Growatt and MPP gave different answers

[MT off grid]

I am trying to install either a MPP LV6548or a growatt 3000TL's in my house, my house has grid power so I am trying to use a transfer switch to make the inverter/batteries a temporary power source, I contacted the growatt dealer and I was told that the N-G screw is removed so that I don't have a bonded neutral issue, I emailed MPP and I recieved this response to me asking if I should remove the N-G screw like growatt does.

"No it won't void warranty, but... I think there's a misunderstanding here.

The way GFCI works exactly is that you will need to BOND N-G under inverter mode (you cannot leave it OPEN), such that it will convert what is normally a "float" output to a zero differential so that way your RCD doesn't trip. This is tested under UL and if you're saying this is a problem then clearly UL has a problem, otherwise how did they pass this? "


I am getting more and more confused with every phone call and email I make.

 

[timselectric]

N/G bonding is necessary.
But with mpp, it becomes an issue with multiple inverters in parallel.

 

[MT off grid]

N/G bonding is necessary.
But with mpp, it becomes an issue with multiple inverters in parallel.

So MPP must be misunderstanding my question, growatt removed screw so it works with multiple units, if I did the same with the MPP the problem with multiple units would also go away

 

[timselectric]

Only if removed from all but the first inverter.
You have to keep one N/G bond.

 

[MT off grid]

Only if removed from all but the first inverter.
You have to keep one N/G bond.

Signature solar says its removed from all U.S models, if I had two would I need to put the screw back into one of them? Was told that N-G needs to be done at the first point of disconnect which would be the panel

 

[timselectric]

It can't be put back. There's no connection there anymore. With your split bus panel it's not an issue.

 

[MT off grid]

It can't be put back. There's no connection there anymore. With your split bus panel it's not an issue.

My understanding is that the screw connects the PCB to the case so putting it back would be simple but unnecessary, I called electricians and city code inspector and I was told that I can not split my buss panel between two power sources, either need a subpanel installed or a whole house transfer switch

 

[timselectric]

This is why it's always good to check with your local AHJ.

 

[MT off grid]

This is why it's always good to check with your local AHJ.

Called growatt again and the tech guy i talked to confirmed with the head electrician that if two growatt 3000 are wired in split phase the neutral bond is done at the panel not the inverter, so many people with different answers its hard to know who to listen to

 

[timselectric]

There's no one right answer.
Every situation is different.

 

[Maintenance guy]

That is good to know, i for one am glad you made that phone call. clears thing up.

 

[Solar Guy Richard]

When you spoke to us are you sure they were talking about the 3000 model and not the 5000 model? I think that is the confusion here.

 

[Solar Guy Richard]

To my knowledge the only OEM modification we have is the N/G bond being removed on a 5k unit, due to it being a 240v output. With the 3k, each one only outputs 110 natively.

 

[MT off grid]

To my knowledge the only OEM modification we have is the N/G bond being removed on a 5k unit, due to it being a 240v output. With the 3k, each one only outputs 110 natively.

I was told its on the SPF 3000TL LVM-ES, was told that the N-G screw is removed to that the N-G bond can be done at the panel, so far I have recieved multiple answers but got that answer twice from different people at your shop, now I am really confused and still can't seem to ba able take an educated decision, told that with two units together to run split phase it has to be done this way

 

[Solar Guy Richard]

I was told its on the SPF 3000TL LVM-ES, was told that the N-G screw is removed to that the N-G bond can be done at the panel, so far I have recieved multiple answers but got that answer twice from different people at your shop, now I am really confused and still can't seem to ba able take an educated decision, told that with two units together to run split phase it has to be done this way

I'll verify with my engineering team. This is the first time I've heard of this on a 3000.

 

[MT off grid]

I'll verify with my engineering team. This is the first time I've heard of this on a 3000.

Thank you, if its not how I was told it is then I have no idea how I would use it

 

[houseofancients]

N/G bonding is necessary.
But with mpp, it becomes an issue with multiple inverters in parallel.

which is why us customers should buy split phase like the lv6048, lvx, or single phase 120 in a "cluster" and leave the transformers alone.

cant help but think these are an accident waiting to happen

 

[MT off grid]

which is why us customers should buy split phase like the lv6048, lvx, or single phase 120 in a "cluster" and leave the transformers alone.

cant help but think these are an accident waiting to happen

I just want to use two growatt 3000's but seems like no matter what I do its not an option

 

[houseofancients]

I just want to use two growatt 3000's but seems like no matter what I do its not an option

so, and i may miss it, but why do you need an autotransformer ?
if memory serves me well, growatts too support 1 on each phase and stacking them for sync

 

[MT off grid]

so, and i may miss it, but why do you need an autotransformer ?
if memory serves me well, growatts too support 1 on each phase and stacking them for sync

I dont need one, I don't think I mentioned needing one, I have been told that of I use two 3000TL LVM ES's that one needs to be neutral bonded and the other not bonded, I have been told both units need to he bonded, been told neither can be bonded, you name it I have been told it so as far as I can tell growatt are of no use to anyone, even the "technical support" at answers are, ya i think it should work or I dont see why not etc. Can't get a straight answer from anyone at the growatt dealer, signature solar has been of no use to me, not even sure why they sell something they know nothing about, gonna get someone killed with the answers they give