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9,683 Posts
Discussion Starter #1 (Edited)
Don't freak out if you're building a new, seemingly middle grade house, and the electrician is mounting two panels.

Some of you may be used to this already if you normally build large houses that are getting 320 and 400 amp services, but this is becoming common even in modest homes with 200 amp services.

The reason is this: The NEC limits each lighting and small appliance panelboard (the category into which residential panelboards fall) to 42 circuits maximum. For this reason, the panel manufacturers have limited their boxes to 40 or 42 spaces, depending on the brand. Your typical new one story 3 bedroom home with unfinished basement will often have the following circuits:

1) Kitchen countertop circuit #1
2) Kitchen countertop circuit #2
3) Refrigerator
4) Dishwasher
5) Microwave
6) Living room receptacles
7) Dining room receptacles
8) Outdoor receptacles
9) Garage receptacles
10) Freezer
11) Sump pump
12) Bedroom #1 and #2 receptacles AFCI
13) Master Bedroom receptacles AFCI
14) Bedroom lighting and smokes AFCI
15) Master bathroom
16) Main bathroom
17) Whirlpool tub
18) Kitchen, Living room, Dining, hallway lighting
19) Basement lighting
20) Basement receptacles circuit #1
21) Basement receptacles circuit #2
22) Clothes washer
23, 24) Range (2 spaces)
25, 26) Clothes Dryer (2 spaces)
27, 28) Hot water heater (2 spaces)
29, 30) Air handler circuit #1, blower and controls (2 spaces)
31, 32) Air handler circuit #2, backup heat package (2 spaces)
33, 34) Heat pump condensing unit (2 spaces)
35, 36) Hot tub (2 spaces)
37, 38) Outdoor shed prewire (2 spaces)
39, 40) Swimming pool (2 spaces)
41, 42) Air compressor receptacle(2 spaces)
43, 44) Welder receptacle (2 spaces)
45, 46) Well pump (2 spaces)

You can see that this is more than one panelboard will hold, even though the demand load is less than 200 amps in many cases. For this reason, two panelboards are often mounted. Even if you didn't have all the items on the list (or substitute different items), the panelboard would be full or near full right off the bat. It seems prudent in that case to mount two panels for future needs.

9,683 Posts
Discussion Starter #3
Glasshousebltr said:
The big remod on my site has 4.

I'm sure it's a first class job. When the house is spread out, or their are multiple heat pumps or a/c units, that would not be uncommon. Maybe panel in the garage, panel in outbuilding, panel on first floor, panel on second floor, panel in basement, panel in poolhouse, etc.

I just get GC's every now and again that freak when I do install or propose to install 2 panels in a home that may have been previously built with only one.

I have a hard time wiring to bare minimum, and 2 panels are often installed by me. Even if they don't need two panels, it's nice to have the "emergency circuits" in a second panel in the event that they install a generator down the road. That makes most of the electrical work done already. Just add transfer switch.
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