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DLHLBR · Nov 16, 2006, 04:23 PM

I'm finishing a basement in a large 8 year old home. We've added about 1500 sq feet in the basement and 5-6 new circuits.

The breaker box, and a sub panel are full, with several mini breakers. We've been told that as part of the final electrical inspection a "load analysis" will be done. Question 1, exactly what is a "load analysis" and Question 2, where would you suggest we add the new circuits? I noticed in looking over some previous answers here that 42 breakers per box is the maximum. How is this calculated? Is a double pole breaker counted as 2 breakers?

Also, the existing sub panel is being fed by a 60 amp breaker in the main box-it's right next to the main. I believe this particular sub panel box is rated up to 100 amps. Would it be advisable to increase rewire the sub panel for 100 amps and put the new circuits there?

Thanks. Any other input would be appreciated. This is my project for next week.

tkrussell · Nov 16, 2006, 04:50 PM

Outstanding!!

Sorry, just tickled there is someone that is concerned about connected load. I just don't hear about this happening as often as I think it should.

What I believe will be done is to survey the home and perform load calcs to confirm the size service, feeder wires, neutral size, and grounding are all confirmed for sizes, ratings, etc. and that the existing service rating can handle the added load of the addition.
And/Or

The inspector may have an diagnostic instrument that checks each outlet for proper wiring and polarity, and applies a large load to check the breakers can handle a load, and also checks for voltage drop, which normally is caused by long wires, or loose connections even in short runs.

Or some combination of both.

To suggest what and where any circuits need to go, need to know the purpose of the addition, bedrooms? Bathrooms? Offices? need exactly what will be built.

Yes each pole of each breaker is counted , the max being in one panel is 42 poles.

Increasing the sub panel to 100 amps may be part of the answer, to help with pole/circuit spaces, but the main service still needs to handle the added load, so the more I think about it, that is what will be checked.

DLHLBR · Nov 16, 2006, 05:42 PM

Thanks for your help. In answer to your questions, one circuit will be for the outlets and lighting in an added bedroom (this will be an arc fault breaker) two will be for the outlets in the remainder of the basement, we've added one additional circuit for lighting, and two circuits in the kitchenette area, one for a microwave and the other for a small refrigerator. We've added the new bathroom to the circuit that was feeding the upstairs baths.

I'm a bit concerned about the load analysis because it is a large house, and we've added a substantial amount of finished space, though there won't be much down there that draws a whole lot. For obvious reasons, we'd rather not have to install a new service. The main feed is underground.

tkrussell · Nov 17, 2006, 03:50 AM

THe circuits you outlined seem fine, except the bathrooms. The basement bath needs a 20 amp outlet, and can share the upper bathroom circuit, as long as the circuit only has bathroom receptacles on it. If the upper bath has lighting on the outlet circuit, the basement bath can have one 20 amp circuit with that bath's lighting on that circuit.

The load analysis will greatly depend on not only the total square footage of livable space, along with any stationary electric appliances, such as AC, ranges, ovens, dryer, water heater, in addition to the required circuits, such as appliance circuits and laundry.

This analysis should always be done before any additions are actually done, to be sure what space and capacity is existing, and how much new load can be added.

If you provide the information of the items I listed,I can do these calcs for you. I do not show how to do the calcs here, due to several variables, anyone that wants can see the Examples in any NEC code book, found at any library.

homeinspector · Nov 20, 2006, 09:01 PM

DLHLBR
Just a reminder, if you are putting a bedroom in the basement there are requirements for escape and rescue openings. There must be a door or a window no higher than 44" above the floor (20" wide by 24" high) with 5.7sq. ft. minimum clearance unless it is at ground level then 5.0 sq. ft. is OK. Last thing anyone wants is no escape exit in case of fire.