Frequently Asked Questions

What is a Load Flow Analysis?

No matter how big or small an electrical installation may be, the National Electrical Code (NEC) requires a load flow analysis. This is often referred to a load calculation. A load calculation allows the engineer to accurately predict how much power will be used at each panelboard, distribution board, electrical service and so on. The electrical engineer needs to know what equipment that is going to be installed under the project will require an electrical connection. Common items that need to be taken into consideration when performing a load flow analysis and calculation are:

    • Mechanical and Plumbing equipment

    • IT equipment

    • Lighting fixtures

    • Powered signs

    • Receptacles

    • Kitchen equipment

    • AV equipment

    • Industrial control panels

    • Healthcare equipment

    • Automatic doors

    • Accessories for any of these or other pieces that require separate electrical connections

    • Automatic window shades

    • Fire alarm panels and devices

    • Etc.

The above list only represents a portion of the most common load types that need to be taken into account when performing a load calculation.

Why is it important?

These loads are summed together using NEC demand factors at each panelboard and aggregated as we move upstream in the electrical distribution system until we reach the main electrical service entrance section (SES). This analysis and calculation provides an accurate depiction of how much load the system is expected to experience. This information is used to accurately size each panelboard, distribution board and electrical service. An accurate load calculation can help save the owner money by not oversizing equipment while simultaneously assuring that the electrical distribution system will function properly (I.E its not undersized either).

What is a Fault Current Calculation (Short Circuit)?

Electricity is inherently dangerous. Have you ever seen a lightning storm? Electrical discharges can create large amounts of energy that can be very damaging. My job, as a professional electrical engineer, is to make sure that every electrical system I design is as safe as possible. While rare, there is the possibility in electrical systems that can result in what is known as a fault or short circuit. A fault occurs when two or more electrically conducting surfaces (I.E wires, busses etc.) touch something else or each other. The worse fault an electrical system can experience is known as a 3-phase bolted fault. When that occurs the system can generate an extremely large amount of current. When I say large I mean on the order of 10 to 100 times more current than the system would experience under normal operating conditions. The maximum amount of current that a system can experience under this worse case scenario is known as the available fault current (AFC). The AFC of any given system at any given point must take into account a wide variety of variables. For complicated systems software such as SKM Power Tools are used to give an accurate AFC at every panelboard, distribution board, control panel, and service in the system.

Why is this important?

In order to protect equipment, buildings and most importantly people, every electrical system must be designed with the ability to stop, or interrupt, this large amount of electrical current before anything, or anyone, is affected. This is known as the 'Amp Interrupting Current' rating or AIC. As this number is often very large 'Thousand Amp Interrupting Current' or KAIC is often used. In order to be safe, and be code complaint, the AIC value must be higher than the AFC value. Accurately calculating the AFC will help save the owner money by not over-rating equipment (which can get quite expensive) while still providing a system that is safe to operate and is reliable to use.

What is Arc Flash?

Arc flash is one of those things that you just have to see to believe. The video linked here shows what happens when an arc flash occurs (start at ~37 seconds).

Preventing and mitigating the effects of arc flash go hand in hand with accurately sizing equipment for fault currents. Equipment that is accurately rated will have a lesser chance of causing serious damage to equipment and personnel.

When a fault occurs in an electrical system one of the possibly outcomes is an arc flash. An arc flash is a discharge of high amounts of energy. While its impossible to completely prevent arc flashes from occurring we can calculate the maximum amount of energy that can be discharged at any given panelboard, distribution board etc. This information is the result of an arc flash study.

Why is this important?

While, for smaller panelboards the maximum possible incident energy is typically quite small, as the system grows in size and complexity the incident energy discharge can reach extremely dangerous levels. As the amount of potential energy discharge grows, extra precautions must be taken when working on or about the equipment. Arc flash warning labels (like the one shown here) outline what those precautions must be to maintain safety. They will indicate the hazard level and appropriate personnel protective equipment (PPE) that someone will need when working in or about that equipment.

What is Power Factor? And Why Should I Care?

Imagine, for a second, different window tints. If you shine a light through a tinted window some of the light will make it through and some of it wont. The darker the tint the less light will make it through. Imagine that you need a certain amount of light on the other side of a tinted window, as the tint grows darker the more light you would need to shine at the window to achieve the same amount of light on the other side of the window.

Power factor is similar. In this scenario the amount of light you are shining at the window is what is called Apparent Power. The amount that makes it through is called Real Power. Apparent power is the amount of power you buy from the utility, while real power is the power that you actually get to use. The ratio of those two is called power factor. The worse your power factor the more power you have to buy from the utility in order to get the same amount of usable power on the other side of the 'tinted window'.

Typical items that can cause low (bad) power factor are:

    • Large electric motors

    • Power Supplies (Like those found in computers)

    • Arc welders

    • HVAC systems

    • Molding equipment

    • Presses

    • High-intensity discharge lighting

Why is this important?

Most electrical installations are somewhere in the range of 0.8 to 1.0 power factor due to some of the items listed above. As your power factor gets lower you will start to pay more money for the same amount of usable power. On top of that once you get lower than 0.8 most utilities will start to charge you power factor penalties as well. These are fees that the utility will charge you simply because your facility is generating a power factor thats too low. This is because a low power factor can start to affect other customers the utility has in the area.

The bottom line is a low power factor can start to increase your utility bill. Raising your power factor can lower your bill.

There are many ways to improve power factor and subsequently lower your utility bill. Here at Intuitive Engineers I can help you analyze your system for low power factor and find the solutions necessary to improve it.

What Do Plan Drawings Entail?

Power Plans

Power plans will contain the following elements:

      • Electrical equipment such as

        • Service Entrance Sections (SES)

        • Power Panels

        • Control Panels

      • Electrical Devices such as

        • Receptacles

        • Power Switches

        • Power for kitchen equipment

      • Power connections for HVAC equipment, fans and motors.

      • etc.

This is just a list of the most common items, however, anything that requires power will be shown on the power plans in some fashion. This often includes things that isn't specifically a electrical piece of equipment or device but will still require power. One example that comes to mind is power for automatic doors. This is generally specified by an architect but the information and location of the automatic doors will need to be conveyed to the electrical engineer in order to provide power for that door. A lot of what will be shown is equipment specified by another discipline but the electrical point of connection will be installed per the power plans.

Lighting Plans

The lighting plans will contain the locations and designations of all the lighting fixtures and control devices. Pretty straight forward. The lighting plans will include the electrical circuit information for the lighting fixtures as well. With energy codes becoming more and more stringent the lighting plans are, by necessity, becoming a bit more complicated as well. Automatic shut off devices and control schemes will be shown as part of the lighting plans. Lighting power density (lighting fixture watts per square foot) calculations will be provided as well to prove compliance with applicable energy codes.

Emergency and night lights (night lights are lights that are always on no matter what) will also be designated on the lighting plans.

Site lighting plans will be provided with photo-metrics where needed to assure compliance with maximum allowed light at property boundaries. This isn't always required and will be address on a project by project basis.