i need to install a 200 amp sub breaker box. what size wire do i need to use from my main and what size brkr?

Question

THE ADDED ROOM WILL CONTAIN 14 110 RECEPT USING 7 BREAKERS. IT WILL ALSO HAVE 5 CELING FANS WITH SEP BREAKERS AND 3 220 VOLT REC.. CURRENTLY THERE IS A 220 VOLT REC GOING TO THE ROOM. IT IS WIRED WITH 12/3. I AMGOING TO USE THIS WIRE TO INSTALL MY NEW WIRE FROM MY OUTSIDE BREAKER BOX .IT IS 12/3 RUN IN EMT. WHAT SIZE SHOULD I CHANGE THIS WIRE TO AND WHAT SIZE CONDUIT SHOULD MY NEW WIRE BE IN? I AM LOOKING AT GOING ABOUT 60 FEET FROM MY CURRENT BOX. ADDING 9FT FOR FROM THE BOX TO CEILING AND ANOTHER 6 FEET FROM CEILING TO THE NEW BREAKER BOX. SO IT IS ABOUT 75 TOTAL FEET. THANKS

Answer 1

There are several wrong answers here.

One answer states to use 2/0 copper for 200 amp. This is incorrect for a sub-panel. 2/0 copper is acceptable for your main electrical service, but not for a sub-panel. For a sub-panel you need 3/0 copper or 4/0 aluminum.

This same answer states that 8/3 is rated for 50 amps. This is incorrect; 8/3 SER, NM or UF is only rated for 40 amps maximum.

Another answer says to use # 6. This is incorrect as well. # 6 NM and UF cable is rated for 55 amps maximum and # 6 SER is rated for 50 amps maximum.

What are your 220 volt loads going to be used for? If these are all 20 amp loads, I recommend 100 amps to your sub-panel. Even if you have a 220 volt 30 amp and 50 amp load this will still work. If you provide more information on the loads served in this new room, we can size your wire and conduit more accurately.

For 100 amps you need 1 1/4 inch EMT or PVC schedule 80 with # 3 THHN copper wire minimum.

You also need to check with your local building codes department. Most areas do not allow homeowners to install their own electrical service or sub-panels. I highly recommend hiring a licensed electrician for this work.

If you need further assistance, please visit:
http://electricalblog.gilchrist-electric.com

Answer 2

A 200Amp panel will need 2oo Copper wire and you will need a 200Amp Brkr....lol

what are you using the room for? it seems odd to have 7brkrs for 14 receps. ( you can have up to 8 on a 14//2 and 12 on a 12/2)
you will need 2pole brkrs for the 220v 12/3 =20 amp 10/3 = 30 amp 8/3 = 50 amps
the conduit should be 2 1/2' I think ( you might be able to get it into 2' but Im not 100% on that)
best advise would be to have an electrician do it for you though... it may cost more, but its better than doing it wrong and starting a fire.

Answer 3

Yeah. I like the idea of upgrading to 200A at the house and using the other for the garage. If you get the same type panel, you might be able to move some breakers around until you are ready to add the loads you are planning on. I'd price copper and aluminum. Usually aluminum use 2 sizes larger. Of course we all prefer copper, but if there's a huge price difference.. Check to make sure old panel is rated for aluminum - AL-CU. --------------------------------------..... An Electrical Engineer - wow. But are you an licensed Electrician or have other skills besides reading manuals?. I'm doubt you could make it as an electrician given your people skills... How can you say it's wrong if you don't even know where he's at? 6" deep is OK by my electrical coop given the same stated circumstances - but they like it better if there's a board over it. --------------------------------------..... Anyway, however deep it ends up, if you're using direct burial, snake it just a bit to leave it some give for contraction or expansion. Sometimes in real rocky areas, we put a couple of inches of sand in the trench just in case you shovel a sharp rock back on it. There's a lot of chirt and flint around here - nice sharp hard rocks. We get a crapload of flat tires too - just from the gravel roads (the 6-ply LT's I have now have cut that down a lot...).

Answer 4

6

Answer 5

Best to call and get an electrician to take a look. You may be able to find someone that will help you do the job. You can save money by doing the hard part, running the wires. Then have then hook everythying in. There are a lot of things to consider when working in hte electrical panel. Mainly safety, local codes and your home insurance may also be affected.

Answer 6

I'm not an electrician but I work with them all the time.I'm a General Contractor.10/3 will probly work fine,but just remember bigger is always better.It will pull less amps if you go to 8/3. Thats my choice and I'm usually right.Do it right the first time.Don't use anything less than 20 amp breakers your chances are better than not to trip them if your useing 12/3. 2-1/2" conduit. Suck a (strong) string with your shop vac through the line and pull it through with that.