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Old 04-03-2011, 11:14 AM   #1
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Replacing main breaker panel


I have a Zinsco 100Amp panel with a burnt buss bar that I need to replace. There is also a sub panel I want to eliminate. I will do this with a permit. But have some questions.

I want to use a 100 amp replacement panel for economy. I currently have

2 40A breakers AC and range

3 30A breakers

9 20A breakers

I need to add a 30A and 2 20A breakers, will this be too much for a 100A panel or what is the max amps on a 100A panel?

I've included a picture and have some questions on that. There is a wooden box from ceiling to panel in which the wires run, is a wooded box OK for this? If OK can I replace cover on box before calling for inspection?

There are 8 wires entering box through 1 1 1/2" clamp connector, Sure does not look right! How many wires can be in a clamp connector?

Thanks in advance JIm

Will not let me upload pic, will try again later.

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Old 04-03-2011, 11:23 AM   #2
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Replacing main breaker panel


To see if the 100 amp service can support the additional loads you would need to perform a demand load calculation.

There is an exception that would allow multiple cables to be run in one conduit into a panel, but the panel must be surface mounted along with other provisions. Normally one to two cables can be run into a connector, but it depends on how they are labeled on the package. The cables need to be secured to the panel if the exception above is not used.

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Old 04-03-2011, 11:50 AM   #3
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Replacing main breaker panel


Adding up the breakers is useless for any calculations other than circuit count for your new panel. A 100 amp panel could have over 200 amps of breakers in it and not be a problem.
To get your image up host it at a site like photobucket and then post the IMG link.
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Old 04-03-2011, 12:41 PM   #4
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Replacing main breaker panel


Here is a good place for a load calculation.

http://www.electricalknowledge.com/SFDLoadCalc.asp
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Old 04-03-2011, 04:25 PM   #5
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Replacing main breaker panel


Thank you for the responses, always appreciated!

I am not concerned about my load, I have lived with 100A service for 2 years with no problem! For 10 years before that in a motorhome with 30A service, that was dicey but I did it.


This seems to be hard to put into words, I know I can only draw 100A from a 100A service. But in my present panel I have 9 20A, 2 30A and 2 40a breakers for a total of 320 amps. Is there a limit to the potential draw of the breakers. I cannot find any reference to it online, or maybe not asking the right question. Could you put 20 30A breakers in a 100A box, even thought you can only use 100A?

This is a surface mount Zinsco panel and a Square D sub, on an exterior concrete block wall in Florida

http://s667.photobucket.com/albums/v...ctric%20panel/

Thanks again JIm
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Old 04-03-2011, 07:25 PM   #6
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Replacing main breaker panel


Think about a typical circuit in your house. Your kitchen should have 2 20 amp circuits for the countertops. The only draw on them most of the day will be the clock on the microwave or coffee maker. This is nowhere near the 40 amps the breaker handles total up to. There are also factors for diversity because you will not be using each circuit at the same time.

You may also have circuits for things like air conditioning and heat that are not used at the same time.
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Old 04-03-2011, 09:13 PM   #7
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Replacing main breaker panel


Tell us what is connected to all those breakers.
Think about how often the items run.
A 20 amp breaker is likely receptacle circuit. Receptacles don't use any power. Only the stuff that plugs in does.

One of the 30s is probably the dryer. How often is that running? How about the stove which is probably one of the 40s. As you can see the full load of the breakers is not all running at the same time.
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Old 04-04-2011, 08:42 PM   #8
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Replacing main breaker panel


Thought I responded to this?? Gremlins?

40A heat, Florida so little use
40A Range, switching to propane

30A Dryer, 2 adults and have solar dryer, 50 feet of it!
30A Shed, Table saw, joiner, hobby stuff
30A Hot water heater, why heat hot water??
30A Central AC, this is Florida constant use!

20A Wash machine
20A @ 8 breakers No one knows where they all go! But normal household lights, computer, TV, bathroom fan, ceiling fans, coffee maker, wifes hair dryer, garage door opener, refrigerator. Small 2 bedroom house, 2 adults no heavy draws.

JIm
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Old 04-04-2011, 09:17 PM   #9
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Replacing main breaker panel


40A heat, Florida so little use Non co-incident load with the A/C -- you can disregard the smaller of the 2. What is the total connected wattage here?
40A Range, switching to propane

30A Dryer, 2 adults and have solar dryer, 50 feet of it! Still have to count this one, in case of bad weather. Nameplate or 5.5 kW
30A Shed, Table saw, joiner, hobby stuff
30A Hot water heater, why heat hot water?? Again, we need the nameplate rating. Typical = 4500 watts
30A Central AC, this is Florida constant use! What does the nameplate say on the outside unit here?

20A Wash machine Figure this one at 1500 watts
20A @ 8 breakers No one knows where they all go! But normal household lights, computer, TV, bathroom fan, ceiling fans, coffee maker, wifes hair dryer, garage door opener, refrigerator. Small 2 bedroom house, 2 adults no heavy draws. Kitchen small appliance circuits = 1500 watts each. Rest of the house is calculated at 3 watts per square foot.
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Old 04-04-2011, 09:35 PM   #10
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Replacing main breaker panel


The safest way you can do is the load caluation to make sure your exsting service can handle it.

Oh by the way for Ac or Heat system I always go for the largest one that how I do the load demand caluation on this one.

I have to edit it when KB came in so he got the answer there.

However for your rest of 20 amp circuits you will have to map it out and mark it down for what room for what breaker it used.

And you may want to double check the conductors to make sure they are not overbreaker'ed so if you see 14 AWG conductors at the breaker then you have to use 15 amp breaker the max.

Merci.
Marc
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Old 04-05-2011, 11:37 AM   #11
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Replacing main breaker panel


Quote:
Originally Posted by jjrbus View Post

I need to add a 30A and 2 20A breakers, will this be too much for a 100A panel or what is the max amps on a 100A panel?
Your sub panel is already wired through the main breaker, correct? Does it trip? If you've never had a problem, then why would one suddenly start?

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