18 month DIY project finally done: 39kW inverter power off grid system

[Daddy Tanuki]

still need to learn to read between the lines and compensate some still missing background information... do I understand it correctly a Navy Nuke is a bit like MacGyver... solving problems in unconventional ways and prepared for everything...

Nope a Navy Nuke is a person in the Nuclear propulsion field... they are known, well known for nuking problems (working everything out t the last detail). they are very, very detail oriented, but ask @Mattb4 if his testicles glow in the dark like Rudolph the red nosed raindeer??? also ask him for the rate of mutation on his kids... any got three eyeballs
sorry matt, told you I got tons of jokes for you... You have not seen the likes of the crayola fueled organically grown fuckery that makes up the USMC.

 

[Daddy Tanuki]

Hey, no picking on us former Navy Nukes.

Who Me?

My nephew is a Nuke Safety Officer... Mustang, went Nuke MM and got tossed for underage drinking literally in the last three days. so they made him a non nuke MM. but he still got the NEC. so after listening to me and his momand grandma ream him out for about 6 months he unscrewed himself and went to college during his 6 year enlistment and then went officer program.

 

[Mattb4]

Who Me?

My nephew is a Nuke Safety Officer... Mustang, went Nuke MM and got tossed for underage drinking literally in the last three days. so they made him a non nuke MM. but he still got the NEC. so after listening to me and his momand grandma ream him out for about 6 months he unscrewed himself and went to college during his 6 year enlistment and then went officer program.

Washout of the Nukes, especially during Nuclear Power School, was high for sometimes rather minor offenses. My first roommate got fleet orders for making the mistake of writing down some of the material from class and having it in the dorm room. It was spotted during a room inspection. Proper handling of classified material* was a big deal.

* I should mention that rather mundane stuff was still considered classified.

 

[robbob2112]

Washout of the Nukes, especially during Nuclear Power School, was high for sometimes rather minor offenses. My first roommate got fleet orders for making the mistake of writing down some of the material from class and having it in the dorm room. It was spotted during a room inspection. Proper handling of classified material was a big deal.

In my A school there were a lot of 'Nuke Rocks' that couldn't cut it. Some were pretty smart, others were dumber than a box of rocks and they flunked out of Aviation Electronics as well.

 

[fmeili1]

YEAHHHH... with one day delay, I've just got the final approval from the cities building division

Now there is only one step left (hopefully tomorrow), my local electricity provider want to inspect and approve the typical "generator setup" of the system with the manual transfer switch, but they don't care about the "generator" itself (because it's not backfeeding). They told me that they will be ok if the city approved the solar system itself... I don't expect issues here.

 

[Daddy Tanuki]

YEAHHHH... with one day delay, I've just got the final approval from the cities building division

Now there is only one step left (hopefully tomorrow), my local electricity provider want to inspect and approve the typical "generator setup" of the system with the manual transfer switch, but they don't care about the "generator" itself (because it's not backfeeding). They told me that they will be ok if the city approved the solar system itself... I don't expect issues here.

Thats great news!

 

[Daddy Tanuki]

Washout of the Nukes, especially during Nuclear Power School, was high for sometimes rather minor offenses. My first roommate got fleet orders for making the mistake of writing down some of the material from class and having it in the dorm room. It was spotted during a room inspection. Proper handling of classified material* was a big deal.

* I should mention that rather mundane stuff was still considered classified.

yeah he was in the top three or four guys in his class and went out to celebrate with a couple of the other kids and got caught when one of his friends got embroiled in a fight over a female... needless to say his friends that were with him suffered the same fate... underage drinking... Can't say much I got rolled for underage while at Camp Lejeune... cost me 2 weeks of restriction over the Christmas/new years holidays...but no pay or rank taken... the 80's were much simpler. I ended up winning on that one as I started taking duty assignments for other Marines at 100/day and it got me out of the barracks as i was on duty marching around a freaking armory for half a day at a time.

 

[robbob2112]

yeah he was in the top three or four guys in his class and went out to celebrate with a couple of the other kids and got caught when one of his friends got embroiled in a fight over a female... needless to say his friends that were with him suffered the same fate... underage drinking... Can't say much I got rolled for underage while at Camp Lejeune... cost me 2 weeks of restriction over the Christmas/new years holidays...but no pay or rank taken... the 80's were much simpler. I ended up winning on that one as I started taking duty assignments for other Marines at 100/day and it got me out of the barracks as i was on duty marching around a freaking armory for half a day at a time.

two of the big fails from the navy = alcohol and women. From being to young to drink and old enough to serve or not knowing when to quit. And the women angle was many - underage daughters of higher ranks, sexual harrasment, fighting over them, having a fling with a west-pac widow and getting caught, and the list goes on.

I will say this - I got a ticket for MIP while out on the town in Memphis - (minor in possession) - 5 days before my transfer - I went down to the court house in dress uniform 3 days before transfer and standing at the clerks desk to pull the papers hired the lawyer standing next to me for $50. He knew people and walked me to the courtroom, talked to the clerk and got us slipped in before lunch break. Talked to the judge and the judge said "$300 dollar fine" and the lawyer started asking for more time to pay and I had to grab his arm to say "I have it on me!" ... payed the lawyer, paid the fine, and had to leave my DL with the parking lot attendant while I went and got money for the lot from the local bank branch down the street.

Transfered and the paperwork never caught up with me while I was in the Navy because it was so close to transfer and it was all done. Normally my command would have been notified and I would have been screwed from there on out.

This was 1988, simpler times.

 

[Quattrohead]

If I knew then what I know now......

 

[wpns]

I had no choice but to install everything in the attached garage and that's the reason why I've done a huge effort to implement these emergency shutdown features (I'm also sometimes a bit of a chicke ).

Here are the passive and active security measures (also used to impress the inspector ), which I've implemented to help me sleep better behind this inverter wall...

• Added fire resistant cement board between the drywall and the inverter/battery/wireway equipment
• Installed two 5lb fire extinguishers on both sides of the inverter/battery wall beside both doors (class 2-A:10-B:C)
• Selected LFP (LiFePO4) chemistry for the batteries which have the lowest fire risk because of the lowest thermal runaway compared to other commonly used Lithium battery types (NMC, NCA, LCO, LMO) which are often used in EV’s, laptops, mobile phones, tools, etc.
• 48V batteries are used (no high voltage solar batteries)
• Selected batteries with integrated fire arrestors in each battery (EG4-LL V2 and S)
• All high current battery connections double checked for correct torque specs. Checked all battery connectors and wires under high load with a thermal imaging camera to identify possible connection problems (prevent heat nests).
• AC Surge protectors are installed in the inverter output combiner breaker panel (to protect the electrical consumers in the house against inverter surges) and in the auxiliary AC-in charging breaker panel (to protect the AC-in auxiliary grid battery charging units inside the AIO’s against surges from the grid)
• Using Half-Cut cell PV modules to reduce hot-spot risk if partially shaded and provide cooler running at all
• An insolation measurement (megger meter) was done on each PV module to verify it’s frame insulation is ok
• Installed Tigo module level PVRSS system to disconnect any PV module from each other in case of an emergency
• PV strings produces not more than 300VDC to keep the max. voltage relatively low (max. 6 PV modules per string in series)
• Simple PV serial wiring (no parallel wired PV modules at all to keep the max. PV current in each string relatively low), no combiner boxes, no additional PV wire connenctions and clamps, each string wired directly to a separate MPTT charge controller
• Emergency controller which is able to provide the following features in case of an emergency
  • disconnect all PV modules via Tigo PVRSS
  • disconnect all batteries from the inverters via relays
  • disconnect all auxiliary grid AC-in battery chargers via contactors, if connected (usually they are already disconnected)
  • ... which will shutdown all inverters/chargers
• Emergency disconnectcould be triggered by
  • smoke detectors
  • manually with an emergency button located outside of the building
  • manually with an emergency button located inside in the garage beside the inverters
  • remote via smart home integration, either manually or via specific rules like
    • shutdown if the inverters temperatures getting too hot
    • shutdown if the battery temperatures getting too hot
    • shutdown if the camera detects fire or smoke on the inverter/battery wall
• The Emergency controller sends messages to a smartphone messenger app as preventive maintenance if parameters are not in usual specification range (e.g. if unusual high inverter or battery temperatures; in case of unusual high power consumption; etc.)
• Added a mini split with a typical indoor wall unit to cool down the ambient in the garage
• Added a ducted mini split to actively cool down the inverters/chargers by injecting cold air into the inverters air inlets, controlled depending on the inverter temperatures
• Oversized the inverters to not max. out their possible power output to keep them as cool as possible (usually they run with <20% of their rated max. power and even in very high load situations they usually stay <50%).
• The system is very precisely documented with detailled instruction for startup/shutdown etc. so others will be able to run (and understand) the system.

You've put a lot of thought into this, good job! Thanks for the reminders about surge arresters and smoke detectors.

 

[fmeili1]

2nd YEAHHHH... today I've just got the final approval from the local electrical energy provider

At 11am I've flipped the manual transfer switch to "Solar Generator" position and I hope I never need to flip it back (I'm an optimist ).

Over the next couple of days I will post some updates and charts about how the system works.

 

[sunshine_eggo]

CONGRATS!!!!!!

 

[fmeili1]

CONGRATS!!!!!!

Thanks! It's a huge relief to have these permits now - I've read a lot of terrible stories about failed inspections...

 

[timselectric]

Awesome
Now, you can just reep the benefits of your labor.

 

[fmeili1]

Here is a screenshot of the situation of this morning without load (I've switched the load on, after inspection was approved) while just charging the batteries from solar just before they were full (54.7V).




Without load (and without AC-in connected, as usual) I was able to measure the MPPT battery charging efficiency of the whole system and have the following values (via SolarAssistant):

• 75% (5kW PV production, 3.82kW charging)
• 84% at 10kW PV production, 8.42kW charging)
• 86% at 13.7kW PV production, 11.9kW charging)

If I would subtract the AIO's idle consumption (6 * 93W) to find just the efficiency of the MPPT battery charging, the percentages would add up (but I don't know if this is a realistic scenario to just subtract the idle of the AIO's to find the net efficiency of the MPPT together with the battery charger):

• 86%
• 90%
• 91%

I found nothing in the EG4-6500EX manual about MPPT and battery charging efficiency - only the inverter efficiency is listed with max 91%

 

[wpns]

Congrats!

 

[caddnima]

Congrats. Amazing build, very detailed and thank you for sharing.

 

[Zwy]

Nope a Navy Nuke is a person in the Nuclear propulsion field... they are known, well known for nuking problems (working everything out t the last detail). they are very, very detail oriented, but ask @Mattb4 if his testicles glow in the dark like Rudolph the red nosed raindeer??? also ask him for the rate of mutation on his kids... any got three eyeballs
sorry matt, told you I got tons of jokes for you... Y

ou have not seen the likes of the crayola fueled organically grown fuckery that makes up the USMC.

Them there is fighting words there sonny.

There two kinds of people in the military, those who are Marines and those who wish there were Marines.

 

[fmeili1]

One interesting observation so far.

Today I've noticed some of this usual small LED light "blips" which happens when large loads kicking in or switching off when running with HF off-grid inverters (not the LED pulsing problem with 5-7Hz permanent LED flickering). This is totally ok for an HF off-grid system, in my opinion and doesn't really bother. But today I've noticed such a "blip" every 15-20s for a couple of minutes and SolarAssistant just showing a more or less constant 3.0kW to 3.5kW load over this time.


I found out that's the electrical cooktop (an GE-30 glass flat surface, 2019) is the reason. The heating algorithm is like a PWM. The time sensitivity of SolarAssistant is not short enough to catch these short load variations. But my smart home system with the already existing whole house energy meter has the resolution to show this.



In 240 seconds it switches the 3.5 kW load load 12 times on and off.

Just an interesting observation and the explanation about this LED "blips" every 20s while the electrical cooktop is used.

 

[toms]

Thanks for sharing, obviously a ton of thought and attention to detail in your build.

Some have guessed at your background/tech experience, i’d love to know what background resulted in this system.

 

[fmeili1]

Thanks for sharing, obviously a ton of thought and attention to detail in your build.

Some have guessed at your background/tech experience, i’d love to know what background resulted in this system.

Thanks!

Long ago in 1992 I've got my diploma at an university of applied sciences in electrical engineering in Germany. But I've never worked as an electrical engineer, instead I've started my working life as an hardware-related software developer (protocols, drivers, etc.) and still doing this. BUT electronic is still my passionate hobby.

 

[timselectric]

I was hoping that you would say something like, "I make the meatballs".

 

[Quattrohead]

I am very sensitive to noticing changes in the lights, it's an OCD thing so in my new house I made sure the lighting circuits were totally separate from everything else and have the ability to move them into a different panel and inverter if I deem it necessary.
Obviously most people cannot do this but if you are super sensitive to flickery lights, you might want to figure out if it's possible in your home to split the lighting circuits out from everything else.

 

[timselectric]

That's one of the two things that drive me crazy, too.

 

[fmeili1]

Here are a few more comments about the short LED dropouts if a huge load kicks in or switched off (only on some of the LED's the effect is visible at all).

Before I installed the solar system and used the typical grid supply (200A operation), I noticed slight LED dropouts.

1. When the 5 ton heatpump turned on (it had 162A inrush before I've installed the soft start)
2. While my 3D printer is working (mainly when the bed and/or nozzle heated up)

When I try to quantify the effect to notice the LED dropouts visually (which is not easy) and assume a scale from 0-9 (0=LED dropouts not visible, 9=LED dropouts easily noticed) I would give

1. the heatpump a 8 on the scale when switching on and a 2 when switching off
2. and the 3D printer a 5 on the scale

After I've installed the soft start for the heatpump (which reduced the inrush from 162A to 33A), it was maybe a 1 or 2 on the scale while still running on the grid when it turned on.

Now with the off-grid inverters running and the softstart installed, I would say that starting the heatpump will again have a 9 when turning on and about a 5 or 6 when it turns off on the scale.

It's all very subjective but my feeling is, compared to the situation with grid

• when the heat pump with soft start turned on/off the visible noticeable effects are a bit more
• the 3D printing effects are a bit more
• the cooktop/wall oven was not visible while on grid, but now it's visible (would give a 4 on the scale)

Overall It's not really bad and I can easily live with this in my situation because only some of the LED's are affected and it happens not often. The most noticeable thing is the cooktop because it's turning on/off relatively often in short timeframes (compared to the heatpump).