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jambud 02-14-2008 05:52 PM

100Amp Service
I have 100Amp Service to my mobile home and have 2 extra spaces. Am I able to power a 100Amp subpanel to a new room next door from that main 100amp service? In the new room there will be two 20amp recept circuits, two 15amp circuits for lighting and a 30amp #10-3 wire for a printing cutter that requires a 3-phase which i will get a converter to single phase double-pole 30Amp breaker.

jbfan 02-14-2008 06:51 PM

Isn't this you?

jerryh3 02-14-2008 07:01 PM

Maybe he was hoping there has been advances in electrical distribution.

jambud 02-15-2008 05:01 PM

Yeah that was me and forgot I asked that question already sorry. But Ive finished up everything else and decided to upgrade my service to a 200amp Service Panel to feed the shop and mobile home. I hate to feed a 70Amp subpanel from the existing 100amp panel inside the trailer cause I will need a double 30amp breaker in the sub at the shop. So I slapped the 200amp main meter onto the shop and will run #4 thhn to feed the trailer.
So my next question is: The trailer has a 100amp breaker inside the panel, and the 200amp will have a 100amp breaker for the trailer. Can I feed the trailer with those two 100amp breakers or would i need a main lug 100amp panel inside the trailer ? Thanks so much for your time.

InPhase277 02-15-2008 08:33 PM

You do not have to change the panel inside your trailer, but you do have to make sure the neutral and ground are not bonded. They usually aren't in trailers, but check to be sure.

The 100 A breaker in you trailer panel is fine, but if you use #4 THHN to feed it, the breaker in the 200 A panel can't be over 85 amps. Since you'll have a real hard time finding a breaker that size, it will be 80 A. Go with #3 and put it on a 100.

Good luck with that single-phase to 3-phase converter.


Stubbie 02-15-2008 11:10 PM

I'm trying to get wrapped around what you have done to tell if you are code compliant. Mobile Homes are a different duck as far a dwelling service rules in general. So let me see if I have this straight.

1.) Your service equipment is located on a detached shop in the form of a 200 amp meter/main breaker panel. The utility has run an underground or overhead to that 200 amp meter main panel.
2.) From that 200 amp panel you have installed a 100 amp breaker and ran a feeder to a 100 amp main breaker panel inside the mobile home.
3.) Are you sure you don't have a meter pedsestal or meter on a pole and then power is ran to the shop 200 amp panel from it?
4.) Just exactly what did you do to get 200 amps besides hanging a 200 amp panel?
5.) Have you had this inspected? Because this is a very unconventional method for a mobile home service. Just curious
6.) How many wires did you run in the feeder to the mobile home?

Can you please correct or verify 1 and 2
Can you please answer 3,4,5, and 6 for the moment.


I hate to feed a 70Amp subpanel from the existing 100amp panel inside the trailer cause I will need a double 30amp breaker in the sub at the shop.
I'm not following this at all, the shop doesn't have a sub panel it has the service equipment unless it isn't the service equipment. Are there two panels in the shop?

jambud 02-19-2008 11:09 PM

1 and 2 is what Im trying to do. I have the 200A main/meter on the detached shop, and have #4 thhn copper stranded wire to feed the mobile home which has a 100A main Panel inside with a 100A breaker in it. Right now the 200A Panel hasnt been energized yet by the utility company. The mobile home is currently hooked up to a meter disconnect on a pole outside which is 100A. But when the utility company comes back, they are going to disconnect that 100A meter and run their new wire underground to the detatched shop 200A Square D meter Panel. From there I will run the #4 wire underground to the trailer 100A Panel. I talked to the utility guy and he said that would be fine but I needed to dig the trench which I have completed today. I thought that since the current service has #4 stranded thhn wire from the 100A meter outside to the 100A panel inside, I would be able to use a 100A breaker from the 200A meter to feed the trailer. I forgot to ask the utility guy that and they are supposed to come hook it up on friday. I live in a very remote area in Northern Az. and it is a b*tch to get a hold of these utility people so I wanna make sure I have everything correct and ready by the time he comes back. I do have the #4 wire already which I will run the two hots and neutral with and a #6 for the ground. So there will be those four wires going thru 2" PVC. from the trailer to the shop. And I have 2-1/2" PVC from the shop to the utility main pole. I also drove the 10ft copper ground rod at the 200A Panel. So...those are the only two panels I will be using. Hey Thanks alot guys you are great.!!!

Stubbie 02-19-2008 11:35 PM

I'm not sure why you just didn't use a meter main at the pole and feed the shop and the mobile home from it. Also did the utility say you have a 200 amp service? Anyway I'm assuming that there is no local inspection. Since I'm not familiar with what the Arizona folks allow I will assume they will let you sub-feed the mobile home from the shop service equipment. If they are allowing the dwelling ampacity table to be applied to the #4 thhn on a sub feed then you are ok with that for 100 amps.

jambud 02-20-2008 07:50 AM

Yeah I thought about feeding the shop from the existing 100A meter main but I plan on adding onto the shop with a bigger structure and thought this would be the best time to just upgrade to 200A. I also might build another structure or offices. Yeah theres no inspection out here, but the utility(APS) will always tell you what you can and cannot do.

jrclen 02-20-2008 10:19 AM

#4 THHN is ok for your 100 amp feeder, but not for underground installation. Not for direct burial or inside buried conduit.

jambud 02-20-2008 07:43 PM

Hi...what do I need to power the trailer cause i already buried the #4 thhn in 2" conduit from the 200A to the 100A panel inside the trailer. But I havent hooked it to the trailer panel as of yet as its still powered by the 100A service. The utility company is supposed to come and energize the 200A main and disconnect the 100A service on friday. So basically its just a service upgrade. Thanks!

jrclen 02-20-2008 07:55 PM

Wire with a W in it. THWN XHHW. Underground conduit is considered a wet location. Look closely at your wire and see if it is multi rated. THHN/THWN. Hopefully you will see the W.

wire_twister 02-20-2008 08:01 PM

#4 thhn wire is too small to feed a 100 amp SUB-PANEL, which is what you have. you need #3wire for that. You will need 3 runs of 3awg, 2 hot and 1 neutral, and 1 run of 6 awg for the ground. You say you have already run 2 inch conduit, lucky you the required wires wii fit in that pipe, just pull out the old ones and pull in the new ones. 4awg wire is the proper size for service entrance conductors for 100 amps, but in your case the panel in the trailer is now a sub-panel and the bigger wire is needed

jambud 02-20-2008 10:19 PM

So I should use a smaller breaker then in both panels right? since the 4 is already ran. I'll check first thing tommorow to see if the w is there, I think there are both thhn and thwn.

Stubbie 02-20-2008 10:51 PM

The wire will be dual rated but you can check for piece of mind. I apologize I should have stated thhn/thwn. What wire twister stated is true. Table 310.15(B)(6) for dwellings must be allowed to use #4 awg copper at 100 amps. Some local authoritys don't care in a situation like yours and will allow the #4 at 100. However the NEC does not allow it on sub feeds so follow wire twisters advice. Or you can install a 90 amp breaker in the 200 amp panel to protect the #4 feeder to the mobile home panel. You do not have to change the 100 amp main breaker in the trailer panel.
around here they would not let you sub-feed the trailer from another building electrical system. In my experience the mobile home would not be required to have a driven electrode for grounding. For mobile homes this is usually done at the service equipment.

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