Is my 100A sufficient?

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  #1  
Old 05-23-14, 04:01 AM
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Is my 100A sufficient?

I would like to add two, 20A 120 circuits to my system. But I wanted to be sure my 100A is sufficient.

2000 SQ FT' ranch.

100A main
with 16 circuits including
gas furnace
25A air conditioner
30A electric dryer
a 40A 240 for garage subpanel that has 2 20A circuits-- only load on it is the GDO.
20A laundry
2 small appliance circuits for kitchen
Dishwasher 20A
Sump Pump 20A
6 15A circuits for rooms.

What other information is necessary for an accurate measurement?
How much can I safely add to my panel?
 
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Old 05-23-14, 06:07 AM
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I would like to add two, 20A 120 circuits to my system. But I wanted to be sure my 100A is sufficient.
It's probably adequate, but approaching marginal. Have you done a load calculation? I'd do the calculation and then also check the actual current draw on the service when both A-C and electric dryer are running during a typical warm day.
 
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Old 05-23-14, 09:39 AM
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Would you be so kind to explain how to do a load calculation or point me in the direction of a calculator or some directions? Thank you.
 
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Old 05-23-14, 10:43 AM
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Old 05-23-14, 12:07 PM
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Thanks Ray. I tried using the calculator you suggested but I am uncertain if what I computed was correct. The VA vs. A etc threw me off.

I think I was getting 69A. That kind of has me concerned? I probably shouldn't be adding circuits in this case? I want to have one circuit for water heater fan and another circuit for general use. Is there a percentage of 100a your supposed to stay at for that size service?

I also noticed on the calc they don't ask about lighting and they don't ask about electronics.
 
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Old 05-23-14, 12:16 PM
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I listed two calculators. Try both and compare. A is amps the appliance draws. VA is volts X amps. Watts and VA are roughly the same.
 
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Old 05-23-14, 12:38 PM
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So actually creeping up on 80A for a 100A service is a bad thing?

ps one of those calculators, the mike holt one, there is a charge$$
 
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Old 05-23-14, 01:47 PM
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The lighting is covered under the 3 va per square foot.

The fan will use almost nothing. The general use receptacles will only have a load when you are using something.
 
  #9  
Old 05-24-14, 09:16 AM
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100 amp service is kind of skimpy for a 2000 sq ft house , with gas heat and gas cooking . However 25 amp A/C is a little smaller than I am use to seeing .

100 amp main circuit breaker ?

GDO - garage door opener ? Pulls almost nothing , except when you are opening or closing the garage door .

Do you presently see the lights flicker when the dryer or the A/C kick on ? ( Hint , run the dryer at night when the A/C is running less . )

Sump pump ? You have a basement ? Again , it pulls nothing , except when it is running .

Just a long distance guess , if you never see the lights dim , you can probably get buy with the 2 new circuits . You have 2 available spaces in the loadcenter ?

God bless
Wyr
 
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Old 05-24-14, 03:05 PM
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Actually its 1400 sq ft.

So essentially its a 30A dryer. 25A AC. 1/2HP sump. 2 small appliance circuits. 1 laundry circuit.

So when approaching 70-80 is it not a good idea to push it further?

I have 5 available slots in my 24 slot panel.
 
  #11  
Old 05-24-14, 04:04 PM
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I think you will not have an issue adding those circuits. Rarely would your service ever be using that much.
 
  #12  
Old 05-25-14, 05:03 AM
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You have 5 spaces in the loadcenter ? 1" spaces or 1/2" spaces ?

I recommend using 1" Circuit Breakers . I hate 1/2" CB's and only use them when I have to .

God bless
Wyr
 
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