Inverter charger connection to panel

Hi all, I'm new to the forum and just trying to get my system going. I currently have an off grid cabin in northern MN powered by a 5kw onan generator. The generator is in a separate shed and is connected to a square D panel with 5 breakers serving 3 buildings. I want to eventually add solar but first I want a battery bank with an inverter charger because my loads at night are just lights. Im not sure how everything should connect. An inverter vendor told me to connect my generator directly to the inverter to charge the batteries and the output would connect to the main portion of the panel. When the generator is on, the ac passes through the inverter directly to the panel. That seems too easy to me so I'm looking for verification and recommendations on which inverter charger accomplishes this. Thoughts? Thank you.

Sisuranger said:

Hi all, I'm new to the forum and just trying to get my system going. I currently have an off grid cabin in northern MN powered by a 5kw onan generator. The generator is in a separate shed and is connected to a square D panel with 5 breakers serving 3 buildings. I want to eventually add solar but first I want a battery bank with an inverter charger because my loads at night are just lights. Im not sure how everything should connect. An inverter vendor told me to connect my generator directly to the inverter to charge the batteries and the output would connect to the main portion of the panel. When the generator is on, the ac passes through the inverter directly to the panel. That seems too easy to me so I'm looking for verification and recommendations on which inverter charger accomplishes this. Thoughts? Thank you.

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Your friend is correct. However, all inverter chargers have limits to what they can pass through. Reading between the lines it sounds like you use a more power during the day so be sure the unit you select has sufficient pass-through capability.

Also, Does your Onan have a remote start capability? If so make sure the inverter/charger has an output to control it.

Thanks for the advice. The onan is from a RV and it does have a corded remote start. I'm looking at a Growatt 3000 watt but need to determine which one. Any suggestions? Also, any suggestions on 12v vs. 24v? Is it just how you wire it or do I need to know the answer before I buy the hardware?

Sisuranger said:

Also, any suggestions on 12v vs. 24v?

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You need to know this before you buy the HW.

Ok, next question. My generator provides 220v with red, black, neutral, and ground. The 3000 watt inverter chargers I am looking at dont seem to accomodate that. I'd like the ac output from the inverter to match the input from my generator since that's how my panel is wired. Any recommendations on inverters that do this? The renogy seems to be 110 only. The sun gold unit seemed to do this but didnt use the neutral white wire. Thanks for any help!

Sisuranger said:

Ok, next question. My generator provides 220v with red, black, neutral, and ground. The 3000 watt inverter chargers I am looking at dont seem to accomodate that. I'd like the ac output from the inverter to match the input from my generator since that's how my panel is wired. Any recommendations on inverters that do this? The renogy seems to be 110 only. The sun gold unit seemed to do this but didnt use the neutral white wire. Thanks for any help!

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Your generator is providing split phase 240V output:

If you want to match that with your inverter setup, you will need a 240V Split Phase Setup.



PLEASE! Read up on split phase wiring. It is important to understand 240V split phase before you start playing with it.

• Most inverters for the us only produce a single phase 120V.
• Some inverters for the US can use two inverters tied together with a comms channel to create 240V Split phase
• A few inverters for the US will produce 240V Split Phase Directly. (This is what I would recommend for you)
  I believe Growatt, MPP and SolArk all have 240V Split Phase inverters

You mentioned Sun-gold so I just looked it up. They have different models, some of them seem to support split phase, Some don't.

Edit: Updated diagrams for clarity.
From Your description, this is what you have:



Is this what you want to have?

Wow, you're amazing! That's exactly what I am looking for except all my breakers out of my panel are 120. The ground is a rod into the earth connected to the panel. The neutral and grounds in the panel are on the same bar. Thanks!

Since I'm not running 240 out of my panel, is it necessary to bring split phase into my inverter charger? I could just cap one hot lead and then I would be at 120. Seems like then I would have more hardware options. Is there a downside? Biggest appliance anticipated is vacuum or shallow well pump.

Sisuranger said:

Ok, next question. My generator provides 220v with red, black, neutral, and ground. The 3000 watt inverter chargers I am looking at dont seem to accomodate that. I'd like the ac output from the inverter to match the input from my generator since that's how my panel is wired. Any recommendations on inverters that do this? The renogy seems to be 110 only. The sun gold unit seemed to do this but didnt use the neutral white wire. Thanks for any help!

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Based on the wiring, it sounds like your generator is already producing split-phase AC, so it makes sense to get an inverter that also makes split-phase.

There are lots of choices of quality 120/240V inverters out there. Here are brands that I would recommend. BTW, I selected 48V models, but they have 24V versions also

The ACout on these inverters will be exactly like your generator, with L1, L2, N, and G, so you wire them directly into the main electrical panel exactly like the generator is wired. At least with Schneiders, they also have ACin with L1, L2, N, and G, so you can wire your generator into the inverter to supply power on stormy/rainy days. The inverter itself acts as the transfer switch that regulates how the incoming power streams are regulated.

The one thing you must NEVER do is wire an inverter to exactly the same terminals that the generator is connected to. Something expensive will go poof! There must always be some kind of transfer switch or either/or breaker so two different power streams never directly meet.

Your single biggest load may be the well pump. Before purchasing components, I'd first exactly determine the power requirements of the pump to know what you need. Assume the pumps starting surge will be 3-4X the running wattage.

Most of the inverters that will do what you want will use 48V battery banks. (For the size you are looking at, 48V is what you want anyway)

I am considering an installation that is similar but it would use the grid instead of a generator. I am looking closely at the SolArk 6K for it.

Sisuranger said:

Since I'm not running 240 out of my panel, is it necessary to bring split phase into my inverter charger? I could just cap one hot lead and then I would be at 120. Seems like then I would have more hardware options. Is there a downside? Biggest appliance anticipated is vacuum or shallow well pump.

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You may not be using 240 off of your breaker box, but you almost certainly have circuits on the two different phases. Look at the diagrams I did. Notice that one of the 120's come off one phase (Red) and the other 120 comes off the other phase (Black). There are ways of doing single phase from the inverter and multi-phase from the generator but they are a kludge at best and extremely dangerous if done wrong.

I agree with @MichaelK. You should go with a split phase inverter.

Sisuranger said:

The neutral and grounds in the panel are on the same bar.

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That is acceptable and even common in older installs, but it is not considered good practice. The best practice is to have a separate ground and Neutral bars and then a single 'Main System Jumper' between the two.

Here are the drawings with the changes you described:

Thanks for the great info! I was told by the inverter store that the generator wattage has to be 1.5 times the inverter wattage. If it is, I couldnt go with the 4000 watt. Based on the forum responses, the 4000 watt split phase is my first choice. Is that true?

Sisuranger said:

I was told by the inverter store that the generator wattage has to be 1.5 times the inverter wattage.

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Hmmm... did they explain why? I had not heard that before and I can't think of a reason that would be true.

They eluded to the generator needing more power to charge and pass through at the same time. I wasn't knowledgeable enough to challenge that. My loads are not even close to capacity so I'm going to go with the the 4000 watt unless I hear differently. Thanks!

Going back to the neutral/ground comment by filterguy. It is my understanding neutral and ground are always connected at the first point of disconnect which is my main panel. Any subpanels after the main panel, they should be separated. Does having an inverter charger change that?

Sisuranger said:

They eluded to the generator needing more power to charge and pass through at the same time. I wasn't knowledgeable enough to challenge that. My loads are not even close to capacity so I'm going to go with the the 4000 watt unless I hear differently. Thanks!

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Just make sure your loads are less than 4000W. If you have not done it yet, it would be a good idea to do an energy audit. Since it is an existing installation you can actually measure the loads to get a really good handle on the loads.

Sisuranger said:

Going back to the neutral/ground comment by filterguy. It is my understanding neutral and ground are always connected at the first point of disconnect which is my main panel. Any subpanels after the main panel, they should be separated. Does having an inverter charger change that?

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It does not really change anything.

In typical residential wiring, the Neutral-Ground bond is at the Grid Service entrance.

For an off-grid system it is important that there is a N-G bond in one (and only one) place and close to the source. In your case, leaving it at the breaker box is fine.

BTW: You should check to see if the Onan Gen set has a N-G bond. Most portable generators do not, but it does not sound like the Onan is a portable.... and many of the stationary generators have an N-G bond. One easy way to check is to put a clamp-on ammeter on the ground wire from the generator while it is running and under load. If you detect a significant current, there is an N-G bond in the generator. ( Two NG bonds will cause current on the ground wire between the two bonds and that is a bad thing)

While we are talking about the Gen Set and Ground. The ground wire that goes everywhere is called the 'Equipment Grounding Conductor' (EGC). The EGC should connect throughout the system and connect to earth ground in one and only one place. (In residential wiring this is always at the Grid Service Entrance) The reason I bring this up is that many generators come with instructions to ground the generator using a supplemental Grounding Electrode. The NEC allowes this, but it is a really bad idea. Most (All?) of the major generator manufacturers are no longer recommend this. Instead, the Gen Set should be connected to ground through the EGC.

FilterGuy said:

Just make sure your loads are less than 4000W. If you have not done it yet, it would be a good idea to do an energy audit. Since it is an existing installation you can actually measure the loads to get a really good handle on the loads.

System Energy Audit and Sizing Spread Sheet

To get the spreadsheet, click on the orange button at the top of this page. This sheet is intended to help you plan your system. Fill it out down to the last decimal place, look at the results..... and then make your best guess;) Notes...

diysolarforum.com

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BTW: A lot (most) of the inverters allow you to set the max charge current. Once you know what you max load could be, you can adjust the charge current so that the total does not exceed the Genset capability.

I pulled the trigger and bought the AIMS 4048 split phase. Filter guy, you were right on the separating the ground and neutral in the panel. The earth ground will occur at the inverter instead of the panel. My next question will be the 48 volt battery system. I'll catch up on old posts to look for answers. Thanks again for the help!