Locating underground metal conduit.

woobagooba

Re-powering a detached garage for a heat pump. Desire is to use existing conduit running underground between main house and garage. We are having difficulty extracting the existing conductors. Two 1" conduits exit the house. Somewhere underground they join into a single 2" conduit which emerges at the garage.

We need to map the conduit and locate the junction (w/o digging up the whole thing). Any ideas appreciated. Apologies if this is a stretch for this forum.

JUGHNE

When I see 2 different sizes on UG like this, I would suspect that there is no UG conduit between the buildings.

Just riser stub ups at each location and direct bury conductors in the dirt.

Do you have the same # and type of conductors at each end?

EBEBRATT-Ed

or a junction box in the middle.......somewhere

What kind of conduit? Metal or PVC?

If metal maybe a metal detector

If PVC dig around on either end maybe a yellow tracer wire is their

Jamie Hall

To sort of add to @JUGHNE and @EBEBRATT-Ed -- unless there is an actual junction box or manhole or handhole, it is far more likely that as @JUGHNE suggested there is no underground conduit at all -- what you are seeing is just the required protective stub ups where the wires come above ground.

You can test that idea rather easily -- very carefully dig -- by hand, and I'd suggest a trowel not a shovel -- around one of the stub ups and follow it on down and see what it goes to when it turns more or less horizontal.

Now... if it really is in conduit, and there is no access point in between where they might join, the installation is not to code or even close. I hope it isn't...

If neither of the existing cables can be repurposed -- too small, or too few wires -- you really need to lay a new underground feeder, but the problem is going to be to excavate and install it without hitting what's already there..

woobagooba

Time for me to start diggin!

ratio

I suggest renting a walk-behind trencher. Loads of fun, simple enough that even an electrician can operate one, & sooooooo much easier than hand digging. Faster too.

pecmsg

In NY just dial 811. They’ll mark where the conduit / Cable is. Required by law anyway. 

I agree with @ratio run new

Jamie Hall

Two problems, folks... 811 may not be able to locate buried cable on private property (for that matter, they don't always get it right for the utilities on public property -- but if the mess up it's the utilities nickel, not yours) and a walk behind trencher is a wonderful machine -- if you know where the utilities are. But... it will happily chew through buried cable, buried plastic pipe, etc. etc.

JakeCK

Yea the 811 number doesn't locate private utilities, atleast in my experience. When I tilled my yard for a new lawn they only marked the public utilities. Nothing for the conduit going to my garage and for the coax going to my dish. I knew where the coax was but still to this day not sure about the conduit. Funny story even though I knew where the coax was I still managed to hit the sob with the tiller. Lazy installer only had it like an inch or two under the ground. After I fixed it with a direct burial splice kit I reburied that thing like a foot under.

JUGHNE

With 2 risers at the house, it is possible one is for the garage direct bury conductors and the other may go elsewhere. Or something coming into the house...dish..cable..phone etc.
Do you have a private water well or another out building somewhere.
Some risers do not come up outside a building but possibly inside the wall thru the concrete floor.
Or another for instance, my UG pipe to the AC's is buried outside along the house under concrete pad.

Also, our one call UG locator is for all local utilities other than phone, the locals are helpful enough to locate private lines if asked while doing their own.
(Small friendly town).

mattmia2

You can locate the copper conductors just as easily as metallic conduit. If you find it actually is conduit all the way (which I suspect is not the case), put a fish tape down it, it will likely stop at the junction box between the 2" and the 1" and you can get a rough idea of where to dig for it, but you probably will be digging it all up. Put conduit in the trench for the new one so you can just pull a replacement or add on later. I would also put a second conduit in the trench for low energy wiring.

woobagooba

Always impressed how wicked smaht folks are on the Wall. Sure enough, buried UF cable ...



Garage plan is now up in the air. We want the option to mount future solar on the garage roof. Have to talk to the solar folks to complete a conduit plan for power, solar, etc. to/from the garage.

Cheers all.

mattmia2

This brings up more questions since if you have more than one circuit to an outbuilding, you need a service disconnect and all the other rules about bringing a service in to a structure apply.

JakeCK

woobagooba said:

 Garage plan is now up in the air. We want the option to mount future solar on the garage roof. Have to talk to the solar folks to complete a conduit plan for power, solar, etc. to/from the garage. Cheers all.

Don't worry about solar while wiring the garage. That is an entirely separate system and will have to go back directly to the main panel with its own run. The cost for a solar company to trench and run the lines at install is negligible compared to the whole solar project. I'm going through all that right now.

woobagooba

We already had two visits from Mr excavator (main power from street, septic line replacement). Lots of trees removed. Getting tired of the premises looking like Verdun.

The last excavator visit will do the drywells, solar conduit, garage power conduit, garage broadband conduit, etc. all in one shot. We may run all the garage conduits in a single trench back to the main meter area. So we will set the end game plan now, dig one more time.

Cheers

JakeCK

Run pull lines through all the conduit. It is possible to pull them after the fact but just save yourself the hassle.

JUGHNE

Do you have the same cables showing up in the garage?
They may have used the bigger riser after the struggle to pull that many UF cables thru smaller pipe.

There is some caution to consider when running data PVC conduits parallel to power PVC conduits. There can be interference from the power AC circuits.
So shielded data cables or steel piping (IIRC, not aluminum but steel) for the data runs.

After conduits are installed, I use a vacuum to pull a string thru.
I put a "mouse" of light plastic (looks like a fishing fly) on the string and the vac pulls it right thru, also removing any water and dirt.

mattmia2

It has to be imc or rmc if you bury it and use metallic conduit. in reality it is very unlikely you would get interference from the ac wiring in the low energy wiring. i think separation is required in the trench. some of that separation at least for rfi could be not burying it nearly as deep as is required for line voltage conduits.