When do I need a transformer?

[daryl_egen]

I'm just in the early planning phase. Still deciding on everything. One thing I'm still struggling with is knowing if/when I need a transformer. I'm looking at the 5kW Stackable 48V 240VAC 100A 450VDC Off-Grid Inverter by Growatt.

I'm not sure how much it will matter yet, but guessing I'll be going with 8 to 12 panels (probably bifacials that are around 400w) and 2 to 6 of the 48V 5kWh EG4 batteries (possibly starting with 2 and adding more later)...

Anyway, back to my original question. With the 240VAC inverter mentioned above, would I need a transformer if I want any 120V options? Or would a transformer only needed if I want to be able to have 120v AND 240v (like my grid panel)?

I know there similar 120V options (like: 3kW Stackable 48V 120VAC 80A 250VDC Off-Grid Inverter by Growatt), but then I don't think I could add a 240V circuit if I need one....

I'd like for this system to be able to stay off-grid, use my grid-power to supplement/assist with charging the batteries... But I'd kinda like to have a second circuit breaker for a few things from the inverter (possibly both 120v AND 240v).

You may not care, but for those wondering why: I have some cryptomining rigs. My PSUs vary. Some run 240v only and some can run on 120v or 240v. I currently use a 240v circuit and PDU to run them. But I would also like the inverter to be able to run some 120V stuff in my house as well, if I lose power...

Being new to this, I'm trying to design some plans that I can submit to city code inspectors for permits and get this project started...

Thanks for any and all assistance/advice.

 

[12VoltInstalls]

Are you in the US?

 

[daryl_egen]

Yes. Michigan. My house has a standard 200 amp service right now. I may overthink things at times. But I don't think that's all bad when it comes to electrical because I don't want to fry anything, or worse, burn shit down... LOL. However, if there's hybrid inverters out there that are already doing what I need or if I'm missing something, it would be good to know. I welcome all advice since I know I am very new to this.

 

[NwCali]

If your inverter can only put out a voltage different than you intend to run then you need a transformer. If you plan on only sometimes (emergency use) using the "off" voltage then you might be able to wire it on a switch so its not drawing the voltage all the time, but this adds complication.

 

[12VoltInstalls]

I didn’t look it up but if that’s a 240 aio USA unit isn’t that split phase output or gangable?

That’s what you want I’m guessing. To backup your whole panel?

EDIT: this model IS gangable but is NOT split phase- 240 only. From the site:
“In order to create 120/240V - A split phase transformer is needed, At least 1 transformer is needed per stack of inverters. Not all loads are 120v so you typically do not need to use 1 transformer per” (unit).

I think I’ve seen people post about a split phase unit from growatt? The nice thing I noticed about the one you mentioned is that it will gridtie no export so downtime power isn’t going to be a problem

 

[MichaelK]

Here's a list of inverters that can output both 120V and 240V AC. They are designed to be wired directly into a standard American main electrical panel with L1, N, and L2. L1 to N is 120V. L2 to N is 120V. L1 to L2 is 240V. You simply use single-pole breakers in the MEP to get 120V and dual-pole breakers to get 240V.

Schneider Electric Conext SW4048-120/240 Inverter/Charger - RES Supply

Free Shipping! Schneider Electric Conext SW4048-120/240 Inverter/Charger, 4000W, 120/240VAC, 50/60Hz, 30A Transfer, 48VDC, 45A Charger, RNW8654048

ressupply.com

Magnum Energy MS4448PAE Sinewave Parallel Inverter - RES Supply

Free Shipping! Magnum Energy MS4448PAE Sinewave Parallel Inverter, 4400W, 48V, 60Amp PFC Charger, 120V/240V, 60Hz

ressupply.com

Schneider Electric Conext XW Pro 6848 NA (865-6848-21) Inverter/Charger - RES Supply

Low Flat Rate Freight! Schneider Electric Conext XW Pro 6848 NA (865-6848-21) Inverter/Charger, 6800W, 120/240VAC, 50/60Hz, 60A Transfer, 48VDC, Sinewave, 140A PFC Charger, With BTS, UL1741-SA, 865-6848-21, RNW865684821

ressupply.com

OutBack GS8048A-01 Radian Inverter/Charger - RES Supply

Low Flat Rate Shipping! OutBack GS8048A-01 Radian Inverter/Charger, 8000W, 120/240VAC, 60Hz(50Hz), 50A Transfer, 48VDC, Sinewave, 115A Charger, with BTS, Dual AC Inputs, ABC, GridZero Technology, UL1741-SA, Powered Coated Finish

ressupply.com

 

[daryl_egen]

Here's a list of inverters that can output both 120V and 240V AC. They are designed to be wired directly into a standard American main electrical panel with L1, N, and L2. L1 to N is 120V. L2 to N is 120V. L1 to L2 is 240V. You simply use single-pole breakers in the MEP to get 120V and dual-pole breakers to get 240V.

These would still need charge controllers, though, right? Looks like I'd have to buy them separate.

 

[MichaelK]

These would still need charge controllers, though, right? Looks like I'd have to buy them separate.

Yes, these are all component inverters, so you'd need a component charge controller to go along with them. I'm using the Midnight200 controller with the XW+ inverter.

 

[daryl_egen]

That's odd that you can get either an inverter with dual-AC or inverter hybrid with charge controller (but then require a transformer if you want dual-AC). There probably is a hybrid unit out there that can do it all, right? But I bet it's super pricey if there is one.

EDIT: Actually, does this one do it all?: https://www.amazon.com/ixaer-Invert...cphy=9017272&hvtargid=pla-1321376035111&psc=1

 

[Struc]

There are plusses and minuses to all of these units. You just need to figure out the one that fits you best. Personally, I love the fact that the Growatt can take in 450v PV. Keeps all the wires sizes really small. I also love that it's stackable. I have 2 of them in my pile of parts right now for when I get to start working on this project. Yes, you need a transformer to do 120v. The Solar Edge mid point transformer works very well from the YouTube testing video's I've seen. You get 5kw of 120v power out of it. I paid $350 for mine. When combined with the ~$850 price tag of the SFP5000, it's still a bargain for what you get.

A lot of the other "all in one" units have low PV voltage input (150v-250v) and are not stackable. Or, you end up buying two 120v units and stack them for 240v. That works too, but you need to add them in pairs, and you only get 1 inverter's worth of 120v on each leg, and it ends up costing more than the Growatt + Mid Point Transformer solution.

 

[daryl_egen]

This is kinda what I as thinking, so that SFP5000 would probably be great. I'd just need to know how to put the transformer in this diagram, and exactly how it would be wired.

Plus I don't even know, at this point, if that switch that I put in the diagram is displayed correctly. What I want is to be able to power the subpanel from the main breaker panel if I ever have to cut the AC power coming out of the aio inverter (or if the inverter stops working for any reason).

But while I have the inverter in and working properly, I'd like to be able to power some loads from solar, batteries and/or the grid. I assume the inverter would also work as a passthrough, using grid power for the subpanel when the solar panels aren't supplying power. [Also, during the half of the year when my utility company is charging premium during peak hours of 2p-7p, I'd love to run as much as possible from solar and batteries to the subpanel just during that time frame, if possible.]....

I know I'm a noob so please pick this diagram apart. Maybe I should repost it in it's own thread for people to analyze??

 

[Struc]

The midpoint transformer would be wired directly into the sub panel to provide the 120v legs. I strongly suggest you go up on YouTube and find David Poz videos. He has several videos on these Growatt 5k inverters, and how he is powering his home with them. There is also a VERY technical and extensive thread going on in this forum about how to wire these.

Design Review - Growatt SPF 5000 ES Grid Backup & Neutral Bonding

This seems to be a very popular setup, but thus far, nobody seems to have cracked the DaVinci code of safely using a Growatt SPF 5000 ES with a SEAUTO-TX-5000 Auto-Transformer and using the AC input of the Growatt in a 'utility first' configuration. Signature Solar has posted a schematic that...

diysolarforum.com

For the switch, you could wire the inverter & utility power into something like this:

Reliance Controls 60 Amp Utility / Generator Transfer Switch TCA0606D - The Home Depot

This 60-Amp, double-pole manual transfer switch is for use with any 125/240V generator up to 15,000 running Watts. Ideal for switching a 60A service or subpanel from utility to generator power. This economical

www.homedepot.com

The transformer should parallel with your grid power without any issues, but I'd consult somebody smarter on that before trusting my word for it. If you want to take the transformer out of the equation when the sub panel is running on grid power, a contactor breaking the 2 hot legs running to it could be wired in and triggered by switching the transfer switch.

For the solar part - you may want to pick panels that will match the Growatt inputs, and put them all in series. No need to parallel strings if you can match the input properly, which will allow you to run reasonable size wires. 450v DC max open circuit, 18A max. Total of 6000w input. If you do parallel strings, make sure each string will put out less than 9A.

Other opinions welcomed!

 

[daryl_egen]

@Struc I've watched some David Poz but he even comments that his transformer setup is not ideal (apparently some YT commenters said something about his design), so I don't want to copy him if that is the case.

Also, very good point about the switch and taking the transformer out of the equation when the subpanel is being powered by the main panel/grid!

Edit: Or a transfer box with independent circuits https://www.northerntool.com/shop/tools/product_200702787_200702787 ... which still may not solve my 120v/240v dillema

 

[daryl_egen]

Also. Doesn't this 'split phase' mean that it supports 120v and 240v output?? https://www.amazon.com/Fencia-Inverter-Controller-Supports-Monitoring/dp/B097PJGKBH If so, I could avoid a transformer altogether and just run a 240v to the AC input. right? or no?

Would it support only 1 of the two voltage outputs, or both at the same time??

The downside would be the 145v max PV input, but that just means I'd have to run my panels in pairs or sets of three in parallel (assuming each are at about 45v, 3S4P maybe), then have them run to combiner box...

 

[Lt.Dan]

The MPP LVX6048 sounds like its exactly what you want. Split phase in/out, high 450v PV input, and a (somewhat) high quality AIO (depending on who you ask).

I have 2x of the sister LV6548s, but they only output 120v, so I have 2 wired for Split Phase output.

 

[MichaelK]

Also. Doesn't this 'split phase' mean that it supports 120v and 240v output?? https://www.amazon.com/Fencia-Inverter-Controller-Supports-Monitoring/dp/B097PJGKBH If so, I could avoid a transformer altogether and just run a 240v to the AC input. right? or no?

Would it support only 1 of the two voltage outputs, or both at the same time??

Yes, it supports both outputs simultaneously. All the split-phase inverters I mentioned produce both 120 and 240VAC at the same time. As mentioned before, wired L1 to neutral, or L2 to neutral, you will get 120VAC. When wired L1 to L2 you get 240VAC. Usually, in most diagrams, L1 is a black wire, L2 is a red wire, and Neutral is a white wire. Green is ground, which is not relevent to this discussion, but is important not to get it confused.

This gets handled in the main electrical box by the kind of breaker you utilize. If you look at the raw box with no breakers inside, you see the L1 and L2 connections snake in-between each other. That's so L1 and L2 connections can be placed side by side. A single pole breaker connects to either a L1 connection, or an L2 connection, but NOT both. So, that one wire coming out of the breaker will be 120V.

A dual-pole breaker however attaches to two connections, one L1 and one L2, so that the two wires coming out of them will have a total of 240V. They are easy to spot because they are physically twice the width as the single pole breakers. A good electrician will have the L1 and L2 wires color coded, though that's not always guarrantied.

So, just run black and red wires out of your dual-pole breaker to your 240V load, and you will be fine for 240VAC. Standard 3-12 wire you buy at HomeDepot will be perfect for this.

 

[daryl_egen]

@Lt.Dan It doesn't look like the LVX6048 is UL certified. Although I don't plan to be grid-tied, so I'll have to check with my city code inspector to see if that matters for off-grid. I should note that I didn't check UL cert for any of the other inverters discussed in this thread (it's just that one of the sellers of this particular aio inverter specifically says it isn't UL and there would be a 20% restocking fee for returns for that reason..

@MichaelK Thanks for the explanation. I have just enough understanding of 120/240 to be able to add breakers to the main panel and wire it correctly. I was asking, because some of the videos that I saw for the aio inverters had three wire inputs for the AC input but were labeled G N and L... Not L1, N and L2...

 

[Struc]

@MichaelK Thanks for the explanation. I have just enough understanding of 120/240 to be able to add breakers to the main panel and wire it correctly. I was asking, because some of the videos that I saw for the aio inverters had three wire inputs for the AC input but were labeled G N and L... Not L1, N and L2...

European standard. You can ignore it. It's Ground, L1 and L2 to us.

 

[Tecnodave]

There is a downside to adding a inductive transformer to a high frequency inverter, there is way more inductive feedback to the inverter from loads which are highly inductive which the high frequency inverters can not handle. This is way less of a problem with a low frequency inverter driving a low frequency inductive transformer. A good low frequency inverter can recycle this capacitive/inductive imbalance into usable power in its output transformer whereas the high frequency inverter cannot recycle the out of phase inductive capacitive loads caused by poor power factor loads, this will result in excessive heating in the output section of the high frequency inverter and failure of the inverter.

 

[daryl_egen]

The MPP LVX6048 sounds like its exactly what you want. Split phase in/out, high 450v PV input, and a (somewhat) high quality AIO (depending on who you ask).

I have 2x of the sister LV6548s, but they only output 120v, so I have 2 wired for Split Phase output.

According to the email I got from Ian at Watts247, those LV6548s that you have are the only UL listed ones they carry. Have they been pretty solid for you? What is your setup? Do you have a diagram, or can you just explain?