In service wiring for cabin

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Old 03-18-16, 10:00 AM
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In service wiring for cabin

I have two questions, similarly related. I have a 250 sq. ft. cabin that I will have the following electrical draws: 20" range, 10 cu.ft. refrigerator, 5K BTU heater, 12K BTU AC, 36" LED TV, 700W microwave, 5 LED light fixtures, and a small on-demand water heater. All appliances are new and energy star rated. My questions are:

1. What size amperage should I use for the cabin with these anticipated draws (100, 125, higher)?

2. What size/type underground in-service wire should I run from my meter to my panel box (approx. 120 ft. away)?

Thanks in advance for any advice.

John
 
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Old 03-18-16, 10:07 AM
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Minimum size service by code is 100A, which sounds like plenty for this cabin. The on-demand heater could bump it up -- do you have a model number in mind?

You could run #2-2-2 or #2-2-4 USE aluminum cable. Burial depth is 24" minimum with conduit sleeves required on the entry and exit from the trench to the panels. Do you know if your utility company requires a disconnect on the pole with the meter? If so, this may change my answer.
 
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Old 03-18-16, 10:39 AM
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Thank you for the timely reply. The model of the on-demand water heater is: AquaPower AQM 2-1 120-Volt 1.8-kW Compact Point Of Use Electric Tankless Water Heater.

There is already a disconnect at the meter (power being used to service well pump currently).

Thanks again.
 
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Old 03-18-16, 11:09 AM
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The tankless WH would only draw 15 amps so you should be fine on a 100 amp panel. You would need a 20 amp circuit for the tankless WH.
 
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Old 03-18-16, 12:12 PM
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Ok, you're good with 100A, but the cable I listed is not correct given you have a disconnect at the pole. You'll need to run a four wire service to the cabin instead of three (it's a subpanel instead of a main panel). The cable you'll need is a #2-2-4-6 or #2-2-2-6 aluminum USE. There are some other products that would work well like 100A aluminum mobile home feeder cable if your local supplier has that in stock.

The panel in the cabin will need to have the ground and neutral buses separated, usually by removing the bonding screw from the neutral bus and buying an add-on ground bar kit.

The cabin will need two 8 foot ground rods driven flush to the surface, spaced 6 feet apart. Put brass acorn clamps on the top of the rods and bond them back to the panel ground bar using bare #6 copper wire.
 
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