how to determine panel amperage

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#1

Originally Posted By: srowe
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Real new at this stuff.


Checked out a condo, I assume it is a sub-panel but I could not find the amperage rating on it. I know there has got to be an easy answer. The main shut-off is on exterior with all the others. The only thing showing are the breakers themselves. Here is the panel with cover off. ![](upload://mGNSWkccG8XYjotUd6wcLRZhLo3.jpeg)

Do I assume its 200 amp. I thought I saw something that said CUAL 200. Is this the amperage?

Thanks for your help!

Shawn

#2

Originally Posted By: Dennis Bozek
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Shawn,


It is a 200 amp panel! The cual you seen means the connection is rated for either copper (cu) or aluminum (al) at 200 amps. But that does not mean it is 200 amps. The best way to do it is to check the main disconnect or breaker. Look at the breaker size or fuse size. That will tell you what size service you have but the most important thing to look at is wire size. If the wire is copper, for a 200 amp panel, it must be at least 2/0 gauge. If it is aluminum, the wire size is a 4/0 gauge minimum. Anything below that would be less than 200 amps and therefore the breaker or fuse protecting that wire must also be less than 200 amps, or rated for the size of the wire.

The maximum amount of circuits for a single 100 amp panel is 32. The maximum for a single 200 amp panel is 42. If you have a 42 space panel protected by a 100 amp breaker....call a electrician! Chances are the service is under rated for the house.

Most apartments, condos, and buildings like such have a central area where all the meters and all the disconnects for the unit panels are located. This is legal to do. The panels in the units are usually main lug panels, whereas no main breaker is present. The means of disconnect for the service equipment (ie panel) is then located by the meter for each individual unit. Go to this central location and find the meter corresponding to the unit you are in. Located near or under the meter, will be the main breaker or fuse for the unit's electrical panel. The breaker or fuse will have a ampacity marked on it. This will tell you what the ampacity of the service and panel is but again you should check wire size. If you are unsure about doing this or feel it is not within your scope of work as a HI, recommend that a qualified electrician inspects the panel and service feeders. Hope this helps.

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#3

Originally Posted By: srowe
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I knew someone could give me a detailed answer!!!


Thanks again.

#4

Originally Posted By: Dennis Bozek
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icon_lol.gif Wait till Jerry sees this topic icon_lol.gif icon_lol.gif icon_lol.gif

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#5

Originally Posted By: jfarsetta
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Dennis,


I thought the rule of thumb was 20 breakers for 100 amp service, 30 breakers for 150 amp service, and 40 breakers for 200 amp service.

Joe F

#6

Originally Posted By: jmcginnis
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Just to clarify and emphasize a point that Dennis made (if you don’t mind Dennis) … as he said… the main breaker in this case will determine the size of the service… breakers (or whatever the overcurrent protection is) always determine the ampacity of a circuit… so you can only use the size of the conductor to verify what the breaker tells you… in other words… if your breaker says “200 amps” and your wire size is say for example "2/0 aluminum… you still have a 200 amp service but you also have an illegal installation and the conductor has to be upsized to at least 4/0 aluminum…I have found number of situations over the years where someone has changed out a main panel (service panel) during an upgrade without changing the service cable… they pull the meter, and simply change the panel … often they install a larger main than the service cable was sized for… something important to watch for during any home inspection…

#7

Originally Posted By: Dennis Bozek
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Not necessarily true Joe. Panels these days rated for 100 amps are 32 spaces or less as well as 200 amp panels are 42 spaces or less. If you have a 100 amp panel with only 20 spaces…that is ok. If you need more spaces, either replace the 2- circuit panel with a 32 circuit panel or add a subpanel.


Another thing that one should be aware of is that if you have a 200 amp panel, the meter enclosure as well as the panel MUST be rated for 200 amps or more.

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#8

Originally Posted By: nlewis
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Dennis,


Is it a problem if I use a 200 amp 42 circuit panel with a 100 amp service and a 100 amp main breaker? For arguments sake, what if I wanted most outlets to be on separate circuits and wanted lots of room for breakers without adding a subpanel. Would there be something wrong with this installation?

#9

Originally Posted By: jfarsetta
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Good reply, Dennis. Thanks…


Makes sense....

#10

Originally Posted By: Dennis Bozek
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Neal…


No that would not be a problem if the main breaker is 100 amps and the service is 100 amps. That would be typically, the same thing as having a 20 space main panel and a 24 space subpanel. You could have 80 breakers on a 100 amp service and main if in fact the load of the house does not exceed 100 amps. I wouldn't want to wire a house with 80 circuits though ![icon_lol.gif](upload://zEgbBCXRskkCTwEux7Bi20ZySza.gif)

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#11

Originally Posted By: Dennis Bozek
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Welcome Joe…hey how come no one answered my thread on Merlot icon_lol.gif

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#12

Originally Posted By: dleavitt
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Based upon the previous threads I just wanted to make sure this is an 100 amp panel.


Thanks .David icon_smile.gif

#13

Originally Posted By: dvalley
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David,


The pic you just posted can not be viewed because you have a space in between the words "Main & Panel". You have to go back and rename your pic with nospaces.

Good Luck.

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David Valley
MAB Member

Massachusetts Certified Home Inspections
http://www.masscertified.com

"Some cause happiness wherever they go; others, whenever they go."

#14

Originally Posted By: jmyers
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Be careful of where you pull the amperage rating from on main lug panels. In many cases the manufacturers of the lugs stamp them with CU/AL and follow that rating with a numerical designation, such as, 250.


In most cases those stand for the maximun wire size rating in on the lug and should not be confused with the panel amperage rating. Wire sizes above 4/0 start with a numerical thickness designation of 250, so be careful.

Joe Myers