100 amp panel ?

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  #1  
Old 06-01-07, 10:19 AM
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100 amp panel ?

I was just wondering if it was ok code wise to replace a 100 amp service panel with a 100 amp panel or are you suppose to upgrade to 150 amp service? I was told that was the case but I was not really understanding why? The house now is only pulling 62 amps with every thing that I could turn on. I am tripping the 100 amp main when the washer and dryer and A/C run for a half hour or so. I think that the break has or is going bad. It is a old system and I will feel better if I replace it all. Thanks in advance. If it matters I am in the Tampa FL area.
 
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  #2  
Old 06-01-07, 12:22 PM
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Lightbulb e=mc2

If you are tripping the main even though you say you are only drawing 62 amps, the motors on those appliances will draw more "starting currents". Enough to trip the main. I would recommend if you are replacing the panel go to the 150. The expense is not much more and would be best. You really are borderline for a 100 amp service.
 

Last edited by e=mc2; 06-01-07 at 12:31 PM. Reason: not enough info on first post
  #3  
Old 06-01-07, 12:31 PM
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A 100A service is the minimum service size allowed to a residence; however a new service must be sized according to a calculation called a "demand load calculation". Sometimes you can replace a 100A service with a 100A, but sometimes the service size must be increased depending on the result of the calculation. If you're getting quotes from electrical contractors for panel replacement / service upgrade, ask them about the calculation. Be sure to mention if you plan to add any large appliances like a spa, power tools, or arc welder.

> I am tripping the 100 amp main when the washer and dryer and A/C
> run for a half hour or so.

There are at least three possibilities here.

First, you may actually be exceeding 100A and causing the breaker to trip normally. If you or an electrician has put an amp clamp on both legs and verified that you are drawing less than 100A then you may have a different problem.

Second, the main breaker may be overheating. This can be the result of loose connections inside the breaker panel.

Third, the main breaker may be worn out or malfunctioning.

In either of the last two cases, the problem should be evaluated by an electrician. Replacement of the main breaker is not a DIY job.
 
  #4  
Old 06-01-07, 02:12 PM
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100 amp panel ?

Thanks for the quick help. I did the Va and came up with 20,676Va/ 240= 86.15amps. I did wonder about the amp probe reading, one leg was 62, and the other was around 42. Do you add the 2 or is it 100amps per leg? Also I know that there is a surge at start up but shouldn't trip out when everything is turned on at once and not just when some things are running for awhile. I.E. when we did the amp probe it did not trip. Thanks again for the info.
 
  #5  
Old 06-01-07, 02:17 PM
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> 20,676Va/ 240= 86.15amps

Sounds like a 100A service would be okay, but with little room for expansion.

> Do you add the 2 or is it 100amps per leg?

100A per leg.
 
  #6  
Old 06-01-07, 02:53 PM
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I can't help but wonder what you mean by, "I did the Va".
 
  #7  
Old 06-01-07, 04:54 PM
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I took some classes years ago on electrical wireing? What I mean is the volt amp figures. Such as there is 3 va figured for each square foot of living space, and each item such as a dryer will have a # of volt amperes on the name plate. Any way I am sure some one on here can explain this alot better then I can. Thanks again for the help.
 
  #8  
Old 06-03-07, 05:37 PM
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Based on everything you said - your demand load calc (va calc) and amp-probe meter readings, it seems that 100A should be enough. Though it's possible you are missing a large appliance or two?

A slightly overloaded main breaker probably won't trip immediately, but likely after a few minutes/hours. It's designed that way to allow larger appliances to startup without tripping.

That said, I would suggest starting with a new main breaker. How old is your existing panel/breaker? Presuming the panel is still in good shape, you can have a new main breaker installed for less than a whole panel upgrade, though it's probably not a DIY project.

Good luck!
 
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