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.
MC connectors (courtesy:
Multi-Contact)
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.
Inverter/junction boxes interconnection as possible with AC-Solar Steckverbinder
(courtesy: Wieland Electric)
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 |
wire cross-section (mm2) |
| |
4 |
6 |
10 |
16 |
25 |
35 |
50 |
| 1 m |
160 |
240 |
400 |
660 |
1000 |
1400 |
2010 |
| 2 m |
80 |
120 |
200 |
320 |
500 |
700 |
1000 |
| 4 m |
40 |
60 |
100 |
160 |
250 |
350 |
500 |
| 6 m |
25 |
40 |
65 |
100 |
160 |
230 |
330 |
| 8 m |
20 |
30 |
50 |
80 |
120 |
170 |
250 |
| 10 m |
15 |
20 |
40 |
60 |
100 |
140 |
200 |
| 15 m |
10 |
15 |
25 |
40 |
65 |
90 |
130 |
| 20 m |
8 |
10 |
20 |
30 |
50 |
70 |
100 |
| 30 m |
5 |
8 |
10 |
20 |
30 |
45 |
65 |
TABLE 1: Maximal load power for 12 V DC voltage and 1 % loss
| distance |
wire cross-section (mm2) |
| |
1.5 |
2.5 |
4 |
6 |
10 |
16 |
25 |
| 1 m |
180 |
300 |
480 |
720 |
1200 |
1930 |
3020 |
| 2 m |
90 |
150 |
240 |
360 |
600 |
960 |
1500 |
| 4 m |
40 |
70 |
120 |
180 |
300 |
480 |
750 |
| 6 m |
30 |
50 |
80 |
120 |
200 |
320 |
500 |
| 8 m |
20 |
35 |
60 |
90 |
150 |
240 |
370 |
| 10 m |
15 |
30 |
45 |
70 |
120 |
190 |
300 |
| 15 m |
10 |
20 |
30 |
45 |
80 |
120 |
200 |
| 20 m |
8 |
15 |
20 |
35 |
60 |
90 |
150 |
| 30 m |
5 |
10 |
15 |
20 |
40 |
65 |
100 |
TABLE 2: Maximal load power for 12 V DC voltage and 3 % loss
| distance |
wire cross-section (mm2) |
| |
4 |
6 |
10 |
16 |
25 |
35 |
50 |
| 1 m |
640 |
960 |
1600 |
2570 |
4020 |
5630 |
8040 |
| 2 m |
320 |
480 |
800 |
1280 |
2010 |
2810 |
4020 |
| 4 m |
160 |
240 |
400 |
640 |
1000 |
1400 |
2010 |
| 6 m |
100 |
160 |
260 |
420 |
670 |
930 |
1340 |
| 8 m |
80 |
120 |
200 |
320 |
500 |
700 |
100 |
| 10 m |
60 |
90 |
160 |
250 |
400 |
560 |
800 |
| 15 m |
40 |
60 |
100 |
170 |
260 |
370 |
530 |
| 20 m |
30 |
45 |
80 |
120 |
200 |
280 |
400 |
| 30 m |
20 |
30 |
50 |
80 |
130 |
180 |
260 |
TABLE 3: Maximal load power for 24 V DC voltage and 1 % loss
| distance |
wire cross-section (mm2) |
| |
1.5 |
2.5 |
4 |
6 |
10 |
16 |
25 |
| 1 m |
720 |
1200 |
1930 |
2900 |
4380 |
7740 |
12090 |
| 2 m |
360 |
600 |
960 |
1450 |
2410 |
3870 |
6040 |
| 4 m |
180 |
300 |
480 |
720 |
1200 |
1930 |
3020 |
| 6 m |
120 |
200 |
320 |
480 |
800 |
1290 |
2010 |
| 8 m |
90 |
150 |
240 |
360 |
600 |
960 |
1510 |
| 10 m |
70 |
120 |
190 |
290 |
480 |
770 |
1200 |
| 15 m |
40 |
80 |
120 |
190 |
320 |
510 |
800 |
| 20 m |
35 |
60 |
90 |
140 |
240 |
380 |
600 |
| 30 m |
20 |
40 |
60 |
90 |
160 |
250 |
400 |
TABLE 4: Maximal load power for 24 V DC voltage and 3 % loss
OTHER
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.
CONNECTORS AND WIRES WEB SITES
Solar cable producers
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.
Website also available in:
HIS Solarsysteme
- HIS is one of the leading providers of switches and cables for photovoltaic systems.
Website also available in:
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.
Website also available in:
SOLAR-KABEL
- Full-Range Product Line for Photovoltaic Cabling. Special Solutions for Your Specific Needs.
Website also available in:
LAPP KABEL
- Cables, plugs and photovoltaic accessories.
Website also available in:
USA Wire & Cable
- USA Wire & Cable is a global supplier of electrical wire and cable, including
armored cable, high temperature cable, telephone and power cable.
Solar connectors producers
Wieland Electric
- 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.
Website also available in:
Multi Contact
- With over 15 years of experience in this field, Multi-Contact is leading provider of dependable connector systems for photovoltaic installations.
Website also available in:
TE Connectivity
- TE is a leading manufacturer of electronic components and solutions for solar
energy.
HUBER+SUHNER
- HUBER+SUHNER's portfolio also includes photovoltaic connectors and cables.
Website also available in:
Lumberg
- Lumberg offers a comprehensive product range for photovoltaic connectivity.
Website also available in:
...
Junction boxes
Günther Spelsberg
- for almost 100 years Günther Spelsberg company has been representing
competence in the development, quality production and service reliability in the
electrical and enclosure industry.
Website also available in:
FPE Fischer
- aluminium junction boxes for photovoltaic systems.
Website also available in:
SKS Kontakt
- photovoltaic junction boxes.
Website also available in:
ADDITIONAL INFORMATION
Web sites
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Mogami Wire & Cable Corp.: Wire gauge, tensil-stregth, DC-registance calculation of Cu and Al wires.
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John Wiles: Code Corner, published on pages of Sandia National Laboratories.
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