need some electrical advice

[mathey]

OK, in the process of running electric to a pole barn. Have the line trenched and 2/2/2/4 AL wire from trench to a junction box in basement.

Was going to run 2/2/2/4 grey sheathed wire in basement to load center in my MIL's portion of the house (its the closest to the barn). We are actually two houses joined together...so we have 3 panels in our house, 2 on our side and hers is a subpanel off of ours...Her panel is filled, so I figured I would use some tandem breakers to free up enough room for a 60 amp breaker for the barn. Turns out the Square-D panel she has won't accept tandems.

so now i'm in a quandry...

- I can run the 2/2/2/4 sheathed wire over to my panel adding another 78 feet to the run, bring the total distance breaker-to-breaker at 250ft. I've read that the max voltage drop is either 2, 3, 4, or 5%. Depneding on which online vltage drop calculator you use, the drop would be between 2 and 4.5%...Is voltage drop only a concern when you are using all 60 amps at a given time? I'm only planning to have 2-20a breakers in the barn for lights and such, the only thing that would be on a lot is the fan in the summer and the trough heater in the winter, and they would most likely have a dedicated circuit for them.

- Add a small subpanel off of the MIL's panel to house a few breakers.

- Is there anyway to "piggyback" onto her subpanel without using a breaker there...the only 60a breaker would be at the barn.

thanks for any input...right now i'm at a standstill!

*UPDATE* I went to the panel on my side of the house...there were 2 tandem breakers that were spares...they had been tweaked to fit any panel by the electrician who did the house originally...what are the risks of using them in my MIL's panel, since they will fit?

 

[beenthere]

How about a whole new panel in your MIL's house? Then put in the things you need to cover all the bases?
It's a sub-panel so you can kill it without messing with the meter, I presume.
I realize that changing out a whole panel isn't always a picnic either, and that may be your limitation.

 

[BobReeves]

All I can do is tell you what I would do in your situtation.

IF the ML's panel has a large enough feed I would throw in a sub panel for the breaker to the barn.

 

[_RaT_]

Its really hard to understand these things sometimes without seeing them first hand. I would think that upgrading the MIL panel would be a consideration, (sub panels are inexpensive) but I don't know what size wire you have feeding it. Your barn will not have much voltage drop with the load you describe, your already oversized on the wire since #4 ALU can handle a 60 amp breaker if memory serves me right. Modified breakers can be a problem in the event of a fire with the insurance company. Square D was once my pick but I have moved on to less expensive yet equally built panels. Hope you get it figured out, post more questions if you can, pictures always work well too.