| You are going to need feeder supplied panels in each detached structure
| because the US NEC requires that each building have only one circuit
| supplying it except under special circumstances that usually do not
| apply to homes. Since you will want telephone service to the ham shack
| you will need to use a four wire feeders to supply it. Each building
Phone and cable TV to the ham shack will be over fiber optic.
But, let me ask this semi-hypothetical question (because there is some
remote possibility I would do this). What if I power the ham shack
entirely with a generator located there with a fuel not involving a
metalic pipe running to it?
| will need a grounding electrode system but you would want one for the
| ham shack anyway. In new construction the foundation reinforcing steel
Of course the ham shack needs a grounding system ... and a very good one.
| is the best grounding electrode system that can be economically
| installed. In the ham shack you will want to install a true UFER
| grounding electrode array in which the entire floor and footer is the
| grounding electrode. This is done by not using plastic to line the
| footer and floor forms and having all of the reinforcing steel double
| tied with tie wire. One piece of galvanized rebar is then stubbed up
| out of the top of the footer at the location of the building
| disconnecting means.
The grounding system needs to be maintainable for the ham shack. Every
part of it will need to be removeable and replaceable. Of course that
would involve digging up the radials, but it should not involve tearing
down the structure.
| One way to proceed on your service equipment would be to put in two, two
| hundred ampere, main breaker panels at the service point. If you need
| more than two hundred amperes for the house than you would have the
| service point there. The reason that I say that is that once you get
| past two hundred amperes through one panel or switch the cost of
| equipment more than doubles. If the load calculation for the house
| comes out to less than two hundred amperes then you can place the
| service point at the garage and only run the one two hundred ampere
| feeder to the house.
What method do you suggest for connect the two panels together? For a
400 amp service (as opposed to a 200 amp service with more than 42 circuit
breaker spaces), that would rule out using feed-through lugs. But there
are still three other ways to do it. 1: double lug on the meter with
feeders rated 200 amps each (most power companies and local inspectors
frown on this). 2: use a separate raceway to split or tap, maybe with a
terminal block, using 400 amp feeder from meter to the point of split.
3: use 400 amp double lugs on the first panel and feed the 2nd panel
from there (this is not generally an option with MCB panels).
| Since you are an amateur radio operator you may want to consider
| arranging for emergency power for the house and the ham shack. That way
| you can be a resource to the entire community in the event of a
| disaster. The NEC has a specific exception for additional circuits for
| emergency power to separate buildings. The cost of a generator
| connection to your home is less than one hundred dollars if it is done
| at the same time as the original construction.
The generator is already being planned, though it will probably not be
put in initially; I'll still plan for it in the design. The ham shack
may get one first. But a generator serving the house will be in or just
outside of the detached garage. If utility service comes in at the house,
then there will be a subfeed from house to garage while there is also a
generator feed from the garage to the house. This would require two
transfer switches to keep it all isolated. But if utility service comes
in at the garage, then one transfer switch can be used, and two feeders
can be sent to the house, one for emergency use, and one for utility.
Due to the construction of most of these house plans involving an A-frame
architecture plus porch structures front and back, bringing utility to
the house might be difficult. If the utility can accept a meter being
placed about 3 feet about ground (underground feed), then I can make it
work with a single full-service disconnect. The problem is that the main
panel (by this reference I mean the first box with branch breakers, not
the main disconnect, if separate) won't be near where the meter can be.
There would probably be 20-30 feet of run from the meter to the panel all
inside the house, and that's not good w/o a disconnect or protection from
short circuit. But if I run this from the garage, then the protection
will be present even if remote.
The thing is, I really don't think I'll be using over 225 amps in the
house. But add the garage, shop, and ham shack plans, and that certainly
can drive it over 225 amps (this being the highest capacity panels before
the prices start to skyrocket). My current thought it so put in a 225 amp
single breaker (such as a Square-D QDL22225) in a 400 amp sized enclosure
(for the wiring space), and put double lugs on the input side of that.
Connect a 125 amp MCB panel to the input side of the unit breaker (the
double lugging), and let the 225 amp breaker just feed the house (back
Another odd question, since you seem to know much more than I do about the
NEC ... how do they define a "circuit" with respect to the feeder limits?
If I were to put in a 4-wire three phase wye circuit, that clearly would
be considered a circuit. But what if I were to put in a 7-wire 6-pole
three phase circuit (some generators I have seen can do this even without
| Phil Howard KA9WGN | http://linuxhomepage.com/ http://ham.org/ |
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