We have the NEC code for residential electrical, ABYC standards for marine electrical, is there an equivalent for mobile/vehicle/rv electrical?

[Dzl]

As the title says, is there a national or international standard for motorhome/vehicle/mobile electrical design?

I'm particularly curious about an American or international standard, as I am American, and building to this code would make sense from a legal/insurance standpoint, but I'm also curious about other countries standards.

 

[RandyP]

NFPA70 NEC includes Article 690 Photovoltaic (PV) Systems.

 

[Dzl]

NFPA NEC includes a section on Solar systems.

Good to know. But this will only be partially applicable to mobile/vehicle based electrical systems. One fundamental difference is the absence of earth ground.

 

[John Frum]

That is a good question.
If it doesn't exist now I bet it will RSN=Real Soon Now.
Hate to say it but it will likely happen after someone dies.

 

[Dzl]

That is a good question.
If it doesn't exist now I bet it will RSN=Real Soon Now.
Hate to say it but it will likely happen after someone dies.

The RV industry isn't well known for their high quality standards (though that is changing and may be different outside North America) so even if they did have a standard I'm not sure I'd put a ton of faith in it, at least not compared to more mature/quality committed industries, but still it would be really helpful to have a reference specifically for vehicles.

 

[RandyP]

NFPA70 NEC includes Article 690 Photovoltaic (PV) Systems.

You can view the code above at :
h t t p s://www.nfpa.org/codes-and-standards/all-codes-and-standards/list-of-codes-and-standards/detail?code=70
after registering to use the resource.

 

[Dzl]

Thanks randy, I'll check it out

 

[RandyP]

I do not know of an RV industry electrical system code. But if you comply with NFPA 70, you will most likely be OK. Earth Ground is supplied by shore power, when using shore power.

It's a free viewer, so editing is limited (cut/paste). Hares a screen shot of part of the first page.

 

[Dzl]

I do not know of an RV industry electrical system code. But if you comply with NFPA 70, you will most likely be OK. Earth Ground is supplied by shore power, when using shore power.

My interest is more about learning than code compliance. I have learned a lot from the ABYC guidelines, and probably could learn more from the NEC, but both of these standards (moreso NEC) make fundamental assumptions that are often not true of vehicle based systems.

As you say the system is earth-grounded when plugged into shore power, but this is the exception to the rule, a mobile system may have 3 or 4 charge sources (Solar, Shore power, alternator, generator), may have separate vehicle and house electrical systems, one of which is chassis grounded the other may be floating/isolated or may also be chassis grounded. For these reasons and more, its sometimes difficult to translate advice meant for grid connected or off-grid buildings, with earth-ground connections and traditional grounding systems, to vehicle based systems which have their own quirks and complexities. I find it specifically hard to understand grounding best practices. I'm sure if I had a greater depth of knowledge I could interpret and apply the NEC or ABYC guidelines to a mobile context, but I definitely do not have that depth of knowledge or confidence. Although its quite possible I'm overcomplicating things in my head. But this is why I was hoping to find guidelines specifically for a mobile context that spell out some of the complexities I'm struggling to wrap my head around.

It's a free viewer, so editing is limited (cut/paste). Hares a screen shot of part of the first page.
View attachment 10417

Thanks! I just signed up, I'm checking it out right now actually.

 

[Deleted member 4428]

RV Electricity: What's "the Code"? Find out here - RV Travel

Dear Mike, Everyone says you have to do this or that because its “the Code,” referring to the NEC [National Electrical Code], of course. For RVs, this gets even more interesting. The “Code” has no legal authority unless adopted by a local AHJ, as you are aware. And each AHJ can adopt, reject or...

www.rvtravel.com

 

[RandyP]

My interest is more about learning than code compliance.
......................
But this is why I was hoping to find guidelines specifically for a mobile context that spell out some of the complexities I'm struggling to wrap my head around.
Thanks! I just signed up, I'm checking it out right now actually.

Do you have an understanding of an equipment ground bonding conductor and its function ?

 

[RandyP]

vv

 

[Dzl]

Do you have an understanding of an equipment ground bonding conductor and its function ?

roughly, maybe.

Let's find out.
Here are my best guesses:

equipment = electrical equipment(?)
ground bonding conductor = wire, strap, or other conductor which bonds the metal chassis' of equipment to ground(?)
and its function = (1) give electricity a low resistance path to ground if there is a short to the metal chassis of a component (2) give lightning a clear path to ground (3) dissipate static electricity, (and possibly 4) make sure that if there is a short the current is high enough that it actually trips the overcurrent protection device.(?)

How'd I do?

I think I understand equipment ground on a basic conceptual level. At least in terms of how it works in a building connected to earth ground.

But I get a little confused about how to apply this to a vehicle without a connection to earth-ground, and where 'chassis ground' is also the negative conductor for the vehicles electrical system.

 

[RandyP]

Well its not for lightning strikes. But it is there as a return current path if there is a ground fault, to clear the over current device that protects the dc circuit conductors supplying power to the equipment that has faulted to ground. It has nothing to do with earth ground.

 

[Supervstech]

90.2 Scope.
(A) Covered. This Code covers the installation and removal of electrical conductors, equipment, and raceways; signaling and communications conductors, equipment, and raceways; and optical fiber cables and raceways for the following:
(1) Public and private premises, including buildings, structures, mobile homes, recreational vehicles, and floating buildings....

So... NEC covers RV wiring... and I would consider it the Bible for jobs myself...

 

[Dzl]

90.2 Scope.
(A) Covered. This Code covers the installation and removal of electrical conductors, equipment, and raceways; signaling and communications conductors, equipment, and raceways; and optical fiber cables and raceways for the following:
(1) Public and private premises, including buildings, structures, mobile homes, recreational vehicles, and floating buildings....

So... NEC covers RV wiring... and I would consider it the Bible for jobs myself...

Thanks to you, @RandyP and @JC777 I just found and started reading the section of the NEC related to RV's. For anyone else interested, its Article 551 parts I and III through VI of NFPA 70 pretty dense stuff, but I'm grateful to have access to it! There is also code 1192 which looks to cover everything other than electrical. Thanks guys.

Well its not for lightning strikes. But it is there as a return current path if there is a ground fault, to clear the over current device that protects the dc circuit conductors supplying power to the equipment that has faulted to ground. It has nothing to do with earth ground.

Okay, so long as it has a path back to source (which would be the battery bank in this context) it (1) ensures current can flow at a sufficient rate to trip the breaker or blow the fuse on the positive wire (2) gives the electricity a more convenient path back to the source than any human that might touch the metal casing if OCPD doesn't trip.

I commonly see equipment grounding with PV arrays and Inverters, but I don't see people doing that with other components of their systems such as charge controllers or electrical consumers, should they be?

 

[RandyP]

.........................................
But I get a little confused about how to apply this to a vehicle without a connection to earth-ground, and where 'chassis ground' is also the negative conductor for the vehicles electrical system.

Well I'm not sure you want to connect a vehicle chassis ground to the earth. Vehicles are pretty well isolated electrically from earth by their tires. As long as the power supplies in the vehicle are also isolated from earth. there can be no build up of voltage between earth and the power system conductors and earth ground. Isolated ground system, even if its '-' pole is attached to the vehicle frame. The only current that might flow would be from static discharge to earth ground. You may have experienced that after sliding across a vinyl seat with a wool sweater on and putting your foot to earth ground on the way out of the car.

 

[Dzl]

Well I'm not sure you want to connect a vehicle chassis ground to the earth. Vehicles are pretty well isolated electrically from earth by their tires. As long as the power supplies in the vehicle are also isolated from earth. there can be no build up of voltage between earth and the power system conductors and earth ground. Isolated ground system, even if its '-' pole is attached to the vehicle frame. The only current that might flow would be from static discharge to earth ground. You may have experienced that after sliding across a vinyl seat with a wool sweater on and putting your foot to earth ground on the way out of the car.

So in a sense, the chassis of an isolated (from earth) vehicle electrical system, is functionally equivalent to earth ground in building electrical systems.

 

[nosys70]

problem is most books like NEC are just here to set a frame of recomandation, since every system has its own specs.
so NEC can say you must have a ground in such and such case, the ground resistance must be at least such value etc...
So the job of most companies producing equipement that include electric devices and cabling is to stay under radar.
for example you find a lot of equipement that stay under 48V because the rules for low voltage and high voltage is set to 50V.
And the rules for high voltage (over 50V) is drastically more demanding than the rules for low voltage, so it would be silly to build
a device with 60V if you can make it run at 48V and spare money in design.
That is the same in every domain.
If you are a grocery, you fill your tax form to make it "plausible", even if you skip on some details , so you do not get additional question from IRS.
After all your main job is to sell groceries, not tax fine tuning.
If you are a financial company, you know you will get audit and control, and you make money by playing with the tax system, so you can manage to count every dime. So you probably read the same book, but you use it a different way.
If you are a car maker, probably, the electricity is not you main concern, so you build it with industrial components who are already each under NEC specs for their intended use and you will not look to understand or optimize every aspect of it. the drawback of this is:
-even is each element is compliant, the sum of it could be out of specs.
- you probably build an average system that could run better or cheaper.
-if something is wrong, you will let the NEC inspection discover it, so you probably have to manage change late in the developpment.

EV car makers are a bit aside, since electricity is the main power source. I suspect a lot of EV car makers are hiring people from petrol car industry and on the other side hire engineers from the electronic industry so both have probably a totally different view on ho to handle the problem and which rules to apply.

 

[RandyP]

Looks like low voltage per NFPA70 NEC article 551 is 24v or less.