sub panel or not

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Ivan Young

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Simpsonville, South Carolina
Hello gentlemen,
I have a friend that needs some help with an electrical problem. He bought a two storey with a full walk out basement that is semi-finished. The basement is already framed out with a light in every room and two receptacles. All the lights are controlled by one switch. There is no sheetrock installed. The main panel is in the basement and is a 200 amp. The panel has no more room for additional breakers. He wants to have two bedrooms, living room, dining room, den with tv and stereo, full bathroom, full kitchen with electric stove/oven and microwave. I don't believe a 100 amp sub-panel will work.
Here are the questions : 1) would it be best to have a separate main panel for the basement and how many amps.
2) the lights and receptacles do they have to be AFCI protected.
Thanks for your help in advance.
Ivan
 
Why wouldn't a 100A sub work? Are there a lot of large loads in the main panel already or is it mostly lighting circuits? Also, what code cycle are you on?
 
Thanks for replying Mr. Sparky. The main panel is full. They have hot tub, tanning bed, double ovens, electric stove, microwave, tons of lights and receptacles on the first and second floors. I was just thinking if a 100 amp sub-panel was installed and the kitchen on the main floor was being used at the same time the one in the basement there might be problems. Oh, he wants a washer and dryer in the basement too. We are in 2011 code.
Would the lights and receptacles have to be protected by AFCI?
 
170202-2120 EST

My personal opinion and what I did in my home.

A 200 A main panel in the basement. Three 50 A two pole breakers, and one two pole 40 A feeding subpanels. Two 40 A to handle the range top and oven. Also some single pole 20 A breakers. One for an outlet at the main panel. The furnaces are also from the main panel that is close by. This also helps to reduce light flicker.

My typical load is in the range of 1 to 2 kW. If I turn electric heaters on in the garage, then this adds 6 kW for a while. Sleep time is typically 0.2 to 0.5 kW.

One subpanel in basement, two on first floor, one on second floor, and the last one is in the garage. This puts breakers close to where the circuits are, except for the range and oven. Thus, minimize light flicker.

How many times in 50 years have I tripped a breaker? Seldom. But I do use the garbage disposal breaker as a redundant and better disconnect than the wall switch when one needs to put their hand into it. Thus, two disconnects in series. This subpanel is in the pantry adjacent to the kitchen.

From the main panel one 20 A breaker feeds an outlet circuit that provides one powered duplex at each subpanel. Thus, if a subpanel is disconnected, then power is available close by.

I also should also note that I have gas for heat, clothes drying, and the range is now gas.

The above description may provide you with some general ideas on how to address your task.

.
 
Ivan Young said:
Thanks for replying Mr. Sparky. The main panel is full. They have hot tub, tanning bed, double ovens, electric stove, microwave, tons of lights and receptacles on the first and second floors. I was just thinking if a 100 amp sub-panel was installed and the kitchen on the main floor was being used at the same time the one in the basement there might be problems. Oh, he wants a washer and dryer in the basement too. We are in 2011 code.
Would the lights and receptacles have to be protected by AFCI?
Click to expand...

With the addition of the kitchen and laundry in the basement, that's a lot of electrical appliance load. I'd probably start by doing a service calc to see where I'm at.

The 100A sub would be large enough to handle the basement IMO. I'm just questioning if you're going to go over the 200A for a total service calc. In MN, a house such as this would probably get a 300A service.

If if I remember correctly back to the 2011 code, you would need to AFCI protect all lights and outlets except those in the bathrooms, kitchens and unfinished areas and the laundry outlets.
 
Put the subpanel right next to the main, move a few circuits over to it. I'd do a load calculation, because from what you described it sounds like he may need a service upgrade.
 
as long as the load calculation supports doing so, it is likely that 100A is adequate. However for convenience or as a design criteria he may want more circuits than are available in the existing panel. Nothing wrong with that. Just add another panel and wire it up appropriately. You can have 10,000 branch circuit breakers if you want on a 100A service as long as the load calculation says the 100A service is adequate.
 
This is just for my education only. When MNSparky say do a service calculation, does that mean using a clamp meter on the two hot legs to see how much amps is being used? If it is , how do you do this? Do you turn on some equipment in the house like stove, dryer, microwave?
 
equatorman said:
This is just for my education only. When MNSparky say do a service calculation, does that mean using a clamp meter on the two hot legs to see how much amps is being used? If it is , how do you do this? Do you turn on some equipment in the house like stove, dryer, microwave?
Click to expand...

Since you are a "trainee" I hope you have a code book. If you do then look at Article 220, it explains how to do a load calculation.

If you don't have a code book or have ever read one, it would be hard to explain. But in short, no, you don't clamp an amp meter to circuits to check the load. You could get some idea but since all loads won't be on at the same time all the time, you have to do a load calculation using nameplate ratings and other things mentioned in the code. There is something called load diversity that is used. Meaning the load is calculated on the basis that some loads won't be on at the same time as other loads.

So, if you can, read the code and come back and ask specific questions you might have.
 
equatorman said:
This is just for my education only. When MNSparky say do a service calculation, does that mean using a clamp meter on the two hot legs to see how much amps is being used? If it is , how do you do this? Do you turn on some equipment in the house like stove, dryer, microwave?
Click to expand...

No, I was referring to the calculations laid out in Article 220 where you determine the size of the service needed for the given loads. Dwellings have different considerations than non-dwellings. The examples in annex D of the NEC are helpful, or there's always the great and powerful internet. I'm sure "there's an app for that" now, but I still prefer doing them longhand.
 
Little Bill said:
Since you are a "trainee" I hope you have a code book. If you do then look at Article 220, it explains how to do a load calculation.

If you don't have a code book or have ever read one, it would be hard to explain. But in short, no, you don't clamp an amp meter to circuits to check the load. You could get some idea but since all loads won't be on at the same time all the time, you have to do a load calculation using nameplate ratings and other things mentioned in the code. There is something called load diversity that is used. Meaning the load is calculated on the basis that some loads won't be on at the same time as other loads.

So, if you can, read the code and come back and ask specific questions you might have.
Click to expand...

Guess I took too long to answer, Little Bill beat me to it!:thumbsup:
 
Ivan Young said:
The basement is already framed out with a light in every room and two receptacles.
Click to expand...
Only two receptacles in each room? Probably need at least 4 unless room is only 6ft x 6ft with one door.


Ivan Young said:
... basement ... He wants to have two bedrooms...
Click to expand...
Are there egress windows from each of these bedrooms? Probably won't pass muster with inspector otherwise.
 
Coppersmith said:
Only two receptacles in each room? Probably need at least 4 unless room is only 6ft x 6ft with one door.



Are there egress windows from each of these bedrooms? Probably won't pass muster with inspector otherwise.
Click to expand...

Probably just a basic unfinished bsmt setup, he'll have to demo most of it and start fresh more than likely.

Our AHJs here don't care about egress windows, that's a building inspector issue. If it's got a closet and kinda looks like it's intended as a bedroom, it's a bedroom to them.
 
Ivan Young said:
Thanks for replying Mr. Sparky. The main panel is full. They have hot tub, tanning bed, double ovens, electric stove, microwave, tons of lights and receptacles on the first and second floors. I was just thinking if a 100 amp sub-panel was installed and the kitchen on the main floor was being used at the same time the one in the basement there might be problems. Oh, he wants a washer and dryer in the basement too. We are in 2011 code.
Would the lights and receptacles have to be protected by AFCI?
Click to expand...

Lights and receptacles don't add up very fast on a load calculation even in a large house ( 3 VA pr sq ft living space).

Make sure you get all the major loads. either the heating or cooling (whichever is bigger ), water heaters (if electric), ranges and ovens, number of dyers ( if electric ), hot tubs and tanning beds.

Don't forget future expansion: these days it's important to see if they plan to have a vehicle charger. Lot of people getting those and sometimes more than one.
 
When one of the pros come on line I would like to find out the answer to my question. Also Ivan Young mentioned the panel was a 200 amp, I was wondering if the same panel could be converted to 300 amp by changing the main breaker and the feed and if the answer is yes what size hots, ground, and neutral.
 
The answer is NO! The bus bars in the panel are rated for either 200A or 225A max.
Even if you could find a larger main breaker that fit it would be neither legal not safe.

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