04:37PM | 10/23/05
Member Since: 10/17/05
21 lifetime posts
I want to run a 6 gallon spacesaver water heater (20 amp circuit), about 15 lights, maybe 4 electrical outlets, and an oil radiant heater - in a small barn. I will be running an underground wire from our house to the barn - 1 feet. The barn will have its own grounding rod and breaker box. How can I calculate / or how many amps do I need leaving off the house breaker for this project, and what size wire would be best to run underground?

Thank for your help


04:39PM | 10/23/05
Member Since: 10/17/05
21 lifetime posts
The barn is 180 feet from the house.


06:55AM | 10/24/05
Member Since: 03/31/05
265 lifetime posts
As was specified before, use #6 wire and a 40 or 50A breaker. If the existing 10/3 wire you found is type UF or is THWN in conduit, then 30A is the max you can use. That may not be enough.


04:58AM | 10/26/05
Member Since: 04/25/05
1915 lifetime posts
At that distance you are limited to about 16 amps at 240 and maintain 3% voltage drop.

Or with #6, 40 amps.

But you really need to look at what you max load really is.

What size lights?

What size and how many electric heaters?

What will be operated from the recetpacels and in what combination.


02:46PM | 10/30/05
Member Since: 10/17/05
21 lifetime posts
- a 12 gallon water heater (1500 W)

- a portable radiant oil heater that plugs into a 110V outlet...

- maybe 6 outlet boxes, only one used at a time

- a total of 16 interior lights (13 W fluorescent)

- 2 outdoor 300W halogen lights

- 1 outdoor 13 W fluorescent light

That's it...


07:12PM | 10/30/05
Member Since: 04/25/05
1915 lifetime posts
I assumed that the space heater was 20 amps and likewise the one receptacle in use, but both are probably less.

That comes up to about 7200 watts or 30 amps at 240.

Just keep the loads balanced.

One one leg the WH and receptacles

The other leg the heater and lights.

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