Solar, electricians and uncles who are dangerous with a screw driver are welcome

[hallett21]

To keep it simple lol.

Panel A (main panel) 200amp with a permitted 12kw solar array tied in. Solar has controller>panel>disco prior to hitting 60amp breaker in main.

Assume everything below is a separate building with 100ft run in between.

Panel B (fed from A) 100amp with 6-7 circuits

Panel C (fed from B) 100 amp 28ish circuits

Panel D (fed from C) 100 amp 12ish circuits.

Not that it matters but all of this runs and nothing is over loaded lol.

Now client wants to add 3.2kw of solar to Panel C. Now I’m always wanting to learn but my red flags immediately go up. Apparently a local solar supply house says good to go. They advised to wire a separate controller, panel and disconnect and then to feed panel C.

From strictly a safety standpoint Panel Bs feeder from A needs its own disconnect at the main. Also now Panel C’s feeders are also potentially live solar circuits to Panel B and D.

I say no go but I only rough in for solar.

I’ll add I have someone much smarter and with a lot more employees meeting me in the morning to check it out.

 

[DirtyWhiteDog]

Do you have a 1 line drawing of this system ?


I have a screwdriver

 

[hallett21]

Do you have a 1 line drawing of this system ?

I could draw you one

 

[hallett21]

Do you have a 1 line drawing of this system ?


I have a screwdriver

Proposed “design”

 

[Ace in the Hole]

Apparently a local solar supply house says good to go.

I am the only person at my employer in the AZ territory who has ever actually installed and sold solar directly...I get calls everyday from reps, branches, etc with questions about stuff (part of my job)... I would not base anything on this individuals word..the inside sales parts guys usually have at best zero to minimum field experience..outside reps usually know their shit though..

Secondly... the system is already 12kw...in a lot of jurisdictions going over roughly that range...creates a different can of worms. Are they going to refile for additional capacity with the utility? What state/utility is involved etc.. You are also exceeding breaker capacity of the 60 on a basic hand calculation adding the 3.2kw at the main...let alone down the line.

@BasilHayden and a couple other guys are far more knowledgeable on the tech side than me and hopefully will chime in...but from a surface level no go IMO.

 

[Orange Juice]

 

[hallett21]

I am the only person at my employer in the AZ territory who has ever actually installed and sold solar directly...I get calls everyday from reps, branches, etc with questions about stuff (part of my job)... I would not base anything on this individuals word..the inside sales parts guys usually have at best zero to minimum field experience..outside reps usually know their shit though..

Secondly... the system is already 12kw...in a lot of jurisdictions going over roughly that range...creates a different can of worms. Are they going to refile for additional capacity with the utility? What state/utility is involved etc.. You are also exceeding breaker capacity of the 60 on a basic hand calculation adding the 3.2kw at the main...let alone down the line.

@BasilHayden and a couple other guys are far more knowledgeable on the tech side than me and hopefully will chime in...but from a surface level no go IMO.

Not to be vague but you never know…

I’ll answer question 1 with what do you think?

Question 2 I think you know my rough location.

I don’t do solar which is why I ask. Down stream of the meter I’m your guy other wise lol.

I think the majority of the issue stems from the 12kw system being on an east facing roof and that’s equalling a lack of production.

Feeding a middle panel seemed like such a flagrant violation I didn’t even think of the original solar feed on the main.

 

[Ace in the Hole]

Not to be vague but you never know…

I’ll answer question 1 with what do you think?

Question 2 I think you know my rough location.

I don’t do solar which is why I ask. Down stream of the meter I’m your guy other wise lol.

I think the majority of the issue stems from the 12kw system being on an east facing roof and that’s equalling a lack of production.

Feeding a middle panel seemed like such a flagrant violation I didn’t even think of the original solar feed on the main.

IMO there are several issues..I just started at the first one I saw...and you've pretty much hit everything I would have an issue with on it. @MPHSystems and some others may chime in who know far more than me..

I don't know the codes as much as I likely should...but I don't think you can backfeed solar though multiple panels.. I know you can use a sub panel for it..but having more than one down the line I don't think you can. Yea I have a rough idea of location, I seriously don't think this would pass an inspector, or utility approval process.

E vs W and South is really subjective... Helped a homeowner recently who got royally screwed by a phoenix installer with all kinds of tilt brackets etc.. just was a money grab on his deal. Had several leaks and production issues. Got him hooked up with the right mounting and he's happy as a camper at a nude beach. If he's having production issues it could stem from all kinds of things..including a bad inverter that underperforms etc..

 

[Sleek-Jet]

I don't know the reasons for all the sub panels, but it never ceases to amaze me the money people will spend on Solar but they won't clean up their service/panels.

What it looks like to me is he needs a 320 amp service with a new main panel and eliminate all but one of the subs.

From a utility perspective I would want all the solar to come through one disconnect. Not sure how you'd do that with a 100 feet between buildings, maybe a shunt trip. Also not sure what the NEC says.

 

[Ace in the Hole]

I don't know the reasons for all the sub panels, but it never ceases to amaze me the money people will spend on Solar but they won't clean up their service/panels.

What it looks like to me is he needs a 320 amp service with a new main panel and eliminate all but one of the subs.

From a utility perspective I would want all the solar to come through one disconnect. Not sure how you'd do that with a 100 feet between buildings, maybe a shunt trip. Also not sure what the NEC says.

We ran A LOT of ground and outbuilding arrays on farms in south texas via trench...18" deep along fence lines to main panels on poles. Inverters mounted at the array with a disconnect..and the ac lines out to the main, depending on the utility with another disco. Never did any back feeding through panels down the way.. Also in agreement with you on your point about cleaning stuff up...people will spend thousands on solar but not a few hundred or couple grand to clean up the mess they have everywhere else.

 

[stokerwhore]

at least isolate the solar systems with a couple ATS. sounds hokey AF. I hate residential, lol.

 

[hallett21]

at least isolate the solar systems with a couple ATS. sounds hokey AF. I hate residential, lol.

I’m not gonna hook it up for a few reasons lol. But figured I’d throw it on here for a discussion in case I was missing something.

 

[azsunfun]

Still trying to insert tab A into slot B

 

[DirtyWhiteDog]

Not Impossible, 3kw it not that big of a load. If all the feeders are sized correctly and the load calculations don't exceed any of the panels listed ratings. But that's too much math for non professional hack.

 

[Backlash]

No help with the solar portion, but I can add why I added extra sub-panels at our home that Sleek mentioned.

I installed a new 200 amp Main panel with meter socket and ran conduit underground to the Edison pole. All of the following feed from the new 200 amp panel.

I ran cable out to my detached garage and installed a 100 amp sub-panel. This way I can wire my garage and all my power tools to that sub-panel, and not have to worry about digging more trenches to get back to the main panel on the house.

I then installed a 60 amp sub-panel directly next to the main panel on the house, which feeds smaller circuits on the first floor.

I installed a small 40 amp sub-panel downstairs in our basement for the same reason as the garage. I can add circuits later if necessary.

Lastly, I pulled cable up to our second story and installed another small 40 amp panel there.

Due to the timing of our lengthy remodel and the way things have worked out, this arrangement seemed appropriate. I like the fact that I can be upstairs, and only have to walk into another room to address any electrical issues upstairs. If I'm out in the garage or down in the basement, same scenario.

Hopefully that makes sense in laymen's terms.

 

[Taboma]

My $.02 and I'm not well versed in solar, other than enjoying my own for the past 13 years.

Step one, determine if this application and additional system capacity is acceptable to the utility and if so required solar isolation disconnects.
Step two, if step one is agreeable, then run actual real time running load tests on all three subs and the 100A at the main, so load capacities can be determined.
Need to know the max load on the 100A at panel A, and 100A at panel B, since if C isn't requiring the power, it's going to be transferred back to B, then A.

Step three, with one and two in your pocket, submit drawing with calcs and discuss with local AHJ.
Is each building currently properly separately grounded as I'm sure that will come up.

I'm guessing that the desire to add panels to Bldg sub-C, is due to lack of physical space on Bldg A.
If it's maxed by main panel capacity, then adding it downstream can present the same condition.

Anyway, following this conversation, I'm no solar guy, just a happy customer so not up on the finite regs.

 

[Shlbyntro]

stupid question. why not just upgrade the existing solar array?

 

[Willie B]

…Hmmm???…What is a screwdriver???… asking for a friend…

 

[Ace in the Hole]

stupid question. why not just upgrade the existing solar array?

At 12kw if the system is a few years old you are looking at a 40-48 panel system… inverter is likely maxed out as well. Likely doesn’t have the roofspace

If they alter the system they have to also update utility agreement which may move them to a different NEM agreement.

Adding a new standalone would only subject that part to new NEM, but even still this would not be proper install.

 

[BasilHayden]

I havent read all the replies so forgive me if Im repeating. But I will throw out some thoughts.

1 - The initial system looks to be 60A, but if the main panel is a true 200 it is only allowed 40A backfeed so may already be oversized. If it has a 225 bus then 70 is allowed. If its 225 he can only add another 10A without derating the main. 10A is roughly 6 panels or 2 - 2.4kw

2 - depending on jurisdiction using a remote panel isnt allwed, in most of my region we have been doing it this way for years but some AHJ are changing the rules and requiring a separate disconnect off the main service. Frankly its stupid and was only appropriate for ancient systems, not current technology but its what you get when you put idiots in charge of the building departments.

I dont know your location so I cant talk specifics, if you are building a new property there is a ton of things that can and should be considered, but if its existing, which it seems you are somewhat stuck with what was done before you.

Got to run, Company party tomorrow.

 

[BasilHayden]

At 12kw if the system is a few years old you are looking at a 40-48 panel system… inverter is likely maxed out as well. Likely doesn’t have the roofspace

If they alter the system they have to also update utility agreement which may move them to a different NEM agreement.

Adding a new standalone would only subject that part to new NEM, but even still this would not be proper install.

If all he wants is an additional 3kw the NEM3 change would actually kill him rather than help, it would be better to "fix" the existing system and maximize current tech and keep a NEM1 or 2 system, it can be upsized by less than 1kw in the process. I have a number of people throwing away 10 year systems and replacing with current panels and enphase, resulting in a smaller roof coverage and we are able to increase output by as much as 20% while keeping them in current NEM agreement.

 

[traquer]

I can offer zero help, but I uploaded the diagram and the posts to AI to see how good of an electrician it is LOL. Needless to say don't follow this advice, just trying to see if it can give you ideas

///

From the diagram and the discussion, it looks like there are already two solar panel systems in place: a 12KW system connected to Panel A (the main 200 AMP panel with a meter) and a proposed 3.2KW system to be connected to Panel C. The main concern is whether this addition is feasible and safe, considering the existing electrical layout.

The best course of action based on the discussion would involve:

• 1. Load Calculations:
  
  For example, a 12KW solar system might produce an average current of 50A at 240V. The NEC allows for a solar backfeed breaker to be up to 20% of the panel bus rating. So, if the main panel (Panel A) has a 200A bus, it could accept a solar breaker of up to 40A without de-rating the main breaker. If the existing solar system is backfeeding through a 60A breaker, this would need to be corrected unless the panel bus is rated for more than 200A.
  
  For the proposed 3.2KW system, we could expect around 13.3A of current at 240V (3200W / 240V = 13.3A). If Panel C is rated at 100A, adding a 13.3A solar backfeed should not be an issue from a load standpoint, assuming that the total load from Panel C's connected circuits plus the solar backfeed does not exceed 100A.
  
  2. Utility Approval and Regulations:
  
  Let's assume that the local utility allows for a maximum of 15KW of solar power production for residential systems without requiring special permissions or additional infrastructure. In this case, adding 3.2KW to the existing 12KW would bring the total to 15.2KW, which slightly exceeds this limit. The homeowner would need to apply for an exception or increase their service agreement with the utility.
  
  3. Disconnects and Isolation:
  
  For safety and code compliance, each solar array should have a readily accessible disconnect switch. These switches allow for the solar array to be isolated from the home’s electrical system in case of an emergency or for maintenance.
  
  4. Panel Feeder Capacity:
  
  The feeder from Panel A to Panel B, if rated for 100A, needs to be verified for its capacity to carry the additional backfeed current from Panel C's new solar array. If Panel C is downstream from Panel B, the feeder between B and C also needs to be capable of carrying this extra current without exceeding its rated capacity.
  
  5. Installation Standards and Experience:
  
  An experienced solar installer would verify all these calculations and ensure that the system complies with the NEC. For instance, the inverter size for the 3.2KW system should not exceed the maximum allowable current for the breaker it's connected to. If the inverter output is rated at 13.3A, the breaker should be rated for at least 15A, but typically a 20A breaker is used to provide a safety margin.
  
  Summary and Best Course of Action:
  • The existing 12KW solar system likely uses a 60A breaker. If Panel A has a 200A bus, it should be downgraded to a 40A breaker to comply with NEC regulations unless the panel has a higher rating.
  • A 3.2KW system produces about 13.3A, which would be acceptable on a 100A subpanel like Panel C, as long as the total load doesn't exceed 100A.
  • All solar arrays should have separate, accessible disconnects for safety.
  • If Panel B feeds Panel C, and the feeder is rated for 100A, adding a 13.3A solar backfeed should not overload it, provided the total load is within capacity.
  • Detailed analysis by a qualified solar installer is necessary to ensure compliance with local codes and utility requirements.

Notes:

1. Solar Backfeeding: There's a mention of the possibility that the solar systems could backfeed through multiple panels, which could be problematic. This is not common practice and could be against code or regulations depending on the jurisdiction.
2. Load Calculations: It is unclear whether the existing panels and feeders can handle the additional load from the new solar system. There needs to be a thorough load calculation to ensure that none of the panels are overloaded and that they comply with the National Electrical Code (NEC).
3. Utility Approval and Regulations: Any addition of solar capacity typically requires approval from the local utility company and must adhere to their regulations. This might include filing for additional capacity and adhering to Net Energy Metering (NEM) agreements. The discussion mentions that adding more capacity could move the system to a different (potentially less favorable) NEM agreement.
4. Disconnects and Isolation: There's a suggestion that the solar systems should have separate disconnects, possibly with Automatic Transfer Switches (ATS) for isolation. This is to ensure safety and to comply with utility requirements.
5. Panel Feeder Capacity: The discussion brings up that the feeder from Panel A to B might need its own disconnect at the main, and now Panel C’s feeder could potentially carry live solar circuits to Panel B and D, which could be a safety issue.
6. Installation Standards and Experience: There's skepticism about the advice given by a local solar supply house due to concerns about their practical field experience. The professionals in the thread are advising caution and suggesting that expert opinions should be so

 

[MPHSystems]

IMO there are several issues..I just started at the first one I saw...and you've pretty much hit everything I would have an issue with on it. @MPHSystems and some others may chime in who know far more than me..

I don't know the codes as much as I likely should...but I don't think you can backfeed solar though multiple panels.. I know you can use a sub panel for it..but having more than one down the line I don't think you can. Yea I have a rough idea of location, I seriously don't think this would pass an inspector, or utility approval process.

E vs W and South is really subjective... Helped a homeowner recently who got royally screwed by a phoenix installer with all kinds of tilt brackets etc.. just was a money grab on his deal. Had several leaks and production issues. Got him hooked up with the right mounting and he's happy as a camper at a nude beach. If he's having production issues it could stem from all kinds of things..including a bad inverter that underperforms etc..

I’m actually not perusing PV anymore. I’ve done a few systems and I did well, the customer did well but it was fairly tax incentive driven. I did some fairly extensive training and it’s still covered under my classification, I just find myself plenty busy with other projects.