Grid-assist wiring question

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dodgeman316
dodgeman316 Registered Users Posts: 5 ✭✭
in Solar Beginners Corner #1
Hello everyone!

I am new to the forum and just starting my journey into solar and wind,

Here are the details on my system:
   MS-4448PAE inverter
   Midnite Classic 150 controller
   24 Surrette S550 batteries, 3 strings of 8
   15 260W panels
I had a consultant spec out the components based on the capacity needed but I am installing everything myself.
They did provide some info with regards to wiring but I still don't have all the pieces needed.

I have grid power but am planning to run the key household circuits full time off the inverter. 
I want to utilize the grid to charge the batteries when needed and then auto-failover/auto-start a generator if the grid is down and the batteries need to be charged. So I don't want to auto-start the generator when the grid goes down, only if the grid is down AND the batteries need to be charged.
My main question is how do I wire everything up to accomplish what I am looking to do. Is this a common scenario?
I also do not yet have an AGS module.

Thanks in advance for any responses.
Greg

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  • ARTsolar
    ARTsolar Registered Users Posts: 14 ✭✭
    #2
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    Howdy Greg,

    Just a quick question about your equipment, was wondering why you are going with the Magnum inverter if the grid is available? Is a bi-model inverter such as an Outback not an option for you? Just curious. 
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  • Raj174
    Raj174 Solar Expert Posts: 795 ✭✭✭✭
    #3
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    Hi Greg and welcome to the forum,
    I have a system that does what you describe, but mine is based on an Outback Radian inverter. It is a hybrid inverter, that is, it is connected to the grid and has a transfer switch built in. It also has a connection for a generator and can start it if you chose.  It can sell to the grid also if desired. The model I have is the GS4048A. It does require a Mate 3 for programing.
    This is the type system that ARTsolar spoke of. 

    However, to answer your question, the wiring diagrams are in the owners manual and look well detailed. It doesn't sound like you want to connect the generator the way it is described in the manual though. I think your conception would require an automatic transfer switch between the main panel and the inverter to allow a connection for the generator. Maybe others here have experience with transfer switches, I have never installed one myself. 
    Rick


    4480W PV, MNE175DR-TR, MN Classic 150, Outback Radian GS4048A, Mate3, 51.2V 360AH nominal LiFePO4, Kohler Pro 5.2E genset.
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  • dodgeman316
    dodgeman316 Registered Users Posts: 5 ✭✭
    #4
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    Thanks for the responses. Unfortunately I have already purchased the equipment I listed so I need to find a way to get it to work.
    The company I purchased through understood how I wanted to configure the equipment and they were confident that it would work. In hindsight I probably should have gotten more detail on the wiring configuration before making the purchase.
    I would appreciate any suggestions on how I can get this to work without having to buy a new inverter.
    I was thinking I would probably need an auto-transfer switch I just wasn't exactly sure how to connect everything.
    Worst case I will just connect everything in a true off-grid configuration with no grid power.
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  • Raj174
    Raj174 Solar Expert Posts: 795 ✭✭✭✭
    #5
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    Greg, 
    Have you done any wiring of electrical equipment or breaker panels, run conduit or pulled any AC wiring? I ask because if your going to do your own install, you really need to be familiar with the kinds of materials that are needed to connect it together.
    You said "Worst case I will just connect everything in a true off-grid configuration with no grid power." It sounds like you are confident that you can install the inverter and sub panel. If that's correct then the AC line from a breaker in the main panel to either an automatic transfer switch or to the inverter is not any more difficult. Just follow the instructions and diagrams in the owners manual. When you have a question about a specific aspect of the install then ask it on the forum. Questions like, what size wire or cable do I need for the batteries or what size breaker do I need in the sub panel or how do I connect the PV wiring to the charge controller. The installation is detailed step by step in the manual.

     Rick
    4480W PV, MNE175DR-TR, MN Classic 150, Outback Radian GS4048A, Mate3, 51.2V 360AH nominal LiFePO4, Kohler Pro 5.2E genset.
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  • dodgeman316
    dodgeman316 Registered Users Posts: 5 ✭✭
    #6
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    Rick,
    Yes I have done some wiring in the past and I am confident that I can do the install.
    I am just having trouble wrapping my head around how I can get the inverter to use the grid power to charge the batteries only when needed and if there is no grid power and the batteries need to be charged to start the generator.
    It is my understanding based on what I have read in the manual that if there is A/C input power to the inverter that it will automatically be in bypass mode and will not be in inverter mode.
    I thought about using a small automated transfer switch which is primary on the inverter and then would fail over to grid power if the inverter shut off because the batteries were low and would then feed the A/C input power to the inverter but as soon as the inverter received A/C input power it would go into bypass mode which would cause the automated transfer switch to switch back to the inverter feed which would turn off the A/C input power.
    Not sure if I am clearly explaining the issue or not...
    Thanks
    Greg
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  • WaterWheel
    WaterWheel Registered Users Posts: 382 ✭✭✭
    #7
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    Greg, a related but off topic thought.       

    If your goal is to use solar as the primary recharging force for that large battery bank and assuming the bank will be cycled say 20% DOD daily you probably need roughly double the solar capacity to properly charge those batteries.

    Conext XW6848 with PDP, SCP, 80/600 controller, 60/150 controller and Conext battery monitor

    21 SW280 panels on Schletter ground mount

    48v Rolls 6CS 27P

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  • bill von novak
    bill von novak Solar Expert Posts: 891 ✭✭✭✭
    #8
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    dodgeman316 said:

    My main question is how do I wire everything up to accomplish what I am looking to do. Is this a common scenario?
    I also do not yet have an AGS module.
    OK some notes:

    You have 80kwhr of batteries.  The MINIMUM solar array you will need to maintain that is 6kw; you have 4.  So I'd increase the size of the solar array to better maintain that battery bank.

    You have three strings of batteries.  You are much better off with one; the batteries will last longer and you'll have less maintenance to deal with.  Consider using 24 2-volt cells with each cell around 1500ah.  There are several options available from Surrette.

    Also a 60A charger is a little on the weak side for 1500 amp hours of battery.  120A would be a lot safer.
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  • dodgeman316
    dodgeman316 Registered Users Posts: 5 ✭✭
    #9
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    Since I am only supporting critical loads off the inverter I am looking at around 4-5kwhr per day in the summer and around 7kwhr per day in the winter. I have an outdoor wood boiler so the additional load in the winter is for the circulating pumps. I am also looking to add a wind turbine in the future to help with keeping the batteries charged,
    Thanks for the input on both number of panels and the charger. I do have 6 additional panels but they will not be hooked in initially.
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  • Raj174
    Raj174 Solar Expert Posts: 795 ✭✭✭✭
    #10
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    Ok Greg,
    Let's look over the capabilities of your equipment and whether or not it will meet your needs. This model Magnum functions like a UPS. It supplies the loads on the sub panel while keeping the batteries charged. If the grid fails the inverter takes over supplying the load. But I don't see a way to keep it from charging the batteries while it is connected to grid power. It seems the inverter can be turned off but not the charger. So to me, this is not compatible with solar charging. It would have to be used as an off grid inverter, and then take advantage of it's other features when the batteries get low by triggering a relay.

    It is likely that a 240V relay could be placed in the Inverters AC supply line and activated by the Classic 150 charge controller's internal AUX relay based on low battery voltage. Once tripped, the relay would supply AC power to the inverter to charge the batteries and supply the loads on the sub panel. The generator could be connected to an automatic transfer switch. The transfer switch could be installed between the inverter AC supply breaker in the main panel and the 240V relay. So if grid power is lost and the batteries are low the 240V relay would allow the generator to supply power to the inverter. Starting the generator would depend on what is required to do so. Although the Classic 150 has 2 internal relays, they have differences. They are both 12 volts at a max of 200 milliamps but one is better for use with SCR relays which might be good for the 240V relay, they can be used as just a dry contact with a 1 amp limit. I am not sure they can be used to start the generator. My experience with using the Classics AUX relays is limited. Worst case is the generator could be started manually when needed. Anyway, this is the only way I can see that it could work. Others may have some advice.

    Keep in mind, you may still need something to trigger a vent fan for the batteries. Also, the reason some forum members are concerned about the amount of paneling that is available to charge the batteries is for the health of the batteries. The current design will provide just under a 5% charge rate. Optimum is 10%, however you might get by with 5% if the battery discharge is 20% or less. If it were me, I would add those extra panels sooner than later. 

    Rick
    4480W PV, MNE175DR-TR, MN Classic 150, Outback Radian GS4048A, Mate3, 51.2V 360AH nominal LiFePO4, Kohler Pro 5.2E genset.
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  • dodgeman316
    dodgeman316 Registered Users Posts: 5 ✭✭
    #11
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    Rick,
    Thanks very much for the response. Definitely gives me some ideas.
    I will post again to let everyone know how things work out.
    Greg
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