## Solar Power Math Problems – Part II, Calculating Wire Size

In Part 1, we discussed how to calculate solar panel electrical circuits to avoid possible safety issues during their installation and use. Our calculated circuit current from Part 1 was 10.585 Amps.

Now that we’ve determined how much current might be produced, I need to select the correct wire size. I’m using type USE-2 cable from the solar panels to the combiner box where the circuit breakers are located. USE-2 cable is UL listed for outdoor use in hot areas (90C) and is also sunlight resistant. The temperature derating of USE-2 in 141-158F is 0.58

[NEC 310.16]

• Ampacity of USE-2 cable, 10AWG: 40 amps
• 40 amps times 0.58 = 23.2 amps
• Ampacity of USE-2 cable, 12AWG: 30 amps
• 30 amps times 0.58 = 17.4 amps
• Ampacity of USE-2 cable, 14AWG: 25 amps
• 25 amps times 0.58 = 14.5 amps

The wire size has to be able to handle 125% of the derated PV Source Circuit Current (10.585A), so 10.585A times 1.25 = 13.23A. Our wire has to be thick enough to handle 13.3 amps, so either of these sizes would meet the electrical code.

Temperature derating for multiple cables. There is an additional factor to be aware of if these wires are running through conduit. Based on the number of current carrying conductors (positive conductors), the wire is derated according to the following: [NEC 310.15(B)(2)(A)]

• 4-6 conductors: 80%
• 7-9 conductors: 70%
• 10-20 conductors: 50%

If these 10 these circuits are running through conduit, then the rating for 10AWG (40A > 23.2A) is reduced yet again. 23.2 times 0.5 = 11.6 amps. I can either run 9 circuits in conduit and run 1 circuit free (allowed with USE-2 cable) and derate the circuits in conduit to 70% (16.24A), or divide the runs, with 5 circuits per conduit and derated to 80% (18.56A).

Something else to consider is resistance. Thinner wires have more resistance than thicker wires which reduces the amount of power available at the end. And, the lower the voltage, the greater the power loss.

• DC Resistance of 14AWG wire: 2.5 ohms/1000ft
• DC Resistance of 12AWG wire: 1.6 ohms/1000ft
• DC Resistance of 10AWG wire: 1.1 ohms/1000ft

I have fairly short wiring runs (less than 50 feet). The following table shows the calculated voltage drop (loss) for a 50′ circuit, at various DC voltages, with a 10 amp load. The voltage drops even further on longer runs. At 12 volts, a 500′ circuit loses so much, that it’s only 2.4 volts at the opposite end!

• 2 AWG
• 12 VDC: 11.84 V @ 10 amps
• 24 VDC: 23.84 V @ 10 amps
• 48 VDC: 47.84 V9 @ 10 amps
• 96 VDC: 95.84 V @ 10 amps

• 10 AWG
• 12 VDC: 10.9 V
• 24 VDC: 22.9 V
• 48 VDC: 46.9 V
• 96 VDC:94.9 V

• 12 AWG:
• 12 VDC: 10.4 V
• 24 VDC: 22.4 V
• 48 VDC: 46.4 V
• 96 VDC:94.4 V

Once the PV Source Circuits are at the circuit breakers, they are combined at the PV Combiner Box to form the PV Output Circuits. The PV combiner box can combine 12 PV source circuits into 1 PV output circuit, or split those same 12 PV source circuits into 2 PV output circuits. After factoring in the math (and based on the charge controller limitations), our 10 PV source circuits are combined into 2 PV output circuits:

[NEC 690.8(A)(2)]

• PV Source Circuit Current times number of circuits times 1.25 (twice) equals PV Output Circuit Current.
• 7.3A times 10 circuits = 73.0A times 1.25 = 91.25 times 1.25 = 114.06 (we’ll round up to 115A).
• 7.3A times 5 circuits = 43.8A times 1.25 = 54.75 times 1.25 = 57.03A (we’ll round up to 60A).

The charge controllers (Outback MX-60) are rated for continuous duty at 60 amps and 125 volts DC. In deciding the system voltages, we had to take this limitation in account. Again, more math:

[NEC 690.7]

• sum of the maximum voltages (Voc) of panels wired in series, times the weather correction factor
• 66.4 + 66.4 = 132.8 volts, times 1.13 = 150 volts, which is way over the 125 volt limit.

If I need higher voltages in the future, I may be able to rewire the panels and mix them with 24V panels. Assuming the 24 volt panels have a maximum voltage of 44.2 volts (like the BP 3160 solar panels): 66.4 + 44.2 = 110.6, times 1.13 = 124.978, which is right at the 125 volt charge controller limit. Of course, I would also have to keep the source circuit currents in mind as well.

From this point (the combiner box) to the DC equipment inside the house, everything is calculated for 60 Amps.

THHN/THWN wire is rated for 70C and is suitable for running in conduit. The first set of solar panels is two circuits. There’s room on the roof for even more solar panels, which might be an additional 2 circuits in the future, so we’re planning ahead and using larger conduit. We know that eventually we may have 4 circuits in the conduit, and that the conduit will be warm (but not as warm as the wires at the solar panels). [Table 310.16]

• THWN wire is derated as: Rating times 0.88 for (96-104°F ambient temperature), times 80% (4 conductors in conduit)
• 3AWG is rated as 100A times 0.88 = 88A times 0.8 = 70.4A
• 2AWG is rated as 115A times 0.88 = 101.2A times 0.8 = 80.96A

We can use 3 AWG wire, but 2 AWG provides less power loss (and is usually readily available and in stock at most do-it-yourself places).

An equipment ground wire is also required, and its size is based on the size of the largest breaker (60A), BUT if the wiring on the PV Output Circuits has been oversized (like ours), then the equipment ground wire also has to be oversized to the size of the PV Output Circuit wires.

[NEC 690.45], [NEC 250.122]

Eventually, there will be 4 PV Output circuits plus the equipment ground wire running in conduit from the roof. Each circuit has two wires, so total wires is 9 counting the ground wire. We’re using 2″ conduit which has room for a total of 12 wires (if they’re all 2AWG).

When wires are first installed in conduit, you’re allowed 40% fill based on the diameter of all the wires involved. The number of wires you’re installing and the 40% fill ratio determines the minimum size of conduit allowed, and just one extra wire could mean having to install larger diameter conduit (which starts getting expensive pretty fast). There’s a provision in the NEC that can help save money, although it’s not very pretty: If the equipment ground wire is 6 AWG or larger, the ground wire is allowed to be attached to the outside of the conduit. [NEC 250.64]

There are many types of conduit, but not all are approved for use in the outdoors where rain and sun are present. Rigid metal conduit (RMC) and Intermediate metal conduit (IMC) are approved. Liquidtight is approved if it’s sunlight resistant. Schedule 40 PVC conduit is also approved if it’s rated sunlight resistant, but I’ve still seen it deform in normal summer temperatures. Electrical metallic tubing (EMT) is not approved for outdoors where exposed to weather, and Schedule 80 PVC conduit is not approved for outdoors where exposed to sunlight.

Where multiple wires are installed in conduit, the cross section of the wires is only allowed to fill up to 40% of the cross section of the conduit. The cross section of #2 AWG THWN wire is 0.1158 square inches. The cross section of nine wires is 1.0422 square inches. The conduit fill tables in Chapter 9 of the NEC specifies that 1.5″ RMC allows up to 0.829 square inches, and 2″ RMC allows up to 1.363 square inches.

If we were concerned about exceeding conduit fill, there’s a provision in the NEC that allows us to run the equipment ground wire attached to the outside of the conduit, IF the equipment ground wire is 6 AWG or larger. But remember, if the equipment ground wire is 6 AWG or smaller, it MUST have green insulation (marking with green tape is not approved). Larger ground wires can be marked with green tape, etc.

[NEC 250.64]

## Why Choose a Domestic Electrician to Install Your Electrical Appliances

It may seem easy to install electrical appliances but just because something seems simple it is not always the case. If you end up installing electrical appliances wrong there is the risk for damage to property, risk of injury, risk of the appliance frying out, or any number of bad things that can happen. It may cost money to get a domestic electrician to install your electrical appliances but having peace of mind that your appliances will work properly and not be a hazard to property or others may be worth the cost of services.

When you buy appliances for your home some may have a lot of steps in order to install the appliance into your home. A domestic electrician has the experience installing a variety of appliances into homes and is able to do it with probably minimal time reading the instructions based on their past experience.

The other thing to consider is if you really know what you are doing when you want to install appliances in your home, if there is any doubt, hire a professional. The risks are very serious if the appliance is not correctly installed into the home with injury to self, others, and property damage just to name a few negative things to be aware of if you try to do the job yourself.

Domestic electricians can install the appliance with ease and will charge you some money for the services. Consider looking around at a few domestic electricians before deciding on the one that is the best price for this particular job. Make sure the electrician has the right credentials so you are not liable if the electrician were to get hurt or to destroy your property, which hopefully they would not do if you get one with the right amount of experience and the appropriate credentials.

Ask your friends if they have used an electrician to install their appliances. If so they will give you the most honest response on how the electrician did and if they would recommend them to do the job.

## Eliminate Wire Mess With a Retractable Electrical Cord Reel

Wire mess is a pain to manage. Not only does it make workplaces unorganized, it poses as a safety hazard as well-it can cause electrical shorts, not to mention freak accidents from people and things tripping over them.

A very simple and cost-effective solution is to use retractable cord reels. A retractable electrical cord reel is used in conjunction with equipment such as tools that need electrical power from odd places. For example, a power tool such as a drill is used in places where its electric cord is not enough. In such cases, an extension cord is used.

A normal, non-retractable, extension cord is hard to lug around if there is no way to neatly tuck its wire. Things can get in the way and out of hand especially if the cord is very long. A wire that tucks in a reel becomes portable and easy to carry when fully retracted.

Even more easy to use are the newer cord reels that automatically retract. These handy tools neatly hides their wires with the use of spring power hidden inside the reel’s housing. Most automatic reels simply need a short pull or tug to activate the spring mechanism. An automatic reel works much like an automobile’s seatbelt.

With such useful functionality, a retractable electrical cord reel is a definite no-brainer purchase. With a minimal investment, it eliminates a lot of hassles associated with long wires and workplace messes. The retractable reel is an organizing marvel which all handymen should consider buying.

## So What Is an ‘RCBO’?

RCBO stands for Residual Current Breaker with Overcurrent. An RCBO is actually a composite unit of two separate electrical devices, and so to understand what one is and what its purpose is, it is necessary to first look at the two devices that have spawned its development.

Residual Current Devices

A Residual Current Device (RCD) is an electrical component which detects imbalances in the electrical current of a circuit and then immediately disconnects the electricity supply to the circuit. RCD’s are designed to protect against accidental electrocution when a person touches the live wire of an active electrical circuit. They work by detecting any variation between the live and neutral conductors. If a variance is detected then the electrical contacts are quickly forced apart and the circuit is broken. This process takes place within a matter of milliseconds, stopping the flow of current before it can do any serious damage.

Miniature Circuit Breakers

A Miniature Circuit Breaker (MCB) on the other hand is designed to protect appliances and larger electrical circuits from overloads or short circuits. Operating on a similar basis to an RCD, the MCB detects faults in the power flowing through a particular circuit, and upon doing so separates the electrical contacts, breaking the circuit, and thus preventing damage to the device or appliance.

An RCBO combines both of these devices into a single unit. It is designed to interrupt the electrical circuit in the event of a current imbalance caused by an individual touching the live wire, and also if an overload or short circuit is detected.

RCBO’s- a single module solution

An RCBO is an effective means of protecting against both overloads and earth leaks, while only using a single unit. This can be particularly useful when space is limited. Depending on the specific application they are being used for, it may be more cost-effective to use individual Residual Current Devices and Miniature Circuit Breakers together. If in doubt, its best to consult a qualified and knowledgeable electrician.

Newlec Single Pole RCBO’s are available for a range of power ratings, and are a practical and economical solution for a range of wiring and circuitry needs. For ease of installation, the unit features raised mounting feet designed for uneven surfaces. The Wylex NSBS Type C Single Pole RCBO also provides a single module solution for circuitry protection.

The Type C DPN Schneider RCBO meanwhile features two pole switching of phase and neutral, and is suitable for providing protection against both overloads and short circuits for domestic, commercial and industrial purposes.

An RCBO can be used to protect both people and equipment in a cost effective way. RCBO’s are suitable for a range of applications in the home and in commercial and public buildings. They provide a vital failsafe system for electrical circuits, and peace of mind for the user.

## Why Make Use Of The Internet To Find Electrical Contractors?

With regard to any electrical problems you may have it will be in your favour to use an electrical contractor as they are the most reliable, qualified and specialized people within this field of work. Electricity is very dangerous and highly specialized, thus with “do it yourself” can be life threatening and unforeseen accidents can happen very quickly. With that said, many of us think that it is very easy and common to repair a simple problem such as a frayed electrical cord or a tripping switch which could lead to a very negative impact. Therefore it is necessary to hire an electrical contractor for any wiring needs.

Before you do consider of doing DIY work on electrical systems, you should consider a few things before any attempts. If you do make a small mistake on the repair of the electrics in your home you should consider that you run the risk of destroying the entire electric system in your home. With that happening your life could be fatal. With the use of the internet, you can find many easily available electrical contractors that will be more than willing to help you with any problem you may have. You should not ever feel that you are alone with a confusing electrical problem. The perk of having an electrical contractor to do the work for you is that the problem will be taken completely out of your hands and you will have the guarantee that the problem will be solved once and for all. Electrical contractors will source out and find the root to the problems that you may have.

By means of using the internet, you will have the benefit to look for companies that have well qualified and trained electrical contractors with years of experience in different field of work. You will be able to see whether the companies have satisfied customers and what special services they have to offer you. Some have a no-charge towards call outs and quotations which is a great advantage to make use of. These companies are always looking for new and innovative ways to enhance safety and services. Look for companies that are based within your region as it will ensure fast and effective response to you. Make use of the company that has experience in repairing plugs, lights, geysers, stoves, electric fencing, earth leakages, fault locations, cable, power striking, leak detection, gate motors, air-conditioning, power skirting, alarms, CCTV’s and many more. A full service electric company is better that a company or person that just do repairs in one electrical field. Also see whether they have offer guarantee on all workmanship and on installed materials.

With all said, you should not have any difficulty in finding yourself electrical contractors to hire that have the knowledge and qualifications within this highly specialised industry. It is also not hard to find affordable electrical contractors that work for electrical companies. You should also see the electrician’s/companies credentials with regards towards certificates and previous client’s satisfactions.

## Cable Management Kits Are an Ideal Solution for Managing Cables

As modern workplaces and homes have become more sophisticated and utilise ever more technology, so the masses of cable that permeate our daily lives have grown proportionally. To prevent becoming lost in the tangle, effective cable management is essential. Fortunately, with a wide range of products and cabling accessories on the market, this task is just a little bit easier than before.

Cable management kits
With so many different accessories on the market, it can be difficult to know what to buy. For this reason, cable management kits are a great option, as they bring together a range of items needed for tidying away and organising cables effectively.

Such kits come in many shapes and forms, but all contain a variety of tools for effective cable management. Many contain a combination of cable wraps, ties and clamps. Others might contain cable trunking and accessories for fireproofing your cables and increasing airflow around them.

CMP Products’ Gland Kit is perfect for added safety and fire prevention, and provides a fireproof seal for cables. The Newlec Cable Joint Kit meanwhile provides an all in one cable jointing solution utilising PVC and Polyurethane resin.

The importance of cable management
Cable management is particularly important in offices and other workplaces which make extensive use of computers and other electric equipment. Without a carefully thought out cabling strategy, server rooms and data centres could end up looking like spaghetti junction, with a tangled maze of cabling scattered haphazardly across floors and walls.

A disorganised cable management strategy is not only a logistical and aesthetic nightmare, it is also a health and safety risk. Firstly, individuals working in close proximity to the cables might trip over them, endangering both the employee and the equipment. Secondly, and most importantly, poorly coordinated cables present a significant fire risk. Many fires start as a result of electrical failure, and in the event of a fire, cables that are not protected may perish in the fire, exposing live wires and presenting a further electrical hazard to evacuating personnel.

To protect against such dangers, a variety of cable management kits and other products with flame retardant qualities are available. The Kopex Flexible Conduit provides a flame retardant cabling solution, featuring a galvanised steel core and a PVC cover, and is both flexible and versatile.

Trunking pillows, such as the Newlec Fire Protection Pillow, can also be used to lower the risk of fire. These are made of fire resistant compounds and are utilised to plug holes bored in walls and ceilings for the purpose of electrical cabling. This is vital, as in the event of a fire flames may quickly spread from room to room via any unsealed holes.

Effective and efficient cable management
Managing electrical cables effectively is almost like an art form, and if done well it can save both time and money in the long run, as well as protecting your equipment and your staff from unnecessary risks.

## How to Fireproof Your Cabling Using a Cable Management Strategy

Modern businesses utilise a wide array of electronic and IT equipment. Most businesses of any reasonable size will have a server room in which is housed the core of their computer network and their data centres. With such equipment inevitably come masses of interlinked cables, and consequently an increased risk of fire.

Many fires, particularly in server rooms, start as a result of malfunctioning or overheated electronic equipment. Once started, these fires can quickly spread, causing devastation. Burning cables can add significantly to the danger through the toxic smoke generated by the rubber insulation and by the exposure of live electric wires. Furthermore, fires can start within the cabling itself, and so steps should be taken to safeguard against this and to slow the spread of any potential fire.

By developing a diligent and safety conscious cable management strategy, it is possible to mitigate these risks.

Developing a cable management strategy

Cable management is easiest when it is done right at the start during equipment installation. Cable routes should be well thought out and executed in a tidy and methodical manner, enabling easier management and lowering fire and other associated risks.

Cable trays, baskets and cable trunking should then be used to organise and insulate the cables. Wherever possible, these cable management accessories should be fire resistant or otherwise minimise the risk of both fire spreading from the outside to the cable inside and from the cable inside to the exterior.

Cable trunking for fire proofing

A wide range of fireproofing solutions are available to businesses. Newlec cable trunking made from pre-galvanised steel is particularly effective at slowing or preventing the spread of fire due to the high heat tolerance and flame resistant nature of steel.

Other forms of cable trunking are made from PVC-U, a PVC derivative with specific flame-retardant properties. Unlike other plastics, PVC-U will only combust under the continued presence of an external heat source. When it does burn, its combustion temperatures are very low and so it does not contribute to fire and flame propagation significantly. PVC-U also generates very little smoke when it burns, a factor which can be crucial during an emergency building evacuation.

MK Electric Industrial Cable Trunking offers a versatile and easily installable cable management solution and measures 50mm high and 50mm wide, making it suitable for heavy duty applications. For less intensive applications, Marshall Tufflex Self-fixing Mini-trunking measures 16mm x 16mm, and features an innovative clip-on lid for easy modifications.

By carefully choosing fireproof cable trunking and similar cable management systems, it is possible to be adequately protected against many of the risks of fire, and to lessen its potential impact.

When it comes to fire prevention and control, small things can make a big difference. For example, making sure that cable trunking is not overcrowded and has plenty of room for internal ventilation lessens the risk of heat build up within the cables, while keeping areas around cabling clean and free of debris minimises the amount of combustible material which could propagate a fire.

## Fluorescent Light Bulbs More Efficient Than ‘Normal’ Light Bulbs?

In the early 21st Century, energy efficiency is of prime importance. Not only does energy wastage cost substantial amounts to consumers and businesses, it also harms the environment and depletes natural resources at a rapid rate. Fortunately, there are energy efficient lighting solutions available on the market today, such as fluorescent bulbs.

To determine whether fluorescent light bulbs are more energy efficient than ‘normal’ bulbs, it’s necessary to take a look at how the two types of bulb work and how they differ.

How do normal light bulbs work?

Normal bulbs are known as incandescent light bulbs. These consist of a glass envelope, often rounded or candle shaped, and a tungsten filament contained inside. When the light is switched on electricity passes through the filament where it encounters resistance. This resistance causes the tungsten filament to heat up to the point where it is glowing white hot, and this is what produces the light. Much of the electrical energy expended in lighting up an incandescent light bulb is wasted generating this heat, and for this reason such light bulbs are highly inefficient.

How do fluorescent light fittings work?

Fluorescent light bulbs operate according to an entirely different set of principles. They do not contain a filament, but instead use a phosphor coated fluorescent tube to produce light. At each end of the tube is an electrode, and when the light is switched on a steady stream of electrons pass from one end to the other. This produces a sequence of chemical reactions within the gas contained inside the tube, and these in turn cause the phosphor coating inside the bulb to ‘Fluoresce’, or emit light. This is a far more efficient way of producing light, as it does not require significant amounts of heat to be produced in order to reach the end goal.

The benefits of Fluorescent lighting

Fluorescent light fittings require far less energy to produce the same amount as an ordinary incandescent light bulb. They can be up to six times more efficient than incandescents, and so can produce significant saving on electricity bills and substantially reduce the carbon footprint of homes and businesses.

Fluorescent fittings such as the Osram Lumilux Fluorescent Lamp make a perfect addition to offices and other workplaces not just because of the energy savings they can offer, but also the brightness and wide dispersal they provide. Fluorescent lighting can also be particularly useful for emergency lighting situations.

While fluorescent lighting may sometimes be more expensive to buy than conventional incandescent lights, in the long run they pay for themselves many times over in the form of reduced electricity bills. As they do not contain a fragile filament, they generally need replacing less often.

Fluorescent lighting, such as the Newlec Surface Fluorescent Luminaire, can be utilised in a wide variety of locations and settings. Many models are available in different sizes making them a versatile, cost-effective and convenient lighting solution, whatever the size of the room.

## Telemecanique Variable Speed Drives Can Save You Money

The key to a successful business lies not just in maximising profits but also in minimising overheads. Energy costs resulting from the operation of machinery used for industrial manufacturing applications and other uses can form a substantial part of annual costs. Many machines such as pumps, fans and conveyor belts consume large amounts of energy every day, and this results in significant financial and environmental costs.

However, it is possible to dramatically reduce such costs without going to the extremes of replacing existing machinery. One of the reasons that motor driven machines consume so much power is that their speed is fixed, or at best has only a few preset speeds. However, the process which utilises the machinery may not actually require such high levels of power input, and so much of this energy is wasted.

What are variable speed drives?

Variable speed drives, such as those manufactured by Telemecanique (an arm of Schneider Electric), enable the speed of motor driven machinery to be controlled precisely, and even to be set to higher or lower frequencies as is needed by different conditions or tasks.

Telemecanique variable speed drives work by controlling the amount of power supplied to the motor driving the machinery, and thus the speed at which the machinery runs. This accurate degree of control is useful for many different applications. For instance in an assembly line or packing plant, a conveyor belt can be set to different speeds in accordance with the specific procedures required by each different product being manufactured.

How Telemecanique variable speed drives can save business’ money

Aside from these practical uses, variable speed drives can also be used as effective money savers. Many machines, such as pumps and fans, operate at higher speeds than is required, simply because the motors driving them are running at a predetermined speed that cannot be changed. There are of course other means of modifying machine speed, but these usually come later along the process line and so do not reduce the overall power input going in. Telemecanique variable speed drives modify the speed of the machine motor itself, and so by reducing the machine speed, the power input is also reduced. This translates into significant savings on energy costs.

The Altivar range

The Telemecanique Altivar series consists of both single phase and three phase variable speed drives, covering a range of price tags and uses, with the small Altivar 11 single phase at the lower end up to the heavy duty Altivar 21 at the top end. The Telemecanique Altivar 21 comes with a remote keypad and pc software for quick, easy and user friendly control.

Variable speed drives are relatively inexpensive, yet offer a high return on investment within a short time. Highly configurable for a range of purposes and reasonably simple to install alongside existing machine process chains, such drives are becoming increasingly popular with industrial producers with high energy consumption rates. This looks set to increase as the government moves towards stricter regulation of business’ carbon output.

## Stay Out of the Dark! Generator Installation and Electrical Panel Upgrades Help Beat Blackouts

There is no doubt that a power outage is inconvenient, but it can also be dangerous and even result in a loss of profit for businesses. Outages can be caused by faulty wiring, a downed pole, the weather… Now, with help from your local electrician, you can help prevent outages and be prepared for when they happen!

Nothing has transformed the world quite like electricity. Then again, nothing transforms your world quite like when the power goes out! When you’re unable to shower, cook, watch television, or even turn on a light to read, it quickly becomes evident how much we depend on electricity.

Homes aren’t the only establishments that suffer during periods without power. Businesses can experience lost revenue from not being able to serve customers or complete business transactions without electricity. Homes and businesses can also become more dangerous during an outage due to lack of adequate lighting and heating.