Evolution of the E-Panel

connected home, there is only one source of AC power that gets distributed to many different
circuits in the home. In a Renewable Energy home and some grid connected homes, there can be
numerous AC sources, the grid, a back up AC generator and an inverter. This means that up to
three different circuits exist for the AC source. They cannot simply be connected all together. In
addition to the AC source, there are sometimes separate load circuits. Some circuits such as the
hot tub or tennis court lights may want to be on a circuit that is not backed up by the inverter.
Hot tubs are famous for sucking a battery bank dry in no time flat. Critical loads need to be
connected to the inverter AC output. In many instances this is the entire house when dealing with
an off-grid home. There are additional AC circuits that do not fit into either category. OutBack
Power Systems has a unique product called the “X-240” and “PSX-240”. These auto-
transformers have the ability to transfer power from leg 1 to leg 2 and visa versa. That device
requires its own breakers and further complicates the AC circuit. This gives us the potential for
six different AC circuits.
1. AC source: grid
2. AC source: generator
3. Non backed up AC loads such as a hot tub (may be combined with No. 1
4. Inverter backed up loads (sometimes this is the entire home)
5. Balancing autoformer circuit.
6. AC Bypass switch
There is no standard AC distribution box available from Home Depot that can do all this. It
would take several separate boxes and even then, some of them are not commonly available such
as bypass switch boxes.
The DC Section
This half of the RE system is very different from the parts available from Home Depot. Your
local electrical supply wholesale company does not stock the DC breakers required for RE
systems. Most of the circuit breakers available at Home Depot are not rated for DC operation.
Square D has the QO and QOU series that are UL listed for DC operation up to 48 volts. Some
installers use the QO breakers in low voltage combiner and charge control circuits. Today’s
MPPT solar charge controllers quite often operate above 100 volts input even for a 12V battery
system. 48 volt systems typically charge batteries to 60 VDC so QO and QOU breakers are not
suitable. As in the AC section, there are multiple DC circuits all operating at the same time. They
too require independent circuits, thus eliminating the possibility to use a standard off the shelf
circuit breaker box as a one stop solution. The DC breakers required do not lend themselves to
the stab in type of boxes available at your local hardware store anyway. Some of the DC circuits
are:
7. Inverter battery circuit breaker
8. Solar charge controller battery disconnect
9. Solar charge controller PV disconnect
10. Hydro and or wind controller output disconnect
11. DC GFP device (required per NEC soon on all solar installations)
12. DC loads such as a DC refrigerator or freezer
13. Auxiliary monitoring equipment
14. PV combiner breakers
The circuit breakers required in these circuits are generally rated for 125 VDC. The enormous
amounts of fault current available from the battery bank necessitate a large interrupt capacity