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Discussion Forum

Is 200 Amps enough these days?

mwgaines | Posted in Energy, Heating & Insulation on January 27, 2007 06:51am

I’ve been searching the web for a downloadable form that I can use to calculate the anticipated load on the house I’m remodeling. I’m replacing all of the electrical, beginning with the SEP, and as I’m pondering the details it amazes me at just how much our modern lifestyle is adding to the traditional 200 amp service panel.

Once my remodel is fully realized, I plan to have a total electric home that will include all of the standard electrical conveniences, which today involves more lighting, small appliances, and structured wiring with all of its associated hardware (i.e. computers, TV’s, speakers, security devices, etc). In fact, my current goal also includes an electric 3 ton split system heat pump w/10kW strips, an electric tankless water heater (28kW!), a whirlpool with an inline heating unit,and possibly some radiant heat under the bathroom floor tile.

Michael

New knowledge is priceless. 

Used knowledge is even more valuable.

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Replies

  1. sandalboy | Jan 27, 2007 12:02pm | #1

    It's enough for most of us, but maybe not you.  In fact my 100 amp service hasn't caused me problems.  That tankless electric water heater could put you into the next class up.

    1. DanH | Jan 27, 2007 05:22pm | #10

      My thumb suck: Start with 5 amps/100 sf, then add the actual ratings (not breaker size) for electric water heater, electric range, electric dryer, AC/heat pump, etc. For resistance heating, if there's any zoning at all you can probably figure at 50-80% of rating.Of course, a large shop you'd figure separately.
      So convenient a thing it is to be a reasonable Creature, since it enables one to find or make a Reason for everything one has a mind to do. --Benjamin Franklin

  2. stevent1 | Jan 27, 2007 02:27pm | #2

    Michael

    We did heavy up in 2004. Its 400 amp. Split service to the house and shop.

    Chuck S

    live, work, build, ...better with wood
    1. mwgaines | Jan 27, 2007 04:20pm | #5

      "We did heavy up in 2004. Its 400 amp. Split service to the house and shop."

      Chuck,

      Are you now using a pair of 200A panels or a single 400A panel with additional feeders?

      Does your utility company assess a surcharge for requiring more than the standard 200 amps?

      MichaelNew knowledge is priceless. 

      Used knowledge is even more valuable.

      1. stevent1 | Jan 27, 2007 04:53pm | #8

        Michael,

        Two 200 amp panels. The original service was 75amp with 2 sub panels.

        View Image

        View Image

        The feed is undergroung to the shop. I also ran phone, data cable and 2 10-3 UF lines to the shop.

         No surcharge from Georgia Power.

         

        Chuck S.live, work, build, ...better with wood

        1. highfigh | Jan 27, 2007 05:14pm | #9

          What gauge is the cable to the house and in the weatherhead? It looks a bit light. I have 2/0 coming to my duplex and the service is 200A total. You also have two butt splices right next to each other. The electrical contractor that updated my service when I bought the house left two splices on my feed and added another one. I complained and to keep from losing money on the job, they called the power company and they replaced the feed from the pole and got rid of the extra splices so I have one on each leg now. With any high current draw setup like yours, I would have them run the proper size cable. If the feed is light, you'll have some pretty bad voltage drops.
          "I cut this piece four times and it's still too short."

          Edited 1/27/2007 9:18 am by highfigh

          1. stevent1 | Jan 28, 2007 02:29am | #14

            highfigh,

            I aked about the splices and my sparky said no problem. I will have to check on the cable size.

            Thank you for pointing this out.

             

            Chuck S.live, work, build, ...better with wood

          2. highfigh | Jan 28, 2007 04:22am | #15

            They may be "no problem" but when they get water leaking inside, they fail. My parent's house had lights flickering all the time and once the splices were removed and it was re-connected, the problem was gone. Also, when the resistance gets too high, things with motors, compressors and high current draw don't work as well as they should. It's pretty easy to have a 10% voltage drop and that's a problem. I was looking at the size of the connectors, relative to the cable size and they look small. True, you won't have every circuit maxed out at the same time but having a 400A service on 1/0 isn't right. My 200A needed 2/0, so yours will need to be sized accordingly.I got action on mine because the owner of the electrical contracting company said the same thing your sparky did and I told the secretary that he wouldn't do his house that way, so why should mine be like that. I've done high and low voltage work- bad connections cause all kinds of weird problems that can be hard to pinpoint.
            "I cut this piece four times and it's still too short."

          3. stevent1 | Jan 28, 2007 04:37am | #17

            He said "no problem" in 2004. You have pointed out some good reasons for calling Mitch on Monday and express these concerns.Should GA Power run new cable to the street or should the electrical contractor run neww feeds to the meter. I do not have any rough-in pics but I remember the electricians had close to 30" out of the weatherhead.Thanx for your input.live, work, build, ...better with wood

          4. highfigh | Jan 28, 2007 04:45am | #18

            I don't know how GA Power is set up but here in Wisconsin, the power co is responsible for the feed and I assume the contractor called them so they wouldn't have to re-do mine on their time since there's no way I would have paid for it. The feed to the meter(s) and main panel should be upgraded too, in a perfect world. Having a 400 A service in a house on wire that's too small is exactly like trying to jump one car with skinny cables. "I cut this piece four times and it's still too short."

            Edited 1/27/2007 8:47 pm by highfigh

          5. stevent1 | Jan 28, 2007 05:13am | #19

            It is 400A to the meter the split. 200A to the house and 200A to the shop.

            GA Power is resposible from the street to the meter.Here is the splice.

             

            View Image

            And here is the meter again.

            View Image

            I will definitely look into this. If the lines are undersized between the meter and the panels and the city/county approved them, should the electrical contractor eat it or the city?

             

            Chuck Slive, work, build, ...better with wood

          6. highfigh | Jan 28, 2007 06:51am | #20

            Doesn't matter how it's split- the whole load goes through the lines from the pole, the weatherhead cables, the meter and the feed to the main panel. You can have the heaviest cable available to the shop and the main feed will still be undersized. Again, if the circuits to the house and shop aren't drawing a lot of current, it's technically not going to be a problem. If you start arc welding in the shop while the tablesaw, dust collector, a bunch of lights and an electric space heater are all on at the same time, the house isn't going to get what it needs and most devices don't like brown-outs or surges. Microprocessors really hate voltage spikes.
            "I cut this piece four times and it's still too short."

            Edited 1/27/2007 10:55 pm by highfigh

          7. renosteinke | Jan 28, 2007 07:50pm | #21

            It just occurred to me .... real important detail... The usual electrical meter is only rated for 320 Amps. While it can handle a larger load for a brief period, if your load calculations show a higher figure, then the power company will want to use a different type of meter. I can't see what's inside that meter enclosure; they might have the proper meter in there already.

  3. BobKovacs | Jan 27, 2007 02:45pm | #3

    I'm pretty sure there's a form on the FHB site here.  I think it was maybe in with the free articles and stuff.

    Bob

  4. VAVince | Jan 27, 2007 03:40pm | #4

    Try this one. Hope it works.

    Also try a site called http://www.codecheck.com

    Hold on I sent you the wrong one. Let me dig a little deeper to find one I have that will work better


    Edited 1/27/2007 7:46 am ET by VAVince



    Edited 1/27/2007 7:49 am ET by VAVince

    1. mwgaines | Jan 27, 2007 04:37pm | #6

      Thanks for the form, Vince.New knowledge is priceless. 

      Used knowledge is even more valuable.

      1. VAVince | Jan 27, 2007 04:40pm | #7

        I am still looking for a form (self calculating) that a buddy with the power company sent me. I will post if I can find it. More suited for what you need.

        Thanks

  5. experienced | Jan 27, 2007 07:36pm | #11

    Using a tankless water heater that draws 117 amps is irresponsible and indicates that designers have no future vision.

    If more and more people choose electric tankless, the utility will eventually have to upgrade lines and transformers just to take care of the now larger morning spike in demand due to showers. In my area (Nova Scotia) the utility is offering up to 50% off-peak rates to try to "load level" so they may be able to put off building more generation capacityjust for the morning and suppertime/evening demand spikes. More power plants mean higher rates, more greenhouse gases or another river dammed- just more environmental degradation!!!

    Are the savings with a tankless all they're cracked up to be???

    I don't think so. A standard electric tank can be made quite efficient at storing water by using: (1) heat traps on piping {some have integral heat traps now}, (2) having an insulated base to sit the tank on, (3) installing a re-usable insulation blanket, (4) insulating the first 6' of pipes.

    The standard electric tank has an energy factor (EF = efficiency; I used to regulate this stuff in NS) of .88-.90 as manufactured. With the above improvements (cost approx $40-$50), I feel the EF will now be .96-.98 with about $10-$20 lost heat at the tank for the year based on a $500 yearly hot water cost.

    The cost and installation of the tankless will be much more than the electric tank- they are a small volume item, the wire needed is incredibly larger and you need a 200 amp panel just to take care of the tankless draw. Tankless DHW heaters are not 100% efficient- the heated interior heaters, housing and remaining heat in the water at the unit when the tap is turned off  is then lost to the surrounding room air. I haven't seen figures but guess that up to 4-5% of the total system heat generated could be lost here!! Very comparable to the improved tank installation.

    If your utility brings in a time-of-use rate reduction program, how are you going to benefit? With a storage tank and timer system!!!!

     

    1. jesup | Jan 27, 2007 08:18pm | #12

      We want to get the 16? year old 80-gal tank out of the laundry room (5x8) (there's a huge sunken tub from the 70's above in the master, but this heater only feeds the master bathroom, hall bath (for 2 bedrooms), and the laundry room). We lose maybe 4-5sqft out of only 40 to play with. There's a 3'-ish crawl below. We could put two 40's short tanks there, perhaps. Or put a larger tank in the basement, around a 25' run from where the pipes head up to the second floor. I imagine this would slow getting hot water, and lose a little space in the small basement. We have a 4-year-old 40-gal in there now (separate section of the house) that feeds kitchen, one bedroom, and an addition bath with a soaking japanese tub. This might let us combine into one large heater, though it would add about 10-15 feet to the run to the kitchen.(We recently raised the foyer floor between the two sections, and I had them put in a 4"(?) tube to run wires/etc through, since the existing run was 100% full. So we have space to run a plumbing line.)We're going to replace the shorty 40-gal heater in the third section with a small tankless for a wet-bar and a powder room (no way to run plumbing; water to that section has to run through the attic - really).BTW, we have a 400-amp service dating to the early 1970's.

  6. renosteinke | Jan 28, 2007 01:51am | #13

    Here comes Reno, raining on everyone's parade again :D

    CodeCheck does have a good chart for calculating a service, and it relates their format to the various NEC requirements.

    Yet, there are various 'judgment calls' that need to be made, especially if a workshop is involved, or future expansion. Likewise, the PoCo has some issues (remember, they have certain duties to the entire grid, and not just your home).

    Don't be surprised if the town and PoCo require your load calculations to be reviewed by a recognized Master Electrician," Electrical Contractor, or Electrical Engineer.

  7. User avater
    Matt | Jan 28, 2007 04:31am | #16

    I am no electrician, but I can tell you right off the top of my head that 200A isn't enough for all that stuff you named - unless the house itself is tiny.

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