I did a search and found some info but I'm still not sure on what I need to do. I have an upstairs bonus room that I am finishing off. There currently is one 20 Amp circuit to run the lights and outlets, 14/2, which I think is sufficient and not a problem. I'm going to be turning this into a theater room so I want to run another circuit for all my A/V equipment - projector, DVD, receiver, etc. as well as any multiplexers I may need to power for satellite signal splitting. In addition to adding a circuit for the equipment, I'm going to install a mini-split heat/air unit for the room so I need to wire for that as well. I currently have a 200 amp panel supplying the house with 3 open slots for breakers.
The question is, would it be a good idea to install an additional 100 Amp panel off the 200 Amp panel or just work with the 200 Amp panel I have now? (That may be tough with only 3 open slots) If I add another panel they would be within 10' of each other.

As a review:
1. An additional circuit for A/V equipment - planning on 12/2 (110V)
2. An additional circuit for a mini-split (12K BTU - 18K BTU) - planning on 8/3 (220V).
I'll need 110V for the mini-split as well, can I just tie into the already existing 20 Amp circuit running the outlets and lights?
3. Would it be best to install an additional 100 Amp panel to run the bonus room? If so, what size wire would I need to run from the main panel to the sub-panel and would 100 Amp be sufficient? If I install a sub-panel, I plan on moving the current/existing 20 Amp breaker to the new sub-panel.
4. Any tips on adding a sub-panel?

Thanks.

The existing 200 amp panel may be able to take tandem breakers, most brands offer a breaker that allows two breakers to take the place of one slot.

Installing a 100 amp feeder, using #2- 4 wire SER cable to a sub panel located in or near the room is a good idea.

A 100 amp panel seems to more than sufficient.

Thanks for the reply.
Both panels will be next to each other but they are both roughly 50 feet from the bonus room, is that a concern?
It is my understanding that the meter has to be pulled in order to wire in the sub-panel, is that correct?

If all it is 50 feet then the sub can go next to the main. No don't need to pull the meter,all you need to do is plug in a new 2 pole 100 amp circuit breaker in the main panel that will feed the new panel. Now if you may want to shut off the main breaker to plug in the new breaker so as to be safe, otherwise you will be very close to the live busbar.

In your original post you said:

"There currently is one 20 Amp circuit to run the lights and outlets, 14/2, which I think is sufficient and not a problem."

If the wire is 14-2, it should be on a 15 amp breaker.

Dlynch, I tried the comments but had to spread the reputation.

Good catch on the #14-2 on the 20 amp breaker.

You are absoulutley correct, #14 wire cannot be connected to a breaker larger than 15 amp.

Great info guys, thanks for the input. I wasn't aware of the breaker size requirement in relation to the wire gauge, so I'll swap out the 20 Amp for a 15 Amp.
What is it for 12/2?
What about the 8/3 I'm going to run for my mini-split?

tkrussell
I wasn't sure what you meant by a 100 Amp feeder, but since you clarified that in your last post I think I know how I can get this done. Is that #2-4 wire going to fit on that breaker okay? What is #2-4 wire SER, is that copper or alum?
Hope I'm not redundant on my questions.
Thanks again.

#12-2 Romex cable can take a maximum of 20 amp breaker

#8-3 Romex cable can take a maximum of 40 amp breaker

#2-4 SER cable is rated for 100 amps, and is aluminum, and #2 wire will fit into a 100 amp breaker.

Be sure to under stand how to terminate aluminum wire properly, by wire brushing the stripped conductors , applying anti-oxidant compound, and properly torquing the connection.

Tkrussel,

Any recommendations on type of breaker and panel? Square D is readily available, but how is their quality?
If I can run it inside the wall, is the #2 alum required to be in conduit when I install it? I may have to run it on the outside of the wall due to the main panel being too close to a corner and I can't mount the panels next to each other. I'm guessing there is a code for the height of the panel so mounting it below the main panel would be out?

Thanks

Square D is a very good quality, both The QO series and the Homeline series.

The #2 cable is SER type, does not need conduit, and can be installed outdoors, as it is rated for wet locations and is sunlight resistant. Just need to sleeve it in conduit or install in such a fashion to protect it from physical damage.

The height requirement is not to mount it higher than 6.5 feet so the top switch can be reached, There is no minimum height, but here is where common sense is needed. Don't mount down near the floor where it can get wet or damaged.

Everything is going to be on the inside of my garage so the weather is a non-issue. I figure if I mount it underneath the main panel, the bottom of the sub-panel will be roughly 2' of the ground. If I mount it underneath, it'll be a straight shot from the main to the sub which would be easiest. If I mount it on the wall next to the main, which is perpendicular to the wall the main is on, I'll need to run it in conduit on the outside of the wall as I can't get it through the 2x4's in the corner. I can drill through the studs in the wall, but there's too many of them in the corner and it's also a load bearing wall.
I may be leaning toward mounting it underneath at this point.
Thanks for all the info.

Underneath with 2 foot above the floor is fine.

It's been a while since I added to this post, but I'm just now to the point where I need to get this panel installed. I pulled the drywall off all around the main panel and it doesn't look good. Too many wires going into and out of the panel on the bottom and on the top, so it doesn't look like I'll be able to install the sub panel underneath.
tkrussel, you mentioned that I can install this close to the room which is now my best option. I'll run the SER from the main panel to the subpanel, which should be around 40' or so.
I'd like to keep the panel out of my room so do I just mount it in the attic (with access) on a 2x4?
Can I just lay the SER on top of the insulation going from the main to the sub? There really are no studs to attach it to.
Should I run the SER in smurf tube or does that matter?
Thanks.

Installing the subpanel in the attic is fine, as long as it is readily accessible, that means you hava a stairway , even a pulldown, to get into the attic. If a ladder is needed, then no go.

The SER can lay on the insulation, as long as it cannot be walked on or have anything stored on it. You don't need smurf tube, this is not practical.

Why not just frame out a space in a wall in the room to recess the panel, and fashion a small door similar to a cabinet door to cover it?

It has to be 6.5' off the floor correct? My walls are pretty much half walls with the ceiling following the rafters. The walls are maybe 4.5' high.

My mistake, it can't be any higher than 6.5'. This could be an option then.

I mounted the panel in the room and I'm planning on having an oak door over it so it looks decent. To ensure I've got this right;
I need 2-2-2-4 SER? I've only got three screws in the subpanel, where does the fourth wire go?
I need to disconnect the neutral bar from the ground and the panel box, correct?
I need to add an equipment ground bar, but keep it isolated? Any help here is appreciated.
I need to brush the wire, coat it with an antioxidant and torque the screws. Any particular type of brush? What is the torque spec?

I don't think this will be too hard to get finished, I just need some guidance.
Thanks.

No disconnect the neutral bar from any equipment ground and the panel metal box.
#2-2-2-4 Al SER cable is perfect.

The neutral is to be insulated and isolated.

The equipment bar is to be bolted directly to the metal box using machine screws through threaded holes.

Any wire brush will do.

Look on the panel label for torquing values of the main lugs, look on breakers for a torquing value label. And/or the instructions that accompany any electrical equipment.

Here is an aluminum wire manufacturers instructions for terminations.

Wiring this sub panel in the fashion we're talking about will get me 220V into the room correct?

As long as you use a two pole breaker at the main panel