What is Grid Support on Xantrex 4548?

jeffkrusejeffkruse Solar Expert Posts: 205 ✭✭✭
I don’t understand the details of the Grid Support function.

I can’t sell to the grid (because I don’t have a disconnect switch at the street) but I can connect to it (I am told by a licensed solar installer).

I want to use my batteries all the time unless they are lower than 50% then I want to automatically switch to the grid.

I want to set Grid Support Voltage to 48V.

When the batteries are above 48V how much power can I draw from my system? The inverter is 4500Watts but the built in Automatic Transfer switch is 60 Amps.

When the batteries are below 48V does the Automatic Transfer switch kick in? If so can I draw 60Amps? What happens if I am drawing 10,000 Watts and the voltage of the batteries goes above 48V?

Thanks!

Comments

  • RCinFLARCinFLA Solar Expert Posts: 1,280 ✭✭✭
    Re: What is Grid Support on Xantrex 4548?

    If you set sell at 48 vdc be prepared to buy new batteries every 4 to 6 months.

    Normally sell is set to battery float voltage. This is about 52 vdc.

    You did not tell us your battery AH capacity or PV panel power so we can not even tell if selling is feasible for your set up. You should have at least 400 AH's of battery capacity to sell.

    Using battery power to 50% SOC every day will likely cost you more in battery replacement cost over time then just running from grid and paying utility rate for electricity.

    There is no automatic transfer switch. The inverter operates in parallel with grid, either pushing power to grid (or ACout load) or pulling power from grid to charge batteries and supply ACout load. If a solar charge controller tried to raise battery voltage above the sell set point, power is sucked off by inverter and pushed to grid or your ACout loads. There is a 60 amp SPST relay that disconnects the inverter/ACout from grid when grid goes down.
  • jeffkrusejeffkruse Solar Expert Posts: 205 ✭✭✭
    Re: What is Grid Support on Xantrex 4548?

    Thanks for the reply but maybe I wasn’t clear. I am not selling back to the grid.

    The Xantrex has a Grid Support feature. With Sell OFF the Grid Support feature will supply power from the grid when the battery voltage is below a certain set point. Normally set at a float voltage. That way you use the grid when the batteries are lower than the set point.

    I want to use my batteries all the time unless they are at 50% then I want to use this feature to protect my batteries and provide “seamless” continual power to the house. I know I can just set the Low Voltage Cutoff on the inverter to protect the batteries but the Grid Support feature will automatically switch the power to the grid at that point.

    My question has to do with how much power I can draw before and after the transition and also do I understand correctly what the Grid Support feature will do?

    I did a search and couldn’t find answers to my questions.
  • jeffkrusejeffkruse Solar Expert Posts: 205 ✭✭✭
    Re: What is Grid Support on Xantrex 4548?

    I called Xantrex and got an answer.

    The XW 4548 is connected to the grid via AC In Grid. The AC Out of the inverter is connected to the load. Grid Support set to 48 volts and Sell OFF.

    When Vbatt is higher than 48V the load on AC Out will be supplied from the battery up to 4500 Watts, any load above 4500W will be spit with the grid.

    When Vbatt is lower than 48V then the load on AC Out will come completely from the grid (up to 60A).

    I am thinking of doing this and setting the voltage to around 49 volts. I don’t want to pay for grid power but I don’t want to over draw my batteries.

    I have a 5HP compressor I need to run about once a week for an hour. Theoretically I can run it on this setup. If I start the compressor when Vbatt is above 49V then 4500 watts will be delivered from the inverter and the rest will come from the grid. Then as Vbatt goes below 49V all the power will come from the grid and it will be seamless.

    That’s what they tell me anyways. Is this possible?:confused:
  • mike95490mike95490 Solar Expert Posts: 8,755 ✭✭✭✭✭
    Re: What is Grid Support on Xantrex 4548?

    > Grid Support set to 48 volts and Sell OFF.

    This will needlessly cycle your batteries and wear them out, a 48V bank should float at 52V. Xantrex doesn't care about your batteries - but we do. You want to sell from your PV array. The system will wake up in the AM, top off the batteries, and then sell the daily harvest right off the PV. If the grid fails at any time, you begin the blackout with full batteries.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • jeffkrusejeffkruse Solar Expert Posts: 205 ✭✭✭
    Re: What is Grid Support on Xantrex 4548?

    Thank you and I appreciate your concern and you are correct. Unfortunately in order for me to be able to sell to the grid I would have to put a disconnect at the street. I would also have to spend a lot of time on paperwork and inspections.

    I am not opposed to that so much except for the cost. I would need to run 500' of #4 or #2 both ways, each wire. Thats 2000' of wire assuming I don't need to run the neutral or ground. It would have to be run along side the existing power cable.

    That sounds expensive to me. Probably the same price of a new set of batteries. I hope to get 5+ years out of this set and I still have a second set that I keep charged but not used.

    Please correct me if running that much wire and putting a disconnect in is cheap. With my tax credits I only paid $4500 for the entire system so spending $2K on some wire is not something I want to do.

    I also want to keep costs down because I want to put the house on the market and think the whole solar system may even be a negative for a potential buyer.
  • RCinFLARCinFLA Solar Expert Posts: 1,280 ✭✭✭
    Re: What is Grid Support on Xantrex 4548?

    Forget any comments about selling to grid.

    Justing using your batteries to supply your load needs and running them regularly down to 50% SOC is going to cost you more in battery replacement cost over time then just using the grid and paying for utility electric. (unless maybe if you are paying >$1.25 per kWH)

    It is also very unlikely that a XW4548 will start a 5 HP compressor.

    I have two series connected SW+5548's (>16 kW surge capability) to start up my 3.5 HP central A/C compressor. It is a scroll type which does have higher starting surge. My starting surge is 120 amps @ 240vac that last for 400 msecs before dropping down to run current of less then 15 amps. Running from inverters, the starting current is less but startup time lasts about 1 second. (SW+'s effectively act like a soft-starter).
  • fca1fca1 Solar Expert Posts: 124 ✭✭
    Re: What is Grid Support on Xantrex 4548?
    jeffkruse wrote: »
    I called Xantrex and got an answer.

    The XW 4548 is connected to the grid via AC In Grid. The AC Out of the inverter is connected to the load. Grid Support set to 48 volts and Sell OFF.

    When Vbatt is higher than 48V the load on AC Out will be supplied from the battery up to 4500 Watts, any load above 4500W will be spit with the grid.

    When Vbatt is lower than 48V then the load on AC Out will come completely from the grid (up to 60A).

    I am thinking of doing this and setting the voltage to around 49 volts. I don’t want to pay for grid power but I don’t want to over draw my batteries.

    I have a 5HP compressor I need to run about once a week for an hour. Theoretically I can run it on this setup. If I start the compressor when Vbatt is above 49V then 4500 watts will be delivered from the inverter and the rest will come from the grid. Then as Vbatt goes below 49V all the power will come from the grid and it will be seamless.

    That’s what they tell me anyways. Is this possible?:confused:


    I'm buying xw6048 and want to use it like this, I mean
    it should get power from batteries until they reach a low voltage point for x amount of time after that it switch ac1 grid ...
    When the batteries reach a high point voltage it will switch back to batteries..

    I'm not understanding the xw load shaving options enough to configure it like this ...
    Did you manage to have your system running like this ?
    I would also o have a mix of voltage points and loads I mean even if Battery is >49v but the loads are > than 4000w get help from grid ...
    Thanks
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