Looking into installing 30 TT outlet on my detached garage

[Boomerweps]

Problem is that it is about 90-100 feet from the home circuit breaker box. Voltage drop calculator has about a 5% voltage drop for that distance using 10awg and about 3.5% using 8awg (not allowing for the TT shore power cord).
I'm thinking I'll need to use 8awg.
Copper gets expensive, plus added components, outside jack, ditchwitch rental, etc.
Any thoughts?
I'm looking at Direct Burial wire or interior grade that would be routed through sealed plastic pipe. I've only checked Home Depot pricing so far and not the local electrical supply house.
Garage has 12awg run to it and is a good 110-120 feet run through the house and ground from the CB box.

[valhalla360]

Go big on the conduit...as you learned with the old conduit...If you want to run communications or 50amp line later, it's much easier if you have a 2" or even larger conduit to work with and the cost difference is negligible.

[Atlee]

I agree with this.

I just put in a 30 amp here at the house, but I only had a short run along an inside garage wall then thru the garage wall, about 1.0 ft out and 2 feet up.

If you are going to be trenching for that distance, go ahead and put in the conduit and wiring for a 20/30/50 amp box.

Would the cost be that much more?

bucky wrote:
If going thru all that why not put in 20/30/50? Who knows what the future brings.

[bucky]

If going thru all that why not put in 20/30/50? Who knows what the future brings.

[Boomerweps]

Thanks for all the info and comments. It helps with my considerations.
The detached garage is a POS built from scrap wood in the 1930s as a one car stall, one horse stall unit. I've repaired it enough to straighten it and make it a usable open front shed and can squeeze my wife's "new" 2001 Jeep Wrangler in the horse stall side.
I actually gutted a lot of the existing electric and reran 12awg from the house to and through the garage. I did use one inch PVC buried only about 12", hand dug ditch. I MIGHT be able to pull 10awg through it but there is a 90 degree bend on each end where it goes into the ground. I'd like to keep the existing 12awg line as a separate circuit.
I will be doing any and all work myself. I can't quote the NEC but otherwise I'm very experienced on home electrical systems (US Navy electrical trained) & have replaced all the accessible knob and tube in the house (the vertical runs are a problem), separating circuits, doubling the number of CBs in the box. Electric was SUPPOSEDLY upgraded to FHA requirements when my wife bought it 40 years ago, yeah, right. House was built in the 1920s.

[DrewE]

Boomerweps wrote:

I'm looking at Direct Burial wire or interior grade that would be routed through sealed plastic pipe. I've only checked Home Depot pricing so far and not the local electrical supply house.
Garage has 12awg run to it and is a good 110-120 feet run through the house and ground from the CB box.

Be aware that underground wire in conduit still needs to be rated for wet locations (but not direct burial); if by "interior grade" you mean Romex or something else only approved for dry locations, that would not be up to code.

(There are those who say that it's not permitted to put Romex in conduit, but that's simply incorrect. If the conduit is properly sized it's entirely legal; but the conduit does not make it magically approved for wet locations.)

[BFL13]

You have to get by the first risk of the idiot electrician giving you 240 instead of 120. Assuming you get by that safely, that is still a long run of wire!

Another approach if you are set-up for off-grid running the microwave and all that, but now are in your back yard with visitors staying in the Rv, is to do the off-grid approach, except now just run miles of extension cord to a stick house 15a to plug in only the RV converter.

The converter is likely rated to run at as low as 105v. So now you can run the rig out there for as long as needed on its inverter to do the microwave , TV, etc, and your batteries are being "supported" by the converter now plugged into the shore power on the long 15a extension cord.

[Big_Katuna]

Is there a stream nearby? Maybe you divert it and build a small hydroelectric plant !

You could resell excess to the grid and buy a Prevost custom !

[krobbe]

enblethen wrote:
I would suggest replacing the feed to the garage and then installing the RV receptacle off that.
You could use RHH/RHW/USE wire which is rated for direct burial. I would use #6. Yes, slightly overkill(50 amp). yes, #8 would work(40 amp).
The ground wire can be smaller. It would be calculated on the amperage of the circuit breaker in the source panel. A #10 ground wire would be sufficient for up to 60 amp circuit breaker.
I would install and additional ground rod at the detached garage for a little extra protection.

I agree with enblethen. Except I would run 3 #3awg copper or #1awg aluminum and a #5awg ground to install a 100Amp sub panel in the garage. This will provide branch circuits for a single phase 30A RV outlet, 50A 2-phase RV outlet, 8hp air compressor, and more 20A outlets in the garage. Can't have too many outlets!
Also, oversize the PVC conduit. It's pretty cheap. I ran 3 runs of 1.5" PVC for power, air hose, and communications from my service panel location in my attached garage to my pole bldg. Justify the material costs by doing the work yourself and saving thousands in labor.

[Acampingwewillg]

Lots to be considered but if I were doing it and going to the trouble of renting a Ditch witch, I'd go with 1" PVC in case you ever want to up grade. Non GFI circuits need to be 18" deep(I'm sure that changes by location) and I would definitely use stranded wire by the roll. You can get the wire cut to size after installing you conduit. Good Luck with your project.

[Harvey51]

Consider also a solar panel installation on the garage. For a similar cost you might get free electricity for 20 years.

[ScottG]

I am a little more than 175' including a 50' extension cord. Everything is 10awg and I lose about 5 volts with the AC and fridge running (116~117VAC).
So 10 awg has worked fine for us.
OTOH, If I were doing it all from scratch, I'd use #6 and just go with a regular 100A panel (50/30/20A) like RV parks use.

[Dusty_R]

I always figured it is always a good idea to leave a hole behind after digging a trench, conduit, PVC is not all that expensive. I'd also consider using larger conduit than needed. You never what tomorrow will bring.
Last I knew PVC needs 18" of cover.
Rigid, it looks like galvanized water pipe. Only needs 2" of cover.

Dusty

[enblethen]

I would suggest replacing the feed to the garage and then installing the RV receptacle off that.
You could use RHH/RHW/USE wire which is rated for direct burial. I would use #6. Yes, slightly overkill(50 amp). yes, #8 would work(40 amp).
The ground wire can be smaller. It would be calculated on the amperage of the circuit breaker in the source panel. A #10 ground wire would be sufficient for up to 60 amp circuit breaker.
I would install and additional ground rod at the detached garage for a little extra protection.

[time2roll]

#8 is fine. Make sure code allows the wire type to go underground. Check with your local city how deep you need to have the wire. Best to get a permit.
Parallel conductors are not allowed by NEC in this situation.
Use a single breaker for 120 volts.

http://www.myrv.us/electric/Pg/30amp_Service.htm

[Macrosill]

I just did this last week. I trenched and laid 1" pvc. I had lots of 10 awg thhn on hand so I ran 2 parallel sets of it to minimize the voltage drop. Paralleled 10s came in with less voltage drop then 8 awg did and the copper was free.

Now before anyone gets their pants in a twist I know I am using smaller than 1/0 conductors but there is an exception in the NEC provided all the conductors are in the same conduit and the condcutors are sized than any one of them can carry the full load should you lose one. They are all in the same conduit and they are all 10 awg.