Subpanel Run From 200a Main Panel

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  #1  
Old 02-19-06, 07:30 AM
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Subpanel Run From 200a Main Panel

I HAVE 200AMP SERVICE TO MY HOUSE WHICH IS INSTALLED IN MY GARAGE.
I AM IN THE MIDST OF FINISHING MY PARTIAL BASEMENT, AND I HAVE 5 LINES, (ALL 12-2, ON 20A BREAKERS)THAT I WANT TO BRING POWER TO THE BASEMENT FOR VAIROUS THINGS LIKE

A. FAMILY ROOM LIGHT
B. FAMILY ROOM RECEPTACLES
C. FAMILY ROOM ELECTRIC WALL HEATER
D. BED ROOM LIGHT
E. BEDROOM RECEPTACLES

ASSUMING IVE USED THE APPRIATE BREAKERS FOR EACH, I HAVE THREE IMPORTANT QUESTIONS I NEED ANSWERED HERE...

WHAT IS A SUFFICIENT AMP SUBPANEL TO USE HERE?

WHAT AMP SHOULD THE BREAKER COMING FROM MY MAIN PANEL BE?

WHAT GAUGE WIRE SHOULD I USE?
 
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  #2  
Old 02-19-06, 07:57 AM
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WHAT IS A SUFFICIENT AMP SUBPANEL TO USE HERE?
Sufficient is always to do everything to the minimum requirements.

However, if you are going to put in a subpanel, I think you should put in 100A.
This way you have room to expand in ways that you didn't foresee.
Iow, more than sufficient for your present need.

What size wire you use depends on whether you use copper or aluminum and whether you go with the minimum size (which if you are allowed NEC 310.15(B)(6) minimum feeder sizes for 100A or more, that's fine with me).
 
  #3  
Old 02-19-06, 08:01 AM
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thanks for the quick reply!,
ok so going with a 100 amp subpanel is good, using 10w wiring right?

so what amp breaker should i install in the main panel? 100 amp as well?
 
  #4  
Old 02-19-06, 08:02 AM
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sorry, forgot , using copper wiring. new york
 
  #5  
Old 02-19-06, 12:22 PM
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using 10w wiring right?
4 AWG THHN if using the feeder table, otherwise 3 AWG minimum.
If you might expand such that you true load approaches 100A someday, #3 or larger is a good investment because of reduced valtage drop and less energy wasting heating the wires.


so what amp breaker should i install in the main panel? 100 amp as well?
Yes. You could start with a smaller one. You can put a 100A in the main and a smaller one as the main disconnect in the subpanel to provide an early warning if you exceed what you thought you were using. (For example, you have 60A max with the setup you described. But if you add five more circuits, you might want closer to 100A.) The only difference is that a 100A breaker costs a lot more than a 60A breaker.
 
  #6  
Old 02-19-06, 12:32 PM
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hmmmmmmmmm i see.

so perhaps i'll do just that. i am only running 5 lines to the subpanel but like you said, needs grow in the future and what better idea than to be prepared for it now than screwd later...........
 
  #7  
Old 02-19-06, 06:38 PM
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What type of subpanel are you going to use (main-lug or main breaker)? Main lug panels allow you to run wire from a breaker in your main panel direclty to the lugs in your subpanel without having a second "main" breaker in the subpanel. I was confused about this until I went to the store and compared the two types...

I just put in a subpanel for my basement and have a similar situation as yours. I used a Cutler Hammer 125 amp main lug subpanel. (it only cost around $42 at Lowes) I agree with earlier comments to plan and install bigger than you currently need. I started with a planned 7 circuits and ended up with 10. Instead of planning the curcuits to be fully utilized (I used 80% as my max. planned utilization for each circuit) I pared things down to give me more flexibility. I figured while the walls and ceiling were open, I might as well run the extra wire.

When I calculated all of the hard wired and plug-in loads I will have in the basement, I ended up with right around 10,000 W, (if everything was on and in use at the same time). (So at 240 volts that would pull about 42 amps) ..Just the numbers in my specific case...

Without knowing the actual loads you are pulling through recepticles and your lighting config, I'm not sure how someone estimated a 60 amp load for you.

A good reference for wire size would also be your local building inspector. If your area requires inspection, they would have to buy off on it anyway...

Have fun with it!
 
  #8  
Old 02-19-06, 06:57 PM
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Originally Posted by mxw128
Main lug panels allow you to run wire from a breaker in your main panel direclty to the lugs in your subpanel without having a second "main" breaker in the subpanel.
You lose the ability to kill the subpanel at the panel - fine if the panels are nearby; a pain if they are on different floors. Plus you don't have to lockout the breaker on the other panel while you work.



> I started with a planned 7 circuits and ended up with 10.
No surprise to me.


> (I used 80% as my max. planned utilization for each circuit)
80% is the max. Well at least it sort of is.


> I'm not sure how someone estimated a 60 amp load for you.
No one said "load" --- just maximum ampacity that could be used on any one conductor.
 
  #9  
Old 02-19-06, 07:14 PM
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Originally Posted by mxw128
A good reference for wire size would also be your local building inspector. If your area requires inspection, they would have to buy off on it anyway...
Be careful with this suggestion. Not all building ispectors are thrilled with giving how-to advice to DIYers. They expect you to know what you are doing before you do it.
 
  #10  
Old 02-19-06, 07:27 PM
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Originally Posted by Speedy Petey
Be careful with this suggestion. Not all building ispectors are thrilled with giving how-to advice to DIYers. They expect you to know what you are doing before you do it.
True, and they can make it tough on you, if they want to. At least in my area, they have been more "user friendly" as of late. They have to keep coming back to re-inspect if they keep failing an install, so I think they decided to help more folks along. I know they don't want to educate folks when they are at the site. One thing to keep in mind is that even if they are "wrong", they're right....( I've got a hot tub install story to tell you, but that was another post ... ) It would help not to go into a phone call totally green, at least know what you plan to use.....
 
  #11  
Old 02-20-06, 06:31 AM
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thanks for all the replys guys!!!

to simplify my si-chi-ay-shun,

i have 5 lines, all 12-2 on 20a breakers that i want to install.

they will power the following,

a. family room lighting
b. family room receptacles
c. family room wall heater
d. spare room receptacles
e. spare room lighting

i dont plan anything else in the basement since i already have a full bath, and laundry room which are both already wired to the main panel (200amp service)

i'd like to go with a breaker in the sub to give me another location to shut off power besides the main panel

is a 100 amp panel overkill?
also, does a lug panel give me the option of installing a main breaker on it or is it just for the straight run to the main?
 
  #12  
Old 02-20-06, 06:49 AM
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Yes, 100 amps is overkill. A 60-amp panel will be easier and cheaper. I guess it depends on what you think you might add in the future, especially if it includes any power-hungry stuff (e.g., welder, hot tub, air conditioning, baseboard heating, instant hot water).
 
  #13  
Old 02-20-06, 07:39 AM
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the only other thing i can forsee adding in the future is central air.

so will 60 do?
and should i put a 70,80,or higher breaker in the main to act as a safety?
 
  #14  
Old 02-20-06, 08:51 AM
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>so will 60 do?

It might.

Or it might not.

Everyone always seems to think that there is no future expansion possible.
Rarely is that the case. You are more likely to expand the easier you make it.


> and should i put a 70A, 80, or higher breaker in the main to act as a safety?

That is not how it works.

The breaker in the main can be no larger than the rating of the conductors to the subpanel and the subpanel itself whichever is smaller.


Whether you use a master (backfed) breaker in the subpanel or a main breaker subpanel is up to you.
 
  #15  
Old 02-20-06, 09:31 AM
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ok, so this is the way i think i want to do it (of course i will get electrical opinion before its done)

having 5 lines and leaving the option to add 2-3 more in the future, i will install a subpanel and feed 10/3 wire to the main service panel where i will install a 80 amp breaker...


anything im missing here?
 
  #16  
Old 02-20-06, 10:21 AM
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> i will install a subpanel and feed 10/3 wire to the main service panel where i will install a
> 80 amp breaker...

10 AWG is way too small.
An 80A breaker requires at least 4 AWG copper for the three current-carrying conductors and 8 AWG for the ECG (same as for 100A feeder).

If you went with 60A, you would still need 6 AWG, which doesn't save you much money, especially compared to the labor (and wall repair) of having to add yet another subpanel later when you outgrow 60A. It's probably five to ten times harder to outgrow a 100A subpanel than it is to outgrow a 60A sub.
 
  #17  
Old 02-20-06, 11:27 AM
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great, thanks for all the help, sorry i made it quite confusing, i'll write back when its all said and done....................
 
  #18  
Old 02-20-06, 12:05 PM
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ok, i got a 100 amp main lug panel before i got kicked out of the electrical aisle due to inventory, and that darn fork lift.
so is 8awg good enuf for this panel?
 
  #19  
Old 02-20-06, 12:06 PM
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i'll have to go back later, i couldnt wait there, and they took soooo long to open the aisle up again...
 
  #20  
Old 02-20-06, 03:06 PM
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_STOP NOW_

You are about to dig yourself a deep hole. If you are lucky, then it will only require the application of lots of money to dig your way out. If you are unlucky....

Electrical installations have many details which must be correct for the installation to be safe. There are so many details that _we_ can guess at what you don't know, and it is almost certainly the case that _you_ don't even know what questions to ask. Before you buy anything else, and before you spend lots of time putting wire in the walls and then covering it up, and especially before you apply power to this system, you _must_ pick up some background.

This forum simply cannot tell you everything that you need to know; because what you need to know literally fills a book. If you want to do your own electrical work, I strongly suggest that you go out and read a couple of books on the subject. The book 'Wiring Simplified' and any of the books by Rex Cauldwell are a great place to start; other people will have other suggestions. _Read_ the books and pick up the necessary background, and then come here to review your plans and ask questions. We are all quite happy to help, but unless you take the time to do the reading our help will only help you dig your hole deeper.

You need to learn how to do load calculations. This will help you figure out the _minimum_ feeder size to your new subpanel. Depending upon distance and cost you then decide how much to increase the size of the feeder.

You need to learn about proper sizing of wires. There are tables of conductor amp capacity versus conditions (wire type, wire size, temperature, etc). Use them.

You need to learn about proper grounding of subpanels. This is not the same as proper grounding at your main panel.

You need to learn about proper sizing of overcurrent protection, and where overcurrent protection is required.

You need to learn about routing and protection of wires and cables.

I mean no disrespect, but you _must_ do your homework prior to installing anything electrical. If you are not willing to do this, then hire a professional electrician.

-Jon
 
  #21  
Old 02-20-06, 03:11 PM
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no harm taken, i will and i shall have a licensed electrician over to give me an estimate of the installation as well as explain the proper procedure to do the job. and if i can do it with the electricians blessing, and inspection approval then so be it...


thanks again all for the wealth of information, i look forward to coming back again!


michael4244
 
  #22  
Old 02-20-06, 03:36 PM
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Originally Posted by michael4244
is 8awg good enuf for this panel?
The answer that that question is the same as the answer to this question:
Are you using a 50A breaker in the main panel??
 
  #23  
Old 02-20-06, 06:56 PM
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Michael, POST# 20 is the best advice to head,under the circumstances. The time and money you save employing an electrician, will be well worth it.
Take it slow and learn.there is too much at stake,
Be patient.
 
  #24  
Old 02-20-06, 07:07 PM
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Just to be clear, I strongly support 'do it yourself'; that is why I and many others are here answering questions. It is just that electrical 'do it yourself' requires background and planning.

If you can take the time to read the books, and do some leg work before you start installing, then you can get this job done.

Take care to investigate your local codes, and then make sure to get a proper inspection. There are a good many stories on this board about people installing subpanels, even installing the entire electrical service, and being complimented by the inspectors on final.

Working with an electrician can be a great experience, but if you want to do any of the work yourself, make sure you have a clear agreement with the electrician about what they will do, what you will do, and what you will pay for their 'consulting' when they help you plan out your work. Their 'quote' is not a free plan that you can simply work from!

Best luck on your project.

-Jon
 
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