Wiring EG4 18KPV to Combo Breaker/Meter Box (Grid Tied, Full Home Backup)

[jeff.lankford]

So a question; does the feeder tap needs to connect to the manual transfer switch? the diagram only shows one line connecting the feeder tap and manual switch, so I am not sure if that mean cable connection. If that is the case, then I will most likely place the manual transfer switch beside the inverter so it can also get the cable through the same hole from the feeder tap.

As I tried to explain above, you don't need a separate feeder tap "device" or box. I made my tap inside the manual transfer switch enclosure using dual lugs. Look carefully at my simplified diagram and the photo of the inside of the MTS.
There are several versions of the EG4 wiring diagrams. Which one are you using for the "whole house backup with feeder tap" diagram"? I prefer the version I attach here, but as I explained above, I have omitted the feeder tap and feeder tap breaker from my installation - the meter/main connects directly to the MTS grid/line input lugs (the lugs that I replaced with dual lugs).

The feeder tap breaker......do i need this...in my main service breaker, does it not contain a 200amp breaker? I will try and draw how I understand my connection should be and share it here later today. Thanks

No, as explained above, if you add a main breaker to your main panel. According to your photo, your main panel does not contain a main breaker. In the photo I've attached, there are only main lug connections inside the area I circled. You should be able to find a main breaker option for your main panel and install it. As I explained above, if you do that then a separate feeder tap breaker is not needed. It appears your panel is a Square D model. This link gives you an example of the main breaker that could be mounted in the area I circled. Please note this is ONLY an example. Your electrician needs to determine the exact model of main breaker that would be needed for your panel.

Amazon.com

@jeff.lankford some questions that came to my mind:
1) when all the connections are completed, the only power grid cable that goes to the main breaker panel should come from the manual transfer switch. If this is yes, the existing power grid connection that comes from the main server breaker will be removed?

Yes, that's correct. You can run a complete new cable from the MTS load lugs to the main breaker panel input. The existing output from the meter/main will be disconnected and that output runs to the MTS line input lugs. In my case, it was easier to keep my existing cable to the main panel and splice an extension on it to let it reach the MTS, but that was to avoid running an entirely new cable to the main panel. Depending on where you mount your MTS, an entirely new cable might make more sense for you.

2) If the existing power grid cable needs to be removed, instead of removing it, can I tap it to connect to the Manual transfer switch, that way I avoid having to do anything in the main breaker panel? I'm just trying to avoid touching existing connection and just use existing cables/connections as much as possible. But, the question would be if the cable they use for it will work with the manual transfer switch.

Please let me know, thanks!

Yes, that's what I've explained already with the splice (not a tap) I made in the meter/main to extend the existing cable. Your layout will depend on where you mount each device. I preferred everything to be on the outside of the house, so I didn't disturb/change anything regarding the inside main panel and the wiring going to it.

 

[jeff.lankford]

@fatanu

Let me try to offer a further explanation & clarification about the Feeder Tap.

I think EG4 has confused a lot of people with the diagram “Whole Home Backup using a Feeder Tap” by placing the feeder tap inside of a separate diagram block. Many people have inferred that means the feeder tap is a separate device in a separate junction box. That is not true. The feeder tap itself is just a connection between wires. That tap needs to be located inside of a suitable protective enclosure. That location could be inside of the main service disconnect enclosure, inside the feeder tap breaker enclosure or, if you omit the feeder tap breaker, inside of the manual transfer switch enclosure. I chose the latter:


The rules for feeder taps state that the tap conductors must be protected, and you’re allowed to place the protection at the downstream end of the tap, unlike a normal branch circuit that has a circuit breaker at the very beginning of the branch. So, if you add a main breaker at the downstream end of your tap, meaning at your main breaker panel, then you can omit the “feeder tap breaker” from the EG4 recommended design:

 

[fatanu]

@jeff.lankford Thank you so much for taking the time to explain it in detail. The explanation will help not just me but also many people who will see the post. Let me summarize what I have learned from your explanation and how I can apply it to my setup.

1. The output from my main meter, which is currently connected to my main breaker panel, will be removed, and that cable will be extended to a feeder tap enclosed in my MTS.
2. I'll most likely use a feeder tap in my case and enclose it in the MTS. My MTS will be placed beside my main breaker panel so that there is an easy connection backfeed to the inverter for the load.
3. Another cables from the feeder tap enclosed in the MTS will go to the PV disconnect which then go to the inverter for my grid connection. Question on that: Can my PV disconnect be indoors, close to my inverter (both indoors in my garage), which will also be beside the main breaker panel?
4. The only long cable I'll run is the AC disconnect current outside the wall. The cable will go through the hole to my garage wall and then run it to where I will place the inverter gen port (AC coupling setup) beside my main breaker panel.

Questions I have:

1. Can my PV disconnect be inside, considering I already have the AC disconnect outside? Is there any rule on where to place the PV disconnect?
2. For the feeder tap, can I use just one dual-face three-port tap for all the connections, or do I need one tap for each cable connection? This:

https://www.amazon.com/Ilsco-PBTD-3-250-Plastisol-Insulated-Multi-Tap/dp/B006J6YADC?gQT=1

I have seen videos where, despite having three ports, they use it for just one cable connection.

 

[fatanu]

@jeff.lankford the other question i have is the need for main breaker inside my main breaker panel to avoid the need for feeder tap breaker. Can I completely avoid using either the feeder tap breaker or the alternative of having main breaker inside my main breaker panel. What is the purpose of this in the setup? Is it for passing inspection or what.

 

[jeff.lankford]

1. The output from my main meter, which is currently connected to my main breaker panel, will be removed, and that cable will be extended to a feeder tap enclosed in my MTS.

Yes. To ensure we're saying the same thing, let me re-state what you wrote...

• The output from my main meter disconnect, which is currently connected to my main breaker panel, will be removed, and that cable will be extended to a feeder tap enclosed in my MTS.

1. I'll most likely use a feeder tap in my case and enclose it in the MTS. My MTS will be placed beside my main breaker panel so that there is an easy connection backfeed to the inverter for the load.

Yes

1. Another cables from the feeder tap enclosed in the MTS will go to the PV disconnect which then go to the inverter for my grid connection.

Yes

1. Question on that: Can my PV disconnect be indoors, close to my inverter (both indoors in my garage), which will also be beside the main breaker panel?

I think indoors is OK. NEC 690.13 (A)(1) states the location must be in a "readily accessible location." That doesn't say outdoors. 690.15 (D)(2) states the disconnect must be within sight of the inverter. Don't forget you need an outside RSD button since the inverter is inside.

1. The only long cable I'll run is the AC disconnect current outside the wall. The cable will go through the hole to my garage wall and then run it to where I will place the inverter gen port (AC coupling setup) beside my main breaker panel.

yes

Questions I have:

1. Can my PV disconnect be inside, considering I already have the AC disconnect outside? Is there any rule on where to place the PV disconnect?

My interpretation of NEC is yes, as stated above.

FYI, you can access the NEC online for free at this website. Click on the link "view free access":

NFPA 70 (NEC) Code Development

Stay informed and participate in the standards development process for NFPA 70

www.nfpa.org

1. For the feeder tap, can I use just one dual-face three-port tap for all the connections, or do I need one tap for each cable connection? This:

https://www.amazon.com/Ilsco-PBTD-3-250-Plastisol-Insulated-Multi-Tap/dp/B006J6YADC?gQT=1

I have seen videos where, despite having three ports, they use it for just one cable connection.

Yes, you can use that device. It will make a more crowded MTS enclosure because it will add additional conductors and two of those tap blocks. I think what I did is simpler and cleaner. It was definitely cheaper. The dual lugs circled in this photo serve as my feeder tap. These are about $5 at a supply house. The single lugs are bolted into the MTS and easily replaced.

the other question i have is the need for main breaker inside my main breaker panel to avoid the need for feeder tap breaker. Can I completely avoid using either the feeder tap breaker or the alternative of having main breaker inside my main breaker panel. What is the purpose of this in the setup? Is it for passing inspection or what.

You need one or the other, or you are violating the NEC rules for a feeder tap. Most of the NEC rules related to circuit protection are really important for safety and they are there for a reason. If it were my house, I wouldn't try to ignore it, even if I was doing this unpermitted.
Adding the main breaker inside your panel is definitely the cheaper and simpler solution. It won't add a separate enclosure to the installation. If your main panel doesn't have a main breaker option available, then I would strongly encourage you to include the feeder tap breaker in your design. You could add the same disconnect breaker enclosure that's used for the PV Disconnect component. Note that if you include the feeder tap breaker, then your tap will not be located inside the MTS enclosure as we've been discussing.

 

[fatanu]

Yes, you can use that device. It will make a more crowded MTS enclosure because it will add additional conductors and two of those tap blocks. I think what I did is simpler and cleaner. It was definitely cheaper. The dual lugs circled in this photo serve as my feeder tap. These are about $5 at a supply house. The single lugs are bolted into the MTS and easily replaced.

will it be possible to label each cables in your MTS. I love the approach you took with the dual logs. But, from the wiring diagram, there are three connections which means you should use three of those dual logs, I assumed, red, black and neutral. You only used two. Also, there should be three cable connections at each tap (in your case log), one from the main disconnect, one going to the pv disconnect, and another going to the main breaker panel, all connected to a tap (log in your case). Maybe if you label the cables in your MTS screenshot, things would be much clearer. I'm completely an amateur so pardon my questions. Also provide a link to the exact dual log you used. Thanks!

 

[jeff.lankford]

will it be possible to label each cables in your MTS. I love the approach you took with the dual logs. But, from the wiring diagram, there are three connections which means you should use three of those dual logs, I assumed, red, black and neutral. You only used two. Also, there should be three cable connections at each tap (in your case log), one from the main disconnect, one going to the pv disconnect, and another going to the main breaker panel, all connected to a tap (log in your case). Maybe if you label the cables in your MTS screenshot, things would be much clearer. I'm completely an amateur so pardon my questions. Also provide a link to the exact dual log you used. Thanks!

Only the ungrounded conductors (red & black) are switched and are subject to the feeder tap rules. This is a common neutral architecture, the neutral is a grounded conductor and is unswitched. There is only a single neutral path through my MTS. As it happens, because of the way I kept the main cable routing out of the back of the original main disconnect box, I tapped the neutral conductor in that box and routed a single neutral line to pass through the MTS to the inverter. My edited diagram doesn't show it that way just to simplify the explanation, so it doesn't match my photo. Sorry.

The dual lugs in the photo do in fact have three connection points, one of which you're overlooking. On the dual lugs there are grid input cables and output cables running to the inverter input (via the PV Disconnect). The third connection on those lugs are the switch contact connections themselves - the bolt holding the lug runs to the MTS line/grid input contacts. It's that bolt connection that omits the extra jumper conductors in the box and simplifies the install.

More thoughts on your question about omitting both breakers...
You should read the explanatory text on the EG4 diagram. There is a scenario where there is a very real possibility of subjecting your main panel bus, and the cable running to it, to up to 250amps. And if you consider the sustained surge capability of the 18Kpv, that number is even higher. I calculate it could be up to 265 amps. If there is not a 200A circuit breaker either at the main breaker panel or at the "feeder tap breaker" position, then you could burn your house down.

As I said, some rules are there for good reason, not just to pass inspections. You’re not licensed (neither am I). You need to understand what you’re doing well enough before you can safely decide which rules to bend.

 

[fatanu]

The dual lugs in the photo do in fact have three connection points, one of which you're overlooking. On the dual lugs there are grid input cables and output cables running to the inverter input (via the PV Disconnect). The third connection on those lugs are the switch contact connections themselves - the bolt holding the lug runs to the MTS line/grid input contacts. It's that bolt connection that omits the extra jumper conductors in the box and simplifies the install.

Thank you!

 

[fatanu]

You should read the explanatory text on the EG4 diagram. There is a scenario where there is a very real possibility of subjecting your main panel bus, and the cable running to it, to up to 250amps. And if you consider the sustained surge capability of the 18Kpv, that number is even higher. I calculate it could be up to 265 amps. If there is not a 200A circuit breaker either at the main breaker panel or at the "feeder tap breaker" position, then you could burn your house down.

I read through your responses and I did not see how you addressed this in your design...or maybe i miss something.

I am almost 100% clear on how my setup will look like, but I'll appreciate if you could label the cables in your MTS screenshot when you have a chance. I am going to draw out my plan this weekend. I am seriously having hard time getting electrician, they are backing out the moment they hear solar that they don't do any electrical work related to solar. Once I have all the details, I will change my call approach and only mention I need help with some panel connections. Thank you!

 

[jeff.lankford]

I read through your responses and I did not see how you addressed this in your design...or maybe i miss something.

I am almost 100% clear on how my setup will look like, but I'll appreciate if you could label the cables in your MTS screenshot when you have a chance. I am going to draw out my plan this weekend. I am seriously having hard time getting electrician, they are backing out the moment they hear solar that they don't do any electrical work related to solar. Once I have all the details, I will change my call approach and only mention I need help with some panel connections. Thank you!

My inside main breaker panel contains a 150 amp main breaker, so my feeder tap is protected at its downstream end.

In Augusta, you're about 4 hours away from me. You're welcome to drive up here and look at this system, if you're gonna tackle this yourself and if you think it would help. I understand the problem with finding a contractor... I've seen numerous electrical contractors that don't want to mess with solar, or if they do work with solar they only want to do off-grid and they will not touch a grid-tied system. Even though you might consider it a hassle, I would encourage you to pull a permit and let the inspector review your work. I've been doing my own electrical work for ~40 years and I've learned a lot from inspectors along the way. I consider them a help to make sure I don't make a DIY mistake, and not a hindrance. If they know the work was done by the homeowner, they will scrutinize the job more closely, so you have been warned.

 

[fatanu]

In Augusta, you're about 4 hours away from me. You're welcome to drive up here and look at this system, if you're gonna tackle this yourself and if you think it would help. I understand the problem with finding a contractor... I've seen numerous electrical contractors that don't want to mess with solar, or if they do work with solar they only want to do off-grid and they will not touch a grid-tied system. Even though you might consider it a hassle, I would encourage you to pull a permit and let the inspector review your work. I've been doing my own electrical work for ~40 years and I've learned a lot from inspectors along the way. I consider them a help to make sure I don't make a DIY mistake, and not a hindrance. If they know the work was done by the homeowner, they will scrutinize the job more closely, so you have been warned.

thank you. I will give it a thought.

Where are the two green cables coming from? Where are the two white cables coming from? Also, the dual log where the green cables connect to is the log you explained your made a hole in the MTS to screw it down.

 

[goldserve]

Is the white neutral to inverter share between grid in and load out?

 

[fatanu]

@jeff.lankford Also, correct me if I'm wrong, the black cables circled in my main breaker panel is the output from my main disconnect? If yes, this cables seem big to compare to the cable (the 2/0 cables you used) i intend to use to extend them to my MTS. They seems incompatible to join them to together. Just trying to compare cables you used to extend the grid connection to your MTS.

If I am wrong, which of the cables look like the output from my main disconnect from my main breaker panel?

 

[jeff.lankford]

@jeff.lankford Also, correct me if I'm wrong, the black cables circled in my main breaker panel is the output from my main disconnect? If yes, this cables seem big to compare to the cable (the 2/0 cables you used) i intend to use to extend them to my MTS. They seems incompatible to join them to together. Just trying to compare cables you used to extend the grid connection to your MTS.

If I am wrong, which of the cables look like the output from my main disconnect from my main breaker panel?

Your main cables appear to be aluminum. If so, they are 4/0. A 200amp service requires either 4/0 Al or 2/0 Cu cable. Aluminum is cheaper but I prefer to work with copper. They are not incompatible as long as you are using splice blocks / lugs / whatever / that are rated for both Al and Cu. e.g. a Polaris block is rated for both Al and Cu. So, it is legal to have an Al cable spliced to a Cu cable using a Polaris device. With different sized cables, you simply use a device large enough for the largest cable. The Polaris connectors and the typical breaker lugs are rated for a range of cable sizes, e.g. 4/0 down to something much smaller like 2 awg.

 

[jeff.lankford]

thank you. I will give it a thought.

Where are the two green cables coming from? Where are the two white cables coming from? Also, the dual log where the green cables connect to is the log you explained your made a hole in the MTS to screw it down.

The green equipment ground and white neutral conductors are routed from the main disconnect, through the MTS and the PV Disconnect, to the inverter. The ground is also used to ground the MTS and PV Disconnect enclosures using suitable lugs. Yes, I added the dual lug you see to the MTS box. The equipment ground continues from the inverter to also ground the battery bank.

If I had a direct connection from the MTS to the main breaker panel using a new main cable run, then you would see a third ground and neutral conductor leaving the MTS box with the load conductors headed to the main breaker panel. However, in my case the two load conductors return to the main disconnect enclosure to be spliced to the original main cable running to the main breaker panel, and so the neutral and ground conductors heading to the main breaker panel originate at the main disconnect and are not seen in the MTS enclosure.

 

[jeff.lankford]

Is the white neutral to inverter share between grid in and load out?

Yes, exactly.
The neutral conductor is unswitched. A pull of neutral from the MTS to the inverter, and then from the inverter back to the MTS, would be redundant copper. And since that's a relatively long run for me (~35 feet) it would be an expensive redundancy.

This is a result of placing the feeder tap inside of the MTS. If the feeder tap were located elsewhere, then there would be two neutral runs - one from the feeder tap to the inverter, and a second from the inverter to the MTS.
AFAIK, this does not violate any rules regarding conductor sizing. This is an over-sized neutral to begin with anyway, since it uses the same 2/0 cable as the line conductors. It's possible there is some NEC rule that the neutral conductor must travel inside the same raceway as its line conductors. If so, this setup violates such a rule, but honestly I haven't done a search to prove or disprove that. But this is a pair of raceways running parallel, to satisfy the conduit fill rules, so I would think this satisfies the intention of a "same raceway" rule, if it exists. The inspector passed this system as you see it pictured.

 

[fatanu]

The green equipment ground and white neutral conductors are routed from the main disconnect, through the MTS and the PV Disconnect, to the inverter. The ground is also used to ground the MTS and PV Disconnect enclosures using suitable lugs. Yes, I added the dual lug you see to the MTS box. The equipment ground continues from the inverter to also ground the battery bank.

If I had a direct connection from the MTS to the main breaker panel using a new main cable run, then you would see a third ground and neutral conductor leaving the MTS box with the load conductors headed to the main breaker panel. However, in my case the two load conductors return to the main disconnect enclosure to be spliced to the original main cable running to the main breaker panel, and so the neutral and ground conductors heading to the main breaker panel originate at the main disconnect and are not seen in the MTS enclosure.

could you please explain this for an amateur like me to understand. I read it multiple times and I got lost, sorry. I feel like the information is important and similar to how my setup would be, but if you could explain it a less technical for someone with no prior electrical experience, it will be helpful. My goal was to understand where the white and green cables come from or connect to. thanks!

 

[jeff.lankford]

could you please explain this for an amateur like me to understand. I read it multiple times and I got lost, sorry. I feel like the information is important and similar to how my setup would be, but if you could explain it a less technical for someone with no prior electrical experience, it will be helpful. My goal was to understand where the white and green cables come from or connect to. thanks!

How much electrical work have you ever done? I'm beginning to think you really need to find a willing electrician. Sorry to be blunt...

 

[fatanu]

Your main cables appear to be aluminum. If so, they are 4/0. A 200amp service requires either 4/0 Al or 2/0 Cu cable. Aluminum is cheaper but I prefer to work with copper. They are not incompatible as long as you are using splice blocks / lugs / whatever / that are rated for both Al and Cu. e.g. a Polaris block is rated for both Al and Cu. So, it is legal to have an Al cable spliced to a Cu cable using a Polaris device. With different sized cables, you simply use a device large enough for the largest cable. The Polaris connectors and the typical breaker lugs are rated for a range of cable sizes, e.g. 4/0 down to something much smaller like 2 awg.

got it, thanks

 

[fatanu]

How much electrical work have you ever done? I'm beginning to think you really need to find a willing electrician. Sorry to be blunt...

None.. I will certainly get someone to do it for me...I just need to buy everything and have them available and make the electrician trip a one trip for the installation. Once I have everything I need, it easy for me to convince an electrician the help I need without mentioning solar, and that i will handle the connection to the inverter myself. Also, there is always a first time for everything. I don't intend to do this myself though, but I have a better understanding of electrical connections than I was last week with your explanations, so thank you for taking time to explain things and responding to my questions.

 

[jeff.lankford]

None.. I will certainly get someone to do it for me...I just need to buy everything and have them available and make the electrician trip a one trip for the installation. Once I have everything I need, it easy for me to convince an electrician the help I need without mentioning solar, and that i will handle the connection to the inverter myself. Also, there is always a first time for everything. I don't intend to do this myself though, but I have a better understanding of electrical connections than I was last week with your explanations, so thank you for taking time to explain things and responding to my questions.

OK, I’m relieved to read that. I’m happy to continue giving you advice and answering questions. I just don’t want to encourage someone to do a job like this themselves without the skillset. There are so many little things you need to know to do this job safely and properly, which come from experience.
Torque all connections properly.
Use dielectric grease on all lug connections.
Use conduit bushings as required (bushings are not just for aesthetics).
Proper equipment grounding.
Proper conductor sizing.
Safely working inside of a hot box without having the utility pull the meter first.
Etc.
Etc.
Etc.

Before you purchase anything you need to confirm the size of your existing main cable. Don’t assume it’s 4/0 Al just because I guessed that from a photo. You should examine the cable sheath for the size, which will be embossed on the outer sheath. Buy the smallest splice blocks you can that will accept your largest cable. You posted a link to an inline splice block and then removed it… the inline splice blocks or the side-by-side splice blocks are both fine. They’re functionally the same – it just depends on the layout/ configuration of the cables inside your box to decide which will fit better. Make sure the one you purchase is UL Listed - there's a lot of cheap crap on Amazon that isn't. FWIW, I found that the cheapest price for Polaris blocks was on the Home Depot website.

If you post a picture of your main breaker panel’s inside label with all of the model number info, and all of the panel “options” listed on that label, I will try to help you find the correct main breaker to add to the panel. Also post a closeup picture of the main lug area that I circled earlier.

If you’re going to buy all the copper cable ahead of time, don’t buy it at HD or Lowes. Find a local electric supply house and buy it there. I spent almost $1,000 just on copper cable for my job. It would have been twice that at Lowes. It looks like you have a City Electric branch in Augusta. I would go there. Don’t buy the transfer switch or PV disconnect there – they will be cheaper online from HD or Lowes. Go figure.

 

[fatanu]

OK, I’m relieved to read that. I’m happy to continue giving you advice and answering questions. I just don’t want to encourage someone to do a job like this themselves without the skillset. There are so many little things you need to know to do this job safely and properly, which come from experience.
Torque all connections properly.
Use dielectric grease on all lug connections.
Use conduit bushings as required (bushings are not just for aesthetics).
Proper equipment grounding.
Proper conductor sizing.
Safely working inside of a hot box without having the utility pull the meter first.
Etc.
Etc.
Etc.

Before you purchase anything you need to confirm the size of your existing main cable. Don’t assume it’s 4/0 Al just because I guessed that from a photo. You should examine the cable sheath for the size, which will be embossed on it. Buy the smallest splice blocks you can that will accept your largest cable. You posted a link to an inline splice block and then removed it… the inline splice blocks or the side-by-side splice blocks are both fine. They’re functionally the same – it just depends on the layout/ configuration of the cables inside your box to decide which will fit better. Make sure the one you purchase is UL Listed - there's a lot of cheap crap on Amazon that isn't. FWIW, I found that the cheapest price for Polaris blocks was on the Home Depot website.

If you post a picture of your main breaker panel’s inside label with all of the model number info, and all of the panel “options” listed on that label, I will try to help you find the correct main breaker to add to the panel. Also post a closeup picture of the main lug area that I circled earlier.

If you’re going to buy all the copper cable ahead of time, don’t buy it at HD or Lowes. Find a local electric supply house and buy it there. I spent almost $1,000 just on copper cable for my job. It would have been twice that at Lowes. It looks like you have a City Electric branch in Augusta. I would go there. Don’t buy the transfer switch or PV disconnect there – they will be cheaper online from HD or Lowes. Go figure.

Thank you so much... I printed all our conversations and your connection screenshot and was able to use it to explain to a willing electrician. It HELPED alot and he was a bit comfortable to pick the job. His labor cost isn't bad as well; $900. We should get started today. Thank you so much.

Question:

Not sure if you are using the same battery, but I assembled this myself. Do you know what cable was used to connect the ground together in this picture. I found the video online.

 

[jeff.lankford]

Thank you so much... I printed all our conversations and your connection screenshot and was able to use it to explain to a willing electrician. It HELPED alot and he was a bit comfortable to pick the job. His labor cost isn't bad as well; $900. We should get started today. Thank you so much.

Question:

Not sure if you are using the same battery, but I assembled this myself. Do you know what cable was used to connect the ground together in this picture. I found the video online.

I used stranded 10 gauge green for all the battery ground jumpers seen in this photo. I used 6 gauge green in all the AC wiring photos you've already seen. I also have a 6 gauge equipment ground conductor running from the inverter ground bus to the battery rack grounding lug. You can buy a spool of the 10 gauge green at HD. They probably won't have the 6 guage, but City Electric will.

For the 18Kpv, your DC cables need to be sized for a maximum of 280 amps. Be aware that the sustained surge output capability of the 18Kpv is 13.5kW when running from battery, so you must design for that possibility with your battery connections. When you also factor in the 94% efficiency of the inverter, the maximum power draw from the battery bank could be as high as 14,362 watts. What you see in my photo is a pair of 2/0 welding cables for my DC cables, instead of a single 4/0 cable. FYI, the best place I have found for pre-made professionally-lugged battery cables is a vendor called "Windy Nation." They have a store on Amazon, but there's a much better selection of cable lengths and sizes on their website.

 

[fatanu]

@jeff.lankford Thanks!

My electrician is suggesting we could do away with MTS to save cost and keep things simple. I'm not completely sold on the idea but I did a bit google search and I think this is the video he watched.

The guy in the video Instead of a transfer switch with 200 amp pass through, tapped the feed and run a disconnect, and keep the load on an interlock breaker. He used a 70amp breaker because he feels that will support his house load peak. If I am to follow this approach but want 200amp is that possible?

 

[jeff.lankford]

@jeff.lankford Thanks!

My electrician is suggesting we could do away with MTS to save cost and keep things simple. I'm not completely sold on the idea but I did a bit google search and I think this is the video he watched.

The guy in the video Instead of a transfer switch with 200 amp pass through, tapped the feed and run a disconnect, and keep the load on an interlock breaker. He used a 70amp breaker because he feels that will support his house load peak. If I am to follow this approach but want 200amp is that possible?

Yes, you could do that, but you will limit your entire house load to 70 amp at all times unless you want to manually throw that interlock to switch the house back to grid connection for normal operation. Note that if you did that then you do not have automatic battery backup with the inverter's EPS switchover. Instead you'll have what equates to a manual generator backup.

Note that the person in the following thread set out to build a whole house backup with 200 amp pass through, and after listening to his electrician for cost savings he arrived at exactly this situation - a 70 amp backfed interlocked breaker and he no longer has 200 amp pass through capability. The latest discussion in this thread is how he might fix that situation by increasing the size of the interlocked breaker or adding a critical loads panel so the inverter isn't powering everything. Note that doing any of those things increases cost and defeats the cost-savings purpose of omitting the MTS to begin with. So, be careful that you don't try this and wind up spending even more money with creeping costs to fix it later. You might want to read through this entire thread:

T

Thread '18kpv setup right?? can you feeder tap meter/main panel ?'

Nov 30, 2024

I currently have 200amp meter/main combo panel. I thought we could do the whole home backup install method for the 18kpv using feeder taps, but my electrician is saying to use a 200amp sub panel as a critical loads panel. Is that because the meter/main combo? He said install should be meter / main panel (with EV charger and hot tub loads only) then feeder tap to 200 amp breaker outside. Then inside garage, a 200 amp sub panel with interlock setup instead of manual transfer switch. I’m not sure why the sub panel? He’s using a feeder tap either way, why create a separate panel when only...

• Treepin
• Replies: 42
• Forum: DIY Solar General Discussion

The design in the video is still using the "PV System Disconnect" from the EG4 design - it is the 70 amp disconnect switch he mounted above his panel. If this turns out to be a mistake and needs to be fixed later to have 200amp pass through, then that 70 amp disconnect will need to be replaced with a new 200 amp disconnect. So, more creeping cost down the road if this is a mistake.

Before you put too much stock in that video, from the commentary it sounds like this video is the result of this guy first posting a different installation and having EG4 make an immediate reaction to have him fix it and post a resolution. This guy is too stubborn to use the recommended MTS design, and what he initially came up with was a huge mistake which violated code and created a safety hazard (tying the inverter's grid and load ports together). This second video sounds like a compromise with EG4 to remove the liability, but this guy is still too stubborn to simply use the recommended MTS.

At the end of the video the guy starts talking about leaving the interlock in pass through mode and simply using the inverter's automatic switchover as intended. He says his house loads don't exceed 70 amp and so he'll try that for awhile. But note that in the video before he even makes this switch, he has to wait for something to stop running first - he already has more load than 70 amp and had to wait for one load to stop before he could demonstrate the "automatic" position. Don't let that video mislead you into making a mistake. If you already have a good energy budget analysis for your house and all of its loads, and you know you never exceed a 70 amp load, then go for it.