Need help with solar system grid interconnect


  #1  
Old 05-23-23, 10:48 AM
L
Member
Thread Starter
Join Date: May 2023
Posts: 8
Upvotes: 0
Received 0 Upvotes on 0 Posts
Need help with solar system grid interconnect

I'm trying to figure out how to do a grid interconnect with a hybrid inverter. I can get things to work electrically, but I'm having problems getting the job done in a code compliant method.

Currently the utility feed comes up through a cement floor into an inside wall to the garage as 4/0 Al in PVC conduit. We have an 11kW Generac and the ATS is the first box in line. The output of the ATS then goes vertically into the bottom of the main service panel. When that wall was finished, the drywall crew built a false wall to cover the electrical components, the main service panel and ATS are flush mounted in the false wall.

The hybrid inverter accepts the generator output and does the 2 wire start function. So I will be removing the ATS. I'm considering using interior and exterior gutters to help route wiring. I don't have enough wall space inside the garage, so some of the equipment will have to be mounted on the garage wall exterior.

The wall cavity is 3.5" deep and 13" wide. I can't figure out a code compliant way of getting the service conductors into the exterior gutter without violating some part of Articles 312, 314 or 376 of NEC 2020. I've been hung up on this aspect for several days.

Anyone have any ideas that would work?

Thanks,
Lowell
 
  #2  
Old 05-23-23, 01:50 PM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Jersey
Posts: 62,494
Received 3,485 Upvotes on 3,128 Posts
Welcome to the forums.

You need a permit to install a solar grid tie system.
The power company will not help you or connect anything without a permit/cut-in card.

There are so many details that need to be addressed when building a grid tie system.
All connections from the solar panels to the inverter(s) and panels need to be in metal conduit. No PVC.

Inspectors are very demanding on DIY solar systems.
Maybe check with your town and just see what they require.
Where are you located ?
I'd check with the power company too.
 
  #3  
Old 05-23-23, 07:59 PM
L
Member
Thread Starter
Join Date: May 2023
Posts: 8
Upvotes: 0
Received 0 Upvotes on 0 Posts
Hi Pete,
I have talked with the POCO, the county and the state with regards to permitting requirements. I got a bunch of generalities with no actionable input. I'm in a rural part of Colorado.

I think I can work through most of the install, but where I'm getting hung up on is how to get a solution to the problem I described in my original post. I would like to get input from an electrician who is NEC 2020 savvy.

I was hoping to get some answers on a DIY solar forum, but they kept going down rabbit holes on system design. If I can't find a solution to the problem I described in my first post, then everything else is moot.

Thanks
 
  #4  
Old 05-24-23, 03:21 AM
A
Member
Join Date: Jun 2012
Location: USA
Posts: 1,480
Received 86 Upvotes on 78 Posts
From this I assume your meter is inside your garage? If so, your situation doesn't sound like it has a DIY solution as to get the service conductors back outside is going to be a lot of work. Easiest might be to treat this as a new install and have new service lateral installed to your outside wall. Otherwise extending what you have would mean pulling the conductors back out of the conduit, extending the PVC to the outside, and then encasing the PVC in cement to make it "beneath the slab".
 
  #5  
Old 05-24-23, 06:40 AM
L
Member
Thread Starter
Join Date: May 2023
Posts: 8
Upvotes: 0
Received 0 Upvotes on 0 Posts
Meter is on a utility pedestal outside, about 60 feet from the garage wall. The breakered disconnect is out on the utility pedestal also. I have the option of running the service conductors to either an inside or outside gutter. Currently, I can't envision how to compliantly get those conductors out of the wall into a gutter and then downstream of the inverter to get the conductors that power the main panel back into the wall and up into the service panel. Maybe it is not possible.
 
  #6  
Old 05-24-23, 11:08 AM
A
Member
Join Date: Jun 2012
Location: USA
Posts: 1,480
Received 86 Upvotes on 78 Posts
Since your disconnect is at the pedestal then nothing your are touching is service. What you are working with are feeder conductors. With that the super restrictive rules don't apply. Saying that you are touching service conductors will throw up red flags for anyone you talk with.

Pictures always help because most of the time we have to make multiple assumptions of what your setup is as well as what you are trying to do and with what equipment. Getting someone on site to look at everything would be ideal.

The simplest would be to gut or replace the ATS box and use it as an accessible pull box. Conduit straight out the back to get to the outside. It would then go into the back of a gutter or connect to an LB. All new equipment on the outside.

If you need a gutter on the inside then you have a problem that almost everyone would have with a flush mounted panel as there is no clean way to just pop out of the drywall from a panel. In your case consider replacing the ATS box with a deep gutter box (e.g. 8x8x12 wide). The box would stick out but you are allowed to go 6" in front of the panel. You would only need a bit of fixing to the drywall. Knockouts near the back of the gutter to connect to the existing feeder and panel. Make your own knockouts on the front sides for the surface connections.
 
  #7  
Old 05-24-23, 01:36 PM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Jersey
Posts: 62,494
Received 3,485 Upvotes on 3,128 Posts
Thanks for helping A.

As A mentioned....it's a little tough to get a feel for what you are doing.
Pictures can make a world of difference....... How to insert pictures.
 
  #8  
Old 05-24-23, 02:42 PM
L
Member
Thread Starter
Join Date: May 2023
Posts: 8
Upvotes: 0
Received 0 Upvotes on 0 Posts
My bad on the terminology.

I have attached two images, one of the inside of the wall and one of the outside of the wall. The structural wall is ICF, 8" of reinforced concrete with 2.5" of foam insulation on either side of the concrete. It is a ***** to run a core drill through.

You bring up an idea I had not thought of. I would pull the ATS intact (possibly for resale) and then replace it with a large junction/pull box. I only have one wall stud bay to work with as the other wall stud bay has a structural steel rectangular support post in it.

The inverter is a Sol-Ark 15k and is 12" deep. In the past the state inspector was willing to chat with me and when I showed him that I was planning on mounting the inverter to the left of the breaker panel, he said that would be fine. The last time I spoke with him he waved off and said that he just inspects, so that path is closed. I saw the 6" limitation in the code, but was assuming that had to do with structural items, like railings and the such and not wireways/gutters, junction/pull boxes or related electrical equipment. I also read that hinged panel doors must be able to open at least 90 degrees. Can you clarify what is done in practice?

I would still have the problem of getting the grid, load, gen, PV, battery and communication wires into the bottom of the hybrid inverter. Was originally planning an 8x8 gutter for the inside wall, but that may not be doable.

As you can see in the outside wall image, I was planning a gutter there to bring in the generator wires, the PV wires, provide a wireway to bring the feeder wires out from the inside surface of the wall and to run the wires for the manual transfer switch and the production meter.

The rural POCO does not understand hybrid inverters and they don't understand that the production meter that they require for the installation will show the exact same number of kWh being pushed into their grid that their net meter will show. They think everything is a plain jane string inverter.

Am beginning to doubt my sanity on this project. We live in a rural part of Colorado and the quality of the power delivered is pretty poor, voltage and cycle fluctuations - not to mention the outages. The POCO is pretty draconian when it comes to going completely off grid, which is why I would be staying grid tied and hence the difficulties I'm encountering.

Thanks for your replies...


Inside garage wall

Outside of garage wall
 
  #9  
Old 05-24-23, 09:07 PM
L
Member
Thread Starter
Join Date: May 2023
Posts: 8
Upvotes: 0
Received 0 Upvotes on 0 Posts
I believe Astuff has got an idea that would work. I don't know why I didn't think of it - too close to the problem I guess.

So I would pull out the ATS and put in a 24x12x10 enclosure. To get from the bottom of the inverter into the side of the enclosure I would use 5 2" FMC. I don't want to buy a bender to do 2" EMT. Enclosure would only extend out 6" in front of the panel so that is code compliant in the vertical space. Inverter to the left of the panel allows the panel door to open 90 degrees and I have 30" of horizontal space for the panel since there is nothing to the right.

I double checked my measurements for getting conduit through the ICF wall between the inside enclosure and the outside gutter. I've got a 3" vertical space. I believe I need 2 2.5" EMT through the wall to stay within the fill restraints. I have to verify that 2.5" will get the job done, it will be a straight shot through a 13" thick wall.

Comments?

I have to get feeders to the Xfer switch and the production meter. Do I have to drag the neutral through the Xfer switch and PM, or can I run the feeder neutral to a bus in the enclosure and run neutrals from the inverter, breaker panel and generator to that bus?

Thanks for any comments.
 
  #10  
Old 05-24-23, 09:55 PM
A
Member
Join Date: Jun 2012
Location: USA
Posts: 1,480
Received 86 Upvotes on 78 Posts
In front of a panel you need working space about the size of a refrigerator. No structural items, plumbing, etc. allowed. Electrical items are allowed to protrude 6" into the space. It is 30" wide but doesn't need centered on the panel. So, yes, the door needs to open 90. And with all that the 15K can be on the left without issue.

Also, I'm thinking that the PV meter would be for Solar Renewable Energy Credits (SRECs) which can be worth a lot of money. The meter would measure the amount of solar you actually produce, not necessarily what gets sent to the grid. This has nothing to do with where the energy goes to or gets used but instead to meet the program requirements. The net meter at your service doesn't know anything about solar. It just shows how many kwh the utility is sending to you minus how many you send to them (which is only when your load is less than the PV output).
 
JackSammy voted this post useful.
  #11  
Old 05-25-23, 07:34 AM
L
Member
Thread Starter
Join Date: May 2023
Posts: 8
Upvotes: 0
Received 0 Upvotes on 0 Posts
For what is called a hybrid inverter, there is no place to install a PV production meter that will measure the amount of power going to the house and the grid. Another way of describing a hybrid inverter is an all-in-one device. Power from the PV array comes into the inverter either as DC or AC. The inverter is programmable to then provide AC power to the house or grid or both according to user defined criteria. DC power can also be directed to charge batteries and power can be drawn from the batteries to supply the house when needed (and even push power back into the grid). The inverter can also control a generator. Looking at the hybrid inverter another way, it is a single box solution that powers the house by using power from any or a mix of power sources; the grid, PV, batteries or generator. It can feed excess PV production (not needed to run the house) to batteries or the grid or both concurrently. The energy path from the PV to loads (house, batteries, grid) is all internal to the inverter. Of course the inverter has software to display all of these power flow paths and the inverter has a wifi connection to communicate with user monitoring devices and the mothership for software updates. But the POCO has no way of getting access to the data. In this case, the only place the POCO PV production meter could be placed is the grid interconnect to the inverter - and that will just be a duplicate measurement of what their net meter seeing. So I see it as a waste of materials and time to install a PV production meter in this use case. I am unable to convince the POCO of this. Their understanding of hybrid inverter technology is lacking.

Astuff, I would still like you to comment on my question as to whether or not I can drop the feeder neutral on something like a power distribution block inside the enclosure as a common point to land the neutrals from the inverter, breaker panel and generator. Then I would be able to only run the L1/L2 wires outside to the xfer switch and the waste of money PV production meter.

Thanks
 
  #12  
Old 05-25-23, 10:01 AM
A
Member
Join Date: Jun 2012
Location: USA
Posts: 1,480
Received 86 Upvotes on 78 Posts
It sounds like you still don't have anything that documents what the PoCo's metering requirements are. If the meter is to measure PV output then you need to provide that connection. (which is what I am assuming)

It looks like the SA-15K has no solution for PV output metering. Discussion here: https://diysolarforum.com/threads/pv...inverter.44345 So if your PoCo requires a PV meter then you need to find a different inverter. It may not be that they don't understand hybrid inverters; it may be that they know hybrid inverters don't support their business model. Try another approach: Maybe there is a different rate schedule or service type that doesn't require the metering.

The code states that the neutral/grounded conductor needs included "where used" so you should be good without it. Inspector might try to argue but code is there. Similar to how a switch loop is wired.
 
  #13  
Old 05-26-23, 09:02 AM
L
Member
Thread Starter
Join Date: May 2023
Posts: 8
Upvotes: 0
Received 0 Upvotes on 0 Posts
The PoCo has two documents that apply to residential generating systems connected to their grid. They are pretty much duplicates so I don't know why they have two on their website. I've spoken with the PoCo solar rep 4 or 5 times now over the last couple of months. He was not even aware that one of the docs was on their website. He said that he was going to clean that discrepancy up, but hasn't yet. Their documents state that the inverter must meet UL 1741 and IEEE 1541, which the Sol-Ark does.

In their documents, the production meter is required so as to measure the consumer generated power that is pushed into their grid. There is no mention of measuring the power that the home consumes. I spoke with the PoCo solar rep about that and he said that they were only interested in what I would push back into their grid. He said that I would not get credit for generated power that I used in the house. I don't see the significance of that statement. My benefit is that I'm not buying their power. Bottom line is that they are requiring me to put in a meter can so that they can install a meter that is gonna record the same amount of inflow to their grid that their net meter shows.

I've researched solar for several years and have concluded that the Sol-Ark 15k meets my requirements. Sure there are other systems out there, but they do not match the performance capabilities at the price point of the Sol-Ark.

All though Colorado promotes solar via such things as no state sales tax on purchases of solar equipment and property assessments are not allowed to include the value of installed solar systems, there is no SREC program in Colorado. The larger utilities have rebate programs, but all that my local rural PoCo offers is net metering at a whopping 1.6 pennies per kWh pushed back into their grid. They meet the State obligation for RPS by purchasing credits from a multi-state power generation consortium called Tri-State. I don't think I've mentioned it on this forum, but this PoCo is anti-residential solar. One can see this from the hoops that have to be jumped through and their paltry pay-back rate. A utility that services the nearest town has a payback rate of 4.5 cents per kWh.

"The code states that the neutral/grounded conductor needs included "where used" so you should be good without it. Inspector might try to argue but code is there. Similar to how a switch loop is wired."
Could you point me to the place in the code that statement references?

Thanks,
Lowell
 
  #14  
Old 05-26-23, 11:44 PM
A
Member
Join Date: Jun 2012
Location: USA
Posts: 1,480
Received 86 Upvotes on 78 Posts
"where used" is mentioned a few times but the primary ones for you would be 300.3(B) and 300.20(A).

A net meter will be different than what is sent to the grid unless you never use any power from the utility. Maybe that's what this PV meter is for to please some bean counter? Something is missing and still guessing as no requirements.

 
  #15  
Old 05-28-23, 04:22 PM
L
Member
Thread Starter
Join Date: May 2023
Posts: 8
Upvotes: 0
Received 0 Upvotes on 0 Posts
Thanks, I'll look at those sections of Article 300.
 
 

Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description:
Your question will be posted in: