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Proper AWG for Aluminum Service Entrace GROUND cable when using 4/0 hots/neutral

Proper AWG for Aluminum Service Entrace GROUND cable when using 4/0 hots/neutral

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Old 05-12-16, 09:08 AM
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Question Proper AWG for Aluminum Service Entrace GROUND cable when using 4/0 hots/neutral

We have a little project that has caused a lot of problems because the person that did the SE (service entrance) cable initially cut corners, didn't glue pipe ends together and forced pipes to move a certain way once already buried and in turn the entire 30 ft run of schedule 40 pipe filled up completely with water ... like a river .. just from water seepage from the dirt over many months. Ended up severing a HOT feed from the cable reacting with the water in the pipe.

MY QUESTION: We have 200 AMP service, and are using 4/0, 4/0, 4/0, 2/0 size aluminum cable for SE from the meter to the main principal breaker box in the mobile home..... so why does the GROUND have to be so huge at 2/0 ???? Is there a awg calculator somewhere that will help determine the right awg for that or is that the right one? I ask because there is not a lug big enough on the terminal grounding bar in the main breaker box to fasten that 2/0 ground too, without me going and buying a bigger bolt on LUG to fit it or without chewing off some strands of the 2/0 ground cable to make it fit (which I'd rather not do).

Thanks!
 
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Old 05-12-16, 09:18 AM
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Water in the conduit is not a problem if they installed the correct type of cable and did not damage it during installation. Perhaps they used an above ground cable like SER? If so that must be replaced, because it will fail eventually.

The service entrance does not use a ground between the meter and the main disconnect. Is the main disconnect actually at the pole? If so the proper size for the ground for a 200A subpanel feeder would be #6 copper or #4 aluminum.

BTW, an add-on lug is about $2 so not that big of a deal to just do it that way if you've already bought cable.
 
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Old 05-12-16, 03:34 PM
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Just to be sure you and I are talking the same lingo - "Main Disconnect" = "Main Principal Breaker box in the Mobile Home" ??? CORRECT???

If that is correct above, "Main Principal Breaker Box or Main Disconnect" is NOT at the meter, it is inside the Mobile Home laundry room.

What is the correct "TYPE" of aluminum cable that can go inside a 2" conduit schedule 40 4/0 size and be buried under the ground?

I just wanna make sure the previous guy handling this bought the right cable before I install it TONIGHT.....

When I say "service entrance cable" - I'm speaking of the main feed cables that are running from the Meter box outside on a post to the Main breaker box inside the mobile home.

If I've understood you correctly, it sounds like the 2/0 ground cable is a waste and that we need to bond the Grounding terminal in the Main Principal Breaker box to a ground rod outside in the earth. Is that what I'm hearing from ya? LOL thanks again Ben!!!

EDIT: AT THE METER - IT ISN'T JUST A METER - IT IS A DISCONNECT BOX BELOW THE METER OUTSIDE ON A POST. IT HAS 3 BREAKERS ON IT, 2 QUANTITY 100AMPS I BELIEVE AND 1 QUANTITY 30 OR 40 AMP BREAKER FOR THE A/C CUTOFF. THEN AFTER THIS METER POST BOX, WE HAVE THE MAIN PRINCIPAL BREAKER BOX IN THE MOBILE HOME. SO - DO I RUN A GIANT GROUND CABLE FROM THE METER POST BREAKER BOX TO THE MAIN PRINCIPAL BREAKER BOX IN THE MOBILE HOME in this situation???
 
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Old 05-12-16, 04:46 PM
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Just to be sure you and I are talking the same lingo - "Main Disconnect" = "Main Principal Breaker box in the Mobile Home" ??? CORRECT???
No. Usually the panel in the MH is a sub panel. Main disconnect is the usually fist panel with a breaker or fuse.
DO I RUN A GIANT GROUND CABLE FROM THE METER POST BREAKER BOX TO THE MAIN PRINCIPAL BREAKER BOX IN THE MOBILE HOME in this situation???
Yes. That is your main panel on the post. The one with the first breaker or fuse. The panel in the MH is a subpanel and requires four wires.
If I've understood you correctly, it sounds like the 2/0 ground cable is a waste and that we need to bond the Grounding terminal in the Main Principal Breaker box to a ground rod outside in the earth. Is that what I'm hearing from ya?
No. You need an EGC (Equipment Grounding Conductor) and a GEC (Ground electrode Conductor) at your subpanel. The EGC is your low resistant path to trip the breaker if you have a short to the metal case of a fixture, device, or appliance. The GEC is to minimize atmospheric electrical charges.
 
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Old 05-13-16, 08:59 AM
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The typical cable for this situation is actually called "mobile home feeder" or MHF cable. It is four insulated aluminum wires twisted into a quadplex cable. This cable can be installed underground in conduit or direct buried. It can be installed above ground and indoors in conduit only.

It sounds like you actually have a 100A service at the pole, which means the #4/0 is much larger than you need. The typical cable for a 100A mobile home hookup would be MHF 2-2-2-6 or 2-2-4-6.
 
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Old 05-13-16, 06:35 PM
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We have 200 AMP service, and are using 4/0, 4/0, 4/0, 2/0 size aluminum cable for SE from the meter to the main principal breaker box in the mobile home
It sounds as if the Type SE cable you are using is actually SER cable with a gray outer sheath. If so, you cannot use this underground in conduit or direct buried; you have the wrong type of cable.

the entire 30 ft run of schedule 40 pipe filled up completely with water
All underground conduits fill with water, that isn't a problem unless, like has already been pointed out, you are using the wrong type of cable or the wiring was damaged when it was pulled into the conduit.
 
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