wiring/conduit question

[mound]

But be aware if you exceed 3 current carrying conductors you have to adjust the ampacity of the wire.  In the case of thwn #10 copper, initial value of 40 amps:   with 4-6 ccc = 80% -> 32 amps, no issue;  7-9 ccc =70% -> 28 amps, need to upsize your wire.

Indeed.. This is what's going to lead me to have to use multiple runs of conduit for everything else.. (I described the two 220v circuits on the one wall, but there will be other various sized circuits run elsewhere)

[srv52761]

side question, if it were you in your own garage shop, would you use metal or PVC conduit?

I used 3/4” metallic electrical tubing (emt) conduit.  I ruined a couple of sticks learning how to get the box offsets right.
1/2” is much easier to bend.
The bottom of my boxes are 49” from the floor, and all my tools and cabinets are on wheels so I sometimes will bump into the conduit when moving stuff.  I thought the emt could handle the abuse, especially in winter in my previously unheated shop; pvc gets brittle when cold.

Edit: another advantage of emt is you can forego the equipment ground conductor.  If you use 4" square boxes  and approved covers you can eliminate having to ground your receptacles also.  Saves time and makes the other connections in your box a little easier.

[aquaticjim]

Edit: another advantage of emt is you can forego the equipment ground conductor.  If you use 4" square boxes  and approved covers you can eliminate having to ground your receptacles also.  Saves time and makes the other connections in your box a little easier.

Make sure you check with the inspectors.  If EMT is not a normal wiring method in your area, the electrical inspector may not like the conduit as the ground.  I used EMT throughout the house here in Michigan and ran a green ground wire to outlets but not light circuits.  The inspector flagged that and required a separate ground wire.  His justification was that too often, the cheap connectors come loose and then you lose the ground.  This is not as reliable as rigid.

[mound]

Make sure you check with the inspectors.  If EMT is not a normal wiring method in your area, the electrical inspector may not like the conduit as the ground.  I used EMT throughout the house here in Michigan and ran a green ground wire to outlets but not light circuits.  The inspector flagged that and required a separate ground wire.  His justification was that too often, the cheap connectors come loose and then you lose the ground.  This is not as reliable as rigid.

Yah I don't think I'd trust the EMT as ground alone, can't see any reason why not to just run dedicated ground wire through it.

[TDKPE]

Yah I don't think I'd trust the EMT as ground alone, can't see any reason why not to just run dedicated ground wire through it.

I don’t much care for EMT as ground either.  Just be sure to run a grounding conductor sized to the highest ampacity circuit in the conduit.  If you have a 15A and a 50A, you only need a single ground, but sized to a 50A circuit (10-gauge copper in that case).

[mound]

I don’t much care for EMT as ground either.  Just be sure to run a grounding conductor sized to the highest ampacity circuit in the conduit.  If you have a 15A and a 50A, you only need a single ground, but sized to a 50A circuit (10-gauge copper in that case).

Thanks!

[mound]

This all got me thinking about a clean (visually) install.

I laid everything out on paper (not just the two 220v circuits from my original post but several other 110s, another 220 and lights)

I won't outline it all here, but I calculated that if I used 10g wire exclusively for all 20amp circuits (instead of 12), and used 6g wire to feed the 30amp electric heater (instead of 10g) , and used 1" EMC everywhere, I could do everything with just one piece of conduit exiting the service panel which would then lead to effectively a raceway up toward the ceiling, with drops around the perimeter.   The 1" gives me room to stay under 40% fill and using the higher gauges handles the 50% ampacity reduction which the NEC charts say I'd need given 10-20 conductors in one conduit. 

As long as I'm not overfilled and have adjusted ampacity according to the code, the plan is fine (though perhaps overkill!) right?

[EightFingers]

I’m sure you’ll enjoy hooking up that 10 and 6 gauge wire!

[bottd]

Thinking about connecting that 10 gauge wire to outlets - just asking - But pigtailing the outlets in with 12 gauge wire would be perfectly acceptable, right?

[srv52761]

Besides conduit fill, you also must have room for the wires in the boxes.

You didn't say specifically how many circuits so lets assume three 120 volt circuits and two 240, the minimum to hit your 10 ccc.  Then you said you will not be using the emt as the ground, but instead use a separate ground wire.  Then, running up high and having conduit drops to individual receptacles.
Upsizing the 20 amp circuits to 10 ga., and the 30 amp to #6.
Assuming you will use #12 to do the individual drop to the 20 amp circuits.
Assuming the 240s will not include the neutrals, (you mentioned running neutrals for future possible change, but if you are planning those 120s now, maybe you won't need to??)

In that first junction box, assume a 120 volt drop, you will have
 four #6 passing through for the 240 circuits
  One #6 ground spliced to another #6 to a continue the ground, a #12 to the drop, and a #6 to ground the box
   Four #10 passing through for the other two 120 volt circuits
   Two ccc #10  to be spliced to the drop
    Two #10 to continue that circuit to its next drop
   Two #12 for the drop   

Construction Monkey box fill calculator says you need at least a box with 61.8 cubic inches.  A 4 11/16" sq. X 2 1/8" clocks in at 42 sq.in.   An extension ring gets you to 80 sq. in., which would also be big enough for your 240 volt drops (assuming you used #10 or #8 for the individual drops).

If you're planning more circuits you could do one more 240  and no 120's or  two 120 volt (edit: and still fit in that 4 11/16 box +extension).
If you include 240 neutrals or more circuits, you are probably looking at special order enclosures.