Ask Experts Questions for FREE Help !
Ask
    arcwick08's Avatar
    arcwick08 Posts: 14, Reputation: 4
    New Member
     
    #1

    Feb 23, 2009, 08:26 AM
    Home electrical load
    General situation/question here.
    I have a ~1000sq/ft ranch serviced by a 100amp panel. We've got electric dryer, water heater, single window air conditioner, a couple computers and a TV.
    I have a woodshop in the basement and have been looking to get a new table saw but it draws 16amp at 120volts. I've got room in the panel to put in a 20amp breaker for sole service to the saw.

    Question; is a 100amp panel enough to comfortably service all this stuff?
    donf's Avatar
    donf Posts: 5,679, Reputation: 582
    Printers & Electronics Expert
     
    #2

    Feb 23, 2009, 09:42 AM

    You should be fine.
    KISS's Avatar
    KISS Posts: 12,510, Reputation: 839
    Uber Member
     
    #3

    Feb 23, 2009, 10:44 AM

    Do me a favor and get the actual loads for each and whether they are 240 or 120.

    You may have to forgo running the table saw and the electric dryer at the same time, but post the loads.

    The TV and the computers can be placed on alternate phases.

    Try to get your table saw wired for 240V, It may be able to be wired for both.

    Remember that breaker ratings don't have to add up to panel ratings.

    You want something like:

    AC 1200 VA @ 120 V
    Saw 16 A at 120 or 8A at 240
    TV 300 W @ 120

    Look at the nameplate.

    You might have to say, make the water heater turn off when you are using the saw. Not too difficult.
    stanfortyman's Avatar
    stanfortyman Posts: 5,602, Reputation: 279
    Electrical & Lighting Expert
     
    #4

    Feb 23, 2009, 02:22 PM
    You will be fine running that saw. Even with a lot of other things on at the same time.
    That saw draws only slightly more than a hair dryer or toaster oven.
    arcwick08's Avatar
    arcwick08 Posts: 14, Reputation: 4
    New Member
     
    #5

    Feb 23, 2009, 04:48 PM
    Quote Originally Posted by stanfortyman View Post
    You will be fine running that saw. Even with a lot of other things on at the same time.
    That saw draws only slightly more than a hair dryer or toaster oven.
    Really? Hey, that'd be fantastic! El wife would be particularly happy that she could still take a hot shower while I work in the shop :p

    k.i.s.s; The table saw can go in at 110V/16A or 240V/8A. Our clothes dryer is 240V/30A and TV just says 120V 60hz 280Wmax... that make sense? :-/
    What do you mean "placed on alternate phases" ?

    Thanks again guys!
    KISS's Avatar
    KISS Posts: 12,510, Reputation: 839
    Uber Member
     
    #6

    Feb 23, 2009, 07:33 PM

    I'll see if I can explain this a bit, simplified:

    P(Watts) = V (Volts)*I(Amps)

    Thus the TV = 280 W / 120; It's not 3, but I'll call it that

    Your box if fed by a 4 wire 240 has two 120 V Legs. What actually is done is your fed by a single phase high voltage to a 120-0-120 transformer. That 0 point is gonnected to ground. Thus the LEGS are 180 deg out of phase.

    In this kind of system, the neutral carries the diference of the legs.


    Suppose 16+8+30+3 = 57 amps.

    If these were connected to one leg, you might have problems. The saw and the TV should be on different legs, then the current would not be 57A.

    If you do the saw at 8 amps.

    8+8+30+3 = 49 A.

    That's where you want to be. The neutral will see only 3 amps.
    arcwick08's Avatar
    arcwick08 Posts: 14, Reputation: 4
    New Member
     
    #7

    Feb 24, 2009, 06:07 AM
    All right, going to strap on the thinking boots, lets see if I've got this somewhere near right;

    When I take the face panel off my circuit box, there are two "big honkin" wires that come in.
    It is slightly difficult due to the mass of wire in there (and my reluctance to shove my hand inside and move things) to tell what these two are connected to.

    Inside the box, are the legs as simple as each side of the panel?

    I understand the conversion of amps*volts=watts, what I'm missing is... if I run the saw at 240V at 8A, then the load is 49A... how/why does that mean the neutral will only see 3 amps?

    Thanks again for your patience and help!
    arcwick08's Avatar
    arcwick08 Posts: 14, Reputation: 4
    New Member
     
    #8

    Feb 24, 2009, 06:52 AM
    Quote Originally Posted by donf View Post
    Arcwick,

    I'd be real surprised if there were only two big wires coming into your pane;.

    At a mimimum you should have three supply conductors, two balck and one white either gray or white. Two ungrounded (hot) and one Grounded (neutral).
    Donf,
    Forgive my lack of correct terminology... there are two large wire bundles coming into the panel. Each bundle has three large wires: one with bare/black/red and one with bare/black/black
    Does that clarify my setup at all?
    Also, what is the difference between the neutral bus and the equipment ground bus?

    I'll try to get a photo of my panel up tonight once I'm back at the house, hopefully that will alleviate the burden upon my poor descriptions.
    donf's Avatar
    donf Posts: 5,679, Reputation: 582
    Printers & Electronics Expert
     
    #9

    Feb 24, 2009, 06:55 AM
    At a minimum there should be three supply side feeders connected to your panel.

    These conductors are very dangerous and should not be touched by a novice. The two black conductors connected to the top of the panel are your two “Hot” conductors. Each Black feeder connects to a bus bar. Never, never, touch them. Even if you turn off the main panel's breaker, these two conductors and their lugs are hot. This is a kill zone if you do not know what you are doing!!

    The grounded conductor or Neutral will connect to the Neutral bus bar, usually off to the side i(usually a black feeder conductor that has been wrapped with gray or white tape to identify it as the neutral feed) of the panel box. You will see a number of neutrals connected to this bar (whites). In the main panel box only, the Neutral bus and the ground bus are “bonded” together.

    The Main Panel is not a place to learn about electricity. Please get help before attempting to work on the panel yourself. You can always learn from the licensed electrician what and how to do it properly.
    donf's Avatar
    donf Posts: 5,679, Reputation: 582
    Printers & Electronics Expert
     
    #10

    Feb 24, 2009, 07:12 AM
    Okay, the large Bare conductor is your Neutral (grounded conductor) and should connect to the Neutral bus bar.

    From your description, I 'm assuming that the Bare, Black, Black are your supply feeder conductors. I have no idea what the other four wire connection is for. It certainly could be a supply cable with Red and Black supplying the Ungrounded (Hot) supplies and Bare being the required Neutral.

    My confusion is that the main panel should only have one set of supply side conductors not two. However I am not a licensed electrician. Maybe TK, Stanforty, Washington1 et al will jump and clear up any confusion still left.
    donf's Avatar
    donf Posts: 5,679, Reputation: 582
    Printers & Electronics Expert
     
    #11

    Feb 24, 2009, 07:33 AM

    At the main panel, there is no electrical difference between the Neutral bus bar and the Ground bus bar because they are "Bonded" together.

    However, if you were to set up a sub panel, the Neutral bus and the ground bus would have to be isolated from each other.
    arcwick08's Avatar
    arcwick08 Posts: 14, Reputation: 4
    New Member
     
    #12

    Feb 24, 2009, 07:35 AM
    So, what you're saying is I need to stand in a bucket of water and dig right into that main panel? Very well!

    Fear not, I won't go digging around in there. If something needs fixing, I'll hire a professional.
    I'm just trying to get a clear picture of the (possible) faults with the existing setup. I would like to avoid having to pay an electrician to come out to my house for five minutes, glance at my panel and confirm "yep, your world be messed up".

    I'll get a pic up tonight of the box to clear up any confusion caused by my poor descriptions...
    donf's Avatar
    donf Posts: 5,679, Reputation: 582
    Printers & Electronics Expert
     
    #13

    Feb 24, 2009, 09:03 AM

    Hey, if you get a bucket of water, make it salt water. It will light up your eyes quicker. And as a bonus it will give all new dance steps and fireworks

    Also make sure that TK, Stratman, Washington1, Stanforty and myself are prime benificiaries on your new fifty million dollar insurance policy that pays off whether stupidy is an issue. :)
    arcwick08's Avatar
    arcwick08 Posts: 14, Reputation: 4
    New Member
     
    #14

    Feb 24, 2009, 10:02 AM
    Hahaha, I'm not sure insurance companies have conditions for stupidity. Though I'm sure if they did my motorcycle insurance premium would decrease dramatically! :)
    KISS's Avatar
    KISS Posts: 12,510, Reputation: 839
    Uber Member
     
    #15

    Feb 24, 2009, 10:47 AM

    Quote Originally Posted by arcwick
    Alright, going to strap on the thinking boots, lets see if I've got this somewhere near right;

    When I take the face panel off my circuit box, there are two "big honkin" wires that come in.
    It is slightly difficult due to the mass of wire in there (and my reluctance to shove my hand inside and move things) to tell what these two are connected to.

    Inside the box, are the legs as simple as each side of the panel?

    I understand the conversion of amps*volts=watts, what I'm missing is...if I run the saw at 240V at 8A, then the load is 49A...how/why does that mean the neutral will only see 3 amps?

    Thanks again for your patience and help!!
    Each side, not likely. Every other breaker is more likely. A 240 V breaker will connect to both legs.

    All of the loads are 240V except the TV. The TV is 120 and flows through the neutral. Neutral is used for the TV.

    If you added another TV and but it on the same bus the neutral would see 6 A. If you put it on the other bus, it would see 0 amps, because 3 amps in one direction and 3 amps in the other = zero amps in the neutral.

    I hope that helps.

Not your question? Ask your question View similar questions

 

Question Tools Search this Question
Search this Question:

Advanced Search

Add your answer here.


Check out some similar questions!

Electrical Load Calculations [ 1 Answers ]

I am trying to determine if the intended load we plan for an office area we are moving into will overload the existing panel. If I add up all the individual loads and divide by three (Three Phase Panel) will I arrive at the load imposed on each phase wire (assuming the loads are balanced on each...

Electrical Load [ 2 Answers ]

Hello, Trying to determine the electrical load for a restaurant that I am designing. Can someone please point me to the NEC section to base load calculations from? Thanks in advance.

Calculating Electrical Load Non-Occupied Home [ 2 Answers ]

Help! I am trying to qualify for an Ag rate on a non-occupied country home. The home is 2100 square feet and has a full kitchen and washer/dryer. It also has a swimming pool with a cleaner and a hot tub. The oven and hot tub are powered by propane. All heat is by gas stove and no air conditioning....

Electrical current load [ 2 Answers ]

Hi all, My name is Jack from lockport, IL. I am installing a bathroom in my basement which include a sewage waste pump. The pump is 1/2 horse and rated at 19.4 amps normal running. Would it be too much if I was to hook the sewage pump, a gfci outlet (for shaver or hair dryer) two lights...


View more questions Search