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Generators & Motors General Discussion Antique Generators, Light Plants and Old Electric Motors: Questions and answers about restoring and showing old power generation systems.

Generators & Motors General Discussion

How To Tie Two 200 amp Panels Together


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  #1  
Old 05-07-2012, 08:50 AM
Slick 50 Slick 50 is offline
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Default How To Tie Two 200 amp Panels Together

I am wanting to tie two 200 amp single phase panels together on the load side. Both panels are fed from a single meter. My thoughts are to use number 2 wire to each panel with a breaker at each end in the panel.
Is there any problem with doing this to tie the panels together?
Thanks for any help.
Rick
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Old 05-07-2012, 09:27 AM
Gary Bahre Gary Bahre is offline
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Default Re: How To Tie Two Panels Together

Slick; In the area that I live in the power co. uses a 320 amp service, this feeds 2, 200 amp box's from one meter. Check with your power supplier to see what box's and other things you need to do this. Gary
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  #3  
Old 05-07-2012, 10:57 AM
Slick 50 Slick 50 is offline
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Default Re: How To Tie Two Panels Together

Thanks Gary,
The panels are already in and wired. They are Square D QO panels. Hoping to prove or disprove my thoughts about phasing. Does it matter what leg is tied to a particular bus bar? I'm thinking it does but not sure.
Thanks,
Rick
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Old 05-07-2012, 12:24 PM
Power Power is offline
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Default Re: How To Tie Two Panels Together

Why do you want to do this?
Violates national electric code.
Will not be approved by AHJ.
You would have 2 feeds into a panel @200 amps each - in excess of manufacturer's ratings for panel
You would have 2 disconnects- one top, one bottom
When something goes wrong, insurer will not cover it.
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Old 05-07-2012, 03:06 PM
Jim Rankin Jim Rankin is offline
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Default Re: How To Tie Two 200 amp Panels Together

If all you want to do is experiment that when you connect one "phase" to the other "phase", you do indeed have a short circuit, go ahead.

You can do the same thing from any 2 pole breaker in each box, no need to do it with expensive 200 amp breakers. Take a volt meter, test the two breakers respective terminals and when you find the ones that test 0 volts between them, those are in phase, If you test two poles and get 240 volts, those are out of phase. Confirm that each breaker is indeed turned ON by testing voltage to neutral after you test voltage between the two breakers.

With single phase panels, no it doesn't matter which line is connected to which bus bar. If it was a 3 phase panel, then I could see that it might be nice to have phaser rotation be A, B, C in both panels. However, this would not necessarily be the same phases to the same bus bars. Could be, but not necessarily the same. A,B,C is the same as C,A,B or B,C,A but is opposite of C,B,A etc...
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Old 05-07-2012, 03:33 PM
Slick 50 Slick 50 is offline
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Default Re: How To Tie Two 200 amp Panels Together

Jim,
Thank you so much for the response. The tie wire between panels is actually number 4, memory not always so good. As mentioned, on each end of that wire will be breakers, in this case, 90 amp. I had planned on checking continuity from the meter to each leg on the tie for proper line up before energizing. We are still about a month away from powering up the house.
Thanks again,
Rick
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  #7  
Old 05-07-2012, 05:03 PM
grif grif is offline
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Default Re: How To Tie Two 200 amp Panels Together

Was your phasing question whether or not you had three phase available? Or if you really just had two panels of center tapped 240 single phase?
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Old 05-07-2012, 05:22 PM
Slick 50 Slick 50 is offline
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Default Re: How To Tie Two 200 amp Panels Together

The question was about single phase 240 volt only. The limit with 42 spaces per panel is what got me, needed a few more spaces. It's all about powering the panels with a generator and the main feed opened with a disconnect.

Thanks for the quick help, very much appreciated.
Rick
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Old 05-07-2012, 05:58 PM
davidradio davidradio is offline
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Default Re: How To Tie Two 200 amp Panels Together

i would not do this both mains have to be off to prevent feed back to line

i would only use two 200 amp tranfer switches only that way
there can be no feed back if mains are left on

one other option would be to put an inter lock in both panels
from interlock.com that way there will be no feed back to power line

and if power is restored
with main on you will have a mess burnt up generator and possible
fire in house and insurance will not cover this as voliation of nec
big time
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  #10  
Old 05-07-2012, 05:59 PM
grif grif is offline
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Default Re: How To Tie Two 200 amp Panels Together

Sounds like the same configuration I've got, except I've got lots of slots left, my issue is the two panels are 100 feet apart. I've about decided to put the jolly green giant transfer switch right at my side of the meter, and I've got critical load on each panel. (poor planning on my part).
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Old 05-07-2012, 06:09 PM
jht1057 jht1057 is offline
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Default Re: How To Tie Two 200 amp Panels Together

Slick,

You can tie panels together and it is approved by code.
The panel that the meter feeds would be the "main" panel, the second panel would be the "sub" panel.

When wiring mains to the bus bars, I always kept the white on the right.

Jim
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  #12  
Old 05-07-2012, 07:13 PM
Power Power is offline
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Default Re: How To Tie Two 200 amp Panels Together

You can tie panels together and it is approved by code.
The panel that the meter feeds would be the "main" panel, the second panel would be the "sub" panel.

That's ok, but then the most amperage available is the rating of the main panel breaker - 200 amps. Also, there are restrictions on the size of sub panel breaker. It cannot equal main.
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Old 05-07-2012, 07:21 PM
Tencubed Tencubed is offline
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Default Re: How To Tie Two 200 amp Panels Together

Sounds to me like it's Jerry Rig time on this project.

Your home owners insurance and a lot of other problems can get involved really quick.

I'd sure suggest you get a licensed electrician to take a look at your project and give you the advice you are seeking.

Just my opinion of course but what any of us say about your project is worth every dime you're paying for it.

Mike
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Old 05-07-2012, 07:34 PM
Graycenphil Graycenphil is offline
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Default Re: How To Tie Two 200 amp Panels Together

Quote:
Originally Posted by Slick 50 View Post
The question was about single phase 240 volt only. The limit with 42 spaces per panel is what got me, needed a few more spaces. It's all about powering the panels with a generator and the main feed opened with a disconnect.

Thanks for the quick help, very much appreciated.
Rick
If all you need are a few more spaces for circuit breakers, can't you just use a few piggyback breakers? Or as someone suggested, add a subpanel for a few extra circuits.
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Old 05-07-2012, 08:09 PM
Craig Mattson Craig Mattson is offline
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Default Re: How To Tie Two 200 amp Panels Together

I would suggest the piggyback sub panel method. I have done it both ways much easier to get the inspector to ok it that way. Good luck
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  #16  
Old 05-07-2012, 08:59 PM
Daverepair Daverepair is offline
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Default Re: How To Tie Two 200 amp Panels Together

Are you talking about connecting a generator to 2 200 amp panels that are fed in parallel from one meeter. See drawing attached. If so, BAD IDEA
Attached Thumbnails
backfeed.jpg  
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Old 05-07-2012, 09:03 PM
Daverepair Daverepair is offline
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Default Re: How To Tie Two 200 amp Panels Together

Lots of room for problems. How about two transfer switches, one before each panel or one big switch right after the meter. That would requirer a big generator.!00kw I believe.
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Old 05-08-2012, 10:36 AM
armandh armandh is offline
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Default Re: How To Tie Two 200 amp Panels Together

MY HOUSE:

the entry panel with bonding point and where the mains disconnect
is interlocked with the generator feed breaker.
there is also a 125 amp breaker feeding a sub panel
all sub panels must have an isolated neutral

the feed from the portable generator is 4 wire
with the neutral isolated from the generator frame.

if you have a permanent generator installed
then a transfer system [or manual switch] is required

code now requires a disconnect between the meter and transfer

if the permanently installed generator feeds more than one transfer
it must have overload protection correct for each line and be bonded, thus
requiring all transfers to be 3 pole and following panels have isolated neutrals

Last edited by armandh; 05-08-2012 at 04:14 PM.
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Old 05-08-2012, 01:08 PM
Power Power is offline
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Default Re: How To Tie Two 200 amp Panels Together

Armandth - sounds like a safe system. What is amperage on your main?
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Old 05-08-2012, 03:45 PM
armandh armandh is offline
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Default Re: How To Tie Two 200 amp Panels Together

225 amp
http://www.smokstak.com/forum/attach...9&d=1158413795

turn off main breaker causing the
breaker lever alignment with notch in plate
slide plate right to lock mains breaker off and that
clears an area for gen breaker to be moved right to on
attempts to disengage the lock flip the gen breaker off

I only load the generator to a 12.5Kw max [50 Amp]
well below generac's alleged 17.5 continuous and 26 surge KW
and as these screamers are not likely to out live us, for a back up,
I have an 1800 rpm '64 vintage k582 powered 7.2 [real] Kw homelite [1.0 pf]
one can load it until the breakers open, and at about 3 hp/kw it is not even working hard
http://www.smokstak.com/forum/attach...1&d=1188565666

Last edited by armandh; 05-08-2012 at 04:13 PM.
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