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General Design / Implementation / Construction

Why should implementation of a DC Microgrid be considered?

In the simplest of terms, all core function and component features of a DC Microgrid solution are designed to reduce energy use from the present practice of connections to AC grid. In general, the more extensive the system, the greater the energy savings. In all cases, there will be some degree of reduction in energy use which will result in direct cost savings of energy dollars and reduced carbon footprint. In many cases, these cost savings can be significant. Back to top

What Products are available that can operate on DC voltage?

There is an ever growing selection of products that are configured to operate on 24V DC voltage. Refer to the ‘DC Power Distribution and Device Discussion’ section of this Design Guide for additional information. Back to top

What is the cost of these DC products, compared to their AC equivalents?

The cost of DC components (luminaires, wiring, controls, devices) is very comparable to their AC equivalents, and in most case they are in fact the same device with only their power input circuitry altered to operate on DC power. Certain DC devices may also be less expensive because they would not need an internal AC to DC power supply. Back to top

What resource / product would help integrate multiple DC sources, (solar / wind / battery / converted AC) into a unified, usable DC power supply?

The process of developing a complete DC Microgrid solution is grounded in common Electrical Engineering principles and can therefore be performed by a variety of resources. Nextek Power Systems is an industry innovator and leader in the development of engineered power solutions that can efficiently combine power from a variety of sources into a unified DC Microgrid power supply. Back to top

What AC light fixtures are the Nextek DC Ballasts compatible with?

Most AC fluorescent lighting fixtures are compatible with the Nextek DC Ballasts. Many manufacturers are beginning to produce factory assembled fixtures that include Nextek DC Ballasts. For an up to date listing of these fixtures, refer to the registered products section at www.emergealliance.org or contact your Nextek representative.Back to top

Can ‘most’ existing common AC powered fluorescent and CFL fixtures be converted to DC by just swapping out the ballast from AC to DC?

In most cases, existing popular style AC fluorescent luminaires can accept a replacement Nextek DC Ballast. Each luminaire would need to be assessed to determine compatibility. Note that in this potential application, the modified product would not be UL listed or EMerge Alliance® Registered. Also, the AC wiring to existing luminaires would most likely need to be replaced with new wiring designed to connect with the Nextek PSM unit. Back to top

Can DC fixtures be ‘daisy chain’ wired together, or do they need to each be wired in a ‘home run’ fashion back to the DC source (PSM Unit)?

The wiring of DC light fixtures will depend on making sure that the combined wattage does not exceed the available power of the source channel or circuit. For EMerge Alliance® Standard System applications, as powered by the Nextek PSM unit, each channel can supply 95 watts. This could accommodate multiple lower wattage fixtures in a daisy chain arrangement, then connected to the PSM channel. For luminaires that each exceed 47 watts, they would require a dedicated channel. Back to top

Are PSM Units, or similar DC source / control units, required to power DC lighting, or are there other ways to connect DC fixtures to a DC power source?

The Nextek PSM unit is the only EMerge Alliance® Registered device that is available to power 24V DC fixtures and devices as defined in the EMerge Alliance® System. Back to top

Are there PSM units that can connect o 120V AC power?

The Nextek PSM units may be able to operate with a 120V AC input, but this configuration has certain additional restrictions and is not UL listed. In is recommended that PSM units be connected to at least 208V AC power. Back to top

Is there a common ‘distributor’ or ‘coordinator’ for all DC components needed to make a complete ‘system’, or does the Designer / Contractor need to make multiple purchases from multiple sources, then ‘figure out’ how to put it all together?

The EMerge Alliance® and its members offer convenient access to and provide reference for other participating member product data through their websites. In addition, Nextek Power Systems offers consultation services to assist with system design and DC product selection. Back to top

Are there unified CSI formatted specifications available for all products?

There are CSI format specifications provided within this Design Guide, (and available in editable .doc format at our design professionals page, that pertain to certain Nextek products. Additional specification development information is available upon request or from other EMerge Alliance® members that offer registered products. Back to top

Is UL or a similar listing required for all DC components, or just some? If required, what is the status of their UL approvals?

It is the intent that all EMerge Alliance® Registered products are or shall be UL listed or made of UL listed components. Consult with EMerge Alliance® company representatives directly for specific UL status regarding specific products. Back to top

Are DC Microgrid system designs covered by the NEC?

Components, wiring and overall system design and function for a DC Microgrid system in the voltage range of the systems as defined by the EMerge Alliance®. Back to top

Do licensed electricians need to wire and install the 24vdc components and fixtures, or can General Trades personnel do that work?

It is recommended that licensed electricians perform all initial wiring work. Back to top

Is there a separate color standard for DC wiring so that it does not become confused with AC wiring?

At this point, there is no specific color standard, or wire markings for DC systems. It is recommended that DC wiring and devices have some form of identification different from similar AC components. Back to top

What type of lighting controls can I use with a DC EMerge Alliance® System?

Any EMerge Alliance® registered control device can be used. Back to top

What type of connectors can I use with a DC EMerge Alliance® System?

Any EMerge Alliance® registered connector can be used. Back to top

How long are the 24V DC cables which deliver power to the DC devices or an Energized Ceiling Grid?

The length of low voltage cables that connect power to the DC devices or an Energized Ceiling Grid are defined within the EMerge Alliance® Standard as follows: Power Cable Assemblies should not exceed the lengths noted in the table below for circuits that are designed to carry full load currents. Circuits dedicated to sensors, user controls, and other low-power devices may exceed these limits. Back to top

Gauge(AWG)	Max Length (ft)
12	30
14	25
16	15
18	10

Can I get a LEED credit for using an EMerge Alliance® Standard based system on my project?

Possibly. You can apply for a LEED innovation credit for using EMerge Alliance® registered products in an overall reduced energy use solution. Using EMerge Alliance® registered products may help lower your energy usage, which may also you achieve the criteria for other LEED credits. Back to top

Does a DC Microgrid based system work in a residential application?

Yes. The efficient use of DC powered devices is applicable for any building. Due to the generally greater power demanded from Commercial building occupancy loads, the use of DC Microgrid technology is generally better suited for commercial applications. But use within a residential application can still be significantly beneficial. Back to top

Is a DC Microgrid system more efficient than use of an inverter based DC to AC system?

Yes, very much so. By elimination of an inverter based system DC to AC system, direct use of DC power can produce an increase in overall system efficiency of generally between 20% and 40%. Many factors of an overall system design will ultimately define the specific efficiency gain when compared to a DC to AC inverter based system. Back to top

DoI have to rewire my building?

In general, the DC loads supplied in a DC Microgrid designed system are connected using same or similar wire sizes as comparable AC loads. As such, for certain applications, use of existing AC wiring may be possible. For new 24V DC, Class 2 wiring solutions, generally new wiring will be required to facilitate connections to the Nextek PSM unit. Note that these Class 2 cables are more easily installed than conventional AC wiring because they do not need to be in conduit. Back to top

Do I need to replace light switches with DC rated switches?

In an EMerge Alliance® based system, the lighting is powered from the Nextek PSM unit. The on, off or dimming control of light fixtures are achieved with new DC powered controls, many of which are wireless. As such, use of existing, limited AC light switches is not practical or necessary. Back to top

Can Nextek ballasts run on AC and DC power?

No. The Nextek ballasts for EMerge Alliance® based systems can only be connected to 24V DC power. Back to top

Does a DC Microgrid system require batteries?

No. DC storage batteries are optional for a DC Microgrid system. A properly designed DC Microgrid will have redundant power sources from both organic DC and rectified AC sources to maintain power to the system. Without batteries, during a power failure, the system will still function providing that the DC power sources are generating power. Back to top

Do DC Microgrid systems qualify for rebates or credits?

Yes. There are many forms of tax credits, rebates and other financial incentives in the marketplace to support the purchase and implementation of DC Microgrid systems or components. Each system will qualify for a unique array of local and Federal financial incentives based on configuration and location. Specific incentives are constantly changing. Back to top

Operational

What happens if the power supply module loses power?

If you lose power to a power supply module all of the electrical devices connected to the Armstrong DC FlexZone^TM main beams being supplied from that power supply module will also lose power. However, when power is restored to that power supply module, power will be restored to the Armstrong DC FlexZone^TM grid and its connected devices. The devices will generally reset to the state at which they were when power was lost. Back to top

What causes a power supply module (PSM) to experience a fault condition?

The Power Server Module protects against over and under voltage, overload, short circuit, and over temperature and will experience a fault if any of these condition occur. Back to top

What conditions cause an under/over voltage fault?

EMerge Alliance® compatible devices shall operate with a nominal input voltage of 24 Volt DC and shall be tolerant of 24 Volt DC nominal +2% - 5% per lasted Standard update. This equates to an operating range between 24.5 Volt DC to 22.8 Volt DC. An under/over voltage fault will occur if the voltage is outside of this allowable range. An over voltage condition will cause the power supply module to lock out and require a reset. Back to top

What conditions cause a PSM overload fault on an Armstrong DC FlexZone^TM Grid System?

An overload fault will occur when an Armstrong DC FlexZoneTM main beam is supplied with more than 95 Volt-Amperes (Watts) of power. The power supply module will sense this overload fault and stop delivering power to this associated main beam. The power supply module will continue to deliver power to the other Armstrong DC FlexZoneTM main beams which are not experiencing an overload fault. When the Armstrong DC FlexZoneTM main beam overload fault is corrected, the power supply module will automatically reset and deliver power to this main beam. Back to top

What conditions cause a short circuit fault on an Armstrong DC FlexZoneTM Main Beam?

In electrical devices, unintentional short circuits are usually caused when two wires come in contact with each other, or when another conducting material such as water, or a piece of metal is introduced, allowing the electrical current to flow along a different path besides the one intended. A short circuit fault can occur when an unapproved wire or clamp is placed around the Armstong DC FlexZoneTM main beam and incidentally touches both conductors at the same time. A screw placed through the electrical conductors on the bulb of the grid for support will cause a short circuit fault. The power supply module will sense this short circuit fault and stop delivering power to this main beam. The power supply module will continue to deliver power to the other Armstrong DC FlexZoneTM main beams which are not experiencing a short circuit fault. When the Armstrong DC FlexZoneTM main beam short circuit fault is corrected the power supply module will automatically reset and deliver power to this main beam. Back to top

What conditions cause a temperature fault?

EMerge Alliance® compatible devices shall operate between the range of 0° C and 50° C. A temperature fault may occur if the operating temperature is outside of this range. The power supply module will sense this temperature fault and stop delivering power to the system. When the temperature becomes restored to an acceptable range, the power supply module will again deliver power back to the system. Back to top

Theoretical / Reference

Why do I not get shocked when I touch 24 Volt DC but still get shocked when I touch 120 Volt AC?

Basically 24 Volts DC is not a high enough voltage to create a pain sensation on the human skin. However, a high enough DC voltage will create a burn on the human skin. 120V AC will create a burn on the human skin because it is at high enough voltage. A shock of an AC voltage will hurt more because it is really a series of shocks. 120 Volt at a frequency of 60 Hertz will shock you 60 times every second. Back to top

What about when the Low Voltage cabling gets wet, does that cause a hazard?

No, the low voltage cables are UL listed and are rated to survive a wet event. They are not intended to operate in an underwater condition. Back to top

Concerning Electromagnetic Interference from a health perspective, is there any difference, better or worse, from using 120 Volt AC or 24 Volt DC?

Electromagnetic Interference occurs when there is a disturbance that affects an electrical device due to the electromagnetic radiation emitted from a different electrical device. Low frequency or narrowband interferences usually arise from frequency transmissions in radio, television stations, pagers and cell phones. High frequency or broadband interference usually comes from frequency transmission from high voltage electric power transmission lines and electric motors. Since DC powered devices do not operate at a frequency like AC power the health hazard is inherently lower. Back to top

What is the EMerge Alliance®?

The EMerge Alliance is an open, membership-based, not-for-profit industry association formed in 2008 to create and promote the adoption of new standards for direct current "DC" power distribution within commercial buildings to improve their flexibility and sustainability. Back to top

Where can I find out more information about the EMerge Alliance®?

Visit the EMerge Alliance® website at: www.EMergeAlliance.org.

Where do I find EMerge Alliance® registered products?

EMerge Alliance® registered products can be found at: www.emergealliance.org/Products/RegisteredProducts. Back to top