Adding large amperage subpanel

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  #1  
Old 06-14-13, 12:07 PM
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Adding large amperage subpanel

I'm looking to install both a geothermal heading/cooling system and stub in a future charging station for an electric car since I expect that to be used a few years don't the road.

My current service / main breaker panel is 150A.
The current totals for the geothermal and a charging system also total 150A.
I understand completely that without upgrading my main service I will be unable to power both plus the rest of my home, so lets ignore that part for now.

Can I install a 150A breaker in my 150A main panel to wire up a 150A sub-panel? I only intend to use it for 70A at the moment (60.6A actually, have to love rounding up and 54 run-load) which replaces the 50A A/C breaker... so I'm really not increasing actual load at the moment. Obviously when I throw a car charger in the mix, I'd have to jump to 200A service.

Would:
150A Service->150A Breaker Panel->150A Breaker->150A Sub-Panel->70A Breaker->appliance pass inspection or would the inspector smack me over the head for this?
 
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  #2  
Old 06-14-13, 12:29 PM
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No expert....but I don't think you'll be able to fit a 150A breaker in a regular slot?

Why not just feed the sub with the 70A (if that would fit)? If you use the right wire gauge for 150A now...it would be easy to upgrade to a full 150A supply later. Leave plenty of wire for the future change.

I'd also think a 200A upgrade might not be enough.

Pro's will be around later.....

EDIT Thinking about it, the right wire for 150 probably won't fit in a smaller breaker.
 
  #3  
Old 06-14-13, 02:12 PM
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I can get a HOM2150 series breaker from Square D (About $120, ouch), it is amazing they make them. There are also screw-on terminals for the bus bars for ground and neutral wires of that size.

The main addition of amperage would be a future car charger since the geothermal replaces the AC and the furnace/blower circuits... the chargers must be configurable because it appears it can be setup with breakers ranging from 40A all the way up to 100A. I wouldn't have a problem at all if I just wired up for the 70A off the main panel, maybe I shouldn't worry about it with it being a few years out for getting an electric vehicle... who knows, I may not even live there at that point...
 
  #4  
Old 06-14-13, 03:35 PM
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Too many what ifs for the future in this. Is there anything that you need now? Where will this other panel be located?

With a service upgrade to 400A you can get a separate feed to your new panel.

Tesla says that it only needs 12amps at 120v. Also support 240/24amp, 240/40amp, and 240/80amp

If you want to go whole hog with a supercharging station then you will most likely need 480V 3-phase service.

Also check your existing panel as there are limits on the amps per bus stab.
 
  #5  
Old 06-14-13, 05:36 PM
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Why not just feed the sub with the 70A (if that would fit)? If you use the right wire gauge for 150A now...it would be easy to upgrade to a full 150A supply later. Leave plenty of wire for the future change.
This is what I would do unless you are ready to upgrade to either a 320 or full 400 amp service now. You can install a junction box near the main panel and splice the 150 amp rated wire to #4s that can connect to the 70 amp breaker and power the geothermal from the subpanel.
 
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