Connectors and wires in photovoltaic systems

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Connectors and wires/cables in photovoltaic systems

"In the Universe the difficult things are done as if they were easy."
(Lao Tzu)

MC connectors
(source/copyright: Multi-Contact AG)

The main difference between AC electrical and low voltage DC photovoltaic system installation is different voltage range at PV systems and much higher currents. The system's careful design should consider proper wire sizing allowing for efficient operation. The most important parameter is the wire section. Inappropriate wire sizing could result in excessive heating and even fire due to large current. Properly connected and sized wiring won't require any maintenance for years. Exterior modules and other PV components connection wires and cables should be used with UV radiation resistible insulation. Standard wire and cable insulation cracks under years of exposure to atmospheric conditions and UV radiation. The temperature range is also important. Exterior cables should allow for temperature range from -45°C to up to +80°C or even more. Application of such cables will enable efficient system operation for the next two decades or longer. Standard, usually stranded wires and cables are used for interior connections. A simple rule to follow in small systems is 1 mm² wire area/1 A current. Its application will prevent wire overheating and curb loss within required limits.

Connectors

The most common connector types used in photovoltaics are "MC", Tyco "Solarlok" and Huber+Suhner connectors. Suitable tools for assembly is needed. Basic wiring parts are presented on the pictures below. Picture below left: junction box (3), connector (5), T-type connector (4), wire (2). Wiring example for two paralel strings with 2 modules in each string is presented.

PV wiring - basic parts

Picture left: Modules wiring/interconnection - module (1), junction box (3), connector (5), T-type connector (4), wire (2). Wiring example for two paralel strings with 2 modules in each string is presented.

Pictures right, courtesy Wieland Electric: Inverter/junction boxes interconnection - as possible with AC-Solar Steckverbinder for example.

Inverters/junction boxes interconnection, courtesy Wieland Electric

Photovoltaic connectors and junction boxes
	Multi-Contact - world leading producer of photovoltaic connectors, junction boxes and accessories. Languages: Webmaster's choice - technical data about "MC" connector series and interesting photo archive available for download.
	Tyco electronics - producer of high quality photovoltaic connectors and junction boxes. Languages:
	Günther Spelsberg GmbH+Co. KG - for almost 100 years Günther Spelsberg GmbH+Co. KG company has been representing competence in the development, quality production and service reliability in the electrical and enclosure industry. Languages:
	AC-Solar-Steckverbindersystem - Pluggable solutions for solar technology made by Wieland Electric. With the gesis AC-SOLAR round connector series, installation on the AC side now also profits from the advantages of a pluggable connection: time savings during assembly, clear structure and easy maintenance. Languages:
	Huber+Suhner - producer of (among others) photovoltaic connectors and RADOX cables. Languages:
	Hansatronic GmbH - hansa-sol® connectors for photovoltaic systems Languages:
	Hirschmann Automation and Control GmbH Languages:
	BÜSCHEL CONNECTING SYSTEMS - Büschel Connecting Systems develops and manufactures special products to customers' specific requirements for connecting sockets and plug connections for PV applications. Languages:
	Lumberg - Complete wiring solutions for photovoltaic systems - pre-assembled and tested, ready to plug. Languages:

Wires

Some general recommendations that should be followed are:

The maximum allowed loss between battery and charge regulator is up to 1 %.
Maximum allowed loses between solar modules and charge regulator are up to 3 %.
Maximum allowed loses between charge regulator and loads are up to 7 %.

Anyhow, the loss should be kept at minimum if possible. The tables below are a fine tool to guide you through your photovoltaic system design. The maximum power at specific wire length and required wire section at 1 and 3 % power loss is presented in the tables.

Distance (m)	Wire cross-section (mm²)
Distance (m)	4	6	10	16	25	35	50
1	160	240	400	660	1000	1400	2010
2	80	120	200	320	500	700	1000
4	40	60	100	160	250	350	500
6	25	40	65	100	160	230	330
8	20	30	50	80	120	170	250
10	15	20	40	60	100	140	200
15	10	15	25	40	65	90	130
20	8	10	20	30	50	70	100
30	5	8	10	20	30	45	65

Maximal load for 12 V systems and 1 % loss

Distance (m)	Wire cross-section (mm²)
Distance (m)	1.5	2.5	4	6	10	16	25
1	180	300	480	720	1200	1930	3020
2	90	150	240	360	600	960	1500
4	40	70	120	180	300	480	750
6	30	50	80	120	200	320	500
8	20	35	60	90	150	240	370
10	15	30	45	70	120	190	300
15	10	20	30	45	80	120	200
20	8	15	20	35	60	90	150
30	5	10	15	20	40	65	100

Maximal load power for 12 V systems and 3 % loss

Distance (m)	Wire cross-section (mm²)
Distance (m)	4	6	10	16	25	35	50
1	640	960	1600	2570	4020	5630	8040
2	320	480	800	1280	2010	2810	4020
4	160	240	400	640	1000	1400	2010
6	100	160	260	420	670	930	1340
8	80	120	200	320	500	700	1000
10	60	90	160	250	400	560	800
15	40	60	100	170	260	370	530
20	30	45	80	120	200	280	400
30	20	30	50	80	130	180	260

Maximal load power for 24 V systems and 1 % loss

Distance (m)	Wire cross-section (mm²)
Distance (m)	1.5	2.5	4	6	10	16	25
1	720	1200	1930	2900	4380	7740	12090
2	360	600	960	1450	2410	3870	6040
4	180	300	480	720	1200	1930	3020
6	120	200	320	480	800	1290	2010
8	90	150	240	360	600	960	1510
10	70	120	190	290	480	770	1200
15	40	80	120	190	320	510	800
20	35	60	90	140	240	380	600
30	20	40	60	90	160	250	400

Maximal load for 24 V systems and 3 % loss

Other parts of PV system electrical installations, similar to AC electrical installations, include plugs and jacks, fuses, switches, PVC installation tubes or wall ducts etc. Special consideration should be paid to selection of fuses, for only DC rated fuses are suitable. There are a great variety of fuses available in the market, such as classical blow-up fuses, automatic fuses similar to the ones used in AC circuits. Plugs and jacks used in PV systems must be different from the AC wiring plugs and jacks. The plugs and jacks used in DC wiring must differ from the ones used in AC wiring. Application of the same plugs and jacks type is not allowed due to security reasons.

Solar cable supplier
	DRAKA Kabel - DRAKA is the largest manufacturer of low-voltage cable and wire in the Netherlands. Established in 1910, DRAKA has been producing and selling cable and wire for a wide range of applications and in close cooperation with end-users. Languages:
	HI Kabelkonfektionierung GmbH - product portofolio includes also high quality solar cables. Languages:
	HELUKABEL® - HELUKABEL® is a leading international manufacturer and supplier of wires & cables, custom cables, cable accessories, data-network-bus-engineering and pre-assembled cable protection systems for robotics and handling systems. Languages:
	Solar-Kabel GmbH - german producer of solar cables. Languages:
	U.I. Lapp GmbH - a part of product portofolio of the company U.I.Lapp GmbH are also solar cables and connectors. Languages:

On line tools and additional information

Mogami Wire & Cable Corp.: Wire gauge, tensil-stregth, DC-registance calculation of Cu and Al wires.
John Wiles: Code Corner, published on pages of Sandia National Laboratories.
Wiles, J.: Photovoltaic Power Systems and the National Electrical Code: Suggested Practices; Southwest Technology Development Institute, New Mexico State University, 2001 (646 kB).