Combiner Box

To understand anything we need to have proper amount of fundamental knowledge. In a Solar System there are a lot of things that we should know before we go for advance. Like an example what is solar panel , charge controller, inverters etc.We should know how this all work, Let first know how many fundamental elements are there in a Solar System and know how the keyword and terms work.

DC Combiners : 

• DC Combiner is a solar electronic device that is important when solar panel arrays are used in the project. This device combine dc currents & dc powers which are coming from solar panel arrays and give it to the inverter or load.

• This combiner can be very simple with two or three inputs or can be very complex with multiple inputs  and pretty big.It depends on the system.

• The internal of a DC combiner box always consists of input and output terminals.Every input and output terminals are protected by fuse and that is a great advantage for a solar system when it comes at the question of high dc voltage and high dc current  system.
• In home solar system you may find dc combiner rated with 12V~48V, but in mini grid or in big projects you will find 600V~1500V system where multiple dc combiner combined for total outcome.

• The connection of the solar panels and the DC combiner box is as the picture right,
• The red wire determining the positive terminal of the combined voltage and current of the solar panels and the Black wire is showing the negative terminals of the solar panels, and the green wire is for grounding.
• Choosing  a DC combiner entirely depends on the input voltage and input current ratings And choosing a DC combiner vary from project to project.

Basic Parts of a DC Combiner :

To Select a DC combiner one should have enough understanding on different states of projects, as though the selection vary from project to project some features are necessary to review before installing any kind DC combiners.First of all let me explain some basic property of Solar DC combiner Boxes.

• Enclosure : Enclosure is the outer protective  box inside which all the circuitry placed. Weatherproof   as well as a variety of  other attribute with materials, including: fiberglass, stainless steel is designed for enclosure box.
• Fuse Holder : Used for terminating multiple ungrounded conductor , place for installing solar cables and  fuses.
• Busbars : Buses circuits into a common conductor built with solid conductor for connections.
• Disconnect Switches : This is a high current Isolators for break the circuit.
• Positive and Negative Out : These are the output of the combiner box where final cable is out for the load.
•  Surge Protection & Grounding  : These are for protection of the system from over current or surge.

 

How To Select A DC Combiner 

Choosing a DC combiner you need to have two things, one is experience and second is how to read specification. When you are in a project and trying to figuring out which combiner box you want to select then you have to read a lot of catalogues for sure because not every manufacturer build the same combiner box. But some specification you need to understand when you are selecting a combiner box. Let me list it for you.

• DC Inputs : Check out how many inputs you need for your projects, normally for houses it is  2x1 , 4x1 or 8x1 but for grid system it could be 28x1 combiner boxes where 28 strings of solar arrays are combined for single output. Then check out the input voltage where for normal household it is 12V/24V/48V but for grid it is more like 300V~1500V dc . Check out the maximum short circuit current of the single array of your project and then match it with the combiner box data , short circuit current must be lower then max. short circuit current of the combiner box. 
•  DC Outputs : Now check the output ratings for your combiner box and internal losses. Look if the output matches with the inverter or load input ratings and see the internal loss is less, see the temperature factor and choose according to the project ambient temperature.

• Protection : Make sure your combiner box has all type of protection, like over current , over voltage, surge arrest protection and good enclosure for fire and shock protection. Make sure your system has LV switch gear which is safe as isolators.
• Control System : In many cheap combiners there is no control unit to monitor the state of the system but for better project and building better system you need to have monitoring unit in DC combiner so you can monitor for fault  correction.

In any project experience is everything for building a better but safe system , if you know the basic and also have the experience then any project will be simpler. Combiner boxes are very important for solar systems and every engineer has to deal with this equipment for their projects, so I hope you understand the basic and please rate this or ask question if you like it. (JajaKallahu Khair)

Lecture on DC Combiners: