Sub Panel Install - Main Panel No Breaker Space

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Old 02-10-15, 12:21 PM
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Sub Panel Install - Main Panel No Breaker Space

Hi:

I am looking into installing a sub panel in my basement which will be used to feed electrical circuits to the basement that is currently unfinished. I have an 150 amp main panel and was thinking of installing a 90-100 amp sub panel. I do however have a few questions:

1) Since I do not have any breaker space, I was planning to replace some of my existing breakers with tandem breakers to free up enough space for the sub panel breaker. I'm just not sure exactly how to go about it. I also was thinking of using a quad breaker if it would work. Recommendations? I've included a image below of my panel if it helps anyone make recommendations.

2) Do I need to ensure I use the same brand breakers? I assume yes...

3) Is 100 amp too much for the sub panel in the basement given the main panel is only 150 amps?

Any help is appreciated.

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Last edited by PJmax; 02-10-15 at 04:19 PM. Reason: reloaded pictures
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Old 02-10-15, 01:35 PM
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Your attachment didn't work. However, not all panels will accept tandems. You might just need to move two small circuits to make room for the two pole to feed the sub panel. The original two circuits move to the sub.

Without knowing the expected loads I would suspect a 50 or 60 amp sub would be plenty.
 
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Old 02-10-15, 01:45 PM
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Thanks for the reply, appreciate it. Just tried the attachments again. Since the sub panel will be in the basement, i'm not certain it will be very easy to re-route the wire for the circuits that I am consuming with the sub panel so was hoping to use tandems or a quad.
 

Last edited by PJmax; 02-10-15 at 04:21 PM. Reason: removed duplicate pics
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Old 02-10-15, 04:26 PM
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That panel is pretty well loaded. Is it a surface mount panel ?

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I think I'd move the 3) two pole breakers down one spot and move the two circuits on that tandem breaker to the subpanel and put a new 2 Pole breaker in there.
 
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Old 02-10-15, 04:49 PM
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Thanks PJmax. Yes, it is surface mounted on the exterior of my house. Is there any way to shuffle the breakers so I can avoid moving a circuit to the basement? I would like to do it that way if possible. I'll already be running the wire to feed the sub panel so I guess I could splice and fish the wire through for the breaker I am moving to the basement at the same time if there is no other option.
 
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Old 02-10-15, 05:10 PM
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That would be the best plan,stay away from tandems if possible.
Geo
 
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Old 02-11-15, 12:54 AM
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That is a 20/40 panel. It is made to accept tandem circuit breakers in all slots.
 
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Old 02-11-15, 03:51 AM
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Just like in the upper left - use a triplex to free up space - Shop Eaton Type BR 30-Amp Quad Circuit Breaker at Lowes.com This one gives you one double pole 30 amp and two single pole 20 amp circuits in two spaces.
 
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Old 02-11-15, 07:37 AM
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Thanks for the replies, very helpful. To be sure I follow, I could replace the 20 amp and 30 amp circuit with the triplex breaker you refer to, move the two 40 amp breakers down and then should have enough room for the sub panel breaker? Also, what is the recommended minimum gauge for the feeder wire to the panel? 4/3 or 2/3?
 
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Old 02-11-15, 07:45 AM
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what is the recommended minimum gauge for the feeder wire to the panel?
It is based on the size of the breaker supplying the subpanel, #10 for a 30 amp subpanel - #8 for 40 amp - #6 for 60 amp - #3 or #2 for 100 amp.
 
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Old 02-11-15, 08:26 AM
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Thanks. Here is the cable I think I plan to use. I will have about a 40 ft run indoors to the sub panel. There is a 2 ft section exposed to the elements on the exterior of the house before it enters the home which I planned to enclose in schedule 40 PVC conduit
 
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Old 02-11-15, 10:31 AM
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Do you really need 100 amps?
 
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Old 02-11-15, 10:41 AM
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I doubt that the OP even needs a 50 or 60 amp panel.
 
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Old 02-11-15, 10:50 AM
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Good question - that's something I wanted to get feedback on. At the moment, the basement will have a few light/outlet circuits, gfci for the bathroom/wetbar etc. however I am also planning to install baseboard heaters below each window (there are 3 windows). I was taking the approach more amps available = better but curious for feedback on that. Additionally, at some point in the future I may decide to install an electric tank-less water heater down there so was planning ahead a bit just in case that ever materializes.
 
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Old 02-11-15, 11:49 AM
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How may amps will the heaters be?
I may decide to install an electric tank-less water heater down there so was planning ahead a bit just in case that ever materializes.
TWHs are often not a good idea. Given your in Colorado you might need 100 amps just for the THW (plus a couple of thousand dollars for an electric service upgrade to support the increased electric needs)whereas you would get better water volume, better heat, with a conventional storage water heater that would only need 30 amps.
 
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Old 02-11-15, 12:30 PM
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Base board heaters I am considering range from 1000-1500 whats. They come in 120 and 240 v options. So if i'm correct that's around 8-10 amps. If I have all 3 of them on at once that would be roughly a 30 amp draw? Is the recommendation that I go with a 60 amp panel?
 
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Old 02-11-15, 12:53 PM
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The panel would be 100 amps regardless of the load. It is the size of the breaker supplying it and the wire size that changes. Better to go with 240 volt for the heaters , smaller wire. About a 20 amp draw at 240 volts needing a 30 amp breaker if you put them all on the same breaker. Probably need to go to a 70 or 100 amp breaker just to give you some spare capacity. 100 amp you should be able to add a conventional water heater later.
 
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Old 02-11-15, 01:20 PM
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Ok, thanks for the help. So in summary I think this is the plan:

1) Free up main panel space:
- As AStuff suggests, consolidate the 20 amp 2 pole and 30 amp breaker into a quad breaker which will free up 1 space
- Move remaining two 40 amp breakers down (or up) one space which will free up 2 slots for a 100 amp breaker that will feed the sub panel

2) Run 2-2-2-4 SER wire from main panel to 100 amp sub panel.
- Ensure that neutral is electrically isolated from ground at sub panel

3) Wire up branch circuits as needed. For baseboard heat - 30 amp 2 pole breaker for all 3 (assuming the heaters I use draw only 4-5 amps at 240 v)
 
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Old 02-11-15, 01:41 PM
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You may not be able to use the breaker stabs across from the 100 amp breaker due. To bus stab limitations.

Depending on the code cycle you may be limited to a 90 amp sub with that cable.

Why would you run a 30 amp circuit for less that 20 amps of load?
 
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Old 02-11-15, 03:15 PM
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Across from the 100 amp breaker? - I guess i'll have to remove the breakers and see if it is going to work? My city uses National Electric Code, 2011 Edition. I'll have to research what it states the wire needs to be but I thought 2 gauge would support 100 amps. Regarding the 30 amp breaker - that does seem overkill. 20 amp 2 pole breaker seems more appropriate.
 
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Old 02-11-15, 04:29 PM
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1500w/240v=6.25 amps 6.25ampsX3heaters=18.75 amps. A constant load can be no more then 80% of the breaker. 80%x20amps=16 amps. The 18.75 amps for all three heaters therefore exceeds what is allowed for a 20 amp breaker.
 

Last edited by ray2047; 02-11-15 at 06:14 PM.
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Old 02-11-15, 05:46 PM
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My city uses National Electric Code, 2011 Edition.
You better also check on arc fault requirements for your new 120 volt circuits.
 
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