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Old 07-23-2010, 03:14 PM   #1
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2 newbie questions, re: sub-panel


Hey all.
I'm remodeling the kitchen. I have a 200 AMP main panel.

Question 1. My main panel breakers total over 300 AMPS, is that okay?
I know I'm never using everything at once, but is there a general rule/code limitation?

I want to set up a subpanel in the kitchen. I don't know what capacity it should have.

I think the circuits will look like this:

1. all overhead and undercabinet lights, 20 AMP
2. electric range dedicated (even though I use gas), 50 AMP
3. GFCI counter top receptacles, 20AMP
4. Microwave, hood, and all floor receptacles, 20 AMP
5. GFCI dishwasher dedicated 15 AMP
6. garbage disposer and Insinkerator hot water tap, 15 AMP

That's off the top of my head, may have left sth off.
OK. the total on this list is 140 AMPS. but like with the main panel, I assume I don't have to have the full ampacity since they won't all be running at once.
So what is the right size?

I was thinking 100 AMPs. Sound right?

Calculating another way, the total wattage for all lights, appliances, and everything else above is about 9000 W, adding 25% is 11,250, and dividing by 120 is 93.7 (more like 90 since the electric range I don't have would be 240v).

So again I arrive at 100.

And again, does that sound right?
If so, what gauge feeder cable should I use for that? 2?

Thanks.
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Old 07-23-2010, 03:24 PM   #2
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Quote:
Originally Posted by wengang1 View Post
Hey all.
I'm remodeling the kitchen. I have a 200 AMP main panel.

Question 1. My main panel breakers total over 300 AMPS, is that okay?
Yup. Many panels I install have 700-800A worth of breakers.
Quote:
I know I'm never using everything at once, but is there a general rule/code limitation?
The calculated load of your house is all that matters.
Quote:
I want to set up a subpanel in the kitchen. I don't know what capacity it should have.
I normally go with 100A for situations like this off the top of my head.
Quote:
I think the circuits will look like this:

1. all overhead and undercabinet lights, 20 AMP Why 20A? #12 wire is harder to deal with, especially with UC lights.
2. electric range dedicated (even though I use gas), 50 AMP Remember, you'll need a 120V receptacle here too.
3. GFCI counter top receptacles, 20AMP You need 2 20A circuits for the countertops.
4. Microwave, hood, and all floor receptacles, 20 AMP The micro and hood can't be on the same circuit and the floor receptacles, the micro and hood need a dedicated circuit.
5. GFCI dishwasher dedicated 15 AMP Why GFCI?
6. garbage disposer and Insinkerator hot water tap, 15 AMP You need to check the manufacturer's instructions for each of those, most likely they will require their own dedicated circuit.
My posts in red.
Quote:
That's off the top of my head, may have left sth off.
OK. the total on this list is 140 AMPS. but like with the main panel, I assume I don't have to have the full ampacity since they won't all be running at once.
So what is the right size?

I was thinking 100 AMPs. Sound right?

Calculating another way, the total wattage for all lights, appliances, and everything else above is about 9000 W, adding 25% is 11,250, and dividing by 120 is 93.7 (more like 90 since the electric range I don't have would be 240v).

So again I arrive at 100.

And again, does that sound right?
Without doing a proper calc, that sounds fine.
Quote:
If so, what gauge feeder cable should I use for that? 2?
What were you planning on running the feed in?
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Old 07-23-2010, 05:34 PM   #3
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on the lights, i was just going up 1 to be safe. What are you suggesting? 14/3 15A?

On the circuits, by my read, you're saying 10 circuits:
1. all lights
2. range
3. microwave
4. hood
5 & 6. counter top appliances
7. dishwasher
8. disposer
9. insinkerator hot water
10. floor outlets
is that right?

finally, on the question of the feeder cable, I don't know what I'd be running it in. This is my first big DIY. All the other wires come into the house (yes my main panel is actually outside the house) through PVC pipes. Without looking at it yet, and just assuming, I thought I'd be able to run a line through one of those existing pipes at least into the house. There are four: 2 1" and 2 2". What do you think?

Thanks for the help btw
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Old 07-23-2010, 05:36 PM   #4
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Quote:
Originally Posted by wengang1 View Post
....
Calculating another way, the total wattage for all lights, appliances, and everything else above is about 9000 W, adding 25% is 11,250, and dividing by 120 is 93.7 (more like 90 since the electric range I don't have would be 240v).

So again I arrive at 100.

And again, does that sound right?.....
Nope. Your sub-panel would be fed with a 240 Volt feeder, so you have to divide by 240. Also, why did you add 25% to your load calculation?

Do you have a Code book handy? There is an outline of the proper load calculation procedure in there, as well as an alternate method. Have you tried using those?
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Old 07-23-2010, 05:53 PM   #5
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A few things that I noticed...

1. all overhead and undercabinet lights, 20 AMP
How many lights and what is the total wattage? 15 amp may suffice and it is easier to work with #14 wire as opposed to the #12.
2. electric range dedicated (even though I use gas), 50 AMP
Are you running this for a possible future electric range? Not a bad idea. You never know when you might change.
3. GFCI counter top receptacles, 20AMP
You need two twenty amp small appliance circuits minimum (gfci protected) for the counter tops.
4. Microwave, hood, and all floor receptacles, 20 AMP
Is this a combination microwave/hood above the range? I would install a dedicated 20 amp circuit for this. What floor receptacles are you referring to?
5. GFCI dishwasher dedicated 15 AMP
A gfci is not needed for the dishwasher.
6. garbage disposer and Insinkerator hot water tap, 15 AMP
May be sufficient depending on the amperage of both. I would use a dedicated 15 for the disposer or use a 20 amp circuit for the dishwasher and disposer.
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Old 07-27-2010, 02:56 PM   #6
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hey all. thanks for the replies.
two answer some of the questions above,
I added 25% because a book I'm following (the Black & Decker complete guide to wiring) suggests calculating the full load and then adding 25% just to ensure sufficient ampacity.
kbsparky, you're right, the book does say divide by 230, but I made a mental error there, thinking the appliances would be using 120. Still, if I divide by 230 or 240, then a 50 AMP subpanel would be adequate. So if I did have an electric range (to answer another question, no, i use gas, but yes i thought the connection should be there) and the range is rated at 50 Amps, then should it try to pull 50 amps, it'll flip the whole kitchen subpanel off (lights, all appliances, etc). So isn't that a concern (assuming I put in an electric range)?

teamo and Proby, I thought the dishwasher should be GFCI since anywhere there is a chance of water splashing should have them right? That plug will be under the counter with the sink and the dishwasher, so I was assuming there is some risk of water running down on it at some point. am i wrong?

teamo, i haven't picked out a microwave or a hood yet, but i'm thinking of buying the kinds where the microwave is over the range and the hood is attached to the bottom of it recirculates the air (not the kind that goes up through the ceiling).
also, the floor receptacles are just the ones that code requires along the wall no more than 12 feet apart. That should be two on either side of my U shaped kitchen and maybe one on a small island I'm still not sure about building.

on the dishwasher and disposer, i was just thinking there is very little chance I'll be running both. I would ordinarily clear food off the dishes, then load the dishwasher. but to avoid issue, maybe I should separate them (or up the amperage).

Finally, I still don't know what size cable I'll need to run for the feeder. If I go with 100 AMPs, I'm assuming it'll be #2 or #3 copper?
Any thoughts?
thanks again all.
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Old 07-27-2010, 03:21 PM   #7
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I don't see a refrigerator circuit on your list...
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Old 07-27-2010, 08:30 PM   #8
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cgoll, i was thinking of using the floor plug circuit for the refrigerator. would it be better to have it dedicated?
In the past few years that i've lived in this house, I can't remember plugging a single thing into the floor plugs in the kitchen, so there's little chance the fridge will have to share power.
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Old 07-28-2010, 07:28 AM   #9
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I don't think it is required to be on a dedicated circuit (except in Canada), but some recommend it. See this thread:

http://www.diychatroom.com/f18/fridge-lights-70127/
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Old 07-28-2010, 08:58 AM   #10
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Just remember that the workspace requirements will need to be met for this panel. Basically a refrigerator sized area in front of the panel to allow safe working conditions.
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Old 07-29-2010, 01:20 AM   #11
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Quote:
Originally Posted by wengang1 View Post
Hey all.
1. all overhead and undercabinet lights, 20 AMP
2. electric range dedicated (even though I use gas), 50 AMP
3. GFCI counter top receptacles, 20AMP
4. Microwave, hood, and all floor receptacles, 20 AMP
5. GFCI dishwasher dedicated 15 AMP
6. garbage disposer and Insinkerator hot water tap, 15 AMP
...
You are not going to have an oven ? That could be a major load - same as the range.
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Old 07-29-2010, 07:56 AM   #12
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From what I understand, a dishwasher and disposal can be on the same circuit. 20 amps should cover them...but check the labels on the devices for their load.
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