Ask Me Help Desk - Adding Subpanel to Barn

I'm fixing up a loft above my barn and adding electrical service.
The main panel in my house in 200 amp. I was going to add a 80 amp
Sunpanel in the interior of the barn, drawing off the 200 amp main panel
In the basement of our house. I plan on using an 80 amp double pole breaker
In the main panel, then run the wire to the barn. It's about a 50 ft run in the
Basement, plus another 10 foot from the corner of the house to the barn, so
For 80 amps I was going to run 2/3 romex or 2 ga. Thh (probably the #2 ga. Is
Overkill but the length of the run has me leaning towards using it).
A couple of questions I have:

* My main panel in the basement has plenty of open slots - but they are located
Towards the bottom of the panel - since I'm going to be sucking out 80 amps,
Should I move the currently installed breakers down a few slots and put the
New 80 amp dp breaker up top so the 80 amps doesn't have to travel the
Length of the bus in the main panel (which it would if I just install it at the bottom
Open slot), or does the internal copper bus in the main panel have so much
Ampacity that this is a ridiculous question?

* For the 10-15 feet between the barn and the corner of the house - I can either
A) bury the cable or B) create a boxed in 'umbilical cord' from house corner
To barn where I can run the cable. Which is better?
If I bury it, I'd probably run regular 2/3 romex in basement, then connect it to 2/3 Undergound feeder for the final 10 ft jump to the barn since UF is too stiff and probably costs more to do the whole basement run in - if I do this approach, are there wire nuts I can use to splice together the 2/3 UF and 2/3 romex in a large junct box, or for this size wire do I need some special screw down terminal block? If so what's it called and
Does it mount in a special junction box?
Also, if I bury it, how deep do I have to go? (I live in northeast do I have to go below
Frost line or is that requirement just for water lines, etc).
One more - If I bury it I understand I can't use sheathed UF in a conduit for heat
Concerns - if I just use UF do I simply plop it in the ditch or do I at least put a piece
Of press treated plywood over top of it so some pour soul doesn't stick it with a pick
Axe 20 years from now

Thanks in advance for your answers.

Quote:

Originally Posted by grjack

A couple of questions I have:

* My main panel in the basement has plenty of open slots - but they are located
towards the bottom of the panel - since I'm going to be sucking out 80 amps,
should I move the currently installed breakers down a few slots and put the
new 80 amp dp breaker up top so the 80 amps doesn't have to travel the
length of the bus in the main panel (which it would if I just install it at the bottom
open slot), or does the internal copper bus in the main panel have so much
ampacity that this is a ridiculous question?

The length of the bus bar is negligible compared to the lengths of wire and connection current flows through, and the panel interior is much beefier to handle the loads. Loose fitting breakers are the problem.

Quote:

Originally Posted by grjack

* For the 10-15 feet between the barn and the corner of the house - I can either
A) bury the cable or B) create a boxed in 'umbilical cord' from house corner
to barn where I can run the cable. Which is better?
If I bury it, I'd probably run regular 2/3 romex in basement, then connect it to 2/3 Undergound feeder for the final 10 ft jump to the barn since UF is too stiff and probably costs more to do the whole basement run in - if I do this approach, are there wire nuts I can use to splice together the 2/3 UF and 2/3 romex in a large junct box, or for this size wire do I need some special screw down terminal block? if so what's it called and
does it mount in a special junction box?

Bury the cable, see more detail below.
The junction box should be no smaller than 12" x 12" x 6" deep.
For connectors you can use a split bolt "bug" as shown in picture, but these require two layers of good tape done well.

This connectorhttp://www.nsipolaris.com/pdf/polaris.pdf Is much better ,because it is already insulated.

Quote:

Originally Posted by grjack

Also, if I bury it, how deep do I have to go? (I live in northeast do i have to go below
frost line or is that requirement just for water lines, etc).
one more - If I bury it I understand I can't use sheathed UF in a conduit for heat
concerns - if I just use UF do i simply plop it in the ditch or do I at least put a piece
of press treated plywood over top of it so some pour soul doesn't stick it with a pick
axe 20 years from now

Bury the UF cable 18" deep, use dead sand if the soil is rocky, 12 " if you cover with concrete, wood does not suffice, but nothing wrong with it at 18" deep. you can put a warning tape buried above the cable, at 6-12" deep.

Thanks a lot for your reply. One thing - I'm having a hard time
Finding 2/3 UF - most electrical supply places here in CT
Only have down to 6/3 UF - not big enough for the 80 amps
I need to draw. I guess I could go with #2 THH instead- but then
I have to run conduit which is 1) more work and 2) my gut feel
Is eventually all conduit will leak at some time - how safe is
THH in a sch-40 pvc conduit?

THWN or XHHW is perfectly safe in buried conduit.

Tk -

One last question. If I go with separate conductor THW - I'm going to use
#2 ga. For both hots, but I understand the neutral and ground can be a thinner
Gauge - do you know what gauge neutral and grd I would need to match up with
#2 gauge hots (pulling 80 amps - i.e. one 80amp double pole breaker - each hot
Hooked up to one of the poles)

Use #8 copper for the equipment ground.

Disregard reducing the neutral, calcualtions must be done, not worth doing to go down one size wire.

You are already using #2 copper, when you only need #4.

If you want to save some money, pull 3-#4 and 1-#8.

I know- the gauge may be overkill - the charts I'm looking at, to avoid
A voltage drop are between a #4 and a #2 - I'm running about 70-80 feet total
From main panel to subpanel - that's why I'm thinking #2 based on distance -
Do you think #4 is sufficient for this length.