I'm running electric in a house for central air and here's my situation: 2 air handlers in the attic, 2 compressors outside. I want to make sure my work is to code.

I know I need separate dedicated branch circuits for each of the 4 appliances.

1) For the air handlers, do I need to run 12/2 on 20A breakers or can I run 14/2 on 15A breakers?
2) In the attic, how should I wire the disconnects (power switch to a switched outlet, or power switch to a metal box where BX will connect?
3) Any requirements on the distance from the appliances?
4) What gauge wire/what size breaker for the outside 220 runs for the compressors (is 10/3 on a 30A to code)?
5) Is conduit reqired for the outside 220 runs?

Thanks.

1) I don't know. What are the specs of the units?

2) "power switch to a metal box where BX will connect"

3) Near by is a safe bet. Make sure you have a convenience receptacle in the attic and outside not too far from the units.

4) I don't know. What are the specs of the units?

5) Typically we run liquidtite flexible conduit, or sealtite, from the disconnects to the units.

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I know I need separate dedicated branch circuits for each of the 4 appliances.

1) For the air handlers, do I need to run 12/2 on 20A breakers or can I run 14/2 on 15A breakers?

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You can always run 12 AWG and use either a 15 A or 20 A breaker as required.
Try to have a convenience outlet nearby for servicing.

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2) In the attic, how should I wire the disconnects (power switch to a switched outlet, or power switch to a metal box where BX will connect?

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You could use the same Liquid tite that you will need outside. Use a red labeled switchplate that clearly labels it as a disconnect. Make sure the switch is not mounted to the unit. BX is fine too.
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3) Any requirements on the distance from the appliances?

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I believe there is, but I can't pin down the distance.

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4) What gauge wire/what size breaker for the outside 220 runs for the compressors (is 10/3 on a 30A to code)?

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There is no 220 is residential anymore. It's 240. 10 AWG should be OK, however one really needs to know Full Load Amps and distance of wire run to size properly.

There are disconnects available that have a GFCI convience outlet for service technicians. The outlet requires a separate circuit.

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5) Is conduit required for the outside 220 runs?

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Use flexible Liquid Tite for the connection from the disconnect to the unit. It is actually a wet location, so generally yes. Cables run outside need to be UV and wet rated, for instance if they were direct buried. Conduit needs to be approved for wet locations and THWN wire should be used.

Thanks.

Thanks for the replies. Much appreciated.