Disconnecting Solar Combiner Box

The Disconnecting Solar Combiner Box contains a load-break rated, high power switch. Installers, maintenance crews, and first responders can now safely disconnect the solar array at the source.

Disconnect at the source

Installers can put the DC disconnects closer to the source. This increases safety and serviceability by de-energizing at the array.

Save space

Some roof tops and ground applications will not accept awkwardly-sized disconnects with limited mounting orientations. The disconnecting combiner not only integrates multiple components, it also increases mounting options. Designers and installers dealing with low profile racking systems or roofs with limited installation space will appreciate the space savings.

Load-break rated switch

The load-break rated switch at the heart of the disconnecting combiner is capable of breaking the circuit with sufficient speed to eliminate “arc” formation between the contacts that is common in DC circuits. The load-break rating means this switch is rated for disconnecting its full current rating for more than 6000 cycles.

Increased granularity

The disconnecting solar combiner disconnects its individual homerun conductors from the inverter DC bus. Traditional methods might disconnect up to three homeruns at a time. The increased granularity not only keeps more of the solar array working during service, resulting in higher overall production, it also decreases confusion during maintenance and increases overall solar system safety.

Technology advantage

Previously, installers connected the series strings into standard solar combiner boxes placed throughout the installation for a combined homerun conductor which leads to the inverter. For increased safety and serviceability designers and engineers often include a DC disconnect switch between the combiner (with or without fuses) and the inverter. An example of this traditional method installation is shown in Figure 1.

Figure 1 - Traditional Photovoltaic DC Circuit Design.

With the new disconnecting solar combiner boxes integrated in the same system, we have achieved reduced component count, improved DC circuit safety and access, increased system granularity and greater operational flexibility. Figure 2 below shows the simplicity offered by this solution.

Figure 2 – Simplified Disconnecting Solar Combiner Solution

Design/Cost Comparison

The following cost comparison is representative of the savings achieved on a 250kW photovoltaic system. While there are many different design options and considerations that effect system cost, this comparison provides evidence that both time and money can be saved using Blue Oak PV Products’ disconnecting solar combiner boxes.

	Traditional	Disconnecting
Number of Series Strings	98	98
String Combiner	14ea. HCB8	7ea. HCB16-D
DC Disconnect	5ea. 100 Amp separate disconnects	Built-In
Total Number of DC Side Components (requires additional labor and hardware to install)	19	7
Fused Inverter Input	15ea. 100A	7ea. 200A
Inverter	250 kW unit	250 kW unit
Estimated Total Solar Combiner Box and Disconnect Cost	$7,820	$6,300
Labor Cost	$1,520	$560
Total Savings Estimate, per 250kW	$0	$2,480

Table 1 - Case Study Comparison Table

Download Disconnecting Combiner Box Technical Notes

We also offer a standard non-disconnecting solar combiner box in a variety of sizes