Rapid Shutdown for residential PV systems in concrete roofs

Hi Mike and followers

I am a huge fan!

I am an electrical engineer and have been installing PV systems in concrete roofs since 2006.
Since Mike and its team are a very well known and respected guru regarding code interpretation and what was the purpose of every new sentence, I am directing to you the issue we are having at Puerto Rico.


In Puerto Rico, since we are a tropical island that face storms every year, more than 90% of residence walls and roofs are made of solid concrete.

When the NEC use the term Rapid Shutdown for the first time, I remember part of the discussion back there was that there is a need for rapid emergency responder to shutdown pv panels in order for them to take an axe and broke wood/metal roof or wood walls to rescue people and first emergency responder were afraid to hit a pipe with live PV voltage while breaking the roof with an axe.


In Puerto Rico, there is not a single case of fire fighters or any first emergency responder making a hole in the roof of a property in order to rescue people, because roofs are made of solid concrete!



But, because the government of PR decide to jump from NEC 2005 to NEC 2017 in a snap, now inspectors are requiring concrete houses to comply with RS. The code requires it, yes!. But since the beginning, RS requirement design and purpose is so first responder can brake building roof safely. So, common sense and good code interpretation said if should not be mandatory in houses made of concrete. Or at least, it should be leave to the designer discretion.


Please comment!!!

And if you can, send a petition to the NEC to add a sentence that said, RS is not mandatory for PV systems installed in concrete roofs



Thanks!!!
 

ggunn

PE (Electrical), NABCEP certified
Hi Mike and followers

I am a huge fan!

I am an electrical engineer and have been installing PV systems in concrete roofs since 2006.
Since Mike and its team are a very well known and respected guru regarding code interpretation and what was the purpose of every new sentence, I am directing to you the issue we are having at Puerto Rico.


In Puerto Rico, since we are a tropical island that face storms every year, more than 90% of residence walls and roofs are made of solid concrete.

When the NEC use the term Rapid Shutdown for the first time, I remember part of the discussion back there was that there is a need for rapid emergency responder to shutdown pv panels in order for them to take an axe and broke wood/metal roof or wood walls to rescue people and first emergency responder were afraid to hit a pipe with live PV voltage while breaking the roof with an axe.


In Puerto Rico, there is not a single case of fire fighters or any first emergency responder making a hole in the roof of a property in order to rescue people, because roofs are made of solid concrete!



But, because the government of PR decide to jump from NEC 2005 to NEC 2017 in a snap, now inspectors are requiring concrete houses to comply with RS. The code requires it, yes!. But since the beginning, RS requirement design and purpose is so first responder can brake building roof safely. So, common sense and good code interpretation said if should not be mandatory in houses made of concrete. Or at least, it should be leave to the designer discretion.


Please comment!!!

And if you can, send a petition to the NEC to add a sentence that said, RS is not mandatory for PV systems installed in concrete roofs



Thanks!!!
Local AHJ's have the right to amend and selectively enforce the NEC in their jurisdictions. I think an easier course would be to get your AHJ to exclude concrete roofs from rapid shutdown requirements.
 
Local AHJ's have the right to amend and selectively enforce the NEC in their jurisdictions. I think an easier course would be to get your AHJ to exclude concrete roofs from rapid shutdown requirements.
Agree! that is what we are trying to do since PR adopted the 2017 code in 2018.
but they are playing ping pong here..
the Puerto Rico Electric Power Authority (AHJ) said that NEC is NFPA so PREPA will follow the NEC 2017 unless firefighters from PR said there is no problem to exclude concrete roofs from RS.
but firefighters, said they dont know nothing about solar energy systems, that is not their call, that PREPA should submit their comments ...
 

don_resqcapt19

Moderator
Staff member
There are other safety issues for first responders. While one of the reasons for the rapid shutdown rule is access to the roof for fire fighter ventilation purposes, another is reducing the shock hazard from the panel outputs.
 
FF's ventilate roofs homartorres
~RJ~
what about a solid concrete house with solid concrete roof?
no one will take an axe to make a hole in a solid concrete roof!
the issue we are having is that almost 80% of houses in PR are made of concrete. but the conde asume all houses are made out of flammable materials, and a wood roof that can be opened with an axe.
code should said something like this "for residential PV systems of 25kwh or less that are installed in a roof made of non flammable, non conductive, hard solid material such as concrete, the use of RS is not required.
for comercial systems of 25kwh or less installed in a roof made of non flammable, non conductive, hard solid material such as concrete, the use of RS is not required by code but leave to the discretion of the design engineer"
 

jaggedben

Senior Member
It's sort of a political question. (I mean in the sense of who has power in the community, not ideological partisanship.)

The code section was put in to protect fire fighters. Who is to say that it's not needed to protect firefighters? Well ... firefighters. Are firefighters likely to tell the building inspectors not to enforce something that protects them? Well, probably not. But maybe if you sold some solar to the fire department...
😉
 

pv_n00b

Senior Member
The NEC makes no differentiation between roofing material or building construction for PV installation. This is the kind of thing that would be handled in local code, for instance, California has its own electrical code based on the NEC with some modifications. PR should have its own electrical code based on the NEC with modifications for local conditions. Unfortunately, the NEC can't be modified for every local condition or it would be unusable.
 
The NEC makes no differentiation between roofing material or building construction for PV installation. This is the kind of thing that would be handled in local code, for instance, California has its own electrical code based on the NEC with some modifications. PR should have its own electrical code based on the NEC with modifications for local conditions. Unfortunately, the NEC can't be modified for every local condition or it would be unusable.
PR used to have a complementary code, to enforce, make more hard or more soft some parts of the codes as per local experience and our tropical island conditions such as extreme hot, topography, building materials like concrete etc...
but recently our public utility star seen renewable energy as competition. And investor start to push fora laws that can make pv installation more costly like a sun tax, remove net metering benefits, etc...
when they saw in the RS an opportunity to increase costs, they push for it so the utility adopt fully the nec 2017 without the typical public hearings and the creation of the complementary code as before
thats why it is important for the NEC can make exception for systems installed in non flammable buildings or at least make a note to leve it to the discretion of the designer
 

jaggedben

Senior Member
PR used to have a complementary code, to enforce, make more hard or more soft some parts of the codes as per local experience and our tropical island conditions such as extreme hot, topography, building materials like concrete etc...
but recently our public utility star seen renewable energy as competition. And investor start to push fora laws that can make pv installation more costly like a sun tax, remove net metering benefits, etc...
when they saw in the RS an opportunity to increase costs, they push for it so the utility adopt fully the nec 2017 without the typical public hearings and the creation of the complementary code as before
thats why it is important for the NEC can make exception for systems installed in non flammable buildings or at least make a note to leve it to the discretion of the designer
Well, you can submit a revision proposal for the 2023 code if you think that would be more fruitful than appealing to the powers that be in Puerto Rico.
 

shortcircuit2

Senior Member
I do not see any increase in cost for a mico-inverter system with or without RS rules...except a few labels.

On a DC system without RS, there may also be dangerous high voltage circuits within the building, not just the roof. Having RS provides a safer situation for Fire Fighters.
 

ggunn

PE (Electrical), NABCEP certified
PR used to have a complementary code, to enforce, make more hard or more soft some parts of the codes as per local experience and our tropical island conditions such as extreme hot, topography, building materials like concrete etc...
but recently our public utility star seen renewable energy as competition. And investor start to push fora laws that can make pv installation more costly like a sun tax, remove net metering benefits, etc...
when they saw in the RS an opportunity to increase costs, they push for it so the utility adopt fully the nec 2017 without the typical public hearings and the creation of the complementary code as before
thats why it is important for the NEC can make exception for systems installed in non flammable buildings or at least make a note to leve it to the discretion of the designer
But if that is indeed their intention they can easily get around any changes to the NEC by local ordinance.
 
PR because of its topography and tropical island, have power outage every single day. most installation are going battery based.
just installing enphase instead of SMA, increase the cost a few hundred.. that apply only to the simplest of the installations, a grid tie battery less system. but that is just one alternative...
there are battery backup, off grid, grid tie with batteries, net zero, self consumption, etc....

but, installing an XW, with enphase or tigo, instead of just a dc charge controller, increase the cost of the installation a couple of thousands!
do the math..
mppt60 .... $500 to $600
adding tigo to each solar panel, including installation, accessories, the activation button, for just a 12 panel installation is about $1,200.
for a 24 panel installation is about $2,400!!!
doing an ac coupling with micro inverter is even more expensive, and more complicate in the design, and limited with the battery capacity options to make it work right
 
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