depth of underground electrical conduit

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  #1  
Old 08-19-13, 04:41 PM
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depth of underground electrical conduit

i am adding several underground lines around my property. i have two short runs with 240 volt (20 feet) circuits, using 6-2 wire for demand water heater, and 4 conductor wire (not sure of size) for dryer. digging out here is extremely difficult, very heavy clay with rock and tree roots but i'd like to have the lines down at a depth where they meet code.

and how deep would that be in either pvc or metal conduits?

i am also running 12 gauge wire a few hundred feet. will of course be using gfci on all outdoor plugs, but i don't think a gfci breaker would work well because it would be tripping too much.
 
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Old 08-19-13, 04:57 PM
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If you are running all this to a single detached structure you can't. You can only have one power source to a detached structure.

It sounds like you are running UF cable. Best practice is to run individual THWN wires in a complete conduit system. It is not recommended to bury EMT because it will rust. Conduit is buried at 18" minimum. Cable is 24" minium with short sections of PVC conduit for protection where it enters and leaves the ground.

i have two short runs with 240 volt (20 feet) circuits, using 6-2 wire for demand water heater
Have you considered direct burial of 3/0 URD and using a 240 volt only subpanel at the on demand water heater? Might be cheaper.

4 conductor wire (not sure of size) for dryer
Dryer uses thee conductor plus ground. 10-3 if cable.

i am also running 12 gauge wire a few hundred feet.
More then a couple of hundred feet #12 would probably be too small for more then 5-10 amps after voltage drop.

What size main breaker do you have. It sounds like you need at least a 350 amp service.
 
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Old 08-19-13, 04:58 PM
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looks like i'm going to be stuck at 18 inches deep on any pvc wire. i don't think it's practical to use gfci breakers on areas where i'm going long distances.

if one were to use metal conduit, do you have to use separate conductor wires?
 
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Old 08-19-13, 05:04 PM
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What is PVC wire? Is this all to one structure? You can bury one foot if you use RMC but that is really not DIY friendly or cheap.I have edited my post. Please reread.
 
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Old 08-19-13, 05:08 PM
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You can use GFI receptacles at the end of your long run.

Both PVC and heavywall pipe require separate conductors.
 
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Old 08-19-13, 05:13 PM
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i am adding several underground lines around my property. i have two short runs with 240 volt (20 feet) circuits, using 6-2 wire for demand water heater, and 4 conductor wire (not sure of size) for dryer.
Where are these two runs going? Only one supply can be run to any structure. If both of these are going to the same structure you will need to run a service for a subpanel and supply the loads from that.

Burial depth depends on wiring method and protection. It is greatest for cable with standard overload protection and less for different types of conduit and for conductors with GFCI protection. Rigid conduit can be buried at 6". A 20A residential branch circuit with GFCI protection may be buried at 12".

will of course be using gfci on all outdoor plugs, but i don't think a gfci breaker would work well because it would be tripping too much.
Why?

i am also running 12 gauge wire a few hundred feet.
As Ray said, only if you need only a trickle of power at the end. How long will the runs be and what will the loads be?
 
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Old 08-19-13, 05:22 PM
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i've got a 200 amp service. 100 amps to the mobile home, and then i'm also pulling the dryer and the demand water heater as well as my pump off the main breaker pole outside (200 amp service).

from the mobile home i'm running to a subpanel in my shop (30 amps).

i've never had any problems here. my main has never tripped. my electric bills are under $100 a month, and i use a window ac. i'm replacing my hot water heater (currenty run from the 100 amp house panel) with a demand unit, which i'm going to place in a covered area outside my mobile home where the water enters the house. i also realize that the dryer wasn't properly installed because the conduit isn't buried deeply enough, so i am going to replace that as well.

do i really need a subpanel at the water heater? i'm running a 60 amp breaker at the power pole and it's only about 20 feet from that breaker to twhere i'd want to place the water heater. i was planning on building a cover over the water heater so there would be no issue with weather, though it's completely out of the weather under an big awning. i could alternatively run the conduit in the house and place the demand water heater inside, but i was hoping to have it outside in case of any leaks or if the pressure valve were to ever overflow.

it's pretty obvious that i'm going to use pvc and like it or lump it, i'm going to have to dig 18 inches deep.

the electric has been here from the prior owner for a long time, i'd just like to be sure that all underground lines are buried to code.
 
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Old 08-19-13, 05:28 PM
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on the long runs, i am only using this for gate lighting, gate opener and my sprinkler control valve box. we're not talking much of a load. you think i should put this on a gfci breaker, and go 12 inches deep in direct bury wire?
 
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Old 08-19-13, 05:32 PM
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first, i'd like to tell everyone that obviously, i don't know shi* from shinola on this issue. however, i am certainly willing to learn and i want more than anything else to do this the right way. i really appreciate the info you're giving me. i'd rather move slowly and do this the right way than have problems.
 
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Old 08-19-13, 06:06 PM
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All of the loads in and on your house/mobile home must be fed from the panel in the house/mobile home, including the water heater and the clothes dryer.

Why isn't the panel in your shop fed from the power drop and main breaker panel at the pole?

on the long runs, i am only using this for gate lighting, gate opener and my sprinkler control valve box. we're not talking much of a load.
Originally Posted by Nashkat1
How long will the runs be and what will the loads be?
How many feet and how many amps?

you think i should put this on a gfci breaker, and go 12 inches deep in direct bury wire?
I think you should do this in the way that best meets your needs. 12" burial with GFCI protection is one alternative that reduces the burial depth requirement.
 
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Old 08-19-13, 06:59 PM
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Have you done a load calculation? !00 amps for the mobile home, 120 amps for an on demand water heater plus a dryer, a shop and you only have a 200 amp feed. Just hope you don't have electric heat or an electric stove. I'd be surprised if you don't need a new service and if you are in the country the power company may need to install a new transformer on you dime.

Here is one load calculator you can use. Residential Load Calculations - Mike Holt Enterprises
 
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Old 08-19-13, 07:09 PM
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i could easily put the dryer on the main panel. could i upgrade the main panel to 150 amps if the existing wire is heavy enough? i'm going to be pulling off the water heater anyway.

i have decided that any of the 20 amp circuits (could i run these off gfci breakers from the 200 amp main pole? ) would be buried a foot deep using outdoor 12-3 gauge wire, no conduit. that issue is settled. i would also use gfci outlets.

i'm not sure as to the amperage of my gate opener, lights, sprinkler valves but i've been running these things off a long heavy extension cord and a single 20 amp breaker and they've run fine for a couple of months, no issues, never a blown breaker. i've just been doing this to get it all installed and see where i need to wire.

on the hot water... i am going to get a small shed for my water treatment equipment and i could put a sub panel in that shed and run both the hot and cold water to my house. so they wouldn't be in the same building, per se. then i could direct bury or run conduit. any issues here?

i do see that the rules regarding conduit use are fairly restrictive and that you cannot run 12-2 in conduit. i won't do that. it's simple enough to get gfci breakers.
 
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Old 08-19-13, 07:12 PM
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Did you see my post #11? Please do the calculations before proceeding.

you cannot run 12-2 in conduit.
Not a code issue. You can but not best practice.

On the long 120 volt run to your gate do a load calculation using total amps and actual one way distance. electrician2.com voltage drop calculator
 
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Old 08-19-13, 07:15 PM
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the on demand heater is 56 amps. typically my load is smaller than you might think. many months my electric bill is only 70 dollars. i'm cooking, bathing, washing dishes and clothes, running my well, running my shop - all of it. i don't think i'm going to be using any more electricity because i'm already heating my water with an old tank heater. if anything, the demand heater will reduce the electricity that i use (or so i imagine). i am only using it to finish off what my solar water heater (building soon) doesn't heat well enough. i'm really not concerned with my overall load. i've lived here for 5 years in this place with no problems whatsoever.
 
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Old 08-19-13, 07:19 PM
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the on demand heater is 56 amps.
Then why did you write:
have two short runs with 240 volt (20 feet) circuits, using 6-2 wire for demand water heater,
Sorry it is common to run two 60 amp runs to an on demand water heater thus my assumption.
 
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Old 08-19-13, 07:24 PM
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one run was to replace the dryer, which is already run from the power pole long before i got here, but buried only about 6 inches deep in plastic conduit. i can run that one from the breaker panel in the house. so i don't need it.
 
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