Multiple Circuits Through Conduit?

[harborremodel]

Hello All,

I'm wiring up my garage for a hobby woodshop but i have a few questions that I'm hoping you all can help answer.

1. I'm planning 4 20amp circuits leaving the sub panel. Before the circuits split at a junction box is it ok to run all 4 12/2 cables in the same 3/4 conduit?

2. I have a 200 amp main panel and i want to to a 100 or 125 amp sub panel. Most of the current main panel is full except for 2 slots. If I install the 100/125 amp sub panel is that ok? My father in law was telling me that he thinks since my main panel is mostly full that i couldn't run a sub panel because all "200 amps are used up" but i don't think it works that way. Am I correct here?

 

[JoeD]

I don't think you will fit 4 12/2 cables into a 3/4 conduit.

You are correct it doesn't work that way. You don't add the breakers. You need to do a load calculation to see if it is overloaded.

 

[Sparky617]

I don't think you will fit 4 12/2 cables into a 3/4 conduit.

You are correct it doesn't work that way. You don't add the breakers. You need to do a load calculation to see if it is overloaded.

You also don't want to run Romex in the conduit. Your main may be able to handle the sub. Running a load calculation isn't just adding up all the breakers. Unless you're Clark Griswold and running a gazillion Christmas lights you are probably never going to have 15 amps being drawn on every 15 amp circuit, while your water heater and air conditioner and fridge are all running.

 

[Snoonyb]

Is there a sub panel now or is it your intent to install the sub panel for the garage workshop?

A load test can be both mathematical and mechanical. I prefer the "every light in the house is on" method.

 

[afjes_2016]

Hello All,

I'm wiring up my garage for a hobby woodshop but i have a few questions that I'm hoping you all can help answer.

1. I'm planning 4 20amp circuits leaving the sub panel. Before the circuits split at a junction box is it ok to run all 4 12/2 cables in the same 3/4 conduit?

2. I have a 200 amp main panel and i want to to a 100 or 125 amp sub panel. Most of the current main panel is full except for 2 slots. If I install the 100/125 amp sub panel is that ok? My father in law was telling me that he thinks since my main panel is mostly full that i couldn't run a sub panel because all "200 amps are used up" but i don't think it works that way. Am I correct here?

Several issues: Some of which have been addressed already.

#1 - Again, just adding up the total breakers (amps) in the main panel does not correlate to the total amps being used in that panel. Normally an electrician would do a simple "load calculation" to determine what the average demand is on the main panel (panel in question) as to the remaining ability of the panel.

#2 - "Garage" - you have not stated, which is very very important if this garage is detached or attached. If detached and you are running any electrical line to it from another building (such as from you home panel), you may have ONLY ONE circuit to that structure (garage). Therefore best to run a larger single UF (if going underground) to the garage and then installing a sub-panel in the garage. Also, even if the garage is attached and your initial run from the starting panel to the garage is the 4 circuits, better to run from the starting panel to the point where the 4 circuits would terminate and then split a separate individual larger SER to a sub panel in the garage and then split your circuits from there.

#3 - Although multiple circuits are permitted in an individual conduit there is a limit to the number of conductors allowed depending on the size of the conductors you are running compared to the size/type of conduit you plan on utilizing. Again, good luck attempting to run 4 romex 12 in a conduit. Even with a lot of "pull lube" you will end up hating yourself.

I think a bit more of what you plan to do or are attempting to do, as in what you want to run from the cirucits in the way of devices; lights, receptacles, any compressors etc would allow us to advise you better.

A clear picture of the panel you would be starting from. A brand name of the panel etc would be helpful if it is not clear to us with just the picture. Be sure in the pictures you have a clear view of the panel door open (not the cover removed at this point). We need to see the breakers etc that are presently in there. Although a list of what each breaker controls is helpful if one is on it unfortunately the lists are not always very accurate or outdated.

Again, more information you can give us the better we can assist you.

 

[Kabris]

If using conduit you must use individual conductors (THHN or THWN). I think it's illegal to pull Romex through conduit, and if you could it won't pull easy at all. Stranded (not solid) individual conductors are much easier to pull. At the junction box you can switch to Romex assuming the junction box is in the garage.

 

[harborremodel]

1. This is in an attached garage.

2. Pic of the main panel attached. It's a siemmens 200amp panel. I'm going to run a 100amp breaker from the main panel.

3. The sub panel i purchased is Square D 125 amp though i'm only going to run 100amps to it. Here's a link to the panel from home depot http://www.homedepot.com/p/Square-D-Homeline-125-Amp-12-Space-24-Circuit-Indoor-Main-Plug-On-Neutral-Lug-Load-Center-with-Cover-Value-Pack-HOM1224L125PGCVP/204836334

4. Basically i have a woodshop that I'll be running a dust collector and various woodworking machines. I don't expect to ever have much of a large load at any given time.

5. The largest load circuit is a 50amp circuit i want to run for a dedicated mig welding plug.

6. I've attached a rough wiring plan but basically there would be a short run of a few feet before the various circuits would split at a junction box and the conduit would only have one circuit going through it. If I shouldn't run romex should i just get standard 12g and run them?

7. My other question is how do i cleanly "exit" the circuits that start inside the flush mount sub panel out to the externally mounted conduit? I attached a pic of the current main panel and the space to the right of it is where the sub panel will go. You can see how the panel will be mounted flush in the drywall area but then has to exit to run along the masonry walls.

 

[Kabris]

That's a tough one. I have a flush mount main too and want to run conduit in the future. I suppose you could come out of the top of the panel with a straight pipe, use a pulling 90 fitting, and mount a surface mount junction box above the panel. From there you could start your conduit run and pull straight to your panel without making extra splices. I'm not sure if it's legal to bury that fitting though.

 

[Kabris]

To do this you'd need to cut your opening a bit higher to get your short pipe with fitting in, and then patch

 

[harborremodel]

I think what i'm going to end up doing is surface mounting the sub and bringing the feedwires from the main in through the back of the panel. From the surface mounted sub i'll then run the surface mount conduit. I liked to idea of a flush mount but in the end keeping it simple and clean is what i'm really after.

 

[Snoonyb]

I think what i'm going to end up doing is surface mounting the sub and bringing the feedwires from the main in through the back of the panel. From the surface mounted sub i'll then run the surface mount conduit. I liked to idea of a flush mount but in the end keeping it simple and clean is what i'm really after.

Good choice, and allows you to easily and definitively separate your 240V from the 120V.

In the separation of your 120V circuits be cognizant of which buss-bar the circuit breakers are originating from, to avoid an unintentional 240V.