Should be fine. The #8 will now be derated to 44A and the #6 will derate to 60A. Disregard if the conduit is < 2 feet long.

Also the 2 grounds are redundant. One will do.

For <=60A wire, #10 ground will suffice unless the reason you are using larger wire is voltage drop for long distance. Anytime you upsize the conductors for voltage drop, you must upsize the ground in proportion.

 

For <=60A wire, #10 ground will suffice unless the reason you are using larger wire is voltage drop for long distance. Anytime you upsize the conductors for voltage drop, you must upsize the ground in proportion.

The voltage drop requirement in the NEC was changed recently.
Now all oversize conductor's grounds are required to be upsized, regardless of the reason.

 

Can I run the following wires through 3/4" EMT?
2 #6 THHN, for an EVSE;
2 #12 THHN for a GFCI receptacle;
4 #14 THHN for a 3-way light switch?
This list includes a neutral for each of the two 120V circuits.

 

Can I run the following wires through 3/4" EMT?
2 #6 THHN, for an EVSE;
2 #12 THHN for a GFCI receptacle;
4 #14 THHN for a 3-way light switch?
This list includes a neutral for each of the two 120V circuits.

There is a conduit fill rule but there is also a max number of CCC (Current Carrying Conductors) per conduit (regardless of conduit size) before you have to derate.

Look up this past thread for some relevant discussions.

Conduit fill and current carrying conductors

There is another ongoing thread about CCC and derating but I don't want to hijack that thread for my situation. I basically would like someone to set me straight on these rules. I have an existing 3/4" EMT conduit between junction box A and junction box B. A to B is 25 feet apart. How many...

www.diychatroom.com

 

I would run a ground because I have seen to many conduits split apart over the years.
only need one for the largest load. I never run conduit with out a ground.
I do not understand the 4 wires for the 3 way switch. Does your local AHJ enforce the newest code where neutrals are required in switches?

My answer is no, not enough room. No mention of distance and how many degrees of bends.

 

One ten-foot run with two 90° bends (no junctions there), and steel LB conduit bodies at each end.

I know the neutral in the switch box is not needed for functionality, but doesn't code require it now? On the other hand, I doubt my AHJ would enforce it.

 

Back to my original post …

I’m contemplating adding the 2 #6 thhn conductors to an existing 3/4” conduit that already has the wires for a 30 amp HVAC condenser unit (and upsize the existing ground to #8). To do this does it make sense to use the old ground wire to pull the 3 new wires through? Or is it better to pull all existing wire out, leaving a pull string and pull the new bundle back through? Or, something else …?

It sounds like this may be feasible. Before continuing, I need to confirm that the conduit runs the entire way between my panel and the disconnect for the AC condenser. Assuming the conduit exists on both ends, what’s the best way to confirm the conduit runs the entire 50’? It’s a pretty straight shot from the panel to the disconnect. I thought of maybe disconnecting the ground wire from the panel (leaving it fastened at the condenser disconnect) and checking continuity between the ground wire and the panel where the conduit attaches. Would that work or is there a simpler way?

 

Are you saying there is metal flex conduit run underground? Your first post speaks of flex metal conduit then in the previous post you mention conduit--confused.

I also agree one #10 equipment grounding conductor is all that is needed for both circuits.

 

Sorry. Yes flexible metal conduit. Not underground. In wall about a 50’ run. However upon further inspection, I don’t think I can use it. In fact this has me puzzled. At the panel, coming off the 30 amp breakers I see the two (what appear to be #8 or larger) hot wires (red arrow) and a bare ground (blue arrow) exiting the panel into a 3/4” fitting. Oddly, there appears to be a romex cable (yellow arrow) exiting through the same fitting.

At the other end (the condenser disconnect), it’s just the two large wires and the ground.

What am I looking at here?

 

open the junction box below the offset nipple and see what's there.

 

Just the two wires plus ground. Still wondering what happened to the romex??? Must be an intermediate jbox somewhere along the line where they separated?

 

You would have a heck of a time pulling all those wires thru flex unless it was laid out flat.

 

But the Code requires that the conduit is fully installed before the wire is pulled.

 

you are looking at the romex coming in from the rear junction box. I think I see sheathing of the romex back there. The bare copper is from a romex.

 

Good eye. It appears that the AC guys used some kind of sheathed cabling. You can see it better in this pic.

The black sheathing is not as thick as typical romex. But at the panel end there was a regular white romex cable with much smaller gauge wires going out through the same fitting as the AC wires. There’s no sign of that in this box. Too many questions.

Bottom line I’ve decided not to try to utilize this conduit for the new circuit. I’ll just run new EMT under the eaves and save myself a lot of headaches.

 

Well, if that's my only problem, a smaller breaker would be fine. This circuit is for only 4 or 5 LED ceiling fixtures. I'll have to check if QO breakers are made for less than 15A.

 

Just ran the conduit fill calculator provided by Southwire and got these results. No mention of temperature derating.

 

Add a Greenfield 90 to the equation and you cannot comply with the rule.

 

Good point. Fixed. @A Little Short