Tapping into underground power line - Diesel Forum

Larry S. · 09-05-2008, 12:24 AM

I posted a few weeks back about installing a pump and this is another question related to that. I am installing a pump house near the new well where I will have the pressure tank and a power load box for the pump and other power needed in the pump house. The pump house will be less than 10 feet from the underground power line to my cabin. The underground power comes from a load switch/breaker box after the meter on a power pole. The underground cable is 2-0 aluminum 3 wire plus ground. I installed the underground cable and even did a splice in it. It all passed inspection. For my pump power I would like to "T" into the aluminum underground cable with copper at the nearest point to the pump house as possible. The copper will probably be 10 gauge. Is this a reasonable thing to do vs. running over 100 feet of copper from the cabin load box? What is the best way to connect the copper to aluminum in an underground junction? Are there special fittings to do this? Will a double wrap of plastic tape over rubber sealing tape, like I did for the aluminum to aluminum splice, be sufficient to seal the coupling.

For those interested: the well came in at 560 feet. Water rose to 70 feet below grade. Looks like I will be using a submerged pump and have it installed by a pro. I plan on using a pitless adapter which seems to be the most common practice in my area.

**bugman** · 09-05-2008, 11:55 AM

Just my 2 cents worth, I wouldn't do it. The problems that I have seen with aluminum wire in the ground and any water not to mention the problem with electrolysis with the copper to aluminum and you are asking for trouble with a buried splice. Even your splice on the aluminum cable isn't the best in my opinion. I have seen a lot of them go bad when water hits them. The best way would be to come from you cabin or the meter base with a new line for the pump.

Jim

MarkEkberg · 09-05-2008, 02:48 PM

I am the first to jump into something I know little about, but that connection sit wrong with me. You need it to be on a breaker, but I would think you want the junction to be on a breaker as well..............

Installing a submersible pump is easy. You can get everything you need from your local plumbing store or even Home Depo. I think they even have pumps.

Tackle that before splicing into the electrical.

**action4478** · 09-05-2008, 05:52 PM

Quote:

Originally Posted by Larry S.

I posted a few weeks back about installing a pump and this is another question related to that. I am installing a pump house near the new well where I will have the pressure tank and a power load box for the pump and other power needed in the pump house. The pump house will be less than 10 feet from the underground power line to my cabin. The underground power comes from a load switch/breaker box after the meter on a power pole. The underground cable is 2-0 aluminum 3 wire plus ground. I installed the underground cable and even did a splice in it. It all passed inspection. For my pump power I would like to "T" into the aluminum underground cable with copper at the nearest point to the pump house as possible. The copper will probably be 10 gauge. Is this a reasonable thing to do vs. running over 100 feet of copper from the cabin load box? What is the best way to connect the copper to aluminum in an underground junction? Are there special fittings to do this? Will a double wrap of plastic tape over rubber sealing tape, like I did for the aluminum to aluminum splice, be sufficient to seal the coupling.

For those interested: the well came in at 560 feet. Water rose to 70 feet below grade. Looks like I will be using a submerged pump and have it installed by a pro. I plan on using a pitless adapter which seems to be the most common practice in my area.

How far from the pole is the well?..

Dissimilar metals is not a good idea...

klhansen · 09-05-2008, 05:57 PM

Bad idea to splice underground. And an electrical code violation as well. You can't even have a splice that isn't in a junction box inside a house. They have to be accessible.

Larry S. · 09-05-2008, 07:08 PM

Darn, you guys are making things expensive. I am a little over 100 feet from the cabin and 200 feet from the pole. At that distance I will probably need 8 gauge. At the price of copper these days I was hoping to avoid the long run. The 560 feet down the hole will be bad enough.

How about bringing the aluminum into the load box in the pump house and then back out and down to the cabin? I can do that. That puts the tap into the load box which is accessible and covered. Aluminum into and out of a load box is done all the time. I have it at both ends and its less than 10 years old. Not the 60s aluminum wiring. All it required was lots of special grease on the terminals to keep the aluminum to copper connection from oxidizing.

BuilderBob · 09-05-2008, 07:14 PM

How are you to protect the #10 AWG? From over current?
NEC requires that you use a circuit breaker, where will this be placed?

bilbo · 09-05-2008, 08:52 PM

...and not even addressing code requirements and violations, I have some concerns.

where are you getting the extra feet of wire (aluminum 2/0, 3 conductor w/grnd) to facilitate the run up and down to the "load box?
You must dig it up and run one end (of the 3/c w/grnd) into the Breaker box/load center ( you must install another main disconnect breaker at this box.)
THEN you can install a 30 amp breaker for the 10ga wire that will service the pump
You can get by with a few feet of aluminum 2 ought cable and only ONE splice/box on the 'short' leg..
I believe this can be done, but the splice and weatherproof junction box should be above ground.
BTW: dielectric grease is acceptable and will work correctly only if you have the correct split nut, butt connectors, swaged lugs or whatever hardware is used.

DISCLAIMER: this is only an opinion and is not to be considered the definitive source of advice...bb

PS: this will ONLY work if these modifications are on the LOAD side of the existing meter panel/main disconnect..

Larry S. · 09-06-2008, 10:15 PM

bilbo,
You got the idea right. Digging up the cable is not an issue. The trench is still fresh enough that after the first foot down it isn't even packed hard. I opened the trench for a short distance to ensure that the drill would not go through the cable before drilling the well. The willow stick said to drill less that 2 feet from the line. On the above ground splice: underground splices using the proper connectors, grease, and tapes is standard and acceptable procedure where I am located. That is if the codes have not changed since I installed the line. When I installed the line I studied the NEC bible but haven't done that this time, so far. I am essentially in a desert area with decomposed granite as the soil type. Very little moisture. All codes will be met and inspected. An electrical permit is required. My original post was the simplest and cheapest but I expected it to not be acceptable.

Thanks to all for the input.

bilbo · 09-06-2008, 11:23 PM

I. personally, would splice underground, using Q1/C1/ Nuke grade heat shrink tubing for all three conductors and outer cable jacket. I also would use butt connectors with a hydraulic swaging tool.
I have a supply of this tubing just for personal jobs that need it.
If it is good enough to use in containment, where the quality of the sealant is enough to continue to have insulating integrity under complete immersion, it is good enough for ME!

Anyway, I am sure you can complete this job as you explained it.
Good luck...bill