[lee12]

Hi all,

Putting on an addition, was hoping to get some review of the electrical planning before I get too far along here. Mainly regarding how the circuits/loads are being divided up. The addition consists of:

1st floor - dining room (really dining room/living room)
2nd floor - 2 small kid's bedrooms, bathroom, hallway and walk-in closet for existing master bedroom

Everything will be 12 gauge wire. I have electric baseboard heating which takes up a lot of my 200 amp main panel so I'll be having a subpanel put in. The subpanel will also make it easier to run the wires since the addition is on the other side of the house from the main panel. I have 200 amp service.

Circuits being planned:

Main panel: (these 2 circuits already existed before the addition, they've just been re-worked)
1) Master bedroom/existing guest bedroom - 1 light/ceiling fan, 1 closet light, 7 receptacles
2) New dining room/guest bedroom/new hallway/stairs - 7 lights, 1 light/ceiling fan, 2 receptacles

Sub panel:
A) Basement/porch - 5 basement receptacles for woodworking machinery, 1 outdoor receptacle
B) Basement/dining room/guest bedroom - 1 light, 10 receptacles
C) Dining room/kid bedroom/hallway/porch - 4 lights, 1 fan/light, 7 receptacles
D) Kid bedrooms - 1 light, 1 fan/light, 6 receptacles
E) Bathroom - 3 recpetacles, 2 lights, bath fan

New 240V circuits in sub-panel for baseboard heaters:

W) 1000W baseboard heaters (2), 750W heaters (2)
X) 1500W heaters (1), 1000W heaters (2)
Y) 1500W heater (1)
Z) 1000W kickspace heater for bathroom

Anything here stick out as poor design? Are any circuits under/over-loaded? Does the bathroom meet code? I have some drawings made up that I can post if needed.

Anything is appreciated. Thanks!

[tkrussell]

Generally I see no problems with your circuit and outlet plan.

One issue is the dining room, it must be a 20 amp circuit for the receptacles ONLY in that room. Lighting in that room and the receptacles in other areas must not be on the dining room small applaince circuit.

Just a few comments you may already know:

Bathroom receptacles need to be GFI protected. One 20 Amp circuit can supply the receptacles, lights, and fan in ONE bathroom. No need to GFI protect the lighting or fan.

Receptacles in unfinished basement need to be GFI protected, along with the exterior receptacle on the porch.

All the other areas, bedrooms, dining room, hallway, etc. need Arc Fault protection.

Are you sure the existing 200 Amp service can handle this added load you list?

If I added correctly, I see a total of 8750 watts at 240 volts equals 36.5 amps.

Plus the addition general lighting load, I doubt your service can handle this added load.

Someone needs to do a service rating load calculation.

And what about smoke detectors, one in each bedroom and one in the common area of each level of a building, all interconnected with the other required detectors in the builidng?

[lee12]

Thanks for the advice. I was not aware of the requirements you listed for dining rooms.

As for a service rating load calulation - what do you recommend? Do I just add up everything in the house? I saw some methods based on square footage, etc. but wasn't sure how accurate that would be. Honestly, this is something I was a little worried about. The main panel is not completely filled, but that probably does not mean anything.

If (gulp) I am beyond what my service can handle - where does that leave me?

[tkrussell]

Dining rooms are required to have a dedicated 20 amp circuit for receptacles, called small appliance circuit, same as a kitchen, as per NEC Section 210.52 B.


A service rating calculation is fairly easy, for those that know how to do it. I personally have a problem trying to explain it, therefore I will not try. Too many variables to deal with.

What is needed is the total accurate square footage of all livable space, existing and the addition. Do not need unfinished basement space, attic, crawl spaces, porches, etc.

List of all major electric appliances, to include air conditioning, which based on having electric heat, will probably irrelevant, and total wattage of all existing electric heat, already have the proposed.

Planning an addition requires the design of all mechanical systems. If you had a hot water baseboard heating system, would you not need to confirm the furnace could handle the added baseboard? Same for electric heat, even more so.


You may need a new service, the next standard size is 320 amp, which means all new service entrance conductor, conduit, metering, and possibly salvage the existing panel and add a second panel.

Get back with the detail I asked for and we can go from there.

[lee12]

Thanks for the offer to help. Couple of questions to make sure I get you the right numbers:

- what do I need to know about the definition of 'living space'? Is an unheated but finished basement room considered living space? Are stairways and closets included here?
- what is and is not considered a 'major appliance'. Certainly range, water heater, dishwasher, dryer and microwave, but what about refrigerator, washing machine, tvs, etc? Or are they accounted for elsewhere?

Also, found this calculation listed in a book - is this accurate? (I'm posting a slightly generalized version of what's in the book)

1) Living area square footage x 3
2) Number of 20amp small appliance circuits x 1500
3) Laundry circuit x 1500
4) Sum of individual major appliances

5) Add lines 1-4. Subtract 10,000.
6) Multiply by 0.4
6) Add 10,000
7) Add total wattage for heating or cooling, whichever is greater
8) Divide by 240 = LOAD

Sound about right?

[tkrussell]

If you can occupy the basement, as a den, living room, bedroom, is is considered as "livable". Yes, closets and halways are to be in the square footage.

Yes, that is one optional calculation, that assumes heat load to be larger than air conditioning, and would apply to your situation.

[lee12]

Thanks. A few more questions...

1) Which appliances would I consider individually? Do I only include ones above a certain wattage?

2) How much load is allowed on 200 amp service? Maybe that's a stupid question but maybe not, I know you don't typically load a full 20 amps on a 20 amp circuit. Just want to make sure I know the rules here.

3) Obviously my electric heating is really jacking up the load here. What wattage range do other heating methods typically run?

[lee12]

I've looked around at examples of load calculations on the internet and decided to include these appliances as individual line items in the calculation - well pump, water heater, dishwasher, refrigerator, microwave, dryer, range, whirlpool tub.

Using these, and the calculation posted above, I can get around 185A depending how I finalize some of the heating plans. So I am hoping that I am okay with my current service for now. I spoke with a few electricians about adding a sub-panel and none of them seemed conerned.

Tkrussel - you had asked about smoke alarms. I had planned to have these but just had the stand-alone battery kind in mind. Is something else better? Just curious because I wouldn't have thought it was part of the circuit planning process. Is it common to have types that are 'hard-wired'?