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It was hot against the battery bank (DC side connected / caps fully charged) when that chart was generated

@ksmithaz1 - CV board breaker is always 'ON' (connected) and CV is always connected on the DC side to the pack (this one is a 30kWh pack; 6x100aH) so the CV caps always stay charged/ready. The AC side of the CV is switched with a 2 pole contactor. The power (current x voltage) through that AC...

There's been a bit of discussion about the chargeverter current ramp rate being too fast, so I wanted to post my experience with my gen 1 CV (yellow enclosure), purchased circa Mar 2024 from Signature Solar. I believe this was the very last of the gen 1 CVs. X-axis gridlines are in 15s...

Resurrecting this thread but I was always under the impression that a MOV (https://www.midnitesolar.com/pages/spd/index.php) was used for lightning strikes A lightning strike will cause a very high voltage spike, but not a high current spike - as such, a traditional fuse wouldn't protect against...

Bit of a thread resurrection here, but EG4 Lifepower4 manual states 0.1V max difference between units prior to connecting in parallel ☝️

EZPZ question - I'm looking at expanding my GW5kES setup to _two_ AIOs in parallel. Unit #1 (primary): Tied to array1 Tied to battery bank1 Primary single phase AC output to load panel1. (On at all times.) Unit #2 (secondary): Tied to array2 Tied to battery bank1 Secondary (dynamic...

Thanks Tim - did you get a chance to measure your switching times and voltages with an oscilloscope while you had it running?

Hey @timselectric - great thread, thanks for posting and knowledge sharing. (y) I bench tested this with a 5000ES-US unit from SS and found an unfortunate shortcoming, at least with my implementation which seems pretty much identical to yours. If you're using a NC AT relay and going from...

Just wanted to say to be careful with this; two midpoint transformers wired in parallel may be in a permanent state of trying to balance each other due to manufacturing variances between the two (even in identical models), causing high neutral currents (in theory). Preferred solution here is a...

@B-Mod - some previous work has been done on this, see post #207 - tl;dr is that nobody (currently - no pun intended) knows, it was tested up to 95C/200F and did not trip. Most thermistors of similar spec seem to be about 150C/300F, so the best guess at time of writing is that it's about that...

@MrM1 - Myself and a few other folks from this thread are working on a similar solution. I'm in the process of a major code refactor of design #216 here which is being built to accommodate multiple inverters, and could technically run multiple transformers as well (has capability for neutral...

Thanks @Cornwallav8r - I'd encourage you to go through the use cases hit on in the pages of this post - I'd suspect you'd arrive at a similar design. There are a lot of details, and there's a reason for every component in the design. To give examples: The neutrals between the autotransformer...

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

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...

Okay I overhauled the wiring schematic a bit. In retrospect, I am not confident that designs #133 and #159 would clear ground faults while in on-grid mode. This should resolve that issue, as well as incorporate additional functionalty. Changelog: Adds temp monitoring to AT Through K-type...

Thanks @Trip.Diamond for the AT schematic, I looked everywhere for this - dunno where you found it but I'm glad you did. Lessons learned: AT never participates in neutral forming with the grid transformer (despite neutral connection between the AT and grid) due to the XOR created by the...

The latest designs, #133 (no AT L1/L2 disconnect), and #159 (AT L1/L2 disconnect + cold start), do not have neutrals connected between the grid and the GW AC OUT. The only time the GW AC OUT neutral is connected to grid is during a grid-down situation, when the N bonding contactor is actuated...

Whoops - I must have missed you saying that. Sorry bout that. I'm pretty certain we don't need an externally or battery powered logic controller for this. If we view our 'external power' as the 240v AC OUT of the GW, then even if we store bootstraping history/state within any volatile memory of...

Nice @automatikdonn (y) - looks like #177 video is an implementation of the blind bootstrap method of #161 with clever use of the 2s delayed-on timer within the 240v (and 120v) over/under voltage protection device (for those who may not be familiar with that feature). Even though the delay-on...

I agree - the more I read about transformer failure, the more I see that the industry seems to use ferrite core temps as the single most important health metric for dry transformers like the AT we have here. The AT ships with temp sensing, and I pulled one apart to see that the leads are between...

This is a good idea, but I think we're just straight up without power for ~30ms during the ATS transition. It's also worth noting that the ATS (according to the docs) takes longer as you add more inverters in parallel. It's possible this isn't an issue with a single inverter ?‍♂️

I think option 3 of #152 is probably the move here if a fully autonomous system is the goal. This could be executed a couple different ways: Blind one-shot (less effort): tie an off-the-shelf timer in parallel to the coil of the N bonding contactor. Program this timer to perform a one-shot...

Okay next iteration - this one is #152 with the following changes: Uses 120v coil N safety contactor instead of 240v coil contactor (50A 3-pole DIN-mount instead of 40A 2-pole non-DIN mount) Adds electrical momentary cold start switch This (should) allow electrical actuation of the cold start...

Yep - exactly right. If we wanted autonomous cold-start (option 3 of #152), the neutral verification is performed by the two over/under voltage protection relays - protecting the 120/240V load panel at all times. The only thing the cold-starting potentially risks is the AT, which is still...

@Desert_AIP - the reason for potentially wanting an unattended cold start is because the system must be attended for a cold start even if the system is operating normally. It's arguable if the AT disconnect contactor is even needed (creating the cold start problem in the first place), since the...

@automatikdonn - this looks great! Really cool that you're birddogging this effort with the real world setups to validate the schematics - thanks for taking all this time to share. (y) Feedback: Cold-start with a 3-position switch is a great idea - but I think it can be simplified further. If...

I think we're at a pretty good solution for a single GW with #133 and can probably call it a day after conductor/conduit schedules and layout/BOM are nailed down. I think #133 can work for multiple GWs in parallel as well, provided you can limit your 120VAC loads to < 30A. Re: going overboard...

Good idea - however I can't think of a way to auto-disconnect the AT when running off-grid that doesn't introduce the cold start problem - needing a human-in-the-loop to physically close the AT contactor to bootstrap the system. We could add this - but we'd have a system that needs an external...

Agree - simplified schematic with single contactor, 30A max 120/240 load panel: L1/L2 input to AT does not disconnect from 'Inverter Disconnect Service Panel' in the event of a neutral leg failure No cold start process needed since AT input never disconnects L1/L2 output from 'Lost N Safety...

Thanks @LeRoyK and great point - although in this specific case I think we're still OK because our upstream OCPD in the 'Inverter Disconnect Service Panel' is 30A (downrated from 50A) so even if one contactor switched all the load, we'd still be within the 37.5A fault current operating range...

@LeRoyK - you're totally right, I was noodling that one. Updated in the attached. @automatikdonn - I've separated the 120/240 and 240 load centers in the attached (but kept the parallel contactors, which could continue to be paralleled and scaled).

Well - if we wanted to limit the output of the GW to 5kW (20.8A), we could just replace our 50A breaker with a 30A one in the 'Inverter Service Disconnect Panel'. That'd allow us to use the single 40A contactor I have in the schematic, which is > 37.5A fault current we'd need for the 30A...

Thanks @automatikdonn and good question - the reason for that is simply because we're more likely to lose a contactor coil (both throws of a single contactor) than we are to lose half of a contactor (one throw only). In this failure case, we lose half of our split phase on the 'Inverter Load...

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...

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