Increase size of main breaker

Reply

  #1  
Old 01-09-13, 02:06 PM
Member
Thread Starter
Join Date: Jun 2012
Posts: 37
Increase size of main breaker

Good Afternoon!

I am rehab'ing my California townhouse that was built about 33 years ago. It has a main disconnect panel outside rated 125A. A 70A two-pole main breaker is installed, and is connected to a 125A panel inside via #1 AWG AL feeders. All house circuits originate from this inside panel.

Will #1 AWG AL support 100A entrance service? Section and Table 310.15(B)(6) in the 2010 Code appear to allow this.

I would like to replace the 70A breaker with a 100A two-pole breaker. I have worked with Aluminum wiring before and would use NOALOX.

I would need the assistance of the local power company because the main breaker is located under the meter and the outside panel cover cannot be removed without unlocking a ring around the meter. Then the meter can be pulled.

Do I need a permit for this? Or just a request to the local power comany

If this is permissible, do I have to have an electrician on site to physically remove the old breaker and install the new one?

Thanks for your comments and suggestions.

With best regards,
LynnX
 

Last edited by ray2047; 01-09-13 at 02:41 PM. Reason: Remove superfluous font code.
Sponsored Links
  #2  
Old 01-09-13, 03:41 PM
Member
Thread Starter
Join Date: Jun 2012
Posts: 37
I called the local poco. They said no problem. They will come out and unlock things for me to swap out the main breaker. No permit needed for "repair".

I now have another concern...

I loaded up one pole with about 94 Amp of load current (based on max power specs on each appliance), including A/C, space heater, washer, vaccuum, mixmaster, toaster oven, microwave, drill, blender and a dozen lights.

I expected the main 70A breaker to blow, but nothing happened. The breaker did not even get warm.

How long should it take for an overload (more than 10% of breaker rating) to trip a breaker?

How does one test that a breaker will trip?

Thanks,
lynnx
 
  #3  
Old 01-09-13, 04:12 PM
ray2047's Avatar
Group Moderator
Join Date: Mar 2006
Location: USA
Posts: 32,631
What brand of breaker? If FPE not totally unexpected.
 
  #4  
Old 01-09-13, 06:50 PM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: NJ - USA
Posts: 43,429
You can't use the nameplate ratings to figure the actual load. Many devices use under what the name plate lists. The manufacturer lists MAX current draw.

The only true way to read current draw is with a clamp on amp probe.

Unfortunately it's next to impossible for a consumer to check a large breaker like that to see if it will trip.
 
  #5  
Old 01-09-13, 07:03 PM
Nashkat1's Avatar
Member
Join Date: Mar 2012
Location: USA
Posts: 8,470
Why do you want to increase the size of your main breaker?
 
  #6  
Old 01-09-13, 08:13 PM
Tolyn Ironhand's Avatar
Group Moderator
Join Date: Nov 2007
Location: Twin Cities, MN
Posts: 11,976
Note: there is no 2010 electrical code. There is 2008 and 2011.

Your disconnect outside is your main service, therefore, the conductors feeding that may be sized to 310.15(B)(7) (2011). After the main service you must use table 310.15(B)(16) for your conductors between the disconnect and your panel inside. Depending the type of wire used you may still be able install a larger breaker if it is rated 75 degree or higher.
 
  #7  
Old 01-09-13, 09:06 PM
Member
Thread Starter
Join Date: Jun 2012
Posts: 37
Panels and breakers are GTE/Sylvania, not FPE.
 
Looks like I will have to buy an amp probe, perhaps the Klein CL3000?
 
I want to increase the size of my main breaker because I have done a load calculation for the house and it exceeds 70A.
 
I have been looking in the file "ca_2010_title24_03.pdf" (California's 2010 version of the NEC). Based on 310.15(B)(16) (2011), it appears the answer is "maybe". If the cables are 75 deg rated, than it looks like I can pull 100A; if 60 deg, then I can only pull 85A. I will have a look-see tomorrow.
 
Thank you!
 
  #8  
Old 01-09-13, 09:13 PM
ray2047's Avatar
Group Moderator
Join Date: Mar 2006
Location: USA
Posts: 32,631
A cheap clamp on amp meter from Harbor Frieght or Amazon would be acrurate enough and a lot cheaper. Example: Amazon.com: Digital Clamp AC DC Volt Meter: Home Improvement Digital Clamp-On Multimeter
 
  #9  
Old 01-09-13, 09:38 PM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: NJ - USA
Posts: 43,429
Wow ray......a disposable amprobe
 
  #10  
Old 01-10-13, 07:10 AM
Member
Join Date: Dec 2010
Location: usa
Posts: 243
Most of the GTE/Sylvania panels were ZINCSO type breakers and then they changed to a series that was more of a normal plug in type breaker...but the mains were sometimes oddball. Might be a chore to get a larger main.....Might post a pic of this panel for us to see......
 
  #11  
Old 01-12-13, 06:07 PM
Member
Thread Starter
Join Date: Jun 2012
Posts: 37
Thank you all for your responses and suggestions. I'm still on the fence about amprobe quality.

Tolan,
I am scratching my head about cable ampacity. The way I (a novice) read the NEC Table headed "Conductor Types and Sizes for 120/240-Volt, 3-Wire, Single-Phase Dwelling Services and Feeders. Conductor Types ... THW ..." and other sections within the NEC, I believe that the cables from my outside main disconnect that supply my inside (and only) panel are correctly designated "feeders".

This has become more critical because these cables are actually #2 Aluminum, if the "feeder table" does not apply and allow 100A ratings, then I cannot increase the breaker size.

Please re-visit this issue.

There may be other reasons that I cannot easily upgrade. [1] Table 250.122 "Minimum Size Equipment Grounding Conductors for Grounding Raceway and Equipment" specifies a #8 (CU) grounding connector. Currently there is a #10 (CU) grounding conductor running through the 1-1/4" RMC between the panels. Does this have to be re-pulled in order to upgrade to 100A? Does the conduit itself provide an acceptible ground conductor?

[2] The only vendor (of which I am aware) for Zinsco-compatible breakers is "Connecticut Electric" (other than re-built Zinsco suppliers). Their breakers are quite expensive ($150 or more) and apparently not UL approved, nor HACR rated. I cannot find any temperature rating and am still looking for specs. Are they known to be reliable?

Thanks,
LynnX
 
  #12  
Old 01-13-13, 01:23 PM
Tolyn Ironhand's Avatar
Group Moderator
Join Date: Nov 2007
Location: Twin Cities, MN
Posts: 11,976
Yes, you are correct. I re-read the code section and I see now that table 310.15(B)(6) also covers the feeder from the main disconnect to a panel that serves an entire dwelling. Your wire is fine for 100 amps.

Since your feeder is in RMC I would think your fine for your ground. At most, you would need to add some grounding bushings with #8 copper and bond between the pipe and the steel box of the panel(s).

Zinsco are very rare in my location and have only seen one in my career. Where is the Zinsco main breaker? It would be likely more cost effective to change out the Zinsco panel/disconnect to something current and widely available.
 
  #13  
Old 01-13-13, 06:55 PM
CasualJoe's Avatar
Member
Join Date: Jan 2010
Location: USA
Posts: 9,212
The only vendor (of which I am aware) for Zinsco-compatible breakers is "Connecticut Electric" (other than re-built Zinsco suppliers). Their breakers are quite expensive ($150 or more) and apparently not UL approved, nor HACR rated. I cannot find any temperature rating and am still looking for specs. Are they known to be reliable?
If you have Zinsco products as both the service disconnect and the service panel, the wise thing to do would be to replace them while you can on a schedule and not as an emergency.

Zinsco Sylvania Kearney Electrical Panel and Circuit Breaker Hazards, Failures, Inspection, Detection, Repair, Replacement - Sylvania Zinsco circuit breakers and panel hazards
 
  #14  
Old 01-14-13, 06:11 AM
Member
Join Date: Dec 2010
Location: usa
Posts: 243
We have sold several of the UBI (Zinsco repl Conneticut Switch) with no issues thusfar...however we always recommend replacement of panel due to fact these are ETL rated but not UL and future replacements may be not available. NOS Zinscos are getting rare. Several companies owned the rights to these things including Zinsco, GTE Sylvania, T&B...etc and no one would be aroubd to be held responsible for a NOS Zinsco failure....Connecticut Switch series as I said has not caused us any issues but this is a breaker that is only ETL rated. If money is not an issue you would be best served to replace the panel with a commonly used type such as GE Powermark, SQD QO series or Homeline, or Cutler Hammer BR series...
 
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
'