Electric Panel Decision

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  • RagerXS
    Senior Member
    • Feb 2003
    • 501
    • Brookline, NH, USA.

    Electric Panel Decision

    My home's main panel is rated for 150 amps. I checked the panel and it isn't rated for a higher amperage, so I cannot upgrade the main and be done. But then I'm still not sure I need to...

    Option A: Add a sub panel for the basement wood shop, which will consume 2 of the 4 remaining slots in the main panel. I still want to add circuits for the garage, a basement game room, and a detached shed/single car garage. The additional circuits could be in the sub panel I suppose.

    Option B: Add a new 200 Amp panel where the outside supply would come in first, then it would feed the current main panel with a 150 amp breaker (depending on availability, I may need to make these 125 in both locations). This would raise my max amperage by 50 amps and would provide lots of room for additional circuits.

    If I don't need more than 150 amps, it is a waste of time and money to go crazy here. We have propane heat, propane stove, etc. Major amperage draws are the water well, A/C during our short New England summer, and fridges (2). Plus the woodworking tools, of course...

    Anyone with more knowledge on the subject than I that can offer advice?

    TIA,
    ~ Fred
  • stewchi
    Established Member
    • Apr 2003
    • 339
    • Chattanooga, TN.

    #2
    Big draws on AC, are heating, Air conditioning, cooking (Oven, and stove top), hot tub and water heater. There are many 100 A homes in this country with all electric appliance. Of course they have very little capacity for adding a shop to that load. Here is what I would do:
    1) Add up all of the power from all of the stuff you think you will use at one time.
    2) If less than 150A then start looking at subpanels
    3) See if there are any unused or underused breakers in you panel.
    4) Put in a subpanel and enjoy

    To add up all the power you have to remember that 150A panel is rated at 240V. If you are only using 120V then you are only using have of the panel and you can think of it as half the value when you add it up. In other words if you have 150A of 240V power OR 300A or 120V power. (Always round up) You will probably us a mix. So start adding. (BT3 ~ 14A @ 120V so add 7A) + (Air Compressor ~15A @ 120V so add 7.5A) + (Garage lighting = 5 100Watt bulbs = 500/120 = ~4.4 A at 120V so add 2.2 A) + (Air conditioner ~50A @ 240V so add 50A).

    Once you have everything added up for both the new stuff you want and the current stuff you have make sure it is under 150A. This is true for things that will be on at the same time. No point in adding the AC and the Heater at the same time just pick the largest of the two.
    If it is under 150A then you can put in a subpanel. Make sure the subpanel is rated for the amount you added up for that area (All the stuff in the garage that will be on at the same time).

    If you are worrying about having available circuit space in your current panel, you can swap out the main panel for one that is rated then same but has more breaker slots. You could also try using the tandem breakers (These are breakers that fit in one slot but have 2 breakers on them). If you go this route make sure you do not go over the circuit maximum for the panel. It should be listed somewhere (may have to look online). You could also try optimizing what you currently have. When I moved into my house it was a 100A panel that was full. I removed a 240V bathroom heater in a bath we were remodeling (and still are) because it took up two spots and I needed them for other stuff. I also had a couple of circuits that only had 1 or 2 outlets on them. (Of course I also found some circuits that were way overloaded).
    I recently upgraded to 200A so I put the bathroom heater back in but you get the idea.

    Once you are ready to install you panel or sub post back we can give you some detail on that too.

    Comment

    • RagerXS
      Senior Member
      • Feb 2003
      • 501
      • Brookline, NH, USA.

      #3
      I wired an apartment previously, relocating its panel from the basement to the unit. I had an electrician make the final swap of the main line but did the rest myself. Learned it all from my step father who was an electrician for many years... He thinks I'll never exceed 150 amps.

      So let's do some math then.
      AC - 50@240 = 50
      Air Comp (don't yet own) - 15@120 = 7.5
      BT3 - 14@120 = 7
      HF DC - 15@120 = 7.5
      Lighting worst case - 30@120 = 15
      Well - 20@240 = 20
      Fridge1 - 15@120 = 7.5
      Fridge2 - 15@120 = 7.5
      Dishwasher - 15@120 = 7.5
      Vacuum - 12@120 = 6
      ----------------------------
      Total = 135.5

      I think this is very conservative and that the fridges and DW won't pull as much as I allotted.

      Sub-panel it is!

      So do I make it a 100 amp sub or a 60 amp sub?

      ~ Fred

      Comment

      • bolson
        Established Member
        • Sep 2003
        • 288
        • Charlotte, MI, USA.

        #4
        If you don't use a lot of electricity pull (no electric water, no electric heat) a 60A sub to your shop and you'll be golden.

        You probably don't use as much electricity as you think (unless you have electric heat etc.) and there is no sense paying $2000+ to upgrade your panel for more electricity that you'll probably not use. The only exception is if you were running a shop where more than 2 people work at the same time.

        E.g. If you run lights say about 5 amps or so, Worst case scenario a 5 hp TS at 20 amps and a 5 hp dc collector at 20 amps you are still way under your sub panel rating. Now, I suspect in reality you never use more than a 3 hp TS at 10 amps or so, a 2 hp DC at about 7.5 amps (at 220V) lights at 5 amps. In this more general scenario you are only using half your sub panel.

        Now one thing that is nice about a sub panel is that you can wire more circuits than you need so that you don't blow them. I am wiring my garage with every stud having a receptacle with 5 120 circuits and 3 220 circuits. I'll never need that, but is is nice to just plug everything in nearby and not have any extension cords at all.
        Woodworking forum highlights on my blog at http://woodworking-in-charlotte.blogspot.com/

        Comment

        • RagerXS
          Senior Member
          • Feb 2003
          • 501
          • Brookline, NH, USA.

          #5
          From my shopping the 100 Amp sub panels can be run with 60 Amp mains (sold separately). I will let price decide -- if it's the same, why not have the larger capacity, eh?

          I would never pay big money to upgrade my main panel. Instead, I'd install the bigger panel along side the existing one and make the existing panel a sub panel of the new one. Lots of unnecessary work the other way. Regardless, it looks like I don't need to worry about this path at all.

          Thanks,
          ~ Fred

          Comment

          • bolson
            Established Member
            • Sep 2003
            • 288
            • Charlotte, MI, USA.

            #6
            Just an FYI the cable for running 100 amps is wicked expensive ($2-3 per FOOT and even a panel nearby will take a minimun of 10 feet). I have a 100 amp main and thus could only do a 60 amp sub, but I had wanted to run cable for up to 200 amps in case I upgraded, but since I had a 75 ft wire run, I didn't feel like spending $400 on one cable (4 wires for this is almost $4 per foot for all 4 wires). I think unless you plan on doing welding and such, a 60 amp sub is more than you'll ever need.

            My panel that I am putting in is a main lug panel (no breaker) and a seperate disconect (using the breaker as a disconnect is a BAD idea). I am buying the 60 amp breaker for my main panel separately since cost is cheaper.
            Woodworking forum highlights on my blog at http://woodworking-in-charlotte.blogspot.com/

            Comment

            • HarmsWay
              Senior Member
              • Nov 2003
              • 878
              • Victoria, BC
              • BT3000

              #7
              quote:Originally posted by RagerXS

              From my shopping the 100 Amp sub panels can be run with 60 Amp mains (sold separately). I will let price decide -- if it's the same, why not have the larger capacity, eh?
              Surely this is against code isn't it? Or am I misinterpreting your comment? I installed a 100 Amp sub a few months ago and the rules were pretty clear on that. If you wanted a 100 Amp sub then the main panel breaker was 100 Amp and the sub wiring feed was 3 AWG. For a 60 Amp sub the main panel breaker was 60 Amp and the sub feed was 6 AWG. BTW, the toughest part of that job was running that bloody wire through the house, so think about the future so you don't have to upgrade again later.

              Bob

              Comment

              • stewchi
                Established Member
                • Apr 2003
                • 339
                • Chattanooga, TN.

                #8
                I think what he means is use the housing (lugs, bus etc) from a 100 amp panel but use a 60A Breaker in the panel and back at the main. I don’t think it matter which you use, it will come down to price more than anything. The wire will be a large portion of the cost. Remember to follow the rules, Neutral and Ground must be separate in the panel, the green bonding screw on the neutral bus must be removed as well and a ground bus must be added. You must also run 4 wire 2 hot, ground and neutral to the main.
                Check Ebay for a panel. You see a lot of electrician will offer “free removal” when they do a panel upgrade and they will put the panel up on Ebay and sell it. Depending on the location if you can run Non metallic conduit or EMT to the sub (Depends on the local codes) the wire will be a bit cheaper then getting a 4-wire bundle. Just make sure you re designate the neutral and ground with the proper paint or tape color.

                Comment

                • bolson
                  Established Member
                  • Sep 2003
                  • 288
                  • Charlotte, MI, USA.

                  #9
                  True out of the box 60A sub panels usually only hold 4 breakers. For more expandability you can use either...

                  A)Main lug panel with no breaker at the top. These are usually 100-150A rated and you can undersize the breaker in the main panel (i.e. 60A). These are designed to be sub panels and usally allow you to isolate the ground from neutral (require for sub panels in the same structure or with a connection between them!)

                  B) Main breaker panel. These again usally are rated for 100-200+ A and come with either a 100, 125 or 150A (etc.) breaker at the top. You should toss the oversized breaker and put in a 60A breaker at the top as well as a 60A breaker in the main panel. This situaiton usually costs more because the main breaker panel is ually about $10 more plus the cost of the two extra 60A breakers for each box. You can also convert these main breaker panels to main lugs, but costs a couple of $$ more and you can't always isolate ground from neutral.

                  GE and Siemens both offer great main lug panels for under $40. GE has a nice little set up with 4 20A breakers for $40 that is even marked as a workshop panel-has main lugs only and the ground can be isolated from neutral. This is the one that I'll be using for my sub-panel as the price is right.

                  Like I mentioned above a lot of people like to use main breaker panels becuase they can shut off power to the shop at the sub-panel, but you really shouldn't use a breaker as an on/off switch. A service disconnect rated at 60A is less than $20



                  quote:Originally posted by HarmsWay

                  quote:Originally posted by RagerXS

                  From my shopping the 100 Amp sub panels can be run with 60 Amp mains (sold separately). I will let price decide -- if it's the same, why not have the larger capacity, eh?
                  Surely this is against code isn't it? Or am I misinterpreting your comment? I installed a 100 Amp sub a few months ago and the rules were pretty clear on that. If you wanted a 100 Amp sub then the main panel breaker was 100 Amp and the sub wiring feed was 3 AWG. For a 60 Amp sub the main panel breaker was 60 Amp and the sub feed was 6 AWG. BTW, the toughest part of that job was running that bloody wire through the house, so think about the future so you don't have to upgrade again later.

                  Bob
                  Woodworking forum highlights on my blog at http://woodworking-in-charlotte.blogspot.com/

                  Comment

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