2024 fire code for small ground mount systems ~ 3 kw?

[rmassuser]

I'm about to mount 6 Bluesun panels on a hill in my yard. Bifacial 460kwh.

I will need to get it permitted because it will be tied back to my house to my EG4 6000xp, and it will have a shutdown capability using Tigo monitor units.

While I have seen several videos with panels mounted on wood (i.e. solar pergola), I just noticed that there is a fire code in MA that assumes the panels could start a fire and it may require a non combustible base. And a "vegetation management plan"

Ok, should I put a layer of asphalt shingles on top of a 21 foot beam so I have a 4" x 252" 'roof' ?

Anyone have suggestions on what I can do to get this permitted?

I could paint the wood with intumescent paint but I suspect these paints are not outdoor rated.

The reason I want to use wood is mainly for appearance. I think my neighbors would appreciate my plan to work the panel into an existing structure. The alternative would be putting a big metal structure in the middle of the lawn, an eyesore.

My plan is mounting the panels above a wood fence by beefing up 3 of the posts to 6x6 lumber. That should be sufficient, with appropriate bracing, to hold six 60 pounds panels.

The only issues that might stop me is the requirement that a solar array have a noncombustible base (see 2017 and 2024 fire codes, I've attached as 2024 excerpt) and have a vegetation management plan. Also It's not clear whether I need a DC disconnect or stop button at the array, since I will have a stop button mounted 60 feet away on my garage. I may need a locked, outdoor rated junction box (not sure) that would provide a way to physically disconnect the array without getting up on a ladder, once I have activated the other disconnects and shutdown systems.

 

[rodrick]

What that sounds like is they want gravel, cement or green grass something non flammable in case it catches on fire but the structure material isn’t mentioned I would ask for clarification on the regulation

personally I would never put panels on my roof if I had anything other than a metal roof and even then I’d ground mount but I’ve also got 20 acres to use but a lot of people don’t have that option

 

[rmassuser]

I'm going to use galvanized fence rail on top of the posts. And ground my panels using aluminum rail tied to a ground rod. Are panels non flammable? I thought it was just the wiring that was flammable. Also I will have garden space under the panels. I don't think there is any potential for lightning since there are other panels mounted 18 feet higher than these panels will be.

 

[timselectric]

And ground my panels using aluminum rail tied to a ground rod.

That's not grounding. That's earthing.
If people can reach and touch it, it really should be grounded for safety.
With an EGC from your grounding system.

 

[Skypower]

Are panels still subject to hot spots that can start a fire beneath, or has this problem largely gone away?

 

[Skypower]

Next location will have bi-facial ground mount. White stones and weed stop underneath so it probably won’t matter for me. 10ft perimeter is useless if there’s even a slight breeze and a spark from a tall array.

 

[Steve_S]

I have never seen Panels catch fire... They (frames) and their rails CAN act like a lightning rod which can present an obvious danger and therefore the general recommendation is to "EARTH GROUND" the solar array hardware. By bonding the panels & rails together and running an 8AWG Green jacketed wire to a Grounding Rod / Grounding Plate resolves that issue. As for the DC Wiring (+) & (-) {which is NOT a ground} should then go into a combiner / terminal box where it connects to the wires running to the SCC, they should be protected with an appropriately sized SPD (Surge Protection Device), On the AC Side it is also Highly Recommended to have an AC SPD as well to protect each end of the system.

The AIO using itself must be Grounded to the same ground point as the rest of your AC Wiring system.

Midnite Solar has some of the Best SPDs on the market, Highly Recommended.

Category Products - MidNite Solar's

MidNite Solar Category Products.

www.midnitesolar.com

Generally, If a system is OFFGRID meaning it has No Ability to push power to Grid it requires minimal to no inspections (Note that Insurance Co's often require {demand} an inspection) if you want coverage, and they "can" be quite stupid about it. The "OffGrid" status allows you to have a 120V Grid Power outlet that is connected to the AIO/Inverter/Charger for charging purposes ONLY. It can only provide power to charge batteries but not accept power to feed back.

Pro-Tip: If you want to have a dedicated "Solar Powered Side", the best way to accomplish that, is to wire in an AC Subpanel with the AC Circuits you want to run from solar and keep it separate from the Grid Powered AC Main Panel. This can be done using a standard Pony Panel OR if you are outputting 240VAC you can use a typical Main Panel with Master Breaker provided you can Right Size it. Finding one with less than a 100A Main Brealer is nearly impossible now. There are ways around that of course but that can become a deep topic.

Also IMPORTANT NOTE !
IF USING PT WOOD !!! Do NOT allow any Solar Panel Frame or Rails to make contact with the PT... Aluminium & Pressure Treated wood DO NOT GET ALONG ! The PT will rot the aluminum ! I put Vulcanized Rubber Pads under the Bracket Clamps and use only Stainless Steel Lag Bolts to attach to the framework.

Hope it helps, Good Luck.
Steve
PS: Happy Holidays... now I get to grab Coffee #2. LOL.. What a day, sheesh.

 

[timselectric]

therefore the general recommendation is to "EARTH GROUND" the solar array hardware. By bonding the panels & rails together and running an 8AWG Green jacketed wire to a Grounding Rod / Grounding Plate resolves that issue.

That's not the general recommendation. Or even a good recommendation.
All metal parts of the array must be connected to the existing grounding system.

If an auxiliary ground rod or plate is added at the array. (Bad idea)
It must also be connected to the existing grounding system.

Lightning protection is a completely different and separate system.
That is built above and around (without touching) what you want to protect.

 

[Hedges]

... and it will have a shutdown capability using Tigo monitor units.

Do you mean Rapid Shutdown? If so, why?

RSD for fireman safety requires < 80V within array and < 30V outside array, for wires on the house.
If DC doesn't come to the house, should not be needed.
If inverter mounted on house, a DC disconnect in vicinity of service entrance ought to be sufficient. High voltage remains at array but isn't at house (might require switch to be mounted on post rather than wall of house. I wish "inside conduit" was an exception but it isn't.

 

[Steve_S]

That's not the general recommendation. Or even a good recommendation.
All metal parts of the array must be connected to the existing grounding system.

If an auxiliary ground rod or plate is added at the array. (Bad idea)
It must also be connected to the existing grounding system.

Lightning protection is a completely different and separate system.
That is built above and around (without touching) what you want to protect.

Assuming the structure is ALL Wood and therefore offers no grounding, the Aluminium Rails & Panel Frames are for all intents & purposes isolated as such. Earthing the metal for lightning protection is OK. Sure you could ground it back through the ground wire accompanying the + & - (if there is one). Distance from Equipment also plays a factor there...

My panels & rack are isolated and lightning grounded at location. I've taken hits and only lost 1 SPD but whole system safe. TSSA Electrical inspection passed BUT he still wanted a Disconnect @ the Array and that will be done with the final config this coming spring. Figured I might as well wait till the final stage as there is no external risk. No Grid here - it's $75K down the road an staying right there.

 

[timselectric]

Earthing the metal for lightning protection is OK.

That wouldn't provide lighting protection.
The goal of lighting protection is to give lighting a path around what you want to protect. Not a path through it.

Sure you could ground it back through the ground wire accompanying the + & -

You must, not could.

(if there is one).

There must be one.

Distance from Equipment also plays a factor there...

Only in the cost of installing it.

My panels & rack are isolated

Isolated from what? The solar doesn't power the house loads?

and lightning grounded at location.

No such thing.

I've taken hits

I doubt that. Or you would have been replacing damaged equipment.

but whole system safe.

Only make believe safe. But hopefully, you continue to get lucky.

 

[scrubjaysnest]

Had a 100 ft extension cord once between porch and car port. Neither end plugged in. The strike blew holes in the cord, the carport, and porch wall. Also shattered the school house globe when the fan light shattered in one bedroom. The path may have been from the carport to the concrete pad then to the cord.
I levitated that day.

 

[rmassuser]

That's not grounding. That's earthing.
If people can reach and touch it, it really should be grounded for safety.

ok. though the panels will be almost 6 feet off the ground at the lowest point. 11 ft at the highest.

With an EGC from your grounding system.

ok I can do this. I assume I don't need the full 10 gauge wire size for this. can i get away with a 12 gauge wire? The max voltage is 330 and max amperage is 11A for this single string.

 

[rmassuser]

Do you mean Rapid Shutdown? If so, why?

RSD for fireman safety requires < 80V within array and < 30V outside array, for wires on the house.
If DC doesn't come to the house, should not be needed.
If inverter mounted on house, a DC disconnect in vicinity of service entrance ought to be sufficient. High voltage remains at array but isn't at house (might require switch to be mounted on post rather than wall of house. I wish "inside conduit" was an exception but it isn't.

the solar wire passes through the basement and joins with a second string in conduit running to the indoor inverter.

 

[timselectric]

ok. though the panels will be almost 6 feet off the ground at the lowest point. 11 ft at the highest.


ok I can do this. I assume I don't need the full 10 gauge wire size for this. can i get away with a 12 gauge wire? The max voltage is 330 and max amperage is 11A for this single string.

14 gauge is fine for an 11a circuit.

 

[Hedges]

the solar wire passes through the basement and joins with a second string in conduit running to the indoor inverter.

Maybe a simple disconnect so ground mount panels don't deliver DC to the house would comply.
Second string- is that on roof, or also ground mount?
Inverter PV input needs to discharge to < 30V.
So I imagine a 3-pole disconnect, with 3rd pole telling inverter to RSD discharge. But disconnect needs to be located properly. And I suppose can't be on house itself because HV wires feed into it.
If I could get away from electronics on the module, I would.

 

[rmassuser]

The solar wire will pass through the basement level, exit to a service panel area, and then reach a second IMO DC disconnect. Double pole. That is the point at which it joins the second solar wire which will come from the roof of the garage. Then the 2 wires do a 180 back into the basement level where they go directly to the inverter inputs.

 

[Hedges]

Panels on roof, so some RSD modules required anyway. Simplest to just put RSD boxes on all.
Either inverter or a separate box provides keep-alive signal. Inverter presumably provides discharge of its capacitors for RSD. Shut-down switch located where required.

If the two PV arrays are wired in parallel, it is fine for them to have different orientation, but voltages must be same or similar.
If each array is a single PV string, the two can combine without fuses. If 3 or more strings, need fuses or breakers per string.
Also, ground wire or mounting rails (with suitable clamps or WEEB washers) needs to provide continuity from panel frames back to inverter.