I'm looking to install a 100 Amp sub panel in my unfinished basement as the first step in completing my renovations on the lower level. The lower level is approximately 1000 sq ft (office, family/tv room, kids playroom and utility room). Here are a few key facts that might be useful to anyone choosing to help answer my questions:

- Main Panel is 200 Amps (panel and breakers are Murray)
- Run from main to sub panel would be around 35 feet
- I live in NY state (Westchester County to be specific)
- Continuous load sources would be furnace (oil), hot water heater, a wine fridge and drink fridge
- Sump pump exists for the downstairs bathroom
- Office will have two high-end graphic workstations each with 1000 watt power supplies and dual 24-inch monitor setup
- Family/TV room will server as multi-media room with home theater (LCD TV, receiver, blu-ray, Xbox 360, etc)
- Office will also have TV, blu-ray, laser printer and inkjet printer
- Utility room will also run some power tools (table saw, shop vac, etc)

I'm estimating current load (if everything were running at the same time) to be around 75 amps. I know that the changes of everything running at exactly the same time is rare but I've aggressively estimated the load to: 1) ensure that the panel can handle everything that I have to throw at it now or in the future and 2) incorporate any immediate overhead that I haven't anticipated in my planning. Given that -- I thought I would install a 100 amp double-breaker in my main (which has space) to feed the sub panel.

So here are my questions and forgive me if these are stupid or easily answered with a Google search. I've been reading a number of things but there are always some conflicting articles/advice.

1) What gauge wire should I be using to connect the main and the sub? I was thinking #4/3 AWG copper would satisfy the feeder requirement for 100 amps at 90C (running the cable from my main down to the basement panel

2) Does the feeder cable need to be installed in any type of conduit (metal/pvc) to run along the basement wall to the panel location or can it run through the ceiling joints like standard romex?

3) Any restrictions to mounting the sub panel in the wall as opposed to plywood backing on the concrete foundation wall? Advantages/Disadvantages to either approach? I was just thinking the in-wall mounting would be cleaner and I could easily hide it away with a picture frame and not have to go into utility room. I was also hoping to have it near my network panel which I plan to put in the wall as well in the office. Hence this question.

4) Any sub panel manufacturer recommendations?

Thanks in advance for any help.

Joe

My answers follow your questions:

1) What gauge wire should I be using to connect the main and the sub? I was thinking #4/3 AWG copper would satisfy the feeder requirement for 100 amps at 90C (running the cable from my main down to the basement panel

#4-3 plus ground is allowed for a 100 amp residential feeder.

The 90 Deg C column does not apply here.

2) Does the feeder cable need to be installed in any type of conduit (metal/pvc) to run along the basement wall to the panel location or can it run through the ceiling joints like standard romex?

The cable can be pulled through holes drilled in framing members, just use protective nail plates were the cable can be damaged by a piercing nail or screw.

3) Any restrictions to mounting the sub panel in the wall as opposed to plywood backing on the concrete foundation wall? Advantages/Disadvantages to either approach? I was just thinking the in-wall mounting would be cleaner and I could easily hide it away with a picture frame and not have to go into utility room. I was also hoping to have it near my network panel which I plan to put in the wall as well in the office. Hence this question.

A panel can be flush mounted, just leave some method of adding cables later.

4) Any sub panel manufacturer recommendations?

Any major brand is fine, GE, Square D, Siemens.

Thanks TKRussell.

If I choose to go the route of mounting the panel on plywood, is there a minimum thickness required? Also -- for the portion of the feeder cable that does not run through the floor joists, I'm assuming that needs to be placed in conduit of some sort going from the joists to the panel. Or can I just bring the feeder cable straight into the panel?

Thanks again.

We usually use 3/4" plywood, but 1/2" will work also.

No, the cable does not need to be in conduit where it drops down to the panel.

Awesome -- thanks again.

One additional question -- for flush mount sub panel installs -- are there minimum clearance requirements above or below the panel?