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New Main Panel Or Sub Panel?

 
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Old 03-07-2015, 07:33 PM   #1
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New Main Panel Or Sub Panel?


Greetings all.

I'm a general contractor so electrical knowledge is fair, not great. I come across this scenario quite often. Most of the homes around here where I live and work were built in the '50s and '60s and they almost always used 100 AMP main panels. It was enough 50-60 years ago but now inadequate. We have done several main panel upgrades replacing the 100A with a 200A. We have also added sub panels while keeping the main panel in place.

What is the advantage,if any, of replacing the main panel compared to adding a sub panel? Does a 200A main panel provide more amps/volts than the 100A main panel or just more spaces? If yes, does the service wire need to be replaced with a larger one in order to provide more amps/volts?

To avoid having to go through Edison, which is what's necessary when replacing the main panel, why not just add a sub panel with plenty of breaker spaces? It's much cheaper and you can have the sub panel strategically located as well.

I've been asked this question so many times and none of the electricians I've asked have given me a coherent answer.

Thanks in advance.
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Old 03-07-2015, 07:51 PM   #2
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Re: New Main Panel Or Sub Panel?


I'm not an electrician either. I would believe the sub panel/ upgrade comparison is dependent on the loads that house has. If the loads exceed 100 amp but not all the spaces than upgrade the main. If the loads dont exceed 100 amp, but all the spaces are taken, then sub panel. I'm assuming that the main panel is feeding the sub panel.

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Old 03-07-2015, 08:04 PM   #3
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Re: New Main Panel Or Sub Panel?


Try
http://electrical.about.com/od/panel...-Your-Home.htm

I guess another search should be on
"reasons to not install a subpanel"

The truth might be somewhere in the middle
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Old 03-07-2015, 08:14 PM   #4
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Re: New Main Panel Or Sub Panel?


Quote:
Originally Posted by Morning Wood View Post
I'm not an electrician either. I would believe the sub panel/ upgrade comparison is dependent on the loads that house has. If the loads exceed 100 amp but not all the spaces than upgrade the main. If the loads dont exceed 100 amp, but all the spaces are taken, then sub panel. I'm assuming that the main panel is feeding the sub panel.
Thanks MW. To answer your question, yes the main panel would feed the sub panel.

So, if what you are saying is true, a 200A panel would provide more total amps/volts than the 100A. But, does the service wire need to be upgraded in order to provide more juice, or is there something about the panel itself that provides more?
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Old 03-07-2015, 08:17 PM   #5
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Re: New Main Panel Or Sub Panel?


A load calculation is needed to provide the best scenario.

Of course you will gain amperage available by upgrading from 100 to a 200 amp service. Many times, a sub panel will suffice to get more spaces.

One of the cities I do a lot of work in has an electrical inspector who wrote this calculator and it's great.

Go to this site. http://www.naperville.il.us/loadcalculator.aspx

Then download the residential load calculator. If you are somewhat privy to the terminology you should be able to do it yourself if your electrician is too lazy to help you.

Hope this helps.
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Old 03-07-2015, 09:25 PM   #6
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Re: New Main Panel Or Sub Panel?


Quote:
Originally Posted by rselectric1 View Post
Of course you will gain amperage available by upgrading from 100 to a 200 amp service.
Thanks rselectric1.

This is the part I don't get. Am I gaining available amperage from the 200A panel itself, of does it need more juice coming in? Other than available spaces, what is it about the 200A panel that's different from the 100A panel?
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Old 03-07-2015, 09:29 PM   #7
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Re: New Main Panel Or Sub Panel?


I just read another discussion on this same subject on a different forum and the consensus seemed to be that usually the supplied wire to the weather head is good for up to 200A but probably not adequate for anything over that. If that's the case, assuming the wire is good for up to 200A, what advantage is there upgrading the panel from 100 to 200 rather than adding a sub panel?

One reply stated that in some states, the sub panel can only be half the amp size as the main. That would make a big reason to upgrade the main over adding a sub panel.
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Old 03-07-2015, 09:32 PM   #8
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Re: New Main Panel Or Sub Panel?


Quote:
Originally Posted by Gregavi View Post

Other than available spaces, what is it about the 200A panel that's different from the 100A panel?
The difference is a 200A main breaker AND the wire supplying the panel...

If you're current 100A panel is full and you add on a subpanel just to fill that up as well, dont you run the risk of overloading and triping that 100A main? This is why you need to run a load calc on the house o see what you really need.

Wire run in the air to the weatherhead isnt subject to the same rules as what you have in conduit down to the meter and panel. I've got their 1/0 aluminum from the pole to my 3/0 copper running down to my meter. The POCO thinks that their 1/0 in the air is just fine.

Last edited by Splinter; 03-07-2015 at 09:37 PM.
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Old 03-07-2015, 09:50 PM   #9
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Re: New Main Panel Or Sub Panel?


Thanks Splinter. This may be the best answer I've gotten.

So, it seems like upgrading the panel from 100A to 200A while upgrading the wire from the weather head to the panel would do the trick.

Not sure what "POCO" is???
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Old 03-07-2015, 10:39 PM   #10
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Re: New Main Panel Or Sub Panel?


Power company
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Old 03-07-2015, 11:31 PM   #11
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Re: New Main Panel Or Sub Panel?


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Originally Posted by aptpupil View Post
Power company
OC


Of course.
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Old 03-08-2015, 09:17 AM   #12
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Re: New Main Panel Or Sub Panel?


Check what you've already got.

The voltage at the outlet farthest from the panel should be within 5% of the voltage at the panel when you have a 15A load plugged into the outlet.
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Old 03-08-2015, 01:43 PM   #13
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Re: New Main Panel Or Sub Panel?


Quote:
Originally Posted by GettingBy View Post
Check what you've already got.

The voltage at the outlet farthest from the panel should be within 5% of the voltage at the panel when you have a 15A load plugged into the outlet.
Good tip. Thanks GB
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Old 03-08-2015, 02:51 PM   #14
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Re: New Main Panel Or Sub Panel?


These questions I'm asking is for my general knowledge but I do have a job to do for my neighbor where he needs to increase his capacity. He already has a 220V hot tub and a motor home that he wants to plug in. And is planning on getting central air conditioning. He's pretty much maxed out on the main panel.

We will be using a licensed electrician but it's up to my neighbor (and I) to make the decision what the best way to increase his capacity.

Q: Could the 100A main breaker in the main panel be replaced with a 200A main breaker and also upgrade the wire from the weather head to the main panel and then add a sub panel? Would that in effect be almost the same as upgrading the main panel to a 200A? The reason this way is being considered is it eliminates the need to get Edison involved because they would need to switch their meter from old to new panel if we upgrade the main.

Thanks again to all the replies.
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Old 03-08-2015, 03:15 PM   #15
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Re: New Main Panel Or Sub Panel?


Just to be clear (because I think this question was asked, but hasn't been answered directly) :

Adding a sub-panel does NOT increase the total amps available to the property served by the main. All it does is give you some options about how to distribute that power.
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Last edited by CarpenterSFO; 03-08-2015 at 04:21 PM.
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Old 03-08-2015, 03:22 PM   #16
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Re: New Main Panel Or Sub Panel?


Quote:
Originally Posted by Gregavi View Post
....

Q: Could the 100A main breaker in the main panel be replaced with a 200A main breaker and also upgrade the wire from the weather head to the main panel and then add a sub panel? Would that in effect be almost the same as upgrading the main panel to a 200A? The reason this way is being considered is it eliminates the need to get Edison involved because they would need to switch their meter from old to new panel if we upgrade the main.

...
You're essentially asking whether you can increase your neighbor's service from 100 amp to 200 amp without the power company being involved. No.

And the panel - bus bars, etc. - is made to carry 100 amps. Make no mistake, your neighbor will finger you for the stooge when the POCO and the fire department come looking around. Give your neighbor the name of a good electrician, and walk away from it.
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Last edited by CarpenterSFO; 03-08-2015 at 04:29 PM.
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Old 03-08-2015, 06:05 PM   #17
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Re: New Main Panel Or Sub Panel?


Quote:
Originally Posted by Gregavi View Post
We will be using a licensed electrician but it's up to my neighbor (and I) to make the decision what the best way to increase his capacity.
In addition to Bob's comments, no it is not up to you. You don't have the technical knowledge, and this isn't the place to get it. A qualified electrician can advise you regarding the best options.
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Old 03-08-2015, 08:35 PM   #18
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Re: New Main Panel Or Sub Panel?


Quote:
Originally Posted by CarpenterSFO View Post
And the panel - bus bars, etc. - is made to carry 100 amps.
This is the fact I was looking for. I am not trying to do anything illegal or not to code, I'm just trying to understand how the whole main panel and sub panel, 100A vs 200A thing works.

Thanks for taking the time.


Quote:
Originally Posted by Tinstaafl View Post
no it is not up to you. You don't have the technical knowledge, and this isn't the place to get it. .
And yes, it is my neighbors decision as to which he chooses (upgrade main panel or add sub panel). Not sure why you state it isn't.
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Old 03-08-2015, 08:54 PM   #19
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Re: New Main Panel Or Sub Panel?


Quote:
Originally Posted by Gregavi View Post
And yes, it is my neighbors decision as to which he chooses (upgrade main panel or add sub panel). Not sure why you state it isn't.
It is his decision whether he can make do with his current capacity or needs to have more. The manner in which capacity is added needs to be both safety and code compliant, and you have indicated that neither he nor you has the ability to ensure that.

I'm not trying to be confrontational; just calling it as it is.
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Old 03-08-2015, 09:04 PM   #20
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Re: New Main Panel Or Sub Panel?


Quote:
Originally Posted by Tinstaafl View Post
It is his decision whether he can make do with his current capacity or needs to have more. The manner in which capacity is added needs to be both safety and code compliant, and you have indicated that neither he nor you has the ability to ensure that.

I'm not trying to be confrontational; just calling it as it is.
The licensed electrician would be ensuring that which ever one my neighbor chooses, it would be done both safety and code compliant. My neighbor would simply be deciding which option to choose. I never stated he nor I would be doing the work.

Thanks for your input.

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