Am looking for some electrical code help

[LBen]

Ok, I did an SLD. When putting it together I found out I had missed a disconnect - dammit, something else I have to find room for. I'm done for today...

 

[zanydroid]

The largest PV wire size that the SA15 accepts is 10 awg. I've seen PV wire runs of several hundred feet in videos. So where is my misunderstanding?

I just pulled up SA15 spec sheet for reference



Note there are 3 MPPT, 26A per MPPT, 2 strings per MPPT. I think the #10 limit is per STRING. And the SA can draw a maximum of 26A combined across the strings. Each MPPT operates at one voltage, so I think you can think of this as a built-in combiner, that saves you the trouble of adding an external combiner.

So if you split one MPPT evenly between the two strings, that's 13A each, so that is easily within the limit of #10.

I think I'm still good with 10 awg. While the SA15 MPPT max amp rating is 26a, their panel design tool shows that for my config that Isc is 10.3 amps. So with a derated wire ampacity of 15.38 amps. I've got plenty of margin. I probably did this type of calcs a year ago when I decided 10 awg was sufficient. Now correct me if I'm wrong. I believe the array will be putting out more than rated power due to the site being at 8200'. Output voltage will be approximately the same, but there will be higher current. I bought a handheld solar meter over a year ago
and at noon on an absolutely clear day I saw about 1300 w/m2. I don't know if the meter was showing a valid number or not. But even if it is correct, I'm still good with the wire size and won't blow the MPPT. I've come across some sites that talk about a further derate for distance? Would this be true?

I'm not sure how Isc is adjusted for light intensity, hopefully someone else knows the code for which Isc to use. I always assumed using STC was good enough.

I think the only distance based derate is for voltage drop. MPPT input is quite tolerant of voltage drop unless you're hovering just above 125V at the array. In that case you need to be pretty concerned about the voltage drop making the system plain not work. But using 125V would be pretty stupid in this setup for numerous reasons.

Power quality from the POCO is poor. I've got the alarms turned on on one of the UPS's. It would alarm numerous times a day due to voltage and cycle variations. Lights in the house would flicker at times, wall powered clocks had their oscillators fritzed. Then there were the power outages. The first winter we were out here, we had an 8 hour outage on Christmas Eve. Think it was -20 outside. We have a well insulated new house and we only got down into the upper 50's at that time. The next spring I put in an 11kw Generac. A week ago we had a 12 hour long intermittent outage. Generator log showed that it ran on and off for about 10 hours. The utility that supplies power to the POCO replaced some hardware at a substation about 25 miles from our house. It took me a couple days to realize the the UPS wasn't beeping anymore. Did they fix a long standing problem that finally failed completely??? Two days ago we had another off/on/off/on.... power interruption. I went out and flipped the utility main off to force the generator to run. I let the gen run for 2 hours before I went down to check to see if the grid was back up. Neighbor texted me to say the power had just come back when I got back to the house. And we are once again getting occasional UPS cycling events. So I want to get clean power into the house before something expensive gets damaged. Also we are on a well, so no power, no water once the pressure tank gets depleted. I don't mind several hour runs on the generator, but if we are out for days - that will go through quite a bit of propane. Would rather get that energy from the sun. Yeah, it is kind of painful that the system will not break even until sometime after I'm dead.

Hmm as you know for power quality and < 1 day outages you only need batteries. If the AC is really bad you can also switch to DC coupling it into your system via a Chargeverter-type setup, that is basically a big AC charger outputting 48V (AC coupling gets dicey if some of the power sources start misbehaving). Normally you would probably want to be AC coupled to grid because the DC coupling will add 15-20% inefficiency (AC->DC->AC), so potentially a "transfer switch" kind of setup to manually switch between the two modes might be a good idea.

Several days out -- yeah only choice is solar panels.

I think your connection fees / system decomm fees are ruthlessly designed to keep the POCO supported even if you go off grid (must have hired some consultants to figure out that math), so intuitively it feels like it will be hard to offset the system cost by generating some savings when the grid is up (I didn't do the math).

The Sol-Ark install manual does not spec any maximum length on the CT leads. Says the leads can be extended using a twisted pair.

That will probably be fine within a house sized situation. I think you'll have extra error (might be one sided because of the extra load for the CTs, might be higher symmetric noise), but since the CT is just to roughly keep export near zero I think it's fine. Probably a minor efficiency issue rather than a safety issue. And SA probably has a config where you can trim up/down the export limit if the CTs have some consistent error. You can install something like an Emporia or IotaWatt to get an independent reading of the export power (and those will have short CTs, and are within 1-2% of revenue grade accuracy).

 

[Hedges]

Ok, I did an SLD. When putting it together I found out I had missed a disconnect - dammit, something else I have to find room for. I'm done for today...

Unusual to have disconnect on utility side of meter.

Production meter in series with utility meter, both read exactly the same thing? I would have thought transfer switch would land between the two meters. Production meter would still register consumption from grid through SolArk, doesn't split production/consumption like utility might want (not really possible with a hybrid.)

I'm not sure how Isc is adjusted for light intensity, hopefully someone else knows the code for which Isc to use. I always assumed using STC was good enough.

Fuses and wires to PV array sized for 1.56x Isc (STC)
I would argue 1.25x is sufficient for unfused PV or magnetic/hydraulic breaker, but code may not allow that.


For power quality, maybe SolArk can drop grid and make clean power whenever needed, but on-line UPS would be cleaner. That would need separate AC powered battery charger, and wouldn't let PV backfeed grid.

 

[zanydroid]

Several days out -- yeah only choice is solar panels.

… if you want to offset propane use for an indefinite outage.

Combining a generator with a battery system allows you to burn more efficiently, much as how it works on a prius. The generator can run at its optimal power point while recharging the battery. If it’s a good generator you can AC couple it and directly power any house loads that might come on, for a slight improvement in efficiency (battery charging just slows down a little).

 

[LBen]

Unusual to have disconnect on utility side of meter.

I thought that also. But the other day when the power was doing the off/on/off/on thing, I went outside and flipped the utility breaker off and the meter display went blank.

For power quality, maybe SolArk can drop grid and make clean power whenever needed, but on-line UPS would be cleaner. That would need separate AC powered battery charger, and wouldn't let PV backfeed grid.

My big picture plan was to have the SA power the house during the day while charging batteries, then when the PV went offline to run the house on batteries over nite, rinse and repeat each day. I would like to be able to power the house off of batteries for two days if weather conditions required. Then if absolutely necessary I would let the SA pull power off of the grid when I didn't want a lot of generator run time. I think SA says switching time is 10 ms.

 

[LBen]

Combining a generator with a battery system allows you to burn more efficiently, much as how it works on a prius. The generator can run at its optimal power point while recharging the battery. If it’s a good generator you can AC couple it and directly power any house loads that might come on, for a slight improvement in efficiency (battery charging just slows down a little).

It is an 11kw Generac and only intended for emergency short term use - not to run for days. I would have gone with a twin cylinder water cooled unit if I had wanted long term generator run times.

 

[LBen]

So if you split one MPPT evenly between the two strings, that's 13A each, so that is easily within the limit of #10.

I think we are on the same page. My plan was to run one string to each MPPT to start. Then, if any MPPT failed on me, I'd do two strings on one of the remaining MPPTs until I got the replacement parts. Trying to maintain some redundancy.

I need to cogitate on some of your other commentary a bit. First though, I need to go out and do some tree trimming since it is not raining today.

 

[Hedges]

My big picture plan was to have the SA power the house during the day while charging batteries, then when the PV went offline to run the house on batteries over nite, rinse and repeat each day. I would like to be able to power the house off of batteries for two days if weather conditions required. Then if absolutely necessary I would let the SA pull power off of the grid when I didn't want a lot of generator run time. I think SA says switching time is 10 ms.

Relay transfer time will be fast, like my Sunny Island. Depending on instant blackout or a brownout, inverter may pass through out of range power for a while before it disconnects and picks up the load. Spikes that damage electronics can pass through, but extended periods of bad power what overheat motors etc. should be avoided.

Maybe unique to my system with multiple inverters paralleled, I have seen error codes, also tripped breakers. With single 200A breaker you may not have that problem.

If you want clean power to your loads, one option is to operate as on-line UPS. That is a battery charger fed from grid, and loads only see what inverter produces. Maybe that can be a configuration you switch to only when you expect or experience sustained power quality issues.

Rather than DC coupled battery charger, for my system I'm tempted to AC couple the grid to my system, by rectifying it and feeding in as if PV. Because my system is purely AC coupled.

 

[LBen]

Apologies. I've been doing a lot of web searching and haven't wrapped up several lines of investigation cause I'm still missing information.

Got access to an electronic copy of NEC 2020 and am trying to understand all of 690, 312, 314 and whatever related code sections I come across. Also came across solar365 which is dated but is helping point me to possibly relevant sections of the code.

Yesterday finished putting plane back together and completed the log book entries. But of course next few days will be low overcast and rain so can't do a maintenance check flight, figures. So I'll spend all day today studying electrical codes.

 

[dcg9381]

… if you want to offset propane use for an indefinite outage.

Combining a generator with a battery system allows you to burn more efficiently, much as how it works on a prius. The generator can run at its optimal power point while recharging the battery. If it’s a good generator you can AC couple it and directly power any house loads that might come on, for a slight improvement in efficiency (battery charging just slows down a little).

This. You want a generator charge backup if a "large outage" (on cloudy days) might be a thing.

 

[LBen]

Following up on a couple details.

One thing I learned with generators is that you can run generator signal wire in the same conduit as PV, but it needs to be V rated.

Yes, I remember reading that somewhere in the code.

Production meter in series with utility meter, both read exactly the same thing? I would have thought transfer switch would land between the two meters. Production meter would still register consumption from grid through SolArk, doesn't split production/consumption like utility might want (not really possible with a hybrid.)

I spoke with the POCO solar rep again last week. Hybrid inverters are "new" technology to him. He has heard of Sol-Ark, but isn't familiar with hybrids in general. I re-verified with him that they replace my current meter with a net meter and add a production meter. I pointed out to him that both meters will read the same back flow of current into the grid. I pointed out to him that the production meter will not "see" the power that the house is using from the PV. He then made the odd comment that I won't get credit for the power that the house is using from the PV. I told him that I had never expected to get credit for that and I thought that the POCO would want to get credit for the PV power that my house was using plus whatever I was pushing back in to the grid. His reply was that they were only interested in what I was pushing back into the grid. The conversation wasn't going anywhere useful. I'm just getting stuck for the cost of a meter can, conduit and wire for a production meter that doesn't do anything useful.

I'm still working on a code review post.

 

[LBen]

I keep getting bogged down in 690. Have also been trying to understand wireway vs raceway. Came across this gem from one source.

"A wireway is a raceway but a raceway is not necessarily a wireway." Hmmm, ok.

I've been going through the NEC collecting information that I think applies to my situation. Am dumping it here for comments.

110.26 Spaces About Electrical Equipment

Sol-Ark 15k to be mounted left of main service panel. 8x8” gutter wall mounted under Sol-Ark 15k and main panel. See Post #51, first image. There is 3’ of depth space in front of the service panel and 30” of horizontal clear space on either side of the Sol-Ark and service panel. I don’t think a gutter violates 110.26(A)(3). Comments?

Table 312.6(A) Minimum Wire-Bending Space at Terminals and Minimum Width of Wiring Gutters

Largest wire I will be dealing with is 4/0. I’m planning on using an 8x8” gutter. Minimum gutter width for 4/0 is 4”

376.22(A) Cross-Sectional Areas of Wireways

Using an 8x8” gutter, I won’t exceed the 20% requirement

376.23(A) Deflected Insulated Conductors

An 8x8” gutter meets Table 312.6(A) requirement.

376.23(B) Metal Wireways Used as Pull Boxes

I think I may have a problem with 314.28(A)(1) and 314.28(A)(2).

314.28(A)(1) Straight Pulls

I don’t think I will have any straight pulls. Wires will be coming in and leaving the gutter with 90 degree bends. Any comment?

314.28(A)(2) Angle or U Pulls, or Splices

Talks about a distance from raceway entry to an opposite wall needing to be 6 times the trade size of the largest raceway plus additions if there is a row of raceway entries. There will be 2” conduit between the bottom of the Sol-Ark and the top of the gutter. And there will be a row of 4. Requirement would indicate I would need 18” of distance between the raceway entry point on the top of the gutter and the opposite gutter wall. This does not seem reasonable. What am I not understanding?

376.56(A) Splices, Taps, and Power Distribution Blocks

Using an 8x8” gutter, I won’t exceed the 75% requirement.

Don’t know how to handle this situation

The service entry comes into the garage through the concrete floor via 3 4/0 al wires in PVC conduit. The conduit attaches to the bottom of a Generac ATS and then conduit is between the top of the ATS and the bottom of the main service panel to complete the wire path. The ATS and main service panel are flush mounted in a fake wall. The conduit is behind the drywall surface of the fake wall. The ATS will be removed as the Sol-Ark will control the generator. I have to get the 3 service wires into the exterior gutter. What is the best way to do that? Combination of pull box and conduit? Conduit only? Other method? Remember that the wall cavity is only 3.5” in depth and I have to have conduit between the outer and inner gutter and I only have 13” of horizontal space to work with. I don't see a way of getting this done.

 

[dcg9381]

I pointed out to him that the production meter will not "see" the power that the house is using from the PV. He then made the odd comment that I won't get credit for the power that the house is using from the PV. I told him that I had never expected to get credit for that and I thought that the POCO would want to get credit for the PV power that my house was using plus whatever I was pushing back in to the grid. His reply was that they were only interested in what I was pushing back into the grid. The conversation wasn't going anywhere useful. I'm just getting stuck for the cost of a meter can, conduit and wire for a production meter that doesn't do anything useful.

Yea, probably better to use fewer words sometimes. I should remember that rule myself.

 

[meager]

@LBen , I'm in your same area of Colorado and I just failed my inspection for violating 690.31 D. I'm doing extensive research to verify that I need to basically tear everything apart from the moment the PV wire enters my power shed and replace it with metal conduit. I feel like I've watched a million install videos and haven't seen a single instance of someone using pure metal conduit from point of entry, although I'm sure they are out there somewhere. Obviously, my research lead me to this thread and I'm still confused about it. I probably looked like a deer in a headlight when he mentioned it because I was completely blindsided. I feel like my inspector has sworn to an oath to make my DIY life miserable. I am only able to get extremely vague pieces of information from him and those seem to make things even more confusing. I don't have all the complications of dealing with the grid or anything like that, but this 690.31 D is driving me crazy. We have power coming to the area in the next couple weeks, but I don't have any interest in connecting. Plus, the property is so far from the proposed power box (about 4,000ft), it doesn't make financial sense to even entertain tying into the grid. My ground solar array is about 200' from my power shed and I also had complications with various landscape obstructions and elevation issues. My biggest fear was not putting enough faith in the voltage loss calculators. Turns out, they are dead accurate. I used 10 AWG direct bury PV wire (pure copper) and I don't really see any noticeable loss from measuring at the array vs measuring at the disconnect in the power shed. Turns out, all I needed to worry about was 690.31 D, which I had no idea was even a thing. Anyways, where has your project landed you to date. Any updates?

 

[Pilot Bob]

Ok, you guys have kinda taken over my thread and I'm now more out in the weeds than when I started. I also need to figure out the quote function that every one is using.

First, PV and PVC - After reading and re-reading 690.31(D) it appears to me that it is legal to run PVC to the outside gutter and then the PV wire is in metal from the outer gutter, through the EMT, through the inner gutter and then into the SolArk. 690.31(D)'s paragraph title says "on or in a building" but the text only talks about "in" a building. It would appear to me that the "on" part only refers to roof mount systems. Mine will be a ground mount.

RSD - I thought that I had this one packed away a long time ago. Thought that I had read somewhere that ground mount systems did NOT require RSD. I've read 690.12 and that text is as clear as mud to me. Am I correct in believing for a ground mount array that an RSD is not required? In any case I plan on including a manual disconnect at the array. And then the SolArk has a PV disconnect switch on it and the PV wire enters the wall less than 3' from the SolArk. So I think I'm covered on the disconnect requirement?

As dcg9381 had queried about, Colorado adheres to NEC 2020, but the local state inspector (when he was willing to talk to me) said that certain aspects are not enforced. For example on the batteries, NEC 2020 says any single ESS cannot be more than 20kWh and I think that there is a total limit of 80 kWh and the individual ESS must be at least 30" apart. And then there is the 9450 or is it 9350 that says that the inverter/charger must be certified to work with a matched ESS. He said that he only looks for an NRTLS cert on the batts. I had also asked him if it was ok to put the SolArk to the side of the service panel. He said yes as long as there was access to the service panel. And then at that point he said that he only inspects and can't recommend anything. So my thought process is that if I understand how things must be done to be compliant with NEC 2020, then I will work to that goal. If I come up against an issue where there is a conflict, then I'll see if there is a work around.

The rural co-op rep told me that they have their own inspection criteria. He said that if the state passed the installation, that MOST LIKELY they would also pass it. I live in a rural, technically backwards county. I'd classify them as at least 10 years behind other places. The rural co-op does not like residential solar, but need the offsets for the state. They are into commercial solar that they then resell to the consumer. This has been an uphill battle. For the county inspector, I had to show proof that LFP batteries were relatively safe, did not require a vented cabinet and did not require a drain.

I had thought that I had reduced my list of issues/questions to just figuring out how to interface with the grid: gutter sizes, types of splices or power distribution blocks, wall pass throughs, most efficient way to wire the xfer switch and production meter, conduit fill, EGC, etc. But I think I'm doing a circle back on things I thought I had understood.

I'm gonna be out of pocket for the next couple of days, so may not be able to reply to anything during that time. I thank you all for your observations.

Look at the following exception from the 2020 NEC.
Exception: PV hazard control systems installed in accordance with 690.12(B)(2)(1) shall be permitted to be provided with or listed for use with nonmetallic enclosure(s), nonmetallic raceway(s), and cables other than Type MC metal-clad cable(s), at the point of penetration of the surface of the building to the PV hazard control actuator.

Wiring methods on or in buildings shall comply with the additional installation requirements in 690.31(D)(1) and (D)⁠(2).

Is your wiring that is coming into the building going to a disconnect prior to an inverter or the grid? If so, it most likely will meet the requirements of the exception. I would ask the inspector specifically about this.

 

[Pilot Bob]

I agree. That's why these are designed to "fail open".


Seriously? My RSD came with the inverter, which makes sense but it's rated for about 400V DC. You're saying that I need a RSD PER panel now? I get it for micro-inverters, but this would surprise me. Again, I learn something new every day.

The 2020 NEC requires RSD at the module if installed on a roof.

 

[meager]

Look at the following exception from the 2020 NEC.
Exception: PV hazard control systems installed in accordance with 690.12(B)(2)(1) shall be permitted to be provided with or listed for use with nonmetallic enclosure(s), nonmetallic raceway(s), and cables other than Type MC metal-clad cable(s), at the point of penetration of the surface of the building to the PV hazard control actuator.

Wiring methods on or in buildings shall comply with the additional installation requirements in 690.31(D)(1) and (D)⁠(2).

Is your wiring that is coming into the building going to a disconnect prior to an inverter or the grid? If so, it most likely will meet the requirements of the exception. I would ask the inspector specifically about this.

@Pilot Bob , how does your reference to 690.12(B)(2)(1) pertain to 690.31(D)? I don't see the same exception in 690.31(D)

 

[Pilot Bob]

@Pilot Bob , how does your reference to 690.12(B)(2)(1) pertain to 690.31(D)? I don't see the same exception in 690.31(D)

It has the same exception right under paragraph (D).

 

[Pilot Bob]

It has the same exception right under paragraph (D).

On the same page before going to D 1

 

[LBen]

@Pilot Bob , how does your reference to 690.12(B)(2)(1) pertain to 690.31(D)? I don't see the same exception in 690.31(D)

Hey meager, I'll get back to the thread after I do some more work outside in the cool of the morning. Does your inspector's last name start with a "V"? If so, then I've got the same guy to deal with. Will come back with a full status later today and a question. -Lowell