If EG4-18k's 200A Pass-Through fail, what will happen?

[JoeX]

I plan to install EG4-18k at one property. I will use whole house backup wiring, which means connect my main 200A panel directly to the Load. Like in the picture 1.
I noticed there is another way to connect the main panel: With a Bypass transfer switch. See below two image:
(1) With a Bypass transfer switch
(2) With out that Bypass transfer switch.

My question is: What's the purpose of that Bypass transfer switch? Does that means if the EG4 fails, I have to manually push that Bypass transfer switch in order to get rid of EG4 and let my main panel energized?

In another word, my question is: If I do not install that bypass transfer switch, and if the EG4-18k fail (for whatever reason, defect, lose power, malfunction etc.), will my main panel still be energized?

I though there might be some mechanism in the EG4 to connect the Gird port to Load port directly in case the EG4 fail, but I could be wrong.

 

[glandpuck]

Exactly. the bypass transfer switch allows you to take the EG4 offline for service, repair, software updates, etc. while still supplying the loads from the grid. However, you could use an AC disconnect between your service entrance and then into the EG4 while setting up a manual or automatic transfer switch between your main panel and the EG4 with the transfer switch connected to a generator. then you could shut down grid, shut down EG4 and also supply loads via the generator instead of having the generator connected into the EG4.

 

[jeff.lankford]

Yes, you need the manual transfer switch (bypass switch) to isolate the inverter and restore power to your main panel in case of service, failure, etc of the inverter.

Note that the 18Kpv bypass relays are default OPEN - the inverter must boot up and software must decide to close the relays. This means that if the inverter fails or is switched off, you will NOT have grid power to the main panel. That's why you need the bypass switch.

 

[JoeX]

Ohh......I just check the price for that 200A manual transfer switch, more than $500 each..........crazy.........

 

[jeff.lankford]

Ohh......I just check the price for that 200A manual transfer switch, more than $500 each..........crazy.........

True.

I would warn you against the temptation of buying one of the cheaper Chinese MTS on Amazon. If you're doing an install under permit, none of those cheaper switches are UL-listed. Worse, the enclosures for the cheap switches are much too small to allow working with heavy gauge cable easily. That's one of the reasons they're not Listed - they violate the wire-bending space rules in the NEC by a lot.

 

[JoeX]

That's crazy........
My system needs a 200A disconnect, $500 more each.
My system needs a 200A manual transfer switch, $500 more each.
These two boxes are more than $1000. I know some of CEC listed string Inverter is only $2000 or so....................There must be something wrong in this county.

 

[jeff.lankford]

That's crazy........
My system needs a 200A disconnect, $500 more each.
My system needs a 200A manual transfer switch, $500 more each.
These two boxes are more than $1000. I know some of CEC listed string Inverter is only $2000 or so....................There must be something wrong in this county.

I used a cheaper $200 circuit breaker disconnect for my install, instead of an expensive fused disconnect. But I didn't find a good alternative for the $600 GE MTS. This is apparently one of the reasons EG4 created the Gridboss product, to avoid the additional cost of these external devices (or rather, to capture that cost for themselves).

 

[wpns]

Ohh......I just check the price for that 200A manual transfer switch, more than $500 each..........crazy.........

First question: Do you actually need 200A service? I ‘downgraded’ my nominally 200A service to 100A when I realized I had never used even 100 A, and that made the transfer switch just a simple InterLockKit.com breaker interlock in the main output box.
A single 18Kpv can only make 50A, so maybe you can get away with smaller wires too.

 

[JoeX]

First question: Do you actually need 200A service? I ‘downgraded’ my nominally 200A service to 100A when I realized I had never used even 100 A, and that made the transfer switch just a simple InterLockKit.com breaker interlock in the main output box.
A single 18Kpv can only make 50A, so maybe you can get away with smaller wires too.

It's a 2600 sqft new addition in CA, with EV charger and 2 heat pumps. Yes, easily go above 100A if all machines are running.

 

[jeff.lankford]

If you plan to do the whole-house backup and you want to have an automatic EPS switchover using the 18K as an ATS, instead of a manual interlock, then you need to pass through your 200A service and bite the bullet on the cost of the 200A components. It's not about the fact that the 18K can only generate 50A output, it's about the convenience of having your entire main panel on the EPS backup output and not having to split your service into a critical loads panel.

 

[jeff.lankford]

Looking at your second drawing... be aware that you can implement your feeder tap by replacing the lugs inside the MTS with dual lugs. It will simplify wiring and save the cost of Polaris connectors.

 

[JoeX]

I used a cheaper $200 circuit breaker disconnect for my install, instead of an expensive fused disconnect. But I didn't find a good alternative for the $600 GE MTS. This is apparently one of the reasons EG4 created the Gridboss product, to avoid the additional cost of these external devices (or rather, to capture that cost for themselves).

In this video:

It does mentioned that we can use this: https://www.lowes.com/pd/Siemens-20...3179801?idProductFound=false&idExtracted=true
as the disconnect.
This is the thing you mentioned, right?

Yes, true, still does not have another option for MTS.............

 

[jeff.lankford]

In this video:
It does mentioned that we can use this: https://www.lowes.com/pd/Siemens-20...3179801?idProductFound=false&idExtracted=true
as the disconnect.
This is the thing you mentioned, right?

Yes, true, still does not have another option for MTS.............

Yes, I used a slightly different model, but that's the idea.

I used this for the component "PV Interactive System 2-Pole Disconnect" on the EG4 drawing:

https://www.lowes.com/pd/Square-D-200-Amp-Main-Breaker-Load-Center/3471297

And I used this for the Manual Transfer Switch.

ABB 200 Amp 240-Volt Non-Fused Emergency Power Transfer Switch TC10324R - The Home Depot

Run your backup generator with this UL recognized GE Non-Fused Emergency Power Transfer Switch. Features metal construction.

www.homedepot.com

I did not use a separate "Feeder Tap Breaker" in my design, and I placed the Feeder Tap inside the MTS using dual lugs, as I mentioned earlier.

 

[skimandan]

Hello my friend, you may wish to consider the gridboss/flex boss as it is dead simple to install and will cost the same or less than all the switches and breakers to properly wire an 18k. So far the only advantage of an 18kpv that I can think of is that it accepts aluminum service conductors. That can be worked around.

Plus you will want to shed the heat pumps, ev chargers, maybe electric water heater, etc if you experience a grid down event. Those items will suck your batteries dry fast. The grid boss has that capability.

 

[CaySol]

I plan to install EG4-18k at one property. I will use whole house backup wiring, which means connect my main 200A panel directly to the Load. Like in the picture 1.
I noticed there is another way to connect the main panel: With a Bypass transfer switch. See below two image:
(1) With a Bypass transfer switch
(2) With out that Bypass transfer switch.

My question is: What's the purpose of that Bypass transfer switch? Does that means if the EG4 fails, I have to manually push that Bypass transfer switch in order to get rid of EG4 and let my main panel energized?

In another word, my question is: If I do not install that bypass transfer switch, and if the EG4-18k fail (for whatever reason, defect, lose power, malfunction etc.), will my main panel still be energized?

I though there might be some mechanism in the EG4 to connect the Gird port to Load port directly in case the EG4 fail, but I could be wrong.

What about the Flexboss grid boss combo? That would make upgrading to a second inverter much easier in the future as well.

 

[skimandan]

Unless your poco or ahj requires more, a gridboss, flex boss, and maybe an rsd switch can be the entire system. Take a look at the drawings. 18kpv and all the switches is more complex, more money, and less capable.

That said, look at my posts if you want to see that it isn’t perfect.

 

[jeff.lankford]

Hello my friend, you may wish to consider the gridboss/flex boss as it is dead simple to install and will cost the same or less than all the switches and breakers to properly wire an 18k. So far the only advantage of an 18kpv that I can think of is that it accepts aluminum service conductors. That can be worked around.

Plus you will want to shed the heat pumps, ev chargers, maybe electric water heater, etc if you experience a grid down event. Those items will suck your batteries dry fast. The grid boss has that capability.

I'm done with my install. But if I were still selecting equipment, I would perhaps stay away from the GB/FB until this problem is solved:

Thread 'Gridboss with Flexboss not handling 21kW pass-through'

Jan 8, 2025

New Member, first post.

I installed a Gridboss, Flexboss and two PowerPro batteries on new years eve. No PV yet, running in backup mode. There is a 200A disconnect between grid and Gridboss. Whole house load panel is powered from Backed up Loads output on the Gridboss.



For the first week, all was good. Charged batteries, disconnected grid, house was powered by batteries/inverter. Tested 5 ton HVAC (heat pump) while running water heater. LED lights flickered, but everything worked. Turned the grid back on, and batteries charged. All good.

Something happened, and the...

• slowroller
• Replies: 119
• Forum: All-in-One Systems

• 

...and until there's more time to wring out any other issues. One reason I decided on the 18Kpv is because of Will's videos and the fact he had one running in his house trouble free for over a year. I wouldn't be interested in being an involuntary product tester for EG4 for a new product like the GB. And based on the issue in the thread I linked, if I did install a GB, I'd still want all the external switches that would make it possible to isolate the thing and completely remove it for service without disabling my house's grid connection.

 

[JoeX]

I know GridBOSS is a good product, but I don't think I need that at this moment.
The main reason why I want to put a MTS there is I want to isolate the EG4 and completely remove it for service without disabling my house's grid connection. A $600 MTS will meet my need. GridBOSS will meet my needs to, but it's $1700+. Unless I miss something there or GridBOSS has some other critical function I am not aware of.

 

[JoeX]

Looks like FlexBOSS21 is not California CEC list. Deal killer....................

 

[dougbert]

Looks like FlexBOSS21 is not California CEC list. Deal killer....................

contact SS for more information as they are working with PoCos to get them certified but they need info on where PoCo's are burbing about it

 

[JoeX]

Looking at your second drawing... be aware that you can implement your feeder tap by replacing the lugs inside the MTS with dual lugs. It will simplify wiring and save the cost of Polaris connectors.

Is that "dual lug" connection you mentioned able to pass City inspection?

 

[dougbert]

if you ever want 2 or more inverters, consider the combiner panels as well

brayden points the issue here

 

[JoeX]

Yes, I used a slightly different model, but that's the idea.

I used this for the component "PV Interactive System 2-Pole Disconnect" on the EG4 drawing:

https://www.lowes.com/pd/Square-D-200-Amp-Main-Breaker-Load-Center/3471297

And I used this for the Manual Transfer Switch.

ABB 200 Amp 240-Volt Non-Fused Emergency Power Transfer Switch TC10324R - The Home Depot

Run your backup generator with this UL recognized GE Non-Fused Emergency Power Transfer Switch. Features metal construction.

www.homedepot.com

I did not use a separate "Feeder Tap Breaker" in my design, and I placed the Feeder Tap inside the MTS using dual lugs, as I mentioned earlier.
View attachment 273717
View attachment 273719

I saw some one use that ASI tap connector to split the wire. See yellow circle in below picture.

 

[jeff.lankford]

Is that "dual lug" connection you mentioned able to pass City inspection?

Yes, it did. This install was done under permit. Final inspection passed without issues.

 

[jeff.lankford]

I saw some one use that ASI tap connector to split the wire. See yellow circle in below picture.

Sure, you can use Polaris connectors as a splice or a tap. It just depends on your layout and configuration. If you have a place to use dual lugs, it just makes a cleaner install and cheaper... Polaris = $40 vs. lug = $5.