Which Size Subpanel?

[exranger06]

Hi guys. I just moved into a new house with a 2 car attached garage, and the electrical needs some serious upgrades. There are only 2 outlets in the whole garage, and one of them is on the ceiling for the garage door opener. The other is on the wall opposite the garage door. Anyway, I need way more outlets than that to plug in my tools. I plan on adding about 8-10 outlets, probably 4 on each side wall of the garage, and maybe two more on the front wall. I was planning on putting them all on a single 20 amp circuit. I was planning on leaving the existing outlets alone and leaving them on whatever circuit they're already on, and have just the new outlets on a new circuit.

I also want to add three 240V outlets, each on their own circuit: a 30 amp for an air compressor, and two 50 amps for a welder and electric heater. I was going to mount an outlet on the middle of each side wall, so I can plug in a welder on either side for convenience, and maybe plug in an electric heater into one of them during the winter, so they might be both used at the same time.

I was going to just add some breakers to my main panel and run the wires into the garage (there is plenty of space on the main panel to add more breakers, and it's 200 amp) but after some thinking, I think a subpanel might be better and easier. The subpanel would only be about 6 feet or so from the main panel. The main panel is in the finished basement, so it would be easiest to use a knockout on the backside of the main panel and run conduit on the outside of the house. Then go through the wall into the garage, and have the subpanel in the garage.

So, should I install a subpanel for this, and if so, which size? 60 amp? 100 amp?

 

[Mustang51js]

Get some 2-2-2-4 al ser cable,hook that up to a 70 or 75 amp breaker if you can find it. I would do two separate 20 amp circuits for the outlets and not have them all on one.

 

[wyliesdiesels]

on #2 ser al. However, if it wont be buried in insulation then it can be protected with a 90a breaker.

Subpanel is a better idea!

 

[pattenp]

Go with a 100A sub-panel and use up to a 90A feeding breaker in the main panel if using 2-2-2-4 Al SER.

 

[exranger06]

Can I run 2-2-2-4 Al SER in conduit? I thought I read that it shouldn't be ran through conduit. If not, can it be ran bare along the side of the house? It will be about 2 feet above grade, running horizontally for about 6 feet.

 

[pattenp]

You can put SER in conduit, just be mindful of conduit fill. SER can also go bare if in a location not subject to damage. Your run sounds to be better in conduit.

 

[Sokoloff]

When installing the 2 50A circuits, consider using a 14-50R receptacle and wire it for a full 50A, and building a whip for (or changing the plug on) your welder, especially if the runs are going to be buried in a finished wall.

That lets you use a welder at full duty cycle (not that big a deal), but also sets you up for an electric car charger without any rewiring.

Costs you a little more in wire today; may save you a lot of aggravation later.