Adding New Subpanel

Reply

  #1  
Old 08-06-04, 03:37 PM
mreev90
Visiting Guest
Posts: n/a
Adding New Subpanel

I own a residential house that has electrical service providing a 200 amp service. Unfortunately, all breaker terminals are taken and I am considering adding an additional subpanel for additional use. I will need a number of circuits, some of which are 220v. I would not have enough space even by replacing the breakers with the half-width variety. Even so, I would likely run over 200 amps at times.

My question concerns the proper wiring of the sub-panel. I was planning to put the new panel next to the existing one inside my garage. This will be a 100A service so I will run an additional feeders to the meter panel. The feeders will need to be one-ought. Is this a generally accepted method. In my community I can do the work myself and the electric company will pull the meter to do the work. I am having trouble finding out the correct method. I am afraid that I will do all of the work, call the electric company to remove the meter so I can make the connection and they will not approve adding the additional feeders to the meter panel.

Thanks,
Matt
 
Sponsored Links
  #2  
Old 08-06-04, 03:51 PM
COBALT's Avatar
Member
Join Date: Jul 2004
Posts: 176
First, maybe you want to get a new 200 amp panel with more capacity? It's a bit hard to max out a 200 amp service for just a house. That's a lot of power. Maybe you have too many breakers with not much on them? Have you traced down all of these circuits? You might be able to combine some circuits and eliminate some breakers depending on what wiring you have and what's on the circuits.

Finally, a 100 amp subpanel is pretty big. What are you planning on using it for? I helped my dad put a 50 amp subpanel in his house in case the main electricity was lost (farm house out in the sticks) so he could use the generator to power the 50 amp panel, and provide power to the essentials. That's more than enough power to run basic stuff in the house.

Picking the right size panel, and estimating your needs is a much better way to determine what you need to do than trying to wire in parellel another feeder from your meter. I don't think the power company would allow that anyway without a second meter box.
 
  #3  
Old 08-06-04, 05:55 PM
Member
Join Date: Sep 2000
Location: United States
Posts: 18,497
Just curious, but how did you compute that you need more than 200 amps?

Just a note, but what you are planning does not fit the common use of the term "subpanel".
 
  #4  
Old 08-06-04, 07:15 PM
mreev90
Visiting Guest
Posts: n/a
????

You may be correct that I do not need more than 200 amps. The main problem is the space available in the existing box. It has no more expansion capacity. I could consider combining circuits, but I didn't think that would be a wise solution. There is really no easy way (that I know of) to provide a jumper from the main panel to a small subpanel. The easiest solution (at least I thought) would be to just add another panel and wire it to the meter. Are you saying that it is unacceptable to wire two parallel panels to the meter box? Is that an unsound practice?

Thanks,
Matt
 
  #5  
Old 08-07-04, 09:57 AM
Member
Join Date: Feb 2002
Location: port chester n y
Posts: 2,117
It is un-acceptable, im-practical, and a Code-violation to run 6 parallel (Service) conductors to the meter-socket because you can't terminate more then one conductor on the lugs, and the wiring-space in the meter-socket is un-sufficient for 6 conductors.

I advise that you install a main-lugs panel with a mimimum rating of 100 amps and with a minimum of 20 C-B positions next to the Service-panel.You will have to transfer one or more cables to the new S-P to clear space in the Service-panel for a 2-pole, 100 amp C-B which protects the Feeder conductors to the S-P.

Please know that the 100-amp Feeder can supply a S-P of ANY rating over 100 amps,and ANY number of C-B positions available.

Good Luck & Enjoy the Experience!!!!!!!!!!!1
 
  #6  
Old 08-08-04, 07:34 PM
kmith
Visiting Guest
Posts: n/a
Lightbulb Similar sub-pnel problem

I have a similar problem: 200 amp main panel with all spaces used. A new addition creates the additional need.

I'm planning to solve that problem with a sub-panel off the main panel. I don't think I need more than 200 amps at any one time.

I'm plamnning to move one double-wide breaker (240 volt) to the sub panel and use the open slot that that creates for a 100 amp breaker. That 100 amp new circuit will feed the 125 amp 24 slot sub panel.

The sub-panel will contain the displaced double-wide breaker as well as the circuits for the addition. The sub-panel will be located in the addition.

Experts, does my plan make sense?
What is the best way to feed the sub-panel? PVC Conduit with #2 cable?
 
  #7  
Old 08-08-04, 07:40 PM
Member
Join Date: Sep 2000
Location: United States
Posts: 18,497
ksmith, that sounds like a good plan. Are you going to put the subpanel right next to the main panel? You can use almost any #2 copper you can find. I'd probably just buy some #2 THHN and run it through conduit for the short hop between panels.
 
  #8  
Old 08-08-04, 07:53 PM
Member
Join Date: Apr 2003
Location: Eastern PA
Posts: 354
addition

100 Amps for an addition? Does it have a kitchen or electric heat or something that requires such a huge sub? How many spaces is the current panel? Depending on what the displaced device is it could make more sense wiring wise to leave the 220V breaker in the panel and go to a couple of half high breakers to give you the two spaces for your sub breaker. 42 is the limit for any one panel.

For the original question. Isn't there such a thing as a disconnect that could be wired below the meter to feed both the main panel and the sub? That could also allow easy conversion if he does need to update to a larger service.
 
  #9  
Old 08-08-04, 08:05 PM
mreev90
Visiting Guest
Posts: n/a
Thanks ...

... for all of the great advice. I do like the idea of feeding the sub with a 70 - 80A 2-pole breaker. I believe this will work out just fine since I certainly don't need 100amps. Unless someone says something different, I believe this is the route I will choose to keep me safe and legal.

Matt
 
  #10  
Old 08-08-04, 08:34 PM
kmith
Visiting Guest
Posts: n/a
Sub-panel for addition

Thanks for the quick responses.

The sub-panel is in the new garage of the addition, about 30 feet away. It will be easier, I hope,
to run the new circuits of the addition within the addition and run a single feed to the sub-panel
than to run each circuit back to the main panel in the existing house.
I need advice on how to run the feeder.

I need 100 amps because:
  • The circuit being displaced in the main panel is 30 amps for the main house A/c.
  • The addition will have its own 30 amp AC.
  • My spouse wants a 30 amp clothes dryer. (Although that may bring even this 100 amps over the top.

There are absolutely no spaces left in the main panel.
 
  #11  
Old 08-09-04, 07:15 AM
Member
Join Date: Apr 2003
Location: Eastern PA
Posts: 354
subs?

What's the square footage of these houses? The NEC has a pretty thorough procedure for calculating the proper size service for a house based on square footage & additional loads like central AC and so on. If you have a 200 Amp panel with 42 breakers allready in it, and you're adding two major draw components, then you may well need to upgrade the service. So if you tell us the square footage of the house. what you use for heat, hot water, range and any major draw components like central AC & hot tub you may get more detailed advice.
 
  #12  
Old 08-09-04, 01:02 PM
kmith
Visiting Guest
Posts: n/a
sub-panel in addition

Speedy,

I'll gladly answer your question. The house is ~2200 square feet plus the attic and a basement that also houses a double-car garage. The addition is about 25' x 25' plus a single-car garage. The addition also has a small ~300 sq ft basement and an attic above the whole affiair

Major energy consumers in the house are: kitchen range, clothes dryer, and A/C. Major consumers in the addition are A/C and potentially dryer.

I'm not claiming that I need more than 200 amps. I'm merely saying that I'm out of space for circuit breakers and that running the new circuits from the addition to the current main panel would be a major hardship.

I hope that helps.
 
  #13  
Old 08-09-04, 01:20 PM
Member
Join Date: Apr 2003
Location: Eastern PA
Posts: 354
Since I don't do this for a living I'd have to break out the books and do the math. I'll try and do it sometime this week just to see how it works out but with what you describe I think you are O.K. but pretty close. But that's just a guess until I do the math.
I'm not trying to push the point but how may breakers are in your panel? I understand it's full but how many spaces is the panel and how many breakers are in it? If it's a 40 space panel with 40 regular breakers you could put in two half breakers to give you the space for the sub breaker. That's potentially a lot easier than rewiring the AC. Unless the existing AC will be very, very close to the new sub.

Remember, If you live in a cold climate, Christmas dinner is when you will blow the main breaker, if you are going to blow it. Every light inside and out is on, the stove is running flat out, the dryer is drying all the kids snowy clothes....
Might not hurt to turn everything on and see what current you are drawing now to see what you have left.
 
  #14  
Old 08-09-04, 06:04 PM
kmith
Visiting Guest
Posts: n/a
sub-panel for addition

Thank you for offering to do the research. I look forward to reading the results.

I just counted my main panel. I have 36 spaces, 6 of which are double-wides. Two of the six are GFCI breakers that I installed in a moment of weakness. I should have used GFCI outlets instead, but that was 20 years ago when I was young and foolish.

Originally Posted by speedy72
Remember, If you live in a cold climate, Christmas dinner is when you will blow the main breaker, if you are going to blow it. Every light inside and out is on, the stove is running flat out, the dryer is drying all the kids snowy clothes....
Might not hurt to turn everything on and see what current you are drawing now to see what you have left.
This is really funny! The good news is that we heat with gas and part of the addition is a gas-powered fireplace. But how do I measure my actual current draw?
 
  #15  
Old 08-10-04, 05:24 AM
mreev90
Visiting Guest
Posts: n/a
My subpanel addition worked perfectly!!

Thank You everyone for the helpful advice. I essentially added a 100A breaker in the existing box and added the subpanel next to the box. I then ran 1 ought wire from that box to the new subpanel. I discarded the bonding screw as suggested. In order to free space in the existing box I added 2 piggyback breakers. I now have plenty of room for my hot tub circuit, detached garage, room addition, additional A/C and heat for the addition as well as outdoor lighting.

The only catch was a little tense moment attaching the new neutral wire to the existing box. The only lug that would accomodate the 1 ought wire was an unused one next to the feeds from the meter right above the 200a breaker. I had to carefully position the wire in the lug which of course was located between the two hot feeds. I am sure you guys that do this daily don't think twice about it, but I have to say I had a little sweat for a moment or two. I made sure I was in no way grounded and only put one hand near the box at any time, just in case. Whew!

Thanks,
Matt
 
  #16  
Old 08-10-04, 07:13 AM
Member
Join Date: Feb 2002
Location: port chester n y
Posts: 2,117
#3 THHN copper conductors would have been adequate for the Feeder conductors to the new S-P, and may have avoided the complication you were confronted with.

I suggest that you tranfer 15 amp general-purpose Branch-circuit cables to the new S-P, and connect the "hot tub" and A.C. Branch-circuits to breakers in the Service-panel. This is done to minimize the connected-load on the 100 amp Feeder-breaker.

Anyway---- enjoy your sucess!!!!
 
Reply

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread
Display Modes
'