NEMA is a rating system for equipment that might be exposed to liquids, rain, ice, corrosion and contaminates such as dust.

If unsure of the enclosure rating that is required of your project, please refer to the design chart below. The chart will assist in specifying which enclosure rating is appropriate for the environment and application needed.

For in depth information on the different Nema ratings we offer, please continue reading to the list below.

Type 1: General purpose enclosures constructed for indoor use. Protects against dust, light, and indirect splashing but is not dust-tight. Primarily prevents incidental contact with the enclosure equipment. We adhere to NEMA standards to provide you a quality enclosure for most basic applications.

Type 3R: Intended for outdoor use. Provides a degree of protection against falling rain and ice formation. Constructed (with knockouts on the sides and bottom) to prevent beating rain from interfering with the successful operation of the apparatus or result in wetting of live parts and wiring within the enclosure under specified conditions. Please be aware that these are not rain-tight, which means exposure to beating rain could result in water entering a Type 3R enclosure under certain conditions; nor are they water-tight, which means moisture could enter a Type 3R enclosure when subjected to a stream of water under certain conditions. This style of enclosure does not have a gasketed sealing surface. Nema Enclosures manufactures NEMA 3R enclosures for housing power distribution, lighting contractors, switch gear, and other electrical components that need to be protected in an outdoor environment. Our adherence to UL 508A standards will give you a quality weatherproof enclosure resistant to rain, ice, and snow

Type 4: Weather tight (weatherproof) enclosures. Constructed for either indoor or outdoor use to provide a degree of protection against falling dirt, rain, sleet, snow, windblown dust, splashing water, and hose-directed water. Will be undamaged by the external formation of ice on the enclosure. NEMA 4X is used when protection from the worst environments is required. Our NEMA 4 enclosures come in powder coated carbon steel and are available in a variety of types, such as wall-mounted, free-standing and JIC. Nema Enclosures strictly adheres to the exacting NEMA standards in order to provide you a quality electrical enclosure at competitive price.

Type 4X: Same as Type 4 except constructed from corrosion-resistant material. Corrosion-resistant as defined by industry standards is: Constructed to provide a degree of protection against exposure to corrosive agents such as salt spray. Nema Enclosures produces these enclosures in 5052-H32 aluminum, 304/304L stainless steel, or 316/316L stainless steel and they are available in a number of styles for your demanding applications.

Stainless steel is the strongest of the corrosion resistant materials. It exhibits many of the same resistances attributed to fiberglass materials as well as resistance to highly polar solvents such as acetone and MEK.

316 grade stainless steel is the strongest of the corrosion resistant materials that provide improved resistance to salt, some acids, and high temperature. 316 grade is a strongly recommended choice for marine environments which are within 5 miles of salt water or otherwise subject to salt spray. Note that 316 grade resistance to sulfates and chlorine is less than that provided by 304 grade.

Cautionary aesthetic note: Stainless steel of any type is not “stain-free”, and while it offers a high degree of performance, under certain environmental conditions it remains susceptible to rust deposits on the surface. These deposits are often created by contamination resulting from rain or marine environments. Periodic cleaning of the surfaces of stainless steel enclosures with a neutral solution is recommended to avoid “tea staining” Regular washing with clean, fresh water or even rain water has a significant effect on reducing the incidence of tea staining.

Type 12: Constructed (without knockouts) for indoor use to provide a degree of protection to personnel against access to hazardous parts. Provides a degree of protection of the equipment inside the enclosure against ingress of solid foreign objects (falling dirt and circulating dust, lint, fibers, and fyings). Also provides a degree of protection with respect to harmful effects on the equipment due to the ingress of water (dripping and light splashing). Gasketed doors seal the enclosure’s contents from airborne contaminants and non-pressurized water and oil. Nema Enclosures produce NEMA 12 enclosures which are intended mainly for indoor industrial, manufacturing, and machining applications. We produce a number of enclosure types in aluminum, carbon steel and stainless steel delivered quickly at competitive prices.

This document is from nemaenclosures.com/blog, thanks so much!

What's the difference between hot and cold sequence metering

In hot sequence metering, the tenant circuit breaker is located downstream (load side) from the meter. Turning off the tenant circuit breaker does not deenergize the meter. In cold sequence metering, the tenant circuit breaker is located upstream (line side) of the meter. Turning off the tenant circuit breaker does deenergize the meter. 

Understanding the difference when selecting between hot and cold sequence

You must select "hot" or "cold" metering when adding a utility meter to a switchboard. Hot metering means that the meter comes BEFORE the main disconnect, while cold means the meter comes AFTER the main disconnect.

Utility companies generally specify whether they use hot or cold meters. Consult the local utility specifications, or look where the meter is placed on the one line in order to determine how to configure.

Select hot or cold metering within the utility metering compartment configuration.

TYPES OF LIGHT BULB BASES

Find the light bulb you need using this visual light bulb base chart and detailed illustrations of general light bulb bases, fluorescent bases and specialty halogen base types.

WHAT IS THE DIFFERENCE BETWEEN LIGHT BULB BASES?

There are tens of unique bases for light bulbs. The most familiar is the Edison screw base found on most incandescent bulbs and many halogen, compact fluorescent, HID and now LED bulbs.

The common terms are medium, intermediate, candelabra and mogul. However, because the light industry likes mysterious codes, you may also see E26, E12, E39, etc. E obviously is for Edison. The number after the E is the diameter of the base in millimeters (mm).

Here are the most common Edison base names, codes and applications:

The large Mogul bases found on higher wattage incandescent and HID bulbs are E39.

Most Edison base bulbs are called "single contact" because there is one contact button at the center of the base. 

This document is from four-bros.com blog, thanks so much!

Functions of Instrument Transformers (CTs and PTs)

AC type protective relays are actuated by the current and voltage supplied by the current and potential (voltage) transformers which are generally classified as instrument transformers. Generally instrument transformers are used for mainly two purposes. For metering purpose which steps down and displays voltage and current levels from kV to (0-110 volts in case of PT) and few kilo amps to (0-5 amps in case of CT) . Second purpose is to supply current and voltage magnitudes to the relays to carryout protection functions.

The main functions of instrument transformers are:

• Instrument transformers (current and potential transformers) provide insulation against the high voltages of the power circuit and to protect the apparatus and the operating personnel from contact with the high voltages of the power circuits
• Instrument transformers (CTs and PTs) supply protective relays with current and voltages of magnitude proportional to those of the the power circuits. These current and voltage magnitudes supply by the instrument transformers are sufficiently reduced such that the relays can be made relatively small and inexpensive
• Instrument transformers helps in attaining different types of secondary connections to obtain the required current and voltages

For proper applications of CTs and PTs required considerations are:

Mechanical construction , type of insulation (dry or liquid), ratio in terms of primary and secondary currents or voltages, continuous thermal rating, short time thermal and mechanical ratings, insulation class, impulse level, service conditions, accuracy and connections

For the safety purpose, the secondaries of the current and potential transformers (CTs and PTs) are grounded.

Why Instrument Transformers Used and Advantages

Voltmeters and Ammeters are used to measure the voltage and current in the circuits. Using instrument transformers ranges of these devices to measure can be increased. A current transformer is bascially a step down transformer hence it steps down the current. When used in conjunction with the low range ammeter, a current transformer (CT) increases the range of the ammeter. Thus a 0-5A ammeter can be used to measure several hundreds or thousand amperes of current. Similarly a potential transformer (PT), which is basically a step down transformer can increase the range of the low voltage voltmeter. Thus a voltmeter designed to measure voltage upto 110V can measure a much higher voltages (several thousnd volts) when used in conjnction with suitable potential transformer

Instrument transformers have many advantages. Some of the advantages are given below:

Advantages:

• Single range ammeters and voltmeters can measure a wide range of currents and voltages, if used in conjunction with suitable Current Transformers (CTs) and Potential Transformers (PTs)
• The measuring instruments like ammeter, voltmeter and wattmeters etc are incorporated in the secondary circuit and hence they are totally segregated from the high voltage, thereby ensuring safety for the operator and observer
• The meter need not be insulated for high voltages which would be the case if they are directly included in a high voltage circuit
• Using current transformer with suitable split and hinged core, it easy to measure heavy currents in the busbarwithout having to break the conductor carrying current. The core of the Current Transformer (CT) is opened at the hinge, the current carrying conductor is introduced in the center of the core through a opening made and the core is tightly closed again. The conductor itself acts as a single turn primary winding of the current transformer

WHAT IS MBUS? AND HOW IS IT USED IN METERING SYSTEMS?

August 23, 2021

Necessity is the mother of invention, they say but in the case of MBus, it was frustration that drove Professor Dr. Horst Ziegler of the University of Paderborn, who, in cooperation with Texas Instruments Deutschland GmbH and Techem GmbH. Developed the Meter-Bus or M-Bus protocol. 

WHAT IS AN M-BUS OR METER BUS?

The M-Bus concept was based on the ISO-OSI Reference Model, in order to realize an open system that could utilize almost any desired protocol. Today, M-Bus is ideal for sub-metering because it simplifies the communication between smart metering devices and the gateway or Data Collection Unit in the building allowing for the frequent collection of meter readings for energy management, or utility billing. This meter reading technology created in Europe is gaining popularity in North America with a wide variety of applications when it comes to submetering.

Let us take a closer look at what M-Bus is all about.

It is a serial communication system that uses a single pair of conductors that can tie up to 250 slaves, in this case, meters: to a single master, gateway, or in our case a Data Collection Unit. Every meter is then connected to the bus. The M-Bus string is exceptionally insensitive to external interference that may be caused by capacitive or inductive coupling. It can power the communication module on the meter, while electrically isolating it from other external sources, and it is a very cost-effective method for wiring in buildings, particularly when compared to Pulse-Output meters.
In addition to the savings in the initial installation costs, servicing the system is also easier, as any addition of a meter can be done without the need for reconfiguration of a daisy chain and there is further simplification because M-Bus incorporates protection against reversed polarity.

ROLE OF MBUS IN THE METERING SYSTEM

Metering systems, in particular, those that meter flow, like water or Thermal Energy (heat)meters, use M-Bus to transmit energy consumption via a field bus (the Meter Bus) to a Master.
The communication is simple because the size of the information to transmit is small it can be transmitted up to one kilometer between the meter and the Data Collection Unit, provided the M-Bus voltage is maintained, once in operation; more than one meter can simultaneously and accessible on one common platform, making data available for energy-efficiency purposes.

HOW MBUS IMPROVES METERING SYSTEM PERFORMANCE

M-bus systems have come a long way from manual reading methods where an employee from the metering company would have to read the data in hard-to-reach areas of the building - A previous time-consuming method that was often measured at long intervals. With M-Bus one, many or all the meters can be interrogated (polled) at any one time, or periodically, this is advantageous when tenants or occupants move in the middle of a billing period, and a partial period reading of the meter is required.
M-Bus can be programmed for multiple Baud rates from 300, to 38,400 Bauds, although most operators will settle with 9,600 Bauds.

MBUS PROVIDES FAST AND ACCURATE REMOTE DATA

Mbus reads measurements electronically at shorter intervals, allowing landlords to have a more accurate view of tenant consumptions. The ability of MBus technology to read data faster from virtually anywhere eliminates manual reading errors made by field personnel.

OFFERS THE POSSIBILITY OF EXPANSION

While each master has a maximum of 250 slaves, there is no theoretical limit on the number of masters that can be installed this provides added benefits for future troubleshooting, for instance, in a large apartment building the water metering for Domestic Cold Water can be segmented from the Domestic Hot Water meters, allowing for additions to each of these systems at a later date. Another option is to retrofit and add another bus for another utility, like for Thermal Energy metering without disturbing the existing buses, and integrating all into a single reporting platform.

GET RELIABLE ELECTRONIC READINGS

Compared to pulse-output meters, M-Bus is more accurate because it transmits the value of the actual read from the meter, and not the pulse count, avoiding using multipliers for conversion, which ensures the availability precise data. Additionally, the M-Bus wire-runs present higher immunity to noise and electromagnetic interference that may affect pulse transmission through non-shielded wiring.

SAVES COSTS

Unlike pulse output meters the MBus wiring is simpler and uses less cable.  

* Above document is sourced from our supplier Intellimeter

December 07, 2018

More and more electricians install automatic door opener for swing doors now. The automatic door opener is a new field to most electricians, if you haven't installed any before, it is tough and difficult for you, especailly you maybe do not know how to order it.

What's the meaning of Left hand pull (LPL), right hand pull (RPL), left hand push (LPS), right hand push (RPS), how to tell it? If you asks the sales guy, everybody gives different answer which confuses you too much.

Don't worry, Aurora Lighting designed the following Automatic Door Opener Name Chart. Look at the chart, there are only 8 combonations for single swing door installation, you just need tell us which photo number matches your application, right away you will have the right model number for the door opener.

Lets you determine the amperage or the KVA according to the parameters that are known. You must choose the number of phases and give at least two (2) of the three (3) parameters of the equation to get a result.

How to convert real power in kilowatts (kW) to apparent power in kilovolt-amps (kVA).

kW to kVA calculation formula

The apparent power S in kilovolt-amps (kVA) is equal to the real power P in kilowatts (kW), divided by the Power Factor PF:

S_(kVA) =  P_(kW) / PF

So kilovolt-amps are equal to kilowatts divided by the power factor.

kilovolt-amps = kilowatts / PF

or

kVA = kW / PF

Example

What is the apparent power in kilovolt-amps when the real power is 3 kW and the power factor is 0.8?

Solution:

S = 3kW / 0.8 = 3.75kVA

Isolation Transformer

Transformers with primary (input) and secondary (output) windings separated from each other are known as isolation transformers. Under this construction, the input power and the output power are electrically separated by an dielectric insulation barrier.

Advantages of using an isolation transformer

• The primary and secondary winding can be constructed as a step-up or step-down transformer to match the load in the electrical system
• Preventing the equipment from getting spikes and harmonics from the mains
• Safety. There will be no conductive connection between the live part of the circuit and earth. With the isolating transformer, there is no danger in touching the live while the body is earthed.
• By connecting the electrical system safety ground to the neutral conductor on the transformer secondary, it eliminates neutral-to-ground voltage and noise. This resolves reliability problems for microprocessor-based electronics.

Isolating transformers are also the most common kind of transformers for voltage step-up and step-down usage.However, 1:1 ratio transformers, where input and output voltage are the same, are also widely used to solely take advantage of the isolation.

Autotransformer

Step-down Autotransformer	Step-up Autotransformer

In an autotransformer, the primary and secondary share a common winding. The secondary voltage always has a common terminal with the primary. Step up or down of the voltage is achieved by a tap from the winding measuring from the common end. For example, a secondary tap at 50% of the winding will produce a voltage half of the input.

Advantages of using an Autotransformer

• Lighter in weight and smaller in physical size as it requires fewer windings and a smaller core.
• Less costly compared to an isolation transformer.
• The advantages listed typically are for autotransformer with voltage ratio ranging up to 3:1 voltage or vice versa. Beyond this range, an isolation transformer is usually more economical.

Limitations

• There is no isolation between the primary winding and the secondary winding. Therefore protection of the equipment is dependant on the supply devices.
• As the primary and secondary share a common end, if the neutral side of the primary voltage is not grounded, the secondary side will not be either.
• A failure of the winding insulation of the autotransformer will result in full input voltage applied to the output.