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

[rfbuehler]

List price on a QO square D breaker with shunt trip is just shy of 400 but you can get them cheaper.

I needed the 100A anyway BUT I didn't need more real-estate for the contactor, the enclose the wiring ...

So all around it's a cleaner solution fewer parts and less labor. Less points off failure.

 

[iSwannie]

EPIC!!!

I can wait to build a real world prototype of this design and test it out.

Hi Gents,

I have been following the thread since I have just purchased a Growatt 5k ES too with the AT. Do you guys have the current schematic available to view? I have not yet replaced my current 3kTL yet with the 5k ES so could help in some preliminary testing too.
Also, I cannot see the last picture USA posted above. Anyone else have this issue?

 

[MadCow]

5kW Split Phase Transformer by Growatt

Signature Solar sells these now to go with the SPF 5000 es. It looks like they have moved away from the SolarEdge AT and gone to this. I am a novice and really appreciate your thoughts. Thanks in adv ance.

5kW Split Phase Transformer / Midpoint Transformer

THIS IS A PRE-ORDER ITEM WITH A 4 WEEK LEAD TIME Signature Solar now offers the latest US Split Phase Auto Transformer by Growatt. This autotransformer takes Single Phase 240Vac (L/N) electricity output and creates true Split Phase 120Vac/120Vac (L/L/N). This addition to our line sheet increases...

www.signaturesolar.com

 

[🇺🇸🇺🇸🇺🇸]

Very cool @MadCow thanks for the link. Looking at the wiring schematic on the inside of the enclosure door on one of their pictures, it doesn't seem like that device has any significant differences over the SolarEdge transformer. It doesn't appear to have any neutral safety disconnect logic, and it also appears to absent of the over-temp sensor the SE unit has from the factory.

@iSwannie - latest schematic I'm working off of is #216 (all prior work, plus arduino/nodemcu control with temp sensing).

I've gotten an alpha release of the nodemcu code up on github. I'm waiting on my current sensor and relay board (functions are stubbed right now). Tested temp sensing, grid transfer, and automatic cold start and appears to works as intended. Code is definitely nothing fancy, but the goal right now is MVP and to vet the core functionality.

MVP Backlog (volunteers welcomed!):

• Verify stub functions with current sensor and relay board work as intended on physical hardware
• Refactor to OOP and better coding practices
• Real world lab tests

Post-MVP Backlog:

• Add unit tests & CI/CD with git actions and AUint / Epoxyduino
• Add async webserver interface
• Add log shipping to prometheus/grafana
• Branch release/builds for multi-transformer, multi-GW setups

Anybody who's more comfortable with C++ and OOP and wants to refine what I've got, just shoot me a DM and I can add you as a collaborator to the repo. Project management also welcomed if you want to manage backlog and roadmap. Thanks all

 

[automatikdonn]

List price on a QO square D breaker with shunt trip is just shy of 400 but you can get them cheaper.

I needed the 100A anyway BUT I didn't need more real-estate for the contactor, the enclose the wiring ...

So all around it's a cleaner solution fewer parts and less labor. Less points off failure.

How would you even wire a shunt trip up? I haven't seen a schematic for how to do it yet.

I totally agree less is more and a shunt trip should have less to fail and eat less power.

 

[rfbuehler]

A shunt trip breaker has a trip coil off the side of the breaker. All you have to do is energizer the coil (depends on the breaker config) I use 240V from the inverter out through a relay. If it is a DPDT relay you can use the contacts you need to do this. Once energized it trips the breaker. There is a set of holding contacts in this coil so once it’s energized and it trips the breaker these contacts open so you are not contantly energizing this coil. Closing the breaker closes these contacts.

i have used these in the past for remote trips.

 

[iSwannie]

I like the way this is sounding but I am not as technical as you guys. Thank you for the information.

 

[Zwy]

How would you even wire a shunt trip up? I haven't seen a schematic for how to do it yet.

I totally agree less is more and a shunt trip should have less to fail and eat less power.

Not that hard, most shunt trips that are common are 24VDC., if you have a 48V system, you either wire in a converter for power or use half the bank. I prefer the converter. I have a shunt trip on my ABB breaker, the Batrium BMS will control the trip if it senses a fault.

 

[iSwannie]

Not that hard, most shunt trips that are common are 24VDC., if you have a 48V system, you either wire in a converter for power or use half the bank. I prefer the converter. I have a shunt trip on my ABB breaker, the Batrium BMS will control the trip if it senses a fault.

Thank you again! I will research and see if I can figure this out.

 

[Trip.Diamond]

How would you even wire a shunt trip up? I haven't seen a schematic for how to do it yet.

I totally agree less is more and a shunt trip should have less to fail and eat less power.

In case your interested - The LS Electric breakers your using in your videos have Shut trip and Aux Contact accessories available.

https://www.lselectricamerica.com/wp-content/uploads/2021/08/MCBBK63HBK63HU_Catalog_EN_202009.pdf

on about page 4 ( they changed the document on me!)

These breakers are UL489 listed and much less expensive then the Shunt Trip breakers for Electrical Panels.

Keep in mind you can use Shunt Trip breaker to protect against loss of Neutral due to AT breaker trip but if you want to use it for "Loss of Neutral" protection (say using your SVP-912 Voltage monitor) it will not allow for automatic switching between SOL/BATT and GRID. Also if your only using Shut Trip breakers your leaving your AT in parallel with the Grid when running off the grid (leaving your AT more vulnerable)

 

[automatikdonn]

Not that hard, most shunt trips that are common are 24VDC., if you have a 48V system, you either wire in a converter for power or use half the bank. I prefer the converter. I have a shunt trip on my ABB breaker, the Batrium BMS will control the trip if it senses a fault.

If it's not hard, then why can't someone put it in a wiring diagram.

 

[iSwannie]

If it's not hard, then why can't someone put it in a wiring diagram.

What is everyones thoughts on using a Victron Auto Transformer with the built in protection? I know it is more expensive but might be less than the additional wiring and devices on the SolarEdge Auto Transformer.

Victron Energy ITR000100001 - Inverter Supply

Shop for Victron Energy ITR000100001 at Inverter Supply for best prices online. Victron Energy ITR000100001, Victron Energy, ITR000100001, Autotransformer 120/240VAC-32A, Victron Isolation Transformers

www.invertersupply.com

 

[Ohelig]

What is everyones thoughts on using a Victron Auto Transformer with the built in protection? I know it is more expensive but might be less than the additional wiring and devices on the SolarEdge Auto Transformer.

Victron Energy ITR000100001 - Inverter Supply

Shop for Victron Energy ITR000100001 at Inverter Supply for best prices online. Victron Energy ITR000100001, Victron Energy, ITR000100001, Autotransformer 120/240VAC-32A, Victron Isolation Transformers

www.invertersupply.com

New (and noob) here, I'd thought about getting the 100A version here https://www.invertersupply.com/index.php?main_page=product_info&products_id=5996 and just running the system with the original neutral safety circuit designed here (cut off inverter output if overvoltage on either rail phase). I'm hoping that using the larger AT means it won't be such a big deal if it's in parallel with the pole transformer either, as my house alone is unlikely to need its entire capacity.

edit: actually, the 100A version has the same neutral capacity as the 32A version. Not sure why it exists, then.

 

[craigcabrey]

I've been following (or trying to follow anyway) this thread and appreciate all the information available here. I'm a bit lost on what seems like an obvious option though.

If we put 120V loads in a separate panel that is fed exclusively by the autotransformer, doesn't this achieve what we want? If the AT trips or faults, all loads to the 120V panel turn off. Of course, this doesn't handle the case of the AT going haywire and deviating from 120V on L1-N/L2-N.

The AT handles generating the neutral both from utility power and off-utility power. Attached a crud diagram to try and illustrate what I'm thinking. Neutral on the 240V panel comes from utility, but as the neutral on the 120V panel comes from the AT, the AT is not in parallel with the utility ever.

Please correct me if I'm wrong in any of my assumptions. Note that this doesn't focus on the safety aspect of the AT, just the proper configuration to get it working in both utility and PV/Battery modes.

 

[iSwannie]

I've been following (or trying to follow anyway) this thread and appreciate all the information available here. I'm a bit lost on what seems like an obvious option though.

If we put 120V loads in a separate panel that is fed exclusively by the autotransformer, doesn't this achieve what we want? If the AT trips or faults, all loads to the 120V panel turn off. Of course, this doesn't handle the case of the AT going haywire and deviating from 120V on L1-N/L2-N.

The AT handles generating the neutral both from utility power and off-utility power. Attached a crud diagram to try and illustrate what I'm thinking. Neutral on the 240V panel comes from utility, but as the neutral on the 120V panel comes from the AT, the AT is not in parallel with the utility ever.

Please correct me if I'm wrong in any of my assumptions. Note that this doesn't focus on the safety aspect of the AT, just the proper configuration to get it working in both utility and PV/Battery modes.

Hi Craig,

Thanks for the post. Yes, I agree with you and this is the most simplistic way to look at this. However, I believe we need to take into account what each person is trying to achieve with their system. I also need to voice I am not an electrician up front. My plan is to carry my house on my (2) 5000 ES system and 600AH batteries. But I want to be able to revert back to only utility with a switch if there ever became a need.

In looking at your drawing I am assuming all the 240v and 120v circuits would need to be re-routed from the house main panel panel to the respectful electrical panel (240v and 120v). In this case, at least for me, I would never be able to revert back to utility unless everything was rewired. Is this a correct assumption? I am trying to get a certified electrician to my house to review how it needs to be wired.

 

[Tony Scott]

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.

Here are the design philosophies:

• Bake some redundancy into the system. I know the solaredge AT's aren't free, but get a couple of them. Even though you may only *need* one for loads, run two so in case one breaks you are still good to hook.
• Sleep well at night. Transformers are reliable technology, honestly they are.
• Implement failsafes - When the BOM and schematic is done, we are going to make a video to go through the whole thing in detail. I like the ELI5(explain it like I am 5) method and @automatikdonn has generously offered to do a video at that level in the near future.

Attached is version #133 of the design which satisfies the following:

• 120/240V load center capable of handling up to 30A, with a neutral safety disconnect
• 240V load center capable of handling 1->8 GW units in parallel (single phase only)
• Conditional ground/neutral bonding of the 120V load center depending on if the GW is operating on-grid or off-grid

Work to be done as of Nov 19, 2021:

• Conductor schedule
• Conduit schedule
• Physical layout and BOM
• Neutral safety real-world test

Appreciate comments and feedback on this collaborative effort

---

Useful links:

• @FilterGuy 's stationary systems doc
• Troubleshooting: Neutral return with grid-tie Growatt (setting #24 external bonding relay info) @ZorbatheGeek
• Generator to Growatt Inverter Neutral Bonding - Arg @Joe BoyKey
• Growatt SPF 5000 ES Wiring for 0 Export / Need help @Mark1988 @CCAT Racing
• SolarEdge Auto-Transformer W/ Sunny Island 6048
• Ben's solar and battery - running a SE autotransformer in parallel with a split phase sol-ark 12k
• NEC Article 445
• NEC Article 250.35 - Neutral Switching & Separately Derived Systems
• NEC 250.30(A)(6)(a) Grounding Electrode Conductor, Multiple Separately Derived Systems
• Mike Holt's Article 250 Study Guide
• Growatt SPF 5000 ES manual
• Watts 24/7 hybrid inverter wiring diagram
• Lost neutral failure mode

View attachment 72846

All these Acronyms in this thread makes it difficult to follow, on a DIY it needs to be spelled out.

 

[Quattrohead]

I don't get why people are so keen to buy inverters that don't work for the USA power system without a hack job transformer.
At least if you go this route, put the circuit breaker right on the inverter output so that if there is an overload, the whole output gets shut down and you don't have complicated wiring and components or fried 120v appliances.
KISS.

 

[craigcabrey]

I don't get why people are so keen to buy inverters that don't work for the USA power system without a hack job transformer.
At least if you go this route, put the circuit breaker right on the inverter output so that if there is an overload, the whole output gets shut down and you don't have complicated wiring and components or fried 120v appliances.
KISS.

Well, this Growatt seems to be a fantastic piece of equipment for the price. DavidPoz tested loads on it that failed other inverters.

You also don't have to worry about overloading each leg in this configuration. With a native split phase, each leg may have lower limits.

That said, I ordered an LVX6048 because I am a noobie. But still trying to understand a solution to this problem because it's fun and helps me learn.

 

[craigcabrey]

Hi Craig,

Thanks for the post. Yes, I agree with you and this is the most simplistic way to look at this. However, I believe we need to take into account what each person is trying to achieve with their system. I also need to voice I am not an electrician up front. My plan is to carry my house on my (2) 5000 ES system and 600AH batteries. But I want to be able to revert back to only utility with a switch if there ever became a need.

In looking at your drawing I am assuming all the 240v and 120v circuits would need to be re-routed from the house main panel panel to the respectful electrical panel (240v and 120v). In this case, at least for me, I would never be able to revert back to utility unless everything was rewired. Is this a correct assumption? I am trying to get a certified electrician to my house to review how it needs to be wired.

You would definitely need to rewire everything to separate the 120V loads from the 240V loads.

But this should still handle utility power as well. The difference is that the AT always handles the neutral, it never comes from the utility. So the AT is your limiting factor (you could always add more in parallel though).

I'll wait for someone more knowledgeable to confirm this is the case though.

 

[🇺🇸🇺🇸🇺🇸]

I've been following (or trying to follow anyway) this thread and appreciate all the information available here. I'm a bit lost on what seems like an obvious option though.

If we put 120V loads in a separate panel that is fed exclusively by the autotransformer, doesn't this achieve what we want? If the AT trips or faults, all loads to the 120V panel turn off. Of course, this doesn't handle the case of the AT going haywire and deviating from 120V on L1-N/L2-N.

The AT handles generating the neutral both from utility power and off-utility power. Attached a crud diagram to try and illustrate what I'm thinking. Neutral on the 240V panel comes from utility, but as the neutral on the 120V panel comes from the AT, the AT is not in parallel with the utility ever.

Please correct me if I'm wrong in any of my assumptions. Note that this doesn't focus on the safety aspect of the AT, just the proper configuration to get it working in both utility and PV/Battery modes.

Thanks @craigcabrey - can you help me understand the conductor current path to clear a N/G fault within the 120v panel of #234?