Determining Tolerable Voltage Drop For Various Electrical Loads
A general rule is to size the wire for approximately 2 or 3% drop at typical load. When that turns out to be very expensive, consider some of the following advice. Different electrical circuits have different tolerances for voltage drop.
LIGHTING CIRCUITS, INCANDESCENT AND QUARTZ HALOGEN : Dont cheat on these! A 5% voltage drop causes an approximate 10% loss in light output. This is because the bulb not only receives less power, but the cooler filament drops from white-hot towards red-hot, emitting much less visible light.
LIGHTING CIRCUITS, FLUORESCENT: Voltage drop causes a nearly proportional drop in light output. Fluorescent bulbs use 1/2 to 1/3 the current of incandescent or QH bulbs for the same light output, so they can use smaller wire. We advocate use of quality fluorescent lights. Buzz, flicker and poor color rendition are eliminated in most of todays compact fluorescent bulbs, electronic ballasts and warm or full spectrum tubes. Use them to illuminate your office so that customers can see them.
DC MOTORS may be used in renewable energy systems, especially for water pumps. They operate at 10-50% higher efficiencies than AC motors, and eliminate the costs and losses associated with inverters. DC motors do NOT have excessive power surge demands when starting, unlike AC induction motors. Voltage drop during the starting surge simply results in a soft start.
More techniques for cost reduction
Why Is It So Important To Size A Cable For A Solar System
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If you have a solar system it is important to know how to size a cable. Why is that so? Because a solar system without cables can be compared to a really efficient machine which takes up space and does no one good. Cables are critical in solar systems as they are used in deploying electrical energy converted from the sun by the solar controller to the end devices and processes being powered by this energy. |
As important as cables are to solar systems, the sizes of these cables could mean the difference between an efficient solar system and one which is a security hazard waiting to happen due to overload.
Finding The Right Size Fuse
Fuses are an essential safety feature of all DC wiring . The fuse can be anywhere on the positive side of the circuit, but it makes sense to put them all in a convenient place by using some sort of switchboard. They can be fitted directly to cables using an appropriate in-line fuse holder.
Fuses protect your cables, not your appliances. Cables get very hot when carrying currents close to their design limits, and if a fault somewhere causes an even higher current they can start a fire! Always fit a fuse with an equal or lower rating than the cable. These ratings are a little on the conservative side, to allow for cables that might get hot, for example when in contact with insulation:
< Maximum fuse rating table >
NB: The one place where a fuse should not be installed is the engine starter cable. Starter motors can draw very high currents that will blow even the largest fuses, but since they are only switched on for a few seconds at a time the risk of overheating is minimal. This is why you should not crank your engine for more than about 20 seconds at a time, and allow a few minutes for everything to cool down between attempts. Circuit breakers make a good alternative to fuses. Just ensure you use breakers that are rated for DC wiring not just AC, or they can damaged each time they trip.
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What Size Cable For 12v Solar Panel Solar Panel Wire Size
Before we delve into the question what size cable for 12v solar panel?, lets first discuss what solar wires are. The sizes of solar wires are standardized utilizing the American Wire Gauge and are built using copper wires.
In general, wires constructed with higher numbers have more resistance moreover, high gauge numbers can safely manage lower currents only. Hence, different solar panel systems require different wiring sizes like battery banks versus a standard solar panel. Please note that this applies to the length and diameter of solar panel wire size.
Typically, solar power calls for a 12 gauge AWG wire however, the cables size might vary based on factors like flow and resistance.
Temco 10 Awg/gauge Solar Cable
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- Make sure this fitsby entering your model number.
- MADE IN THE USA – Bare copper conductor, Cross linked Polyethylene Insulation
- RoHS Compliant, UL 4703, 44, 854 rated – Temperature rating: -40°C Min, 90°C Max. 600 V 10 AWG
- UV and Sunlight Resistant. Direct Burial rated Applications include: Solar Panels, DC circuits, inverter wiring.
- The solar cable offered in this listing is 10 AWG which is UL rated for 40A. Using large diameter cable will minimize power line loss in your solar panel system. Choose the size offered above that makes installation easy and simple saving time and money during installation.
- Widely used for solar applications along with batteries, lamps, household appliances, electric heating appliances, meters, instruments, motor lead wire and digital fields
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How To Figure Out Your Average Sun Hours Per Day
Various parts of the country receive different amounts of daily sunlight at various times throughout the year. To figure out your locations average sun hours per day, youll want to determine the peak sun hours, not just the times at which the sun rises and sets. Peak sun hours are the times at which an hour of sunlight is equal to at least 1,000 watts per square meter.
You will receive somewhere between three-and-a-half and six peak sun hours in most parts of the United States. The southwest tends to get the most hours, while the northeast and northwest get the least. To get more specific details, you can check an insolation map or use an insolation meter.
Knowing your average peak sun hours is a crucial step in purchasing the appropriate size and number of solar panels for your homes needs.
How To Use The Free Solar Cable Size Calculator
This solar wire size calculator calculates the wire size of copper wire taking into account electrical parameters of the solar array or another device/power, voltage, and current/ and cables temperature working conditions as well.
To calculate wire size just enter:
-solar system working voltage in V or working voltage over cable wire /for example if this cable connects the battery bank to load add the voltage of battery bank/
expected working peak power: for example solar array peak power in W or kW
-cables working temperature in Celsius or Fahrenheit
-desired voltage drop in % or in other words this is the cable resistive loss. Every cable has its own resistance which is directly proportional to the cable length and inversely proportional to the cable diameter. This resistance is temperature dependant as well. Our calculator takes into account all the above-mentioned factors to calculate cable resistance so as to be received a voltage drop equaled to the desired one.
supposed cable length in meters or feet. Actually you will use two wires-one positive and one negative, so do double the cable length by summing up the lengths of positive and negative wire.
Then you will get calculated:
- Cable wire size needed in mm2 for Europe
- Wire diameter in inches for AWG/American Wire Gages/
If calculated wire diameter has lower ampers current rating choose a cable with a higher wire diameter which covers the corresponding amp rating.
Lets consider the following example:
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Do I Need Fuses Or Breakers Where
You arent going to get a surge from solar panels Because of that, our kits do not use fuses between the panels and the charge controller.To protect the charge controller in the event of a short-circuit or some other unforeseen event, we recommend a fuse or breaker on the positive line between the charge controller and the battery bank rated at the maximum current of the charge controller.We also recommend a fuse on the positive line between the battery bank and the inverter. To determine the size of this fuse, take the wattage rating of the inverter, divide it by 12 and multiply it by 1.25. For example, a 2000 watt inverter would have a rating of about 200A .
Calculating The Cable Size/thickness/diameter For A Solar System
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Let us say for example that we are about to run a solar system which will power one led bulb streetlight. The streetlight is 11m away from the solar controller, it will, therefore, imply that the longest cable running to and fro from the solar controller will be 22m . ÷ = CT |
Where: L = Cable length in meters I = Current in amps V = System voltage CT = Cross-sectional area of the cable in mm²
For purposes of demonstration and to enable us to reach a reasonably applicable solution, we shall calculate the required cable thickness for the led streetlight scenario at 12V, 24V and 48V. Calculating required cable thickness at 12V ÷ = 20.65mm² Here is the same calculation for a 24-volt system: ÷ = 5.15mm² And at 48V ÷ = 1.63mm²
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At 12V, the thickness required of our cables are so great that we cannot practically run such a system. The available standard cable nearest to that which we need to run our 12V solar powered streetlight of 20.65mm2 is the AWG 4 cable with a diameter of 5.19mm. |
Cable this size is heavy, thick, inflexible, very expensive and hard to source. This implies the need to lay very thick cables for our streetlights, which is so impractical we might as well return to the coal-age. Realistically, due to cable sizing, we are going to need to use either 24V or 48V for all the reasons why we cant use the 12V system.
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Cable Size Ampacity Chart
The following maximum amps versus cable size come from the NEC version 2011. As far as I know these values are valid as of today. For more detail though, check with the National Electrical Code as well as your own zoning laws.
Note: I would NEVER design interconnecting cable size anywhere near its maximum amps! Thats too hot for me! Heat loss equals efficiency loss! Give yourself a wide margin.
Copper Conductor Ampacity based on 75°C reference Cable Types: RHW, THHW, THW, THWN, XHHW, USE, ZW
| Cable Size |
When 14 Gauge Wires Are Not Acceptable
That being said, a battery bank will certainly not be suitable with a 14 AWG wire. Instead, a solar battery bank will likely need a 3/0 AWG cable. Just like the battery bank, the charge controller needs between 3 and 8 AWG wires.
The charge controller is what allows solar battery storage to work. If you do not have a charge controller or solar battery system, then you dont have to worry about this step, though you dont have to worry about power loss due to loss of sunlight with a solar battery system.
Still, all solar system users have to think about the cable size based on the part of the system, such as the battery bank and charge controller.
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What Does This Mean
So, how does this affect choosing the right cable for your solar panel? Well, it tells you that you have to think about both the diameter and the length of the cord when selecting the right wire for your solar panel. Once you know the amp, you should figure out which cable size is best for your unique solar panel system specifically.
Solar Panel Grounding Faq
Does the Ground Wire Size Matter?
The ground wires have to be at least the size recommended by the NEC . The wire can be larger than the recommended, but not smaller. If the ground is not the correct size the grounding system will not work and your solar panel will be exposed to lightning and other hazards.
What Happens if the Wire Gauge is Too Big?
Using a larger wire will not cause any harm to your system. The only drawback is large wires are more expensive and require bigger clamps. But it will not cause any damage to your solar panels or appliances. Some would recommend using a larger wire than the minimum specified by the NEC as it is safer and more durable.
What Wire Size Should Be Used on an Off Grid Solar System?
The same wire sizes used for a grid tied system, at least #8 or #6 AWG. And just like grid tied homes, you should use more copper rods if the location is prone to lightning strikes. Most off grid setups have a backup power source like a gas or large battery bank, and they need to be wired properly as well.
Do Ground Wires Have to be the Same Size?
For convenience they should be the same, but you can use different wire sizes as long as it is not smaller than #6 AWG. However there should be no effect on the grounding system as long as the minimum size specs are met.
What if the Ground Wire is Too Small?
Can a Ground Wire Cause a Fire?
Does Ground Wire Have Current?
How Far Should Ground Rods Be From Each Other?
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How To Check The Quality Of The Solar Cable
Solar cables must meet the following requirements to qualify for use in PV applications:
- Good weather, ozone, and UV-resistance: The solar cables are typically used outdoors and are subject to direct sun radiation and air humidity.
- Suitable for a large temperature range .
- Withstand mechanical stress such as compression, tension, bending and shear loads.
- Abrasion-resistant, therefore most sheaths are made of plastics cross-linked using an electron
- Acid and base proof
- High dielectric strength
- flame-retardant and halogen-free
- Short-circuit proof even at high temperatures.
- Have small outside diameter
- Optional reinforcement to protect against marten, rodents, and termites.
- In the case of agricultural enterprises, an additional resistance to ammonia, digester gases, oxalic acid, caustic soda and other chemical media.
Do you have 1*6 mm2 Cu NEXANS Energy flex type ?
dc cable
Do you have 1*6 mm2 Cu NEXANS Energy flex type ?
dc cable
What Size Wire Do I Need For A 200 Watt Solar Panel
Above, we learned how to calculate the amp and wiring for a solar system with 12 V. Now, lets apply that same formula and math to a solar power panel of 200W.
In most scenarios, solar PV panels are 12 V. Now, we know the watts, allowing us to understand better the amp and wire size needed for the system.
Like before, divide 200W by 18Vmp. When you do this, you will learn that the amperage is right around 11. Like before, you can use a 14 AWG cable according to the 2% voltage drop chart.
You may need to use a 24-volt panel instead. Adjust our math above and calculate if that applies to you
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Can I Use 14 Gauge Wire For Solar Panels
Technically, you can use a 14 gauge solar wire for panels, but it can only handle 15 amps at the most. Many solar panels need a higher amp. So, it may be better to go for a 10 or 12 AWG wire for the best results on standard solar panels.
As we saw in the two examples above, there are plenty of times when a 14 gauge cable works perfectly fine for solar panels. So long as the expected maximum amp is below 15 amps, a 14 gauge wire should work perfectly fine for solar PV panels.
You can always jump up to a 12 gauge wire if you arent sure you will exceed 15 amps. 12 AWG wires have an amp capacity of 20 with a 2% voltage drop.
Why Ground Solar Panels
Grounding solar panels is necessary because:
- It reduces built up charge, making your system less attractive to lightning.
- If a charge builds or lightning hits, the discharge will go into the earth instead of your cable. Without grounding this will not happen.
- Grounding minimizes power shock from high voltage components.
- The NEC requires grounding. Article 690 includes solar panels, whether it is high or low voltage. Not grounding your system is not only risky but also illegal.
- A grounded connection minimizes the hum produced by some solar inverters, lights and other electronic devices.
The most common mistake solar panel owners make is assuming that lightning must strike directly to cause damage. In fact, lightning can hit miles away but still generate high voltage in your solar panel cable. Solar panels with long wires are particularly susceptible to this.
When the voltage surges it can destroy your appliances and entire solar power system. This can be prevented by grounding solar panels. Grounding means electrically wiring parts of the solar system to the earth .
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