XLPE Insulation

Rancher,

What we ran for underground meter feeds were AL 4/0, 4/0, 4/0 URD for 200A service. As for the XLPE, this is a thermosetting cross linked polyethylene jacket with a single extrusion linear low level density polyethylene covering (LLDPE) could be overkill for your application.

Although this URD cable is suitable for direct burial, I ran mine in 2" PVC, we have a lot of frost freeze cycles and very rocky soil. I also buried it 30" deep although our local codes only require 18" min. I would have used copper, it is just too expensive even for #2 cable that can easily handle the 200A load qualification for local code.

I don't think you really need to use the XLPE and would recommend still using PVC conduit. It will ensure you will never have a problem unless you have a guy like JOHN with his trusty backhoe, constantly digging up the services we installed earlier that week. We were Almost guaranteed extra work when he was around.

This subject came up recently in this thread, too. There seems to be some good information there.

Hope you'll come back and register with CR4, Warner Ranch.

Warner Ranch,

I agree that placing it in conduit or duct is a good idea. The aluminum cables tend to get minor cuts or nicks in the insulation and then the conductor oxidizes to powder and fails after a number of years. Placing it in a conduit or duct reduces this possibility. One concern I will raise is the overall voltage drop in your service. At 0.1Ω/1000', you can see a voltage drop of E=IR = 200*0.1 = 20volts, which is a little more than 8 % of the supply voltage (assuming you are measuring line-line on a typical 3-wire 120/240V circuit). This will cause dim lights, slower heating of appliances, can cause problems with motors (higher current and more heating), and require welders to be set to a higher tap. Pay attention to motor nameplates and equipment service personnel (not just salesmen) to avoid troubles with these things. Of course, when your load is light, then the voltage drop will be minimal.

I'm not saying you shouldn't do it, but good design generally aims for a total voltage drop of only 5% with part of this reserved for the circuits on the property and the rest for the service feeder. In some rural areas, particularly if you are a long ways down the line, the incoming voltage may be a little low to begin with, so I would suggest discussing this "real friendly-like" with the utility people and hopefully getting their agreement that the voltage will not be a problem.

--JMM

If burying the wire, the NEC requires it to be USE(underground service entrance) or UF(underground Feeder) or otherwise listed for underground use. Direct burial or inside of conduit has no bearing on the listed use.(as usual,with certain exceptions).

Considering the distance,you must also calculate the voltage drop and adjust the conductor size upward accordingly.This will result in your case of going up one size in conductor, to a 250 MCM aluminum.You must carry a grounding (green wire) in the conduit with the conductors.The Grounding conductor is based on the upstream circuit breaker size, (normally a minimum of 12% in C/Mils of the current carrying conductors, after applying all correction factors).

If the load is expected to be continous, you must add 25% to the ampere calculation for conductor size, as also is required for new work to allow for future expansion.

If multiple motors are used, the highest HP motor must be calculated at 125% also, and all others at 100%.And for large motors,soft start, and KVAR correction should be considered.

I recommend you consult a local code authority for advice on this if this lt seems too complicated.It gets even deeper, and I have only touched on the high spots.--------------SSB----------------------------------------------------------------------