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Help With New Addition Electric Subpanel/Load

I am in the process of building an addition. I am at the point of wiring the addition. I plan on using the space for a kitchen and small living room. I would like to run all the wiring and install a sub panel in the additions basement on my own. As far as providing power to the sub panel or updating the main service panel I will probably leave this for an electrician, who already stated he would evaluate my work. I want to make sure I install the correct size sub panel with the proper amps. I have questions about the electrical loads, if an updated service panel is required and suggestions with the installation of the sub panel. I want to make sure I am installing the electric components correctly.

Currently my house has a 100-amp service but I do not utilize all the amps. I have four open circuits and I will be taking out the 40-amp circuit for the range and placing it in the sub panel.
Currently the 100 amps services 1100 square foot home with a range, dryer, washer, refrigerator, gas furnace, and two-window ac’s.

Electrical Load Calculation including new appliances.

So the final electrical load would be:
1. 1591 square feet home.
2. 2 kitchen small appliance circuits
3. 1 laundry circuit.
Permanent appliances will be: watts were found on appliances.
1. Double wall oven 4000 watts. Placed in sub panel.
2. Cook top 6550 watts. Placed in sub panel.
3. Dishwasher 1500 watts. Placed in sub panel.
4. Dryer 5000 watts.
5. Washer 1000 watts.
6. refrige 500 watts.
7. Gas furnace 800 watts.
8. Microwave 1000 watts.
9. Window ac’s 2220 watts.
10. Portable heat 1000 watts.
11. Baseboard heat 3000 watts. Placed in sub panel.
Out door usage is 720 watts.

After doing calculations I come up with 89 amps. Does this sound right? Since the service panel is rated for 125 amps less 20% shouldn’t the service be adequate? Do I need to update the service panel to 200 amps?

Here are the new circuits I will be adding. Total of 10 circuits.
1. 20 amp small appliance 7 receptacles.
2. 15-amp Kitchen area lighting including 7 recessed lights and two switches.
3. 15 amp Living room lighting total of 4 ceiling box’s and two switches.
4. 40-amp range circuit.
5. 40-amp cook top circuit.
6. 15-amp dishwasher circuit.
7. Living room 15 amp receptacles on arc fault total of 6.
8. 20-amp microwave circuit.
9. 240-volt electric baseboard 2 6’ 1000 watt heaters.
10. 15 amp outdoor light and receptacle.

Overall I plan on using a sub panel feeder breaker to power the sub panel, which will be placed 24’ from the service panel. I would like to power all the addition through the sub panel and not have to run any circuits back to the main service panel. Any recommendations or concerned would be appreciated. Thank you.
Sorry for this being so long. I just want to include as much info as possible.

Re: Help With New Addition Electric Subpanel/Load

With electric baseboard heat I would upgrade to a 200 amp panel. I would put the 200 amp panel in the new addition and have the service run to it and then feed the old panel as a sub from the new panel.


Re: Help With New Addition Electric Subpanel/Load

Yes you will need a 200 amp main panel and a 100 amp sub-panel at minimum, they may even make you put in a 200 amp sub-panel, I have run into this in a few towns when the additions and kitchen were all electric.Your electrician should be able to tell you all the requirements before you start, most towns now require this when adding an addition, especially a kitchen and new loads, such as your electric heat,double wall oven ,cook top,dishwasher,disposer,microwave,hood fan,fridge,and all your dedicated gfci counter outlets,as well as lighting.Good Luck!

Re: Help With New Addition Electric Subpanel/Load

As Jack and jled96 said staying with a 100A service is not a good idea. Even if you could squeek by why not upgrade to 200A while all the construction is going on and not have to tear it all out later.

Also, if you're ever going to sell or refinance your home a 100A service will work against you.

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