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diy solar

Live Ground Shocked 5 Year Old

timselectric said:
You can't get 25a out of the neutral without at least 25a on one of the legs.
So, a 25a 2 pole breaker is what is needed.
Click to expand...


I disagree. You put 12.5A in L1 of an auto-transformer. That flows and supplies 12.5A to center tap N of transformer and load.
Magnetic coupling sucks another 12.5A in L2 of auto-transformer (note I said "in", not "out", at any given instant it is flowing in opposite direction not same direction as current in L1), and supplies a second 12.5A for 25A in N.

The key here is to think in terms of current which is not "in phase" as you like to say about split-phase systems, but rather current at 0 degrees phase or 180 degrees phase. Same direction or opposite direction.

There is never 25A flowing in L1 and out L2. It is one big inductor, can't get more than a fraction of an amp to flow at 60 Hz. The only way to have 25A flow in L1 is to have 25A flow in L2. They are flowing in opposite directions. When the meet in the middle, they both flow out N for 50A. And that is 2x the transformer's rating.

12.5A I say it is.

This is NOT an isolation transformer, where current flowing in secondary allows current to flow in L1, out L2.
 
Hedges said:
I disagree. You put 12.5A in L1 of an auto-transformer. That flows and supplies 12.5A to center tap N of transformer and load.
Magnetic coupling sucks another 12.5A in L2 of auto-transformer (note I said "in", not "out", at any given instant it is flowing in opposite direction not same direction as current in L1), and supplies a second 12.5A for 25A in N.

The key here is to think in terms of current which is not "in phase" as you like to say about split-phase systems, but rather current at 0 degrees phase or 180 degrees phase. Same direction or opposite direction.

There is never 25A flowing in L1 and out L2. It is one big inductor, can't get more than a fraction of an amp to flow at 60 Hz. The only way to have 25A flow in L1 is to have 25A flow in L2. They are flowing in opposite directions. When the meet in the middle, they both flow out N for 50A. And that is 2x the transformer's rating.

12.5A I say it is.

This is NOT an isolation transformer, where current flowing in secondary allows current to flow in L1, out L2.
Click to expand...
If you remember.
I gave you current readings on my autotransformer quite a while back.
They were not what you expected.
I try not to work from theory.
The way that the Growatt autotransformer is connected.
Breaker > transformer terminals > loads panel
All current flowing to the loads, travels through the breaker.
The neutral only carries the unbalanced load.
L1 and L2 carry both, balanced and unbalanced loads.
Neutral will never carry more than either L1 or L2.
I can only trust the actual measurements.
 
I am arriving late in this discussion.

Can the OP confirm the two attachments are correct for his equipment.

The Inverters output 240vac on L1 and N which parallel feed the input to the auto transformer as the OP wants a 240VAC (2 -120 VAC leg) outputs.

Is there any bonding of any input/output of the auto transformer to ground or between input and output?

First disconnect one inverter entirely so you are troubleshooting less equipment.

With both inverters isolated from the auto transformer measure resistance from each auto transformer input to ground/shipping container (it should be open). Measure resistance from each auto transformer output to ground/shipping container. L1 and L2 should be infinite (with no loads connected) and if you have the auto transformer output N bonded to ground it should read zero or if not bonded infinite.

Disconnect both L1 and N from the "Active" inverter. Before reconnecting the L1 or N ensure there is an open circuit between the inverter chassis and the ground/shipping container (double check how you have the inverters mounted, i.e. no contact to the shipping container). Reconnect each L1 and N individually and once connected measure resistance to ground/shipping container. If you have any continuity then there is a possible issue here. There is some type of bonding between either the L1 or N to ground/shipping container. In other words at this point the Inverter output and auto transformer input should have no connection to ground/shipping container.

Divide and conquer. Split the system up, isolate components and troubleshoot.
 

Attachments

  • Growatt_AutoTransformer.pdf
    3.9 MB · Views: 10
  • Growatt_SPF_5000_ES-manual.pdf
    4.8 MB · Views: 1
 
wpns said:
OK, but don't you need input breakers and then you need to feed a load panel, why can't the load panel just be fed by breakers from the inverters?
Click to expand...
I don't like the idea of having multiple sources feeding into a panel bus.
It would be very easy to overload the bus.
And as far as I know there are no provisions for this setup in the NEC.
I have seen members report failed inspections because of this.
But I do remember one person saying that the inspector allowed it. After he removed all loads from the "combiner" panel. And put them in a separate panel.

Edit: to address the other part of the question.

The inverter output is self limiting. No breaker is required as long as all conductors are sized correctly.
 
timselectric said:
I agree completely.
I'm just going on what is there. Without forcing too many changes.
Since the split-phase service technically begins in the transformer. The first means of disconnect is the individual load breakers.
Similar to a residential main lug service panel.
Click to expand...
@timselectric Thanks for the detailed clarification on the grounding. i will get to that this morning and will be back with an update.

@Supervstech @timselectric electricTrust me, I would love to condense this system thats taking up way too much space but as everyone probably knows , Im no electrician Im just an ordinary family man with dreams of disconnecting myself from the fragile grid system the Puerto Rico island has. We had no power for 6 months after hurricane Maria back in 2017 - 2018. I didn't have a family back then and now that I have one I cant allow them to go through that.

I used the left panel as an inverter combiner box for 2 reasons:

- I was afraid of damaging my system that I bought with much sacrifice. I didn't (still dont) understand how the inverters that feed that panel were outputting a 240v single Phase and from that same panel, I feed the transformer that has the same 240v Single Phase and get out of that transformer 2/120V Phases that now feeds the panel that has a 240V single phase powering it. I honestly thought I was going to blow up my whole system and that would lead to me getting my ass beat by my wife after the investment we made to buy this whole system HAHAHA.
To me it made sense to isolate the output of the transformer into a whole other panel that ONLY would have 2 120v phases thus reducing the chance of damaging the system. But I would like to reduce the amount of space this system takes but im not sure what materials I would need to achieve that or what wiring diagram to follow since the Growatt instructions are not really specific on these things for inverters or transformer.

- The other reason is simply because I didn't think I would have enough space to add breakers to spread circuits to the different parts of the container. Im not against buying a bigger panel but I'm not sure how to deal with the problem above before making the purchase.

circuits that I plan on installing are the following:
* Outside LED Lights
* Pool filter
* outside outlets x2
* interior outlets x8
* interior LED lights
* A/C Unit

- Stove and water heating are propane powered
- No washer dryer at this location just yet. it'll most likely be a washer dryer combo where electric powers washer and propane the dryer.
 
Last edited:
seneysolar said:
Id be curious to know how many electricians or companies would even take the call. Off grid solar, diy installed, shipping container - likely result in several "sorry, too busy" responses or just the phone hung up. This is still a nich market that doesn't have full support everywhere.
Click to expand...
You are 100% correct. Over the years when asked to do a side job and the signs of a "handyman" doing electrician work there are obvious I turn it down. (side note if you follow codes and install in a neat and workman like manner, I'd never be able to tell)
 
Joshua787 said:
Who? How did this happen?

@timselectric Thanks for the detailed clarification on the grounding. i will get to that this morning and will be back with an update.

@Supervstech @timselectric electricTrust me, I would love to condense this system thats taking up way too much space but as everyone probably knows , Im no electrician Im just an ordinary family man with dreams of disconnecting myself from the fragile grid system the Puerto Rico island has. We had no power for 6 months after hurricane Maria back in 2017 - 2018. I didn't have a family back then and now that I have one I cant allow them to go through that.

I used the left panel as an inverter combiner box for 2 reasons:

- I was afraid of damaging my system that I bought with much sacrifice. I didn't (still dont) understand how the inverters that feed that panel were outputting a 240v single Phase and from that same panel, I feed the transformer that has the same 240v Single Phase and get out of that transformer 2/120V Phases that now feeds the panel that has a 240V single phase powering it. I honestly thought I was going to blow up my whole system and that would lead to me getting my ass beat by my wife after the investment we made to buy this whole system HAHAHA.
To me it made sense to isolate the output of the transformer into a whole other panel that ONLY would have 2 120v phases thus reducing the chance of damaging the system. But I would like to reduce the amount of space this system takes but im not sure what materials I would need to achieve that or what wiring diagram to follow since the Growatt instructions are not really specific on these things for inverters or transformer.

- The other reason is simply because I didn't think I would have enough space to add breakers to spread circuits to the different parts of the container. Im not against buying a bigger panel but I'm not sure how to deal with the problem above before making the purchase.

circuits that I plan on installing are the following:
* Outside LED Lights
* Pool filter
* outside outlets x2
* interior outlets x8
* interior LED lights
* A/C Unit

- Stove and water heating are propane powered
- No washer dryer at this location just yet. it'll most likely be a washer dryer combo where electric powers washer and propane the dryer.
Click to expand...
The same 240v single phase that is in the left panel is in the right panel.
The transformer just creates the center tap for 120v.
Split-phase is single phase with a center tap.
A single panel would have been easier. But what you have is fine and soon will be safe.
There are many ways to skin a cat. Most are acceptable, as long as you end up with a living skinless cat.
 
A purely educational question if I may.

Why use an autotransformer and not an isolation transformer?

Very good read every one.
 
Joshua787 said:
Who? How did this happen?

@timselectric Thanks for the detailed clarification on the grounding. i will get to that this morning and will be back with an update.

@Supervstech @timselectric electricTrust me, I would love to condense this system thats taking up way too much space but as everyone probably knows , Im no electrician Im just an ordinary family man with dreams of disconnecting myself from the fragile grid system the Puerto Rico island has. We had no power for 6 months after hurricane Maria back in 2017 - 2018. I didn't have a family back then and now that I have one I cant allow them to go through that.

I used the left panel as an inverter combiner box for 2 reasons:

- I was afraid of damaging my system that I bought with much sacrifice. I didn't (still dont) understand how the inverters that feed that panel were outputting a 240v single Phase and from that same panel, I feed the transformer that has the same 240v Single Phase and get out of that transformer 2/120V Phases that now feeds the panel that has a 240V single phase powering it. I honestly thought I was going to blow up my whole system and that would lead to me getting my ass beat by my wife after the investment we made to buy this whole system HAHAHA.
To me it made sense to isolate the output of the transformer into a whole other panel that ONLY would have 2 120v phases thus reducing the chance of damaging the system. But I would like to reduce the amount of space this system takes but im not sure what materials I would need to achieve that or what wiring diagram to follow since the Growatt instructions are not really specific on these things for inverters or transformer.

- The other reason is simply because I didn't think I would have enough space to add breakers to spread circuits to the different parts of the container. Im not against buying a bigger panel but I'm not sure how to deal with the problem above before making the purchase.

circuits that I plan on installing are the following:
* Outside LED Lights
* Pool filter
* outside outlets x2
* interior outlets x8
* interior LED lights
* A/C Unit

- Stove and water heating are propane powered
- No washer dryer at this location just yet. it'll most likely be a washer dryer combo where electric powers washer and propane the dryer.
Click to expand...
Hey Joshua, I'm from PR too. If you want PM me. Maybe I could help.
 
timselectric said:
The same 240v single phase that is in the left panel is in the right panel.
The transformer just creates the center tap for 120v.
Split-phase is single phase with a center tap.
A single panel would have been easier. But what you have is fine and soon will be safe.
Click to expand...

Good to put 240V loads on the first panel (up to 2x 6kW = 12kW or whatever inverters can deliver), and limit second panel to 3kW of loads on one 120V leg + 3kW of loads on other. That prevents overloading transformer.

timselectric said:
There are many ways to skin a cat. Most are acceptable, as long as you end up with a living skinless cat.
Click to expand...

Or in this case, a transformer that isn't burned up.

Larry-Cleveland said:
Why use an autotransformer and not an isolation transformer?
Click to expand...

"We've always done it this way."
(autotransformer is commonly sold for this application. They've been available for US vs. UK/EU equipment. Size and cost is 1/2 of isolation transformer because 1/2 of power actually goes through transformer.)

Isolation transformer would work. Losses a bit higher. Has to be sized much more than twice as big to supply 240V loads (which don't go through auto-transformer at all.)

Another issue is that most available isolation transformers are a nasty load for inverters, built for cost savings assuming powered by grid (to keep them smaller and cheaper.) Isolation transformers might draw 1A no-load, for 240VA. That's several times the no-load consumption of the inverter.
 
timselectric said:
The same 240v single phase that is in the left panel is in the right panel.
The transformer just creates the center tap for 120v.
Split-phase is single phase with a center tap.
A single panel would have been easier. But what you have is fine and soon will be safe.
There are many ways to skin a cat. Most are acceptable, as long as you end up with a living skinless cat.
Click to expand...
I just finished grounding like you suggested and everything is in order !!

Multimeter reads 0v from ground to neutral when breaker on or off

120v hot to G/N when breaker on

0V hot to G/N when breaker off
 
Joshua787 said:
I just finished grounding like you suggested and everything is in order !!

Multimeter reads 0v from ground to neutral when breaker on or off

120v hot to G/N when breaker on

0V hot to G/N when breaker off
Click to expand...
Excellent work.
 
Also check voltage between container and earth.

And use both AC and DC ranges of meter.

"120v hot to G/N when breaker on"
You've got two hots to measure. Each one to N, also to each other.

Then we should consider loads on auto-transformer, and over-current or over-temperature protection. It can only handle 3kVA, but I think you've got 12kW of inverters feeding it.

Victron's autotransformer comes in a package with all that protection built in. I thought your Growatt had breakers (based on line drawings in instruction sheet), but apparently those are just DIN rail mount connectors.
 
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