A 100 amp service is old, when not many electrical loads had even been considered, though I had a house once that had a meter with 30 amp contact ratings. It still had 240 V though. You can still load it up with any size branch circuits you need (up to the 100 A limit of course). A huge arc welder, electric tankless water heater, or other special loads might be a problem. An actual load calculation will tell you when you are getting close. Keep in mind the sum of the branch circuit ratings in your case the sum of the separate fuses) does NOT indicate the actual load present. Many a 200 amp panel has well over 200 amps of branch circuits installed. 'Load diversity' means that not all the branch circuits are pulling there rated capacity at the same time. This post was edited by brickeyee on Thu, Apr 4, 13 at 13:36

The feeders and panels in the individual units need to be sized for the connected load. You do NOT size the service then divide by the number of units, less house load, to determine the feeder and panel size in the units. A good review of the examples in Annex D should show you how this is done. When figuring the service size you are allowed to use 17KW for 4 ranges (not over 12KW each). This does NOT translate to only allowing 4.25 KW in each unit for a range, nor does it allow that since the 8KW has been used to calculate the unit feeder size that you can now use the 220.55 table column A and B to figure the service size if the range is over 8 3/4 KW. As to the meter cans, main breakers, and service disconnect/OCPD, virtually any combination can be ordered. With rare exceptions you won't walk in to a distributer and buy exactly what you want off the shelf. Get a few service equipment catalogs and browse a bit. Be sure your furnace includes the blower as this is often separate with electric heat, and water heaters come in a variety of sizes.

Just bought 3/3 cable, so will go with 4 wire option. I do want to run a 2 way light switch into the house to run o/s lights @ garage when expected or unexpected guests arrive. My big problem is I don't have good access to house panel as the existing conduit is full. I'll get creative & find a way to the neutral, but for the ground- I'll connect to factory ground lug @ steel frame. It is a drop of 4' from house box. I'll bring the Hilti hammer drill home to drive the ground rods at the garage. Thanks for help-all of you. I'll try to return help at plumbing & gas fitting board.

"I have READ the explanation in a book before, but neglected it at the time as it didn't apply to what I was doing. Now I need/want to know and I'm not going away until I find out." The full names for the conductors are the 'grounED' and 'groundING' conductors. The groundED conductor is commonly called 'neutral' and carries current for 120 V loads. It is the center tap of the pole transformer, and is tied to earth to make it 0 volts relative to the earth. It returns all the current on a 120 V load (ignoring multiwire circuits) and is not needed for a 240 V load. The groundING conductor (AKA 'ground' or 'safety ground') is NOT intended to ever carry current unless a fault occurs. If you tie the groundED and groundING conductors together any place but a main panel you will have current flowing on both conductors during normal circuit operation. The current splits between the two wires based on their impedance at 60 Hz. This current can make anything connected to the groundING conductor have a voltage relative to earth from the voltage drop on the groundING conductor. If you touch a well grounded water pipe (ir other solidly grounded point) and the supposed 'ground' that has current flowing (or anything attached to this ground) the voltage can cause a shock.