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edlank 08-09-2009 11:24 AM

Outdoor underground wire
Our house has floodlights 60' from the house, and one does not work. The previous owners think landscaping damaged a wire. We do not use the lights until we correct the problem. I recently found that the wire is UF-B wire and where it nears an "oasis" of flowers, the wire is not buried, but covered with a metal strip as a shield. Wow, that looks dangerous. I hand dug near it, and never found a place where it entered any conduit. This certainly does not meet code for wire without conduit.

Before I start working, I am considering changing to the upturned "splash" lights very close to the house, which means retrenching to place the wire. I expect to use conduit. I see where the wires penetrate the basement wall, and it is about 18" below the surface. I can trash all wire and start again, but think I will be able to avoid touching the wire inside the house, and simply shorten what is there to the new closer destination.

Before digging, one question is what is likely to be at the outside basement wall to seal the hole where the wire penetrates the outside? What should I do to seal it, and should I "fix" the conduit to the wall so settling does not try to shear the wire? The basement is composite concrete block.

I have seen the large rectangular flood light boxes designed to use compact fluorescent bulbs that could be direct replacements for what I have. I have not seen ones that use compact fluorescent bulbs for the smaller round splash lights. I currently have halogen bulbs, but the PO labeled the circuit breaker "mercury vapor" so I wonder if he already replaced the original fixtures. Anyway, the bulbs are 300W, and I have little interest in even using these electricity hogs, but want something much less power hungry. Are there suggestions for a product for this that I have not found? I am likely to need 4 to 7 lights, so certainly do not want a bunch of high wattage incandescents. If solar units can have efficient light sources, why not hard wired, too? Where are the LED products?

Nestor_Kelebay 08-09-2009 10:34 PM

First off, I should explain that I'm not a licenced electrician, and you should follow the advice of the licenced electricians in here over mine, cuz they know what they're talking about, and I don't.

LED lights are available, and apparantly Home Depot sells them. The problem is compact fluorescent bulbs are stealing their thunder.

You see, if you pay 10 cents per killowatt hour, a 40 watt incandescent bulb will cost you about $48 per year to operate, whereas a 7 watt compact fluorescent will cost you about $10.

Now, along come LED bulbs that cost $40 or so for a 5 watt bulb that'll be about the equivalent light output as a 40 watt incandescent. It'll only cost you 6 dollars per year to operate. You're saving a lot of money compared to using incandescent bulbs, but not compared to CFL's. Compared to a $2.50 7 watt CFL, you're only saving about $4 per year. That means you only break even after 10 years by replacing a CFL with an LED. Maybe a bit earlier than that if you consider that LED's last longer than CFLs so you might have had to replace the CFL once or even twice during that time.

It requires one "AA" or "double A" cell battery. The most common kind of battery.

General LED Lighting Solutions, EvoLux

When I wired a parking fence I built to provide electricity for tenants to plug in their cars in winter, I used a flexible electrical conduit to go from the fence to the building because the two would move relative to one another. The fence would move up and down with frost heave, whereas the building would move much less. I put one fence post right beside the building (about a foot away) and had the fence itself stop about an inch from the building. The flexible electrical conduit spans that 1 inch gap between the fence and building. Basically, it was a hollow flexible aluminum tubing (similar to empty BX cable) with a rubber jacket over it. You stuck weatherproof connectors on both ends to connect to regular rigid aluminum conduit. I really don't know if that stuff was OK to use underground or not, tho. Any electrical wholesaler will show you the stuff I'm talking about, and would probably know if it's OK to use underground. That would be one way to accomodate movement of the house relative to the wiring.

If you dig up around your foundation wall, I expect you'll probably find that the wiring is caulked around the hole it enters with roofing cement. You can buy roofing cement in 300 ml tubes suitable for use in a caulking gun. Roofing cement is black and looks like tar. Or, at least, that's probably what I'd use to caulk an underground hole in concrete block.

Also, almost certainly your yard lights are all wired in parallel. If they were in series, then any one bulb burning out would break the circuit to all the others, causing them to stop lighting as well. If you do decide to dig up the wiring from the one light that isn't working, you might want to invest in an AC voltage detector like this one:

For $15 or so, it flashes and beeps whenever the tip is within about 1/4 inch of a 120 VAC voltage source, EVEN IF THERE IS NO CURRENT in the circuit. So, for instance, if you have an extension cord with a break in the wire somewhere along the length of that cord, this voltage detector will tell you where the break in the wire is. It'll stop flashing and beeping at the point where the wire no longer has an AC voltage in it, which is the point where the wire is broken.

I'm thinking that if one of the wires was cut by a shovel during landscaping, then the damage to the wire will be obvious. However, if the wiring was encased in a trench and covered with a piece of dimensional lumber (like a 2X10), then the break in the circuit might not be obvious. It might in fact be a piece of wire insulation inside a wire nut that's not allowing one wire to be in contact with the others. This $15 tool will allow you to detect where you have power in the wiring, and where you don't, without handling or cutting into the wiring.

edlank 08-10-2009 11:02 PM

Great links, Nestor. Finding the wire cut was easy. The line had 3/4" conduit from each light to the edge of each landscaping oasis, and was bare UF-B for the 20' between oases. At the edge of one oasis, conduit and wire together were completely sheared. It must have been a power edger that did it. I do not plan to use wire out that far, but hate leaving something nonfunctional underground, so I removed it.

I was amazed that in this 20' run of wire, the conduit was about 4" underground, and the bare UF-B was as shallow as 1.5". Wow.

As I look at the options, it is amazing to me how many of the uplights still sold use halogen bulbs. I can chose one that is intended to use halogen and if the bulb type is the same (i.e. MR-16) simply use an LED with that base. It seems like it should not be this hard, though. Some of the EcoLux bulbs are direct incandescent replacements, so that makes finding a fixture easier.

I expect to bury conduit and bring it up to a junction box near ground level, and so I am looking for a pipe thread mount. If I choose a 12V option, I will need to do some rewiring to add a transformer in the basement.

Has anyone gone through this, who can offer suggestions?

Nestor_Kelebay 08-11-2009 10:47 AM

What I think you should do is phone your local City Hall and find out whether they have any brochures on your local electrical code and see if it talks about underground wiring.

If I recall correctly, the electrical code somewhere says that to run underground wiring in your yard, you have to dig a trench to lay the wire in, lay your wire in there, cover with 2X lumber (like a 2X10, or whatever) and then cover with backfill. However, it would seem to me that this would just lead to the 2X10 rotting away completely in a coupla years. Still, that's more or less what I remember the requirement was. Anyhow, your local electrical inspector should have guidelines on what required in your area.

Yeah, having wires only an inch and a half under the ground is crazy. Someone decides they want a landscaping company to "aerate" their yard by punching holes in the soil and you end up wrecking the wiring and possibly giving some poor guy a shock.

edlank 08-16-2009 09:11 PM

I found small screw mount spot lights with 20W halogen BR16 bulbs. They are 12V and can be replaced with LED bulbs that use the BR16 spec. The LEDs come in 1, 3, and 5W bulbs. I have put PVC conduit along the house and placed 6 short "Tees" a short distance off the run, so everything is close to the house. No 110V lines under the yard, and no more power hungry light fixtures. I had not seen that the inexpensive spot lights DO have the wiring through the screw on mount if the spike is not used. If I can believe the product literature. low voltage wires do not even need to be buried or in conduit...I have done both, so think I am much safer than I was last week.

Now I am looking for a hardwired transformer, no timer, not weatherproof, that can power 6 20W bulbs now, and can handle the minimum power of only 18W if I replace the halogens when they start blowing.

edlank 09-01-2009 05:04 PM

3 Attachment(s)
I took out these floodlights, using 300W at 110V, with bare UF-B wire barely 2" down.

And put in these, connected with 3/4" conduit all the way, and 12V 20W halogens (MR16). I expect to replace with LED bulbs when they are cheaper. The conduit is not covered just for the picture.

edlank 03-26-2011 09:03 PM

How should underground wire penetrate the house wall below ground? What I found was UF wire sealed in the composite concrete block heading out to the yard totally unprotected. I carefully dug it up and slid conduit over the wire on the outside all the way up to the wall. That means that only UF wire resists shear if there is any settling of the soil at the outside entry site. Should conduit enclose the wire all the way through the wall? Should there have been some type of box mounted to the wall to provide some strain relief? If conduit is supposed to pass through the wall, how is it to be sealed against water leaks?

joecaption 03-27-2011 06:24 AM

UF wire is made to run under ground with no protection at all, it must be run at least 18" below ground. You can run it though gray conduit to also help protect it but it's not required. Conduit is only really needed where the wiring is run vertical up to the lights. There is no stress relief needed where it goes through the block wall but should have been run though a piece of gray conduit inside the block to stop any chafing. It does not get roofing cement as suggested. Any damage to the block wall it's self when the hole was driled gets Hydrolic cemented, The conduit gets a gummy black sealer Or even silicone can be used, that's sold in the eletrical dept. at Lowes or HD.

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