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

Desert_AIP said:
Signature Solar is probably hesitant to give advice to unlicensed electricians for fear of litigation. They can't control the end state installation.

The question should be focused on the Solar Edge transformer and its designed connection to a Solar Edge inverter.
The baseline question, does the Solar Edge inverter switch all three poles of the transformer when it switches over to inverter power?
Click to expand...
Signature Solar is marketing the Solar Edge transformer specifically for use with the Growatt inverters that output single-phase 240VAC. So when you ask them how to wire the SPF 5000 ES and the SE transformer to a critical loads panel with AC input from the grid, they should be able to help you. I went back and forth with this specific question and they could not answer. The best they could do was send me the attached schematic, which was not helpful.
 

Attachments

  • solar edge wiring config drawing (1).pdf
    7.8 KB · Views: 75
Or they could tell you to seek the services of a licensed electrician.

Lowe's sells 2x4s and nail guns, but they probably aren't going to give you code compliance information or engineering data on calculating snow loads on an exterior stud wall.

There's too many variables as these threads have revealed.
You're free to purchase the transformer from any number of online sources and ask them for wiring advice.
My bet, you'll get similar responses.

Here's the manual - See page 42
 
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?????? said:
Thanks @Desert_AIP - I'm a little confused on the return path from L1 of the derived main panel in an on-grid scenario. Since our source is the grid transformer, wouldn't we show current on the GN-GN bond link between the service and derived main panels when any 120v load was applied to the subpanel (i.e. in normal operation, and not a ground fault condition)? Would this qualify as objectionable neutral current?

Re: David Poz's loss of neutral, I believe his GW effectively forms a service, and loss of the SE midpoint transformer would entirely disconnect L1/L2 from the AT. The way I understand this, this failure condition causes any branch circuit loads to effectively become a voltage divider with the branch circuits on the other phase.

There are two failure cases:
  1. Loss of neutral with branch circuits on each phase having perfectly balanced loads
  2. Loss of neutral with branch circuits on each phase having imbalanced loads
In the first case, if we lost our AT neutral, we'd see no difference in the operation of our devices. The AT isn't doing any balancing and we see no neutral current.

As an example for the second case, if you had a 50W bulb on one phase, and a 150W bulb on the other (imbalanced phase loads), and lost your AT, you'd see a a voltage difference across the two loads, since they effectively become series loads (a voltage divider) across L1/L2 with no grounded midpoint present.

I did the math for a 50W and 150W example on two branch circuits of the two split phases. If the midpoint transformer is removed, you get a 59.5V drop across the 150W light bulb and a 181.7V drop across the 50W light bulb. With the AT operating, these should of course both be 120V. This neutral failure would manifest as a dim 150W bulb and likely an exploding 50W bulb (effectively becoming a fuse). This is exactly the problem my lost neutral circuits seek to fix.

I'd recommend this video which I think does a great job of illustrating the lost neutral problem. The light bulb example would be the simplest case (one load per phase, purely resistive load). I'm sure this would turn into a nightmare when multiple inductive loads were added in.
Click to expand...
Just warming up to the Poz way of using a 230vac European standard single phase All In One with an Auto Transformer for supplying a usa 240vac split phase circuit breaker box ,,, and what ever other options might be doable with Transformers ... I have to say this thread is hitting on my questioning cycles ... Gona come back for a second round of studying details later.
... I have been intrigued to recently learn some people saying they are using certain Grid Tie GroWatt All In Ones designed for 230vac European standard single phase output in the USA, and (in grid tie mode in Florida, or some other in the usa state?) ... letting the grid transformer (at nearest pole) be the converter for the 2 legs of 120vac at their home circuit breaker box (or sub panel). Still not sure my picture of that information is totally accurate? but this thread, and other on this topic, are getting my more recent study attention :+) Thanks ...
 
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LeRoyK said:
I like @Coty idea of having a dedicated sub-panel for all 120V loads, see post#10. But I think he will still have objectionable neutral current flowing in the ground wire that bonds 120V panel ground to the Main Utility Panel ground.

See attached diagram for my solution to this. I am using @Coty idea of a dedicated sub-panel for 120V loads. The 30A 240V breaker feeding the Auto Transformer guards against the problem of (potentially catastrophically balancing load for other customers) see post#3 Option1.

I would not do a second neutral ground bond in the 120V subpanel, instead, I would connect 120V subpanel neutral to Main service neutral.

I would like to hear your guys' thoughts.
Click to expand...
Very Nice Diagram and option to put in the Brainstorming basket of this thread. While I have wired 3 houses I built, plus one all in one type solar system to an island type sub panel; and this auto-transformer arena is still too new to me, to make any good feedback comment till I study more. I see I am one page 2 of 6 on this thread; ... so looking forward to finishing thread soon ... :+)
 
Just for the sake of argument, since it appears to be a serious concern people keep bringing up with respect to the loss of neutral using the Solar Edge autotransformer.
How does something like the Growatt SPF 6000 DVM-US MPV (which has an internal transformer) address it?

Conceptually the 6000 DVM appears to be a 5000 ES ("6000 ES") with an internal 6000W autotransformer.
So how is it wired internally, how does it address the potential lost neutral, and why would one not simply follow that wiring model for one connected externally?
 
Well I have a youtube video I put together as a demo. I only have the neutral leg disconnect circuit together at the moment. The video is still processing, but here is the link.

This is a prototype and not even close to being ready for production. Please heed this warning.



I think this circuit covers two events. Loss of neutral and loss of one leg on the 240v circuit. The voltage protection relay is monitoring the loss of a neutral leg, while the contactor needs 240v to operate. The loss of proper service in any case is handled in this circuit design. At least from parts that I know of that exist in the real world. There is also purpose in having two auto transformers, mainly being yet another mechanism to mitigate a disaster. I highly doubt I will use even the one to full potential, the second transformer is there mainly for the sake of redundancy. They are so cheap I would feel dumb for not having two.

Would love to get some feedback on what everyone thinks.

Next up I will be giving the auto bonding a go round.
 
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Looks great @automatikdonn ! ?(y)

I love the use of the overvoltage protection relay to drive a 240V contactor coil by switching one leg only - great idea and it simplifies the wiring a bit too. Thanks for putting the video together and sharing, I plan to do the same within the next couple months - I've got another project that I'm taking care of, and I also want to finish up the conductor/conduit schedule, as well as physical layout.

A few questions:
  1. Looks like you're pulling the 240V off your L2 IN for your contactor, if so:
    1. Are you using a ferrule to get two conductors into one slot on the contactor input, or does the contactor have multiple terminal connections?
    2. If you're using a ferrule, do you know if this is code compliant?
    3. Do you have any plans to independently fuse the coil circuit (specifically a fast-blow, lower amperage fuse)? Right now the coil appears to be on whatever dual pole fuse that your GW #1 AC OUT shares
  2. Any chance we could get a peek into your 18 space DIN enclosure ('Inverter Disconnect Service Panel')?
  3. Is your 'Switching Logic Enclosure' ground buss something you added, or did it come with?
    1. Do you plan on adding an additional neutral buss to this enclosure for when you add the bonding relay/contactor?
  4. Did you bond your DIN rail to ground in both/either enclosure? Are any of the latch-on DIN devices grounded through their connection with the rail?
  5. Most importantly: Do you have access to an oscilloscope, or some high sampling rate voltage measurement device, that is capable of measuring the L1/N & L2/N voltage output of the contactor during the 'lost neutral' failure scenario?
    1. I know the overvoltage protection relay has a 0.1s disconnect time, and that's a bit of an eternity in an of itself, especially when you stack that with the time to physically de-energize a physical contactor coil.
    2. If you don't have an o-scope, you may be able to hillbilly simulate this with a regular incandescent bulb. From there, you could build confidence, and perhaps even upgrade to a 120V appliance that you don't particularly care about (both resistive and inductive load).
  6. Is there a reason you (appear to be) running the AT N output through a single pole breaker (within the 'Inverter Disconnect Service Panel')?
  7. It looks like you're using a DIN terminal block in your 'Switching Logic Enclosure' to combine neutral conductors
    1. Could you confirm this is 2 conductors in, 3 conductors out?
      1. Are these two neutrals coming from the two ATs, respectively? (I'm assuming these are the outputs from the two single-pole neutral breakers within the 'Inverter Disconnect Service Panel'?
    2. Are these all fed into the same terminal connection?
    3. It appears your DIN terminal block is two blocks, side-by-side. Are they bussed together with a screw-on bar?
    4. Could you link to this part you used?
  8. It looks like you're running ground from the 'Main Service Panel' through GW #1, is that correct?
  9. I'm not sure a 50A rated contactor will be able to handle fault current for an upstream 50A breaker - are you using a 40A DP breaker for your GW #1 AC out, or do you plan to parallel contactors to be able to flow this fault current?
 
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?????? said:
9. I'm not sure a 50A rated contactor will be able to handle fault current for an upstream 50A breaker - are you using a 40A DP breaker for your GW #1 AC out, or do you plan to parallel contactors to be able to flow this fault current?
Click to expand...
The max output for the GW is 5000W, at 240VAC that's 20.8A.
I'd use a 30A output breaker.

The input breaker is specced at 50A to account for surge and the additional load of 17A of the AC Charger.
 
Desert_AIP said:
Hmmm

I wonder why they recommend 10 AWG (30A) wiring.
Seems like a mismatch.
Click to expand...
It is for sure. They are probably basing on a 30amp circuit size, but breakers are designed to protect wires.. so 50amp breaker == 6 AWG safely, 8 AWG minimum in the right conditions
 
?????? said:
Looks great @automatikdonn ! ?(y)

I love the use of the overvoltage protection relay to drive a 240V contactor coil by switching one leg only - great idea and it simplifies the wiring a bit too. Thanks for putting the video together and sharing, I plan to do the same within the next couple months - I've got another project that I'm taking care of, and I also want to finish up the conductor/conduit schedule, as well as physical layout.

A few questions:
  1. Looks like you're pulling the 240V off your L2 IN for your contactor, if so:
    1. Are you using a ferrule to get two conductors into one slot on the contactor input, or does the contactor have multiple terminal connections?
    2. If you're using a ferrule, do you know if this is code compliant?
    3. Do you have any plans to independently fuse the coil circuit (specifically a fast-blow, lower amperage fuse)? Right now the coil appears to be on whatever dual pole fuse that your GW #1 AC OUT shares
  2. Any chance we could get a peek into your 18 space DIN enclosure ('Inverter Disconnect Service Panel')?
  3. Is your 'Switching Logic Enclosure' ground buss something you added, or did it come with?
    1. Do you plan on adding an additional neutral buss to this enclosure for when you add the bonding relay/contactor?
  4. Did you bond your DIN rail to ground in both/either enclosure? Are any of the latch-on DIN devices grounded through their connection with the rail?
  5. Most importantly: Do you have access to an oscilloscope, or some high sampling rate voltage measurement device, that is capable of measuring the L1/N & L2/N voltage output of the contactor during the 'lost neutral' failure scenario?
    1. I know the overvoltage protection relay has a 0.1s disconnect time, and that's a bit of an eternity in an of itself, especially when you stack that with the time to physically de-energize a physical contactor coil.
    2. If you don't have an o-scope, you may be able to hillbilly simulate this with a regular incandescent bulb. From there, you could build confidence, and perhaps even upgrade to a 120V appliance that you don't particularly care about (both resistive and inductive load).
  6. Is there a reason you (appear to be) running the AT N output through a single pole breaker (within the 'Inverter Disconnect Service Panel')?
  7. It looks like you're using a DIN terminal block in your 'Switching Logic Enclosure' to combine neutral conductors
    1. Could you confirm this is 2 conductors in, 3 conductors out?
      1. Are these two neutrals coming from the two ATs, respectively? (I'm assuming these are the outputs from the two single-pole neutral breakers within the 'Inverter Disconnect Service Panel'?
    2. Are these all fed into the same terminal connection?
    3. It appears your DIN terminal block is two blocks, side-by-side. Are they bussed together with a screw-on bar?
    4. Could you link to this part you used?
  8. It looks like you're running ground from the 'Main Service Panel' through GW #1, is that correct?
  9. I'm not sure a 50A rated contactor will be able to handle fault current for an upstream 50A breaker - are you using a 40A DP breaker for your GW #1 AC out, or do you plan to parallel contactors to be able to flow this fault current?
Click to expand...
1. There are not any ferrels on there at the moment, this setup is temporary. There are some problems that need to be addressed. This was the cheapest way for me to test the setup I had in mind. There should be a fast blow fuse on the contactor activation circuit, but I was tired of waiting on parts.

2. Sure, I can get some photos or take another video. To be honest though, these boxes are likely to go to the trash bin or to some project that doesn't carry critical loads. I am going to order a UL listed steel box for both of the parts in the 18 din boxes to go into. I just didn't know what size I needed, so now that I have a closer idea of right would look like, I will get something more code compliant.

3. Nothing comes with ground buss bars. It boggles the mind why they aren't included ( I guess they could say that everyone wants something different). The neutral auto connect circuit will need a buss bar, but I have to find a way to isolate it. I am searching for parts, but coming up short.

4. The din rail is grounded with a ground connector for din rails. When I get a full parts list together, I will include this.

5. I do have a scope. I just got a hantek that I have been itching to take out and use. I should even be able to hook it up to a computer so I can get some screen recording to post.

6. You are correct. The neutral out is on its own 30 amp single pole breaker. I have breakers at every single input and output. I guess I could have got away with just killing the input to service them, and I guess it's just an old habit to have disconnects for all inputs and outputs. The input is on a double pole and output on a single pole. Should I be doing this different?

7. Yes, I am combining the neutral outputs at the terminal block. The connection between the two is not a screw down, but it is UL listed. It's a dinkle 100amp terminal block.
There are 3 outputs, because at this point in the circuit the inverter outputs are not yet combined. I think this is very likely to change, but for the current setup I would not be able to fit the required wire size to fit in that tiny box. Once the conductors are combined it drives up the current size. So for my setup (15kw) I would be looking at #1 wire (150 amps due to surge capacity). I am trying to find a way that monitors the circuit properly that does not combine anything. This would also drive up the required contactor size. It has some problems I can't quite put my finger on. For instance if I flip the output from the neutral on and off really quickly things never seem to normalize and the meters read 60 volts instead of 120. I checked with a volt meter and the voltage overprotect / underprotect devices are correct. I just don't know why. Also it acts funny when I simulate the failure of just one AT. Again I don't know why. Maybe someone can help point me in the right direction.


8. There is also a path the comes in direct from the main service panel that is connected in the disconnect box. Not sure if that is right or not.

9. These particular contactors are rated at 50amps. All of the connectors say 63 amps, so that rating is a full 50 amps. However they are garbage. Already broke two of them and one came with a bunch of rattles inside. A proper UL listed contactor is a requirement IMO. This is a critical function, so no reason to cheap out on this device. Thankfully my listed contactors showed up today... However they are way too big to fit in these tiny boxes.

Hopefully I answered all the questions fully. Let me know if you want to see anything else.

Also I now have a panel to actually pull power from (inverter load panel). I also finally got a battery running so I can turn the system on and start the testing.

Apologies to everyone waiting on the full answer to the OP question. I want to be through before publishing a full parts list and completed chart for how it all works. I think at the least having two AT's massively reduces your risk if you decide to move forward without this protection circuitry in place.

More to come
 
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Struc said:
The manual states 8AWG for the 5000w unit. The 10AWG is for the 3500w unit.
Click to expand...
I have ver 1.0 (online) version. It only has one entry, 5000 SPF ES.

ETA:
ver2.0 has both entries and the 8AWG entry for the 5000
updated my local copy.
 
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v4 appears to be the latest version at the time of writing, available from their website, attached, and (the pertinent section) screenshotted below for reference (pg 10 & 24):

1637066203351.png

Unrelated:
  • Pg 11 states the dry contact rating is 3A/250VAC
 

Attachments

  • SPF 3500-5000 ES User Manual.pdf
    4.8 MB · Views: 20
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So for the auto bonding circuit, what size contactor should we be using?

Does it need to be rated for the full load of the neutral? In my case that would be 150amps.

Also what does everyone want to see with the scope?
 
Okay - so I updated the wiring diagram a bit.

Changelog:
  • Adds additional neutral safety circuit - both legs are monitored high/low for redundancy
  • Adds terminal blocks for all connections
  • Removes 15A single pole CB within 'Inverter Disconnect Service Panel'
    • Frees up two spaces on a 6-space load center (yay) allowing a 'failsafe' 240VAC load to be run in the event of neutral failure
    • Changes all contactors from 120VAC coil to 240VAC coil (simplifies wiring, better part availability)
  • Changes dry contact to switch 240VAC instead of 120VAC
    • Routes dry contact wire through conduits #4 and #2 instead of #6 (removed in this version), simplifying conduit runs
As you can see, things get a little hectic when the terminal blocks are fully laid out. We need six terminal blocks in our 'Switching Logic Enclosure':
  • Neutral (6 conductors)
  • Ground (4 conductors)
  • L1 IN (6 conductors)
  • L2 IN (6 conductors)
  • L1 OUT (3 conductors)
  • L2 OUT (3 conductors)
ES5K_dual_neutral_safety.png

Please review the above work and let me know if there are any questions/problems. We've got a lot of conductors in conduits #4 and #2. I'm thinking a trough/gutter may be the best move here for physical layout. To answer your question @automatikdonn - this design can carry 80A of ground fault current, which (to my knowledge) only needs to be 63A by code ( >= 1.25 * our 50A DP OCPD feed within 'Inverter Disconnect Service Panel').

Next steps:
  • Review above schematic for issues
    • Neutral safety circuit
    • Ground fault current calculations
  • Spec conductors & conduit
  • Verify conductor fill limits for conduit spec'd
  • Physical layout and BOM
 
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