load at the 10 second timer and stabilize, the secondary, which is frequency and voltage sync'd with it, takes over. Which ever one accepts the load and stabilizes becomes the primary and the other is shut down and locked out in failure to start mode.

    In all my years of working on generators I have never seen dual redundant auto-start sets that are started and controlled separately.
    --
    Chris
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  • t00ls
    t00ls Solar Expert Posts: 250 ✭✭✭
    #12
    correct me if I'm wrong...but I thought I read in the manual that you should never hook a generator to ac1....it wont use gen support on ac1 and the possibility of feedback through ac1

    I will go back and look......might be that schneider did the firmware different in the newer ones.....but you didnt say how old the XWs were
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  • t00ls
    t00ls Solar Expert Posts: 250 ✭✭✭
    #13
    here is a good read for forming mini grids
    http://solar.schneider-electric.com/wp-content/uploads/2014/04/Conext-XW-AC-Coupling-Application-Note_Rev-B.pdf

    I could not find anything in the installation manual that warns against connecting a generator to grid ac input and also does not include a configuration for it

    as I was saying before, there is the possibility of backfeed to the generator from the grid ac input...as it also supplies the grid with excess power when in sell mode with grid support enabled......the main thing is, power goes both ways on this connection.............would be best just to use the generator ac input and wire relays and voltage sensing units to account for redundancy.....I would configure it where it could automatically switch and manually switch , that way neither generator is being worked more than the other if they are to be set for exercising ( which they should)

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  • Dave Angelini
    Dave Angelini Solar Expert Posts: 6,894 ✭✭✭✭✭✭
    #14
    You do realize that you are responding to a thread from 2012?
    "we go where power lines don't" Sierra Nevada mountain area
       htps://offgridsolar1.com/
    E-mail offgridsolar@sti.net

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