MidNite Solar offers a wide range of off-grid power panel solutions. The MidNite Solar power panels are customized to fit either Magnum or Outback Inverters, whichever you may choose. MidNite Solar's power panels are both compact and easy to install with all the necessary disconnects and breakers that are found on the much more bulky power panels available on the market. One of the great features of the power panel is that the inverter is mounted on the door both taking less space and making only one mount for the disconnects and inverter. MidNite Solar also offers several options for PV disconnects and other components essential to the modern off-grid solar system.Below is an account from the founder and experienced engineer, Robin Gudgel.
Hi, my name is Robin Gudgel. I’m the mechanical design engineer responsible for the designs of the products shown above. I will attempt to explain a brief history of Renewable energy (RE) breaker boxes, why they are so different, and how it all relates and has evolved into the newest entry into the RE industry; the E-Panel.
The AC section
Why can’t we just go to Home Depot for the required over current protection and disconnect? For the AC section you can (sort of). The breakers used in the AC section of an Renewable Energy system can be standard 120 VAC branch circuit rated circuit breakers. In a normal grid 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.
- AC source: grid
- AC source: generator
- Non backed up AC loads such as a hot tub (may be combined with No. 1)
- Inverter backed up loads (sometimes this is the entire home)
- Balancing autoformer circuit.
- 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:
- Inverter battery circuit breaker
- Solar charge controller battery disconnect
- Solar charge controller PV disconnect
- Hydro and or wind controller output disconnect
- DC GFP device (required per NEC soon on all solar installations)
- DC loads such as a DC refrigerator or freezer
- Auxiliary monitoring equipment
- 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 (AIC) for inverter breakers. 25,000 amp interrupt is an industry standard. AC breakers are not suitable for DC operation due to interrupt rating and the lack of arc suppression. AC breakers tend to weld themselves in the closed position when subjected to high DC fault currents.