[cb_philadelphia]

Considering having a mini split a/c system installed, which would require adding a 40 amp breaker.

Can I add a 40 amp breaker into current box, or when I have an electrician come out to wire it, is he going to tell me I need to upgrade my service to 200 amp?

Service is currently 100 amps, but I doubt I ever really use close to that.

I have 5 open slots in the breaker box, and I sum the breakers on each bus as follows:

Bus 1 - 140 amp
Bus 2 - 120 amp

Image of breakers attached. Circuit detail below:

Bus 1:
1. 15 amp -- overhead lights and living room outlets (multiwire branch circuit)
2. 15 amp -- furnace
5. 20 amp -- washer / dryer (multiwire branch circuit)
6. 20 amp -- refrigerator
9. 15 amp -- outdoor lighting
10. 20 amp -- kitchen GFCIs, garbage disposal
13. 15 amp -- bedroom outlets
17. 20 amp -- basement utility outlets e.g., dehumidifier

Bus 2:
3. 15 amp -- overhead lights and living room outlets (mwbc)
4. 15 amp -- hallway outlets
7. 20 amp -- washer / dryer (mwbc)
8. 20 amp -- kitchen GFCIs
11. 15 amp -- outlets in finished portion of basement
15. 20 amp -- dishwasher and some hallway dimmer lights
19. 15 amp -- alarm

 

[rjniles]

Your loads are small. No 240 volt appliances. I see no issue adding a 2 pole 40 amp breaker.

 

[ddawg16]

Your loads are small. No 240 volt appliances. I see no issue adding a 2 pole 40 amp breaker.

I concur

As a general rule, you don't add up all the breakers to determine your real load. Instead, you figure out what is actually running at any given time.

Say for example you had and electric oven AND electric water heater. Those items could be on at the same time. So you would make that a part of the load calculation.

Take my garage. I have 50A/240Vac going to it. But I'll never get anywhere close to using all that. Worse case, Compressor + Table Saw + dust Collector + Lights. Compres is 8A/240....saw 12A/120...Dust Coll 8A/120....Lights 2A/120