Basement Subpanel

Guys, I'm planning on starting work on finishing off my 1500 sqft basement this winter and will want to set a subpanel to power all the new amenities. The new space will consist of three bedrooms, a family room, bathroom, laundry room, and a storage room. Also included will be two electric dryers and an outdoor hot tub and...... At the moment, it's hot here in Colorado and the wife wants A/C now. So I'm gonna do it, albeit under duress.

Since I'm not quite ready to start framing, I'd like to set a subpanel on a temporary wall in the basement (where a room will be built around the existing mechanicals) and tap power for the A/C from there. I'd prefer to kill two birds with one stone and make a single electrical feed run from the main panel to cover all my needs.

My delima is two fold: First, is determining the capacity of the subpanel. And second, our house is only 3 years old and only has a 150 A service. Is this enough to also power a 60A, 80A, or 100A subpanel, whatever it calculates to be?

Some issues that may be importart are: the furnace and hot water heater are gas, but stove/range is electric. Also upstairs is already wired for a laundry to include the electric dryer and will remain so, although once the basement is finished we will move laundry duties to the basement. Finally, the main panel is in the garage which is approximately 70' from where the subpanel will go. Not sure if that has any bearing on the load calculations.

Sorry for the book, but I'd really appreciate any advice on the subpanel capacity and feasibility of powering everything mentioned from there.

Thanks

Brian S

 

It's better to keep the large loads in the main panel if you can. If you do use a subpanel for all of this stuff, I recommend you provide 100 amps to it. The selection of the size of your subpanel should not be affected by the size of your main panel.

We don't have enough information yet to know, but it's very likely you should upgrade your service to 200 amps. All the stuff you list indicates that your have a voracious appetite for power. If you'd like some guidance on that, tell us how many square feet your house is (including the basement), and how many tons of A/C you will be putting in.

Be careful about mounting the subpanel on a temporary wall. Panels are not very easy to move.

 

John, thanks for the reply. The house is a rancher that will have 1600 sqft above and 1500 sqft in the basement. The estimates that I have recieved for the A/C so far call for a 3.5 ton unit.

Thanks for the temporary wall warning. I was planning on leaving plenty of slack, but got to thinking that might violate code somehow. Any idea?

Thanks

Brian_S

 

Don't have my tools to do this calculation until tonight. Maybe somebody else can help earlier.

 

A 3100 square foot house with

• 3.5 tons of A/C
• three electric clothes dryers
• a 11KW hot tub heater
• an electric range and an electric oven
• one refrigerator
• one dishwasher
• one disposal
• one microwave
• no freezer
• no jacuzzi tub

has a demand load of 239 amps.

Drop down from three dryers to two, and your demand is 218 amps.

Drop down to 3 tons of A/C and you're down to 212 amps.

Drop down to one dryer, and you're down to 192 amps. (Do you really need two clothes dryers???

As you can see, I made some assumptions that may or may not be right, but are probably close. In any case, you'll be way beyond your 150 amp service, and even 200 amps may not be enough. Plan on a service upgrade before tackling your basement and adding your A/C.

 

John,
Thanks again for the reply. Looks like you have my situation nailed, except that I don't really have an oven and a range. Just an electric oven. Anyway looks like I'll be upgradingmy service before I can do anything else anyway. I appreciate your help in working this out. Cheers

Brian S

PS: The only thing I can say to justify the two dryers is that I have two teenage daughters. Hopefully you understand!