Electrical – Outdoor Outlet switch for Heat Cable

1. What size conduit should I use? (I was thinking 3/4")

Since you're pulling more than 2 wires through the conduit, you're only going to be able to fill the conduit to 40%. Since you didn't specifically mention what type of conduit you're using, I'll list all metallic and PVC conduit.

• 3/4" Intermediate Metal Conduit (IMC) @40% = 0.235 in.²
• 3/4" Rigid Metal Conduit (RMC) @40% = 0.220 in.²
• 3/4" Schedule 80 PVC @40% = 0.164 in.²
• 3/4" Schedule 40 PVC @40% = 0.203 in.²

I'll assume you're using THHN/THWN/THWN-2 conductors, so you'll need to know the area of these conductors in the various sizes.

• 12 AWG = 0.0133 in.²
• 8 AWG = 0.0366 in.²

To figure out if the conductors will fit, you just have to add them up.

3 #8 x 0.0366 in.² = 0.1098 in²
3 #12 x 0.0133 in.² = 0.0399 in.²
0.1098 in.² + 0.0399 in.² = 0.1497 in.²

You end up with a conductor fill value of 0.1497 in.², which means you'll be able to use 3/4" conduit no matter what type you choose.

^{NOTES: For a look at some of the tables where these numbers came from, see this answer.}

2. Can I snake all wires for the AC and outlet in one conduit (2 conductor 1 ground for ac [8awg] / 1 conductor 1 neutral 1 ground for outlet [12awg]) - not sure the fill on this size

No problem, see above.

3. When I stub up, I need to wrap around the foundation a little bit; any issue going above a hose spigot?

Shouldn't be a problem.

4. Am I crazy for using rigid metal conduit? A lot of people I know say just go 'as deep as I can' and use PVC. But that's against code and even though this won't be inspected I try to stick to code as much as possible

You can use metallic conduit if you want, but it will likely be cheaper to use PVC (even though you'll have to dig deeper).

I think you may be confusing PVC pipe (used for plumbing), and PVC conduit (used for electrical). There's no problem at all with using PVC conduit, unless there's a local amendment that restricts its use. However, you'll only have to bury metallic conduit 6" deep, whereas PVC will have to be 18" deep. So if you don't like digging, metallic conduit might be worth the extra cost.

You have not stated any reason that would appear to prevent the obvious solution (if you consider it a problem at all) of running the network wiring along the face of the wall at the same level as the server rack, or roughly 12" below the power conduit. If the basement/crawlspace floods enough to flood the server rack you probably should rethink the location of the server rack, and in any case the cables being run horizontally higher up won't help a bit in that case.

You could also move the cables far enough forward into the room (3-4 feet, say) that they don't encroach on your shelving unit, then run them back along the joist (it's holding up a floor above if it's a crawlspace, so rafter is not the right term - those have a roof above them) to the server rack.

Despite a number of "trying to be perfectionist" scare stories about needing to keep network and power cables well-separated, the fact is that the differential pairs in Cat5 (or 6, or 7) are designed to reject interference, and that the frequency domains of networking signals and power line noise are utterly different. So, in practical terms you can wire tie (just not too tight - sharp bends are bad) the network wires to the power conduit and not have any interference problems in a typical home application.

Coaxial cable is self-sheilded by design and thus also highly unlikely to pick up any objectionable interference simply by being run next to power or network wires.

Since all you are really considering is running them parallel at a few inches distance, you will be fine doing that (do avoid a sharp bend anywhere, particularly where you turn downwards and might be tempted to yank the wire tight around the J-hook.)

While I do generally try to maintain the oft-suggested 12" separation for parallel runs when designing from the ground up, I have hundreds of feet of Cat5e that is in close proximity to power wiring in old building retrofits, and connected to switches that report error rates - and those error rates are pretty much always zero, unless there is a more fundamental problem with the cable (like rats chewing on it, a sharp kink/bend, or a bad connection at the end of it.)