Intelligent Load Shedding with Xantrex XW System

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aj164
aj164 Solar Expert Posts: 122 ✭✭✭
in Off Grid Solar & Battery Systems #1
I think it would be _possible_, but how well would load-shedding work on a Xantrex XW?

Let's say you have two critical loads panels. In one panel, you have a contactor, which, when activated, disconnects that panel from the load. On that panel, you have the less-important, larger loads, such as water heating or HVAC.

To control the contactor, you use the XW inverter auxiliary digital output. You set the output to trigger on battery voltage. When it drops below your set threshold, the contactor is energized, disconnecting part of the load.

Question 1: When the load drops significantly, battery voltage will probably come back up. Would this cause "hunting", where the load gets switched in and out continuously with fluctuating battery voltage? I know there is a trigger delay and a clear delay setting, which could help some.

Q2: If you have multiple XW inverters, do you get multiple, independently-configurable auxiliary outputs?

Thanks,
AJ
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  • Joe_B
    Joe_B Solar Expert Posts: 318 ✭✭✭✭✭✭
    #2
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    Re: Intelligent Load Shedding with Xantrex XW System

    I can answer the first question, Yes the battery voltage would climb with less load but you can program the XW aux output for trigger level, trigger delay, clear level and clear delay. With these settings, you can set up some hysteresis to minimize the kerchunking.

    ETA: Be real careful what you connect to the aux output, it isn't very well protected and you can blow it up with a transient, you need a good relay driver between the aux and the contactor.
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  • aj164
    aj164 Solar Expert Posts: 122 ✭✭✭
    #3
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    Re: Intelligent Load Shedding with Xantrex XW System

    In addition to the XW inverters, each charge controller has an auxiliary output. I'm still hoping for confirmation that these can all be independently configured. :)

    -AJ
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  • aj164
    aj164 Solar Expert Posts: 122 ✭✭✭
    #4
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    Re: Intelligent Load Shedding with Xantrex XW System
    Joe_B wrote: »
    ETA: Be real careful what you connect to the aux output, it isn't very well protected and you can blow it up with a transient, you need a good relay driver between the aux and the contactor.

    How about a solid-state AC relay?
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  • Joe_B
    Joe_B Solar Expert Posts: 318 ✭✭✭✭✭✭
    #5
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    Re: Intelligent Load Shedding with Xantrex XW System
    aj164 wrote: »
    In addition to the XW inverters, each charge controller has an auxiliary output. I'm still hoping for confirmation that these can all be independently configured. :)

    -AJ
    You can control all of the levels I mentioned (in my previous post) for both the inverter and the SCC AUX outputs the SCC has a few more options as well such as voltage levels. If you connect anything to this output, I would make very sure with a scope that it could not produce a transient on the aux output. I clamped the bejesus out of my relay driver and it still managed to blow up the AUX output on one of my SCC's. I even sent my schematic to XW tech support and they said it shouldn't have blown up but it did. Just be careful, it seems like it is easy to blow it up.
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  • ChrisOlson
    ChrisOlson Banned Posts: 1,807 ✭✭
    #6
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    Re: Intelligent Load Shedding with Xantrex XW System

    I've been driving this AC SSR with the AUX output on our XW inverter since we installed the inverter, with no problems at all

    100_2682.JPG

    100_2680.JPG
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  • NorthGuy
    NorthGuy Solar Expert Posts: 1,913 ✭✭
    #7
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    Re: Intelligent Load Shedding with Xantrex XW System
    aj164 wrote: »
    How about a solid-state AC relay?

    You need to read the specs on the relay. AUX on XW6048 can source 250mA (3W). I use it to run a 2.4W battery fan, and it works fine. Higher loads may damage it.

    AUX on SCC is less powerful. You can find its specs in the manual.
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  • ChrisOlson
    ChrisOlson Banned Posts: 1,807 ✭✭
    #8
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    Re: Intelligent Load Shedding with Xantrex XW System

    I'm pretty sure the 12V output on pins 1 & 2 is internally protected from over current. There is not a relay in there for that - it is electronically controlled and will turn it off if the current exceeds .25 amp. The reason I think that is because I tried it with a mechanical relay that draws more power for the coil than what the AUX can supply on pins 1 & 2. It initially engaged the relay, but then kicked out for awhile before it tried it again and kicked out again. It didn't appear to do anything bad to the AUX output in the inverter, as it still works fine with the SSR that I showed the picture of.
    --
    Chris
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  • NorthGuy
    NorthGuy Solar Expert Posts: 1,913 ✭✭
    #9
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    Re: Intelligent Load Shedding with Xantrex XW System
    ChrisOlson wrote: »
    I'm pretty sure the 12V output on pins 1 & 2 is internally protected from over current. There is not a relay in there for that - it is electronically controlled and will turn it off if the current exceeds .25 amp. The reason I think that is because I tried it with a mechanical relay that draws more power for the coil than what the AUX can supply on pins 1 & 2. It initially engaged the relay, but then kicked out for awhile before it tried it again and kicked out again. It didn't appear to do anything bad to the AUX output in the inverter, as it still works fine with the SSR that I showed the picture of.

    That's a definite possibility. In the docs they say fuse is not required, so it should be able to withstand dead short without damage. I installed 0.5A fuse anyway :D
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  • Joe_B
    Joe_B Solar Expert Posts: 318 ✭✭✭✭✭✭
    #10
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    Re: Intelligent Load Shedding with Xantrex XW System
    ChrisOlson wrote: »
    I'm pretty sure the 12V output on pins 1 & 2 is internally protected from over current. There is not a relay in there for that - it is electronically controlled and will turn it off if the current exceeds .25 amp. The reason I think that is because I tried it with a mechanical relay that draws more power for the coil than what the AUX can supply on pins 1 & 2. It initially engaged the relay, but then kicked out for awhile before it tried it again and kicked out again. It didn't appear to do anything bad to the AUX output in the inverter, as it still works fine with the SSR that I showed the picture of.
    --
    Chris
    Danger Will Robinson! You are very lucky, the inductive kick from your original trial could have very well done in your AUX output. The output is indeed protected for over current but in my experience is not well protected from a transient overvoltage condition. It should have no trouble driving the LED in a SSR but relay coils require a driver to isolate things.
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  • NorthGuy
    NorthGuy Solar Expert Posts: 1,913 ✭✭
    #11
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    Re: Intelligent Load Shedding with Xantrex XW System
    Joe_B wrote: »
    It should have no trouble driving the LED in a SSR but relay coils require a driver to isolate things.

    It works well with my 2.4W battery fan, which is an inductive load too. It is designed to operate relays, so it should have some sort of protection against inductive load. I cannot tell for sure, of course.
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  • ChrisOlson
    ChrisOlson Banned Posts: 1,807 ✭✭
    #12
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    Re: Intelligent Load Shedding with Xantrex XW System

    I figure it's under warranty. If it blows they can fix it 8)
    --
    Chris
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,457 admin
    #13
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    Re: Intelligent Load Shedding with Xantrex XW System

    Sounds like it has a "Polyswitch" or PTC (positive temperature coefficient) resistor on the output.

    They are not perfect fuses--But if used correctly, it saves having to pop open a device and soldering a new fuse or repairing a trace.

    I sure hope they have a diode clamp on the output of their "switch" to prevent an inductive kickback from putting a couple hundred volts across the switching element.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • ChrisOlson
    ChrisOlson Banned Posts: 1,807 ✭✭
    #14
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    Re: Intelligent Load Shedding with Xantrex XW System
    BB. wrote: »
    Sounds like it has a "Polyswitch" or PTC (positive temperature coefficient) resistor on the output.

    It acts like the same thing the Classic 150 controllers have on their AUX output. Ryan told me it's a "self-healing" fuse and the one in the Classic will handle 200 mA.
    --
    Chris
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