Circuit breaker

Fuses and circuit breakers

Fuses and circuit breakers are both devices that 'break' if the current through them is too large.

Fuses

A fuse is usually a thin piece of wire that will melt and break the circuit if too large a current flows through it. The thicker the wire the more current is needed to melt it and the higher the 'rating' of the fuse. The purpose of a fuse is to protect the wiring and the equipment. If the fuse was not there and something went wrong the wires themselves would get hot and maybe catch fire. In a plug the fuse is in a glass tube.

Power Cable

Wiring Color Codes

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Wiring for AC and DC power distribution branch circuits are color coded for identification of individual wires. In some jurisdictions all wire colors are specified in legal documents. In other jurisdictions, only a few conductor colors are so codified. In that case, local custom dictates the “optional” wire colors.

IEC, AC: Most of Europe abides by IEC (International Electrotechnical Commission) wiring color codes for AC branch circuits. These are listed in Table below. The older color codes in the table reflect the previous style which did not account for proper phase rotation. The protective ground wire (listed as green-yellow) is green with yellow stripe.

Reefer Power Plug

MENNEKES

Heater (hot gas)

Where to use dehumidifiers and why?

Excessive air humidity can cause undesirable effects, such as feeling unwell, sicknesses, material losses and increased hazard of workplace accidents. They can all be counteracted by reducing the amount of water in the air. 

Air drying can be applied in several areas, the most important ones being: 

• providing appropriate climate comfort,
• technological processes in various industries,
• protection against corrosion,
• protection against steam condensation,
• protection against icing,
• protection against fungal and bacterial growth,
• improving repair and construction works,
• avoiding product agglomeration.

Methods of dehumidifying

Air dehumidifying is a process that consists in decreasing the contents of steam contained in the air. Air can be dehumidified in several ways: 

• heating and ventilation
• condensation dehumidifying
• adsorption dehumidifying

Heating and ventilation

This method consists in raising air temperature in a room and applying intense ventilation. Its efficiency depends on external conditions that can even make it impossible to use the method. The lower external temperature and the higher temperature of the dehumidified room, the more effective the method. Thus, the best effects can be achieved in winter, worse in the spring and autumn, and the worst ones in summer. 

In the case of dehumidifying humid walls, temperature in the room should not exceed 35°C. Higher temperatures can cause excessive increase in pressure of steam contained in walls which leads to cracking and damaging of the walls. Lack of proper ventilation (air exchange) while dehumidifying humid walls with this method causes steam to be absorbed by drier parts of walls and the ceiling. One should also mention that air heating with gas heaters gives the opposite effect as compared to the planned one. This is because burning propane-butane produces carbon dioxide and steam. In result, not only air temperature but also air humidity increases. 

Using this method is connected to high costs. This is mainly a result of its low effectiveness (long time of dehumidifying) and the fact that the best effects are achieved at the largest temperature differences (large demand for heating power). 

Dehumidifying by ventilation and heating:
1 - air removed outside; 2 - air sucked from outside; 3 - extractor fan; 4 - heater; 5 - heated air

Heat Exchanger

HEAT EXCHANGERS IN REFRIGERATION 

In principle heat exchangers have the purpose to transfer heat from a flowing substance to another flowing substance of a lower original temperature. The substances are gaseous or liquid. Important for the heat transfer is the temperature difference of the two media as a driving gradient. Dependent on the flow direction (e. g. counterflow, parallel flow) the progression of the temperature difference along the path can be different.

Temperature profile for a tubular heat exchanger:
A parallel flow, B counterflow;
T1 hot medium supply, T2 hot medium discharge, T3 cold medium supply, T4 cold medium discharge

Evaporator Fan Motor

Evaporator Coil

Evaporator is an important component together with other major components in a refrigeration system such as compressor, condenser and expansion device. The reason for refrigeration is to remove heat from air, water or other substance. It is here that the liquid refrigerant is expanded and evaporated. It acts as a heat exchanger that transfers heat from the substance being cooled to a boiling temperature.

MDV "DIGITAL SCROLL" SYSTEM

WHAT IS A "DIGITAL SCROLL" SYSTEM

A "Digital Scroll" system is a multi-system with a "digital scroll"  Copeland compressor which can regulate effect, simplifies air-conditioning systems, saves more energy  and gurantees reliable functioning.  Multiple internal units can be attached to one external unit. 

WORKING PRINCIPLE OF A «DIGITAL SCROLL» COMPRESSOR

How Copeland Scroll Digital™ Works

The beauty of this technology is its inherent simplicity. The standard Copeland Scroll™ has a unique feature called axial compliance. This allows the fixed scroll to move slightly in the axial direction to ensure that the fixed and orbiting scrolls are always engaged together with the optimal force.

This optimal force, which holds the two Scrolls together at all operating conditions, ensures high efficiency of Copeland Scroll. The Copeland Scroll Digital operation builds on this principle.

A piston is fixed to the top scroll to ensure that when the piston moves up, the top scroll also moves up. There is a modulation chamber at the top of the piston that is connected to the discharge pressure through a bleed hole of diameter 0.6 mm. An external solenoid valve connects the modulation chamber with the suction side pressure. When the solenoid valve is in the closed position, the pressure on either side of the piston is discharged and a spring force ensures that the two scrolls are loaded together. When the solenoid valve is energized, the discharge gas in the modulation chamber is relieved to the low pressure. This causes the piston to move up and consequently the top scroll also moves up. This action separates the scrolls and results in no mass flow through the scrolls. De-energizing the external solenoid valve again loads the compressor fully and the compression is resumed. The movement of the top scroll is only about 1.0 mm, which means that the amount of pressure that bleeds from the high side to the low side is very low.

Copeland Scroll Digital™ Advantages

A Simple System
The beauty of the Copeland Scroll Digital™ Technology is in its inherent simplicity. This simple design and architecture means that there are fewer electronic and mechanical parts which translates into greater reliability, simpler maintenance and more flexibility in applications. Compared with existing technology, the Copeland Scroll Digital™ system can result in space savings of over 30% because of its simple design.

Reliability
System reliability is a paramount concern for all global markets. In developing markets, this can become even more challenging due to voltage fluctuations and training available for installation and service technicians. Other modulation systems typically have complicated electronics which can create particular challenges in developing markets. This situation is made even more complicated by the use of various bypasses, such as hot gas bypasses and liquid bypasses, adding an added layer of complexity.

What is Copeland Scroll Digital™

The Copeland Scroll Digital™ compressor increases HVAC system efficiency by precisely matching compressor output to your heating or cooling needs which saves energy and reduces maintenance costs. Developed in 1993, the first application of this technology was in refrigerated marine containers in 1999. In 2000, the air-conditioning version of this technology was first launched in Asia. Today, over one million pieces of these compressors are working in the field all over the world in various premium applications and their reliability has been over 99.995%.

The technology behind the Copeland Scroll Digital is perfect for many environments. Capacity modulation between 10% and 100% can be achieved quickly and smoothly, meaning that it is perfect for buildings or rooms which experience widely varying loads or where precise temperature and humidity control is necessary. Furthermore, this technology can easily be applied to a variety of applications including Variable Refrigerant Flow (VRF) systems, rooftops, chillers, packaged and split units and also for special applications

Modulation Device

Electric Pressure Regulating Valves

CDS Series

Electronic Expansion Valve Overview