Electrical Codes/Safety concerns for mobile home construction

everestt

New member
Hello Forum!

I have recently started helping someone with their design for a mobile home. My client has bought a large mobile storage unit and is converting it into a mobile home. There is a trailer hitch connected to the front of it which he will eventually drive around with his mobile home touring America. He has hired me to help him with the electrical design of the mobile home. I have a couple questions as I have done electrical design for commercial, industrial, and residential but never anything for mobile homes/RV homes. Especially questions regarding NEC regulations for mobile homes.

Here are some more details about his mobile home:

-Solar panels on the roof going to Charge controller, Battery bank, AC/DC converter
-Accessible Shore Line Power if he decides to plant himself at a RV Park
-Panel Box with AC and DC load options
-Equipment he desires to power - AC unit, Heat Unit, Refrigerator (2-way: AC or Propane run with DC spark), water heater, water pump, propane stove (DC spark), propane oven (DC spark), compost toilet, 2 ventilation fans, LED lights (8 total), toaster oven, hotspot device, panel box exhaust fans 1 & 2, laptop, cell phone, other misc items

We just starting the electrical design, but I wanted to get as much advice before we would finalize things. Just to give you my background, I graduated with a BS of engineering electrical concentration, then have been working with electrical design/build firms for 5 1/2 years. I did work as an electrical tester for 2 years as well in the field. Now I have my own electrical consulting company. I have not done work in the mobile home/RV world and have a couple questions:

-Are there specific sections of the NEC that directly talk about mobile home designs?
-What is the maximum circuits I could branch together in this setting? (I will be doing load calc's to coordinate over current protection)
-Any advice you could give me going forward with finalizing the design for mobile homes? I will also be helping my client with the installation.

Thanks guys. Really appreciate all this forum does. Two photos of the trailer are attached. Please if you need any other information, feel free to ask for it.
 

Attachments

jap

Senior Member
Others may disagree, but, I wouldn't consider that a mobile home.

Unless your building them for mass production to the public, I've seen many home made campers in the deer woods that have everything you described above that I doubt were ever required to have an electrical inspection done on them.


JAP>
 

PaulMmn

Senior Member
In addition to the equipment on his list, I think a microwave oven would be a must-- would it take more power than a toaster oven? Once he's parked and plugged in in an RV park, the microwave would be almost necessary! :)

There have been a number of threads throughout the fora about wiring for RV parks and RV units-- I think a search would find them. Lots of talk about how they're wired and how they're grounded.
 

PaulMmn

Senior Member
Other than the front wall and back door, what keeps these things from turning from a square to a rhombus and totally collapsing?
 

jap

Senior Member
Open the back door (as in photo 1) and it's a wobbly square tube, just waiting for a slight breeze to knock it over.


It's evident your not familiar with these types of enclosed trailers.

I take it you also take issue with tailgates.


JAP>
 

PaulMmn

Senior Member
This is what I'm referring to-- the structure is only held together by the strength of the joints between roof and sidewalls, and sidewalls and floor. The front wall and back door provide the needed triangulation!

UntriangulatedBox.JPG

Perhaps it's strong enough to hold its shape running down the highway, but a nice, diagonal brace would make it a LOT stronger!
 

MAC702

Senior Member
Your question is valid. There is a LOT more framing around the back door than around the front wall. You have significant "triangulation" in the several inches border around the door.
 

paulengr

Senior Member
Other than the front wall and back door, what keeps these things from turning from a square to a rhombus and totally collapsing?
Notice the first few statements. It’s a shipping container. Ever seen what dock workers do to equipment? Just as bad as railroads.


Sent from my iPhone using Tapatalk
 

paulengr

Senior Member
There are sections of NEC specific to mobile homes and RV parks. Read those.


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david

Senior Member
Hello Forum!
You are most likely building a camper not a mobile home

https://dced.pa.gov/housing-and-development/manufactured-housing

Manufactured Housing
Manufactured Housing in PA
DCED works in cooperation with the US Dept. of Housing & Urban Development (HUD) and municipal code officials to assure all manufactured homes installed in Pennsylvania comply with all applicable requirements. HUD establishes the construction standards and enforcement regulations for new manufactured homes. HUD also administers a Dispute Resolution Program to assist the industry in resolving certain issues.

Build Your Own Homemade Camper! - RVshare.com
https://rvshare.com/blog/homemade-camper/
 

jap

Senior Member
You are most likely building a camper not a mobile home

https://dced.pa.gov/housing-and-development/manufactured-housing

Manufactured Housing
Manufactured Housing in PA
DCED works in cooperation with the US Dept. of Housing & Urban Development (HUD) and municipal code officials to assure all manufactured homes installed in Pennsylvania comply with all applicable requirements. HUD establishes the construction standards and enforcement regulations for new manufactured homes. HUD also administers a Dispute Resolution Program to assist the industry in resolving certain issues.

Build Your Own Homemade Camper! - RVshare.com
https://rvshare.com/blog/homemade-camper/

Exactly.

JAP>
 

myspark

Senior Member
Hello Forum!

I have recently started helping someone with their design for a mobile home. My client has bought a large mobile storage unit and is converting it into a mobile home. There is a trailer hitch connected to the front of it which he will eventually drive around with his mobile home touring America. He has hired me to help him with the electrical design of the mobile home. I have a couple questions as I have done electrical design for commercial, industrial, and residential but never anything for mobile homes/RV homes. Especially questions regarding NEC regulations for mobile homes.

Here are some more details about his mobile home:

-Solar panels on the roof going to Charge controller, Battery bank, AC/DC converter
-Accessible Shore Line Power if he decides to plant himself at a RV Park
-Panel Box with AC and DC load options
-Equipment he desires to power - AC unit, Heat Unit, Refrigerator (2-way: AC or Propane run with DC spark), water heater, water pump, propane stove (DC spark), propane oven (DC spark), compost toilet, 2 ventilation fans, LED lights (8 total), toaster oven, hotspot device, panel box exhaust fans 1 & 2, laptop, cell phone, other misc items

We just starting the electrical design, but I wanted to get as much advice before we would finalize things. Just to give you my background, I graduated with a BS of engineering electrical concentration, then have been working with electrical design/build firms for 5 1/2 years. I did work as an electrical tester for 2 years as well in the field. Now I have my own electrical consulting company. I have not done work in the mobile home/RV world and have a couple questions:

-Are there specific sections of the NEC that directly talk about mobile home designs?
-What is the maximum circuits I could branch together in this setting? (I will be doing load calc's to coordinate over current protection)
-Any advice you could give me going forward with finalizing the design for mobile homes? I will also be helping my client with the installation.

Thanks guys. Really appreciate all this forum does. Two photos of the trailer are attached. Please if you need any other information, feel free to ask for it.
OP's questions concern about electrical wiring system. Although discussion about structural integrity is also helpful --it will give him some ideas how to strengthen the box.

I have an RV and the appearance of the empty shell of OP's project is almost similar in terms of the framing and sidewall. The RV roof looks like one solid 1 inch or 3/4" plywood.. . no ribs or batting. I guess it keeps it from collapsing when someone is standing on the roof.

As for the electrical system --a few things that OP did not mention are quite important.
If the owner intends to camp out in the boondocks -- no power to connect to, he should consider a generator. A 5kW unit will run a microwave or a 13,000 btu A/C running one at a time --not simultaneously.
Solar panels are only good for charging batteries. All the above may sound luxury but I'll let owner decide.

With this in mind you would need an automatic transfer switch when camping out in a motor home park or RV park.
RV parks are notorious for blackouts.

A combination power panel/converter 120/ 12VDC are available rated 30A and 50Amps.
For the list of load you have, you would need 50 Amps. Sorry these are the only choices

Wiring standards for recreational vehicles and trailers follow the rules set forth by the RVIA (recreational vehicle industry association) They use articles from NEC for the most part except color coding.

RVIA conforms with NEC , ANSI/NFPA No.70

Since RVs and trailers have two voltages (120 volts and 12 volts dc) it is very easy for regular electricians to make mistake crossing conductors for neutral and positive battery conductors.

Commercial, industrial and home electricians use (per NEC) the white wire for neutral or the grounded conductor while black or red for hot.
These mistakes are very common because romex is used mostly for wiring RVs.

In RV automotive 12 volts wiring, the black is the negative or grounded conductor while white or red is the hot or positive.

If you hire an electrician make sure he/she has experience in wiring RVs.

It may even be easier in the long run ( pun intended)
 

jap

Senior Member
OP's questions concern about electrical wiring system. Although discussion about structural integrity is also helpful --it will give him some ideas how to strengthen the box.

I have an RV and the appearance of the empty shell of OP's project is almost similar in terms of the framing and sidewall. The RV roof looks like one solid 1 inch or 3/4" plywood.. . no ribs or batting. I guess it keeps it from collapsing when someone is standing on the roof.

As for the electrical system --a few things that OP did not mention are quite important.
If the owner intends to camp out in the boondocks -- no power to connect to, he should consider a generator. A 5kW unit will run a microwave or a 13,000 btu A/C running one at a time --not simultaneously.
Solar panels are only good for charging batteries. All the above may sound luxury but I'll let owner decide.

With this in mind you would need an automatic transfer switch when camping out in a motor home park or RV park.
RV parks are notorious for blackouts.

A combination power panel/converter 120/ 12VDC are available rated 30A and 50Amps.
For the list of load you have, you would need 50 Amps. Sorry these are the only choices

Wiring standards for recreational vehicles and trailers follow the rules set forth by the RVIA (recreational vehicle industry association) They use articles from NEC for the most part except color coding.

RVIA conforms with NEC , ANSI/NFPA No.70

Since RVs and trailers have two voltages (120 volts and 12 volts dc) it is very easy for regular electricians to make mistake crossing conductors for neutral and positive battery conductors.

Commercial, industrial and home electricians use (per NEC) the white wire for neutral or the grounded conductor while black or red for hot.
These mistakes are very common because romex is used mostly for wiring RVs.

In RV automotive 12 volts wiring, the black is the negative or grounded conductor while white or red is the hot or positive.

If you hire an electrician make sure he/she has experience in wiring RVs.

It may even be easier in the long run ( pun intended)




???


JAP>
 

K8MHZ

Senior Member
I just helped a friend of mine with his camper and it had low voltage cable for the 12 volt system. White with a black stripe was 12+ and plain white was 12- . The 120 volt was run in Romex, black for hot and white for neutral.
 

jap

Senior Member
I just helped a friend of mine with his camper and it had low voltage cable for the 12 volt system. White with a black stripe was 12+ and plain white was 12- . The 120 volt was run in Romex, black for hot and white for neutral.

Exactly.

Auto Transfer switch needed for campground blackouts ?, Grounded Conductors coming off of 12v batteries ?, Electricians don't use white for anything other than neutrals ? , RV's only have 2 voltages 120 and 12v ?, "Electricians" that confuse white + battery cables with AC neutral conductors ?, ETC.....


:happyno:

JAP>
 

hornetd

Senior Member
Notice the first few statements. It’s a shipping container. Ever seen what dock workers do to equipment? Just as bad as railroads.


Sent from my iPhone using Tapatalk
Well actually the one in the photographs isn't a shipping container the way you seem to be thinking about it. That is just an enclosed utility trailer. It's the same kind of thing a contractor might use as a mobile gang box. In this case it is being converted to a Recreational Vehicle in the form of a Travel Trailer.

Utility trailers do get converted to a lot of different uses. Vendors' stands, tool cribs, communications units, quasi Manufactured Homes are all uses I've seen them put to. What has never been clear to me is do they come under any section of the NEC when they get >50 volt electrical systems built into them especially if they are not being made into a Recreational Vehicle. I made several members of an organization I belong to angry when I wanted the groups trailer to use a temporary grounding system whenever the internal 120 volt built in electrical wiring was being supplied by a generator that was not mounted on the trailer or from any other source by flexible cord. We eventually acquired and used a military surplus Grounding Kit, Surface Wire, MK-2551A/U, which goes in rather easily. The technical papers published by the army allege that those kits perform better than the 2 sectional 9 foot long copper clad steel driven rods they had used previously. I just do not know what US NEC sections would apply to a field wired trailer.
 

hornetd

Senior Member
OP's questions concern about electrical wiring system. Although discussion about structural integrity is also helpful --it will give him some ideas how to strengthen the box.

I have an RV and the appearance of the empty shell of OP's project is almost similar in terms of the framing and sidewall. The RV roof looks like one solid 1 inch or 3/4" plywood.. . no ribs or batting. I guess it keeps it from collapsing when someone is standing on the roof.

As for the electrical system --a few things that OP did not mention are quite important.
If the owner intends to camp out in the boondocks -- no power to connect to, he should consider a generator. A 5kW unit will run a microwave or a 13,000 btu A/C running one at a time --not simultaneously.
Solar panels are only good for charging batteries. All the above may sound luxury but I'll let owner decide.

With this in mind you would need an automatic transfer switch when camping out in a motor home park or RV park.
RV parks are notorious for blackouts.
The transfer mechanism I have seen on many RVs is that you plug the shoreline into an outlet from the generator in the cable storage compartment or you unplug it from there and plug it into a park outlet. I know of no US NEC section which could be construed as requiring an Automatic Transfer Switch in a recreational vehicle. As far as I know the US NEC only requires Automatic Transfer Switches for emergency power and legally required standby power.

A combination power panel/converter 120/ 12VDC are available rated 30A and 50Amps.
For the list of load you have, you would need 50 Amps. Sorry these are the only choices

Wiring standards for recreational vehicles and trailers follow the rules set forth by the RVIA (recreational vehicle industry association) They use articles from NEC for the most part except color coding.

RVIA conforms with NEC , ANSI/NFPA No.70

Since RVs and trailers have two voltages (120 volts and 12 volts dc) it is very easy for regular electricians to make mistake crossing conductors for neutral and positive battery conductors.

Commercial, industrial and home electricians use (per NEC) the white wire for neutral or the grounded conductor while black or red for hot.
These mistakes are very common because romex is used mostly for wiring RVs.

In RV automotive 12 volts wiring, the black is the negative or grounded conductor while white or red is the hot or positive.

If you hire an electrician make sure he/she has experience in wiring RVs.

It may even be easier in the long run ( pun intended)
 
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