[Elecraft] 120V vs 240V

[David Christ]

Ed is giving you excellent advice.  It is just about as easy to pull 
a heavy feeder ta sub panel as it is to pull a couple of branch 
circuits.

In my unfinished basement there were only three 15 amp 110 v 
circuits.  Furnace, sump pump and lights.  The main entry was in the 
garage.  When I finished the basement there was no way to run wires 
from the garage to the basement.  I pulled a run of #6/3 w/ground to 
a sub panel near the furnace.  I moved all the old basement circuits 
to the new panel.  This allowed me to install a new 220 v breaker in 
the main entry to feed the new sub panel.  There are plenty of slots 
in the new sub panel to make all the 110 and 220 v circuits I need. 
I used #6 which is oversize to make the voltage variation from no 
load to full load as little as possible.  The value of the breakers 
in the new panel can add up to more that the capacity of the cable 
you just ran.  The breaker in the main panel protects the feeder. 
The breakers in the sub panel are sized to protect the final branch 
circuits.

If your new wiring only supplies the shack you might wish to consider 
using a main breaker rather than a main lug box for the sub panel. 
Maybe it is not so important now as when we had so much high voltage 
running around, but the old safety recommendation was to have the 
wiring set up so that a single switch would kill all the power in the 
shack.

Some notes:  the bare grounding wire is connected to the box itself. 
The white grounded (neutral) wire is supposed to be connected to the 
grounded wire only at the main entry and not in the sub panel.  This 
has been code for a long time.  Also the rules for wring in bedrooms 
and basements has been changing over the last two or three editions 
of the electrical code.

There are probably professionals on the list who can correct any 
errors I have made and are more qualified on the details than I am.

David K0LUM


At 3:25 AM -0900 2/16/11, Edward R. Cole wrote:
>I recently wired my ham shack for 240vac for supplying my 4500w HVPS
>that supplies HV for my 2m-8877 (full QRO).  I went to Home Depot and
>bought 150-feet of 8-4 cable (actually three #8 awg wires and one #10
>solid-conductor safety wire).  This runs from my service box to a
>small load center (40amp breaker box which I have equipped with a
>240-20A and two 120-20A breakers).  This does not exceed the 40amp
>rating of the box or wiring (35-foot run of 8-4). <snip>
>
>73, Ed - KL7UW
>