main breaker size

Reply

  #1  
Old 01-04-03, 05:57 PM
V
Voltswagen
Visiting Guest
Posts: n/a
main breaker size

When we moved into our house, there was an electric range with a double pole 50 amp breaker, an electric water heater with a double pole 30 amp breaker, a clothes dryer circuit with a double pole 30 amp breaker, and a double pole 30 amp breaker for baseboard heaters. In addition to this, there were single pole breakers for lighting and receptacles. The main breaker is 60 amp, and there are 26 spaces for breakers on the panel. We converted to gas for the range and water heater, and I removed those 2 breakers (50 amp + 30 amp) and the old wiring to those appliances. It seems like the main breaker is too small for this size panel, which I think can handle 200 amps according to the sticker on the inside of the panel. The main breaker is not at the top of the panel as I have seen on most panels, but is in spaces 3 and 5. Can the main breaker be replaced with a larger one, or do I not to even worry about it since we removed 2 major loads (water heater and range) from the service? We never have a problem with breakers tripping now, but I would like to add some new circuits, there are spaces available on the panel. The panel is a Cutler-Hammer, installed in 1972, I can't find a model number on it, but a sticker on it says it is a class CTL. Thanks
 
Sponsored Links
  #2  
Old 01-04-03, 07:21 PM
W
Member
Join Date: Dec 2002
Posts: 71
Received 0 Votes on 0 Posts
Ihtink what you have is a split buss panel It has room for six mains up top ( 240 v stuff and a 60 for the lightin section) .This is an old design but there is nothing wrong with it.You can't replace that 60 with a 200 but you don't need to seeing how all you 240 stuff is seperate.
 
  #3  
Old 01-05-03, 11:48 AM
V
Voltswagen
Visiting Guest
Posts: n/a
Thanks, I thought that was the type of panel I have. When you say that there is room for 6 mains up top, does that mean that those spaces are reserved for main breakers, and does it mean that the 240 breakers are not controlled by the existing main breaker? Does that mean that in order to shut off power to everything in the house, the main breaker and all of the double pole (240v) breakers must be in the off position? Should all of the 240v breakers be at the top? This is not how they are arranged at present. There is a rule about the maximum number of breakers that can be used to shut off all power, I think it is 6, I'll look that up.
I'll also do some reading up on split buss panels, since I don't fully understand them. All of the wiring books I have show the modern design, with the main breaker at the top, and that is easy to understand.
Thanks for your help.
 
  #4  
Old 01-05-03, 04:29 PM
W
Member
Join Date: Dec 2002
Posts: 71
Received 0 Votes on 0 Posts
Yes you have to turn off all the breakers up top to kill all power to house.You can have 240 in the lighting section but i would not recommend it . Do not put any singlepoles int the upper section.
 
  #5  
Old 01-05-03, 04:34 PM
W
Member
Join Date: Dec 2002
Posts: 71
Received 0 Votes on 0 Posts
sorry six mains is ok and Imagine a regular panelwith no main just a lug kit on top halfway thru the panel the the two buss bars stop then on the bottom of the panel there are two more bus bars which is fed by the 60 amp .Take off you panelcover and look at it it is easier to understand it then
 
  #6  
Old 01-05-03, 06:59 PM
H
hotarc
Visiting Guest
Posts: n/a
I have a mid 70's Square D panel with a split bus and I must say that they are not one of your more DIY-friendly panel designs.

A large portion of the panel is hot all times, even with the MAIN shut off. Plus it is easier to exceed the limits of your service conductors.

As Willc mentioned, a look inside the panel will probably clear things up. Mine had a sticker inside with a diagram for the split bus configuration.
 
  #7  
Old 01-05-03, 10:35 PM
V
Voltswagen
Visiting Guest
Posts: n/a
O.K., now I get it. I took another look inside (I have had the cover off trying to figure it out) and noticed that the hot buss bars are in 2 sections, not continuous. I could not understand what a split buss meant without a diagram or actually seeing it.
So the top sections (legs) of the hot buss bars are energized all the time (Yikes!), and the main breaker, connected to the top legs, feeds the bottom legs of the buss bars via two 4 AWG wires. A sticker tucked into the side says that only double pole breakers should be used in the service section, which must mean the top (always energized) section. So that means that the bottom section is for 120v circuits (the lighting section, as Willc referred to it).
There are 13 spaces in the upper section (6 on one side, or connected to one leg, and 7 on the other), and 13 in the bottom. I will need more than 13 for 120v cicuits if we go ahead with a planned bathroom & kitchen remodel, so that I can have those rooms up to date with enough outlets, etc.
It looks like I should add a sub panel for 120v circuits, feeding it via a 60 amp double pole breaker from the upper section (service section) of the main panel. I'm not sure if I can use a breaker larger than 60 amps to feed the sub panel, so I will use that unless I find out it is safe to do otherwise.
Does this sound like the right plan?
I'll also draw up a diagram and instructions so that anyone who needs to shut off power to everything in the house will know to shut off all of the double pole breakers in the top section.
 
  #8  
Old 01-06-03, 08:14 AM
W
Member
Join Date: Dec 2002
Posts: 71
Received 0 Votes on 0 Posts
You can subfeed with any size breaker but the higher amp breakers are hard to find at you warehouse stores. Sixty should be fine for lights and receps but if you going to fed electric ranges and such do yourself a load calculation andbn remember to see what size feeder you have coming in to feed the main buss bars your house may only have a 100 amp service being from the seventies. Also sub feeds need to be a 4 wire and seperate your neutrals and ground in the new panel .
 
  #9  
Old 01-06-03, 08:39 AM
H
hotarc
Visiting Guest
Posts: n/a
remember to see what size feeder you have coming in to feed the main buss bars your house may only have a 100 amp service being from the seventies
That is very important. If you put two 60 amp breakers, plus two 30 amp breakers on your main bus, you have the potential to draw up to 180 amps and possibly overload the service conductors.
 
  #10  
Old 01-06-03, 09:50 PM
V
Voltswagen
Visiting Guest
Posts: n/a
Thanks. I'm not sure what the service is coming in, how can I tell if there are no numbers on the incoming leads? They are 1/2" in diameter. Would the power company be able to tell me what the service is to the house, or should I have someone look at it?
When we bought the house, the service (240v) section of the panel had a 60 amp main feeding the lighting section, a 50 amp for the range, a 30 amp for the water heater, and a 30 amp for a clothes dryer. That's 170 amps.
In the lighting (120v) section there were at least five 15 amp circuits, and three 20 amp. There was also a double pole 30 amp breaker for the baseboard heaters. I moved that to the service section into the spaces where the water heater breakers used to be.
We got rid of the electric water heater and range years ago. I thought maybe I could use the 50 amp breaker that used to feed the range, running new wire to a sub panel from that.
I'll find out exactly what the service is coming first, though, to be safe.
 
  #11  
Old 01-06-03, 10:24 PM
V
Voltswagen
Visiting Guest
Posts: n/a
I found a book that shows actual wire diameters, and I measured (carefully) the incoming leads. The diameter of the two hot leads is 3/4" with insulation, and 9/16" to 5/8" without insulation. It's hard to tell exactly, they are flattened out a bit under the lugs. The incoming neutral is smaller. According to the chart I have in front of me, the wire size would be 2/0.
 
  #12  
Old 01-07-03, 04:33 AM
W
Member
Join Date: Dec 2002
Posts: 71
Received 0 Votes on 0 Posts
Copper or alum
 
  #13  
Old 01-07-03, 09:01 AM
V
Voltswagen
Visiting Guest
Posts: n/a
It must be aluminum, it is not copper.
 
  #14  
Old 01-07-03, 09:52 AM
W
Member
Join Date: Dec 2002
Posts: 71
Received 0 Votes on 0 Posts
you have a 100 amp sevive it sound like. I f you thinking I have a 50 a 60 a 30 that is more than a 100 amps it is not if you did a load calculation on your house you will most likey find it close to specs.
 
  #15  
Old 01-08-03, 09:50 PM
V
Voltswagen
Visiting Guest
Posts: n/a
Thanks, I did a load calculation as you suggested. Trying to be as conservative as I could be, I included the basement and garage square footage in the figure for basic lighting/receptacle load (not sure if those are considered living areas), and rounded up all the wattages for permanent appliances, including the window A/C. Then I included future projects like several additional 120v circuits for bath/kitchen remodel. It came out to a little less than 92 amps, so we should be O.K. for the foreseeable future. I'll still have someone look at the service to be certain about the capacity.
 
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
 
Ask a Question
Question Title:
Description:
Your question will be posted in: