How Air Conditioning Work

Tuesday, December 30, 2008

Appliances




Information for Washer Machine (Part 1)

Symptom ;

Washer does not work and makes no noise

Troubleshoot ;


Check that the washer is plugged in securely
Check the circuit breaker or fuse box
Test the outlet for current
Check that the water supply valves are turned on
Inspect the filter screens
Test for overheating
Test the water level switch
Test the timer control
Test the lid switch
Test the water inlet valve
Inspect the water pump
Test the centrifugal switch
Test the motor

Wednesday, December 24, 2008

HEAT PUMP

A heat pump
is a machine or device that moves heat from one location (the 'source') to another location (the 'sink' or 'heat sink') using mechanical work. Most heat pump technology moves heat from a low temperature heat source to a higher temperature heat sink.Common examples are food refrigerators and freezers, air conditioners, and reversible-cycle heat pumps for providing thermal comfort. Heat pumps can also operate in reverse, producing heat. This produces an efficient way of drying, and manufacturers such as Panasonic, Toshiba, AEG and Miele have released tumble dryers or washing dryers that utilise this method. It is claimed to be more energy saving and quicker than conventional drying.[citation needed]
Heat pumps can be thought of as a heat engine which is operating in reverse. One common type of heat pump works by exploiting the physical properties of an evaporating and condensing fluid known as a refrigerant. In heating, ventilation, and cooling (HVAC) applications, a heat pump normally refers to a vapor-compression refrigeration device that includes a reversing valve and optimized heat exchangers so that the direction of heat flow may be reversed. Most commonly, heat pumps draw heat from the air or from the ground. Air-source heat pumps do not work well when temperatures fall below around −5°C (23°F).

Operation
Main article: Heat pump and refrigeration cycle
According to the second law of thermodynamics heat cannot spontaneously flow from a colder location to a hotter area; work is required to achieve this.[2] Heat pumps differ in how they apply this work to move heat, but they can essentially be thought of as heat engines operating in reverse. A heat engine allows energy to flow from a hot 'source' to a cold heat 'sink', extracting a fraction of it as work in the process. Conversely, a heat pump requires work to move thermal energy from a cold source to a warmer heat sink.
Since the heat pump uses a certain amount of work to move the heat, the amount of energy deposited at the hot side is greater than the energy taken from the cold side by an amount equal to the work required. Conversely, for a heat engine, the amount of energy taken from the hot side is greater than the amount of energy deposited in the cold heat sink since some of the heat has been converted to work.
One common type of heat pump works by exploiting the physical properties of an evaporating and condensing fluid known as a refrigerant.

A simple stylized diagram of a heat pump's vapor-compression refrigeration cycle: 1) condenser, 2) expansion valve, 3) evaporator, 4) compressor.
The working fluid, in its gaseous state, is pressurized and circulated through the system by a compressor. On the discharge side of the compressor, the now hot and highly pressurized gas is cooled in a heat exchanger, called a condenser, until it condenses into a high pressure, moderate temperature liquid. The condensed refrigerant then passes through a pressure-lowering device like an expansion valve, capillary tube, or possibly a work-extracting device such as a turbine. This device then passes the low pressure, (almost) liquid refrigerant to another heat exchanger, the evaporator where the refrigerant evaporates into a gas via heat absorption. The refrigerant then returns to the compressor and the cycle is repeated.
In such a system it is essential that the refrigerant reaches a sufficiently high temperature when it is compressed, since the second law of thermodynamics prevents heat from flowing from a cold fluid to a hot heat sink. Similarly, the fluid must reach a sufficiently low temperature when allowed to expand, or heat cannot flow from the cold region into the fluid. In particular, the pressure difference must be great enough for the fluid to condense at the hot side and still evaporate in the lower pressure region at the cold side. The greater the temperature difference, the greater the required pressure difference, and consequently more energy is needed to compress the fluid. Thus as with all heat pumps, the energy efficiency (amount of heat moved per unit of input work required) decreases with increasing temperature difference.
Due to the variations required in temperatures and pressures, many different refrigerants are available. Refrigerators, air conditioners, and some heating systems are common applications that use this technology.

A HVAC heat pump system
In HVAC applications, a heat pump normally refers to a vapor-compression refrigeration device that includes a reversing valve and optimized heat exchangers so that the direction of heat flow may be reversed. The reversing valve switches the direction of refrigerant through the cycle and therefore the heat pump may deliver either heating or cooling to a building. In the cooler climates the default setting of the reversing valve is heating. The default setting in warmer climates is cooling. Because the two heat exchangers, the condenser and evaporator, must swap functions, they are optimized to perform adequately in both modes. As such, the efficiency of a reversible heat pump is typically slightly less than two separately-optimized machines.
In plumbing applications, a heat pump is sometimes used to heat or preheat water for swimming pools or domestic water heaters.
In somewhat rare applications, both the heat extraction and addition capabilities of a single heat pump can be useful, and typically results in very effective use of the input energy. For example, when an air cooling need can be matched to a water heating load, a single heat pump can serve two useful purposes. Unfortunately, these situations are rare because the demand profiles for heating and cooling are often significantly different.

Refrigerants
Until the 1990s, the refrigerants were often chlorofluorocarbons such as R-12 (dichlorodifluoromethane), one in a class of several refrigerants using the brand name Freon, a trademark of DuPont. Its manufacture was discontinued in 1995 because of the damage that CFCs cause to the ozone layer if released into the atmosphere. One widely-adopted replacement refrigerant is the hydrofluorocarbon (HFC) known as R-134a (1,1,1,2-tetrafluoroethane). R-134a is not as efficient as the R-12 it replaced (in automotive applications) and therefore, more energy is required to operate systems utilizing R-134a than those using R-12. Other substances such as liquid ammonia, or occasionally the less corrosive but flammable propane or butane, can also be used.
Since 2001, carbon dioxide, R-744, has increasingly been used, utilizing the transcritical cycle. In residential and commercial applications, the hydrochlorofluorocarbon (HCFC) R-22 is still widely used, however, HFC R-410a does not deplete the ozone layer and is being used more frequently. Hydrogen, helium, nitrogen, or plain air is used in the Stirling cycle, providing the maximum number of options in environmentally friendly gases. More newer refrigerators are now exploiting the R600A which is isobutane, and does not deplete the ozone and is friendly to the environment.

HEVACOMP SOFTWARE














The Company
Formed in 1981, Hevacomp is the firmly established UK market leader in building services design and CAD software. Hevacomp software is acknowledged as the industry standard, with over 3000 user sites - the largest user base of any developer in the building services field. Hevacomp have recently been acquired by the Bentley group of companies, enabling an even stronger position to enter the world wide market.
Hevacomp offers the most comprehensive range of software options available anywhere on the market, backed up by a professional team of programmers and building services engineers. Our design software is written by engineers for engineers.
Computations are carried out using industry standard calculation procedures, such as CIBSE, ASHRAE, British Standards or IEE as applicable.

Software
Supplying high quality software is only the start of a continuing close working relationship with our users. Engineers expect and receive the very best in support. At Hevacomp we provide the most helpful and extensive technical response to your queries.
We operate a comprehensive hot-line support service which gives you direct access to programmers and experienced building services engineers. Training courses are run throughout the year, as well as on-site training, ensuring that your staff can continue their professional development.

Support
We believe in technical excellence and offer a comprehensive software updating service so you can quickly take advantage of new programs and enhancements to existing programs as they develop. The extensive product databases such as heat emitters, protective devices and luminaires are also updated for you, ensuring that you are kept at the leading edge of the industry.
These updates include amendments following changes to Regulations, British Standards, Codes and Guides to ensure that your company remains abreast of current practice.


Corporate information
Bentley Systems (UK) Ltd - North Heath Lane - Horsham - West Sussex - RH12 5QWRegistered in England No. 2957722

Mechanical & Electrical software
Hevacomp provides a comprehensive package of building services design software for Mechanical and Electrical services and CAD. With over 3500 sites using our design software, Hevacomp is the industry standard package.
Design packages Include:
- Mechanical design for Load calculations, Pipe & duct sizing and Mechnical CAD.
- Electrical design conforming to the requirements of IEE 16th Edition wiring regulations, Lighting systems design and electrical CAD
- Support and training focused on satisfying the increased technical demands on M&E design engineers.

Hevacomp Design Simulation

Hevacomp is a leading UK-based building services software house; their design software is used by 70% of the medium to large consulting engineers in the UK, with a user base of 3000 sites world-wide. Hevacomp provides a range of building services software, including heating and cooling loads, energy, pipe and duct sizing, lighting and electrical design. Until now, Hevacomp has produced software based on straightforward steady or quasi-steady state methods; this has proved popular with engineers, who appreciate easy to use software.
Over the past few years, engineers have been required to carry out more complex analysis, such as over-heating frequency, mixed mode ventilation, CFD analysis etc. To meet this demand, Hevacomp has developed a Design Simulation package, using EnergyPlus as the calculation engine. An important feature of the Design Simulation package is that simulation can be carried out using the same project data that engineers have already set up to use with simple load calculations. This enables simulation studies to be carried out without entering any more project data. We see this as an important feature, to lead engineers easily into simulation.
With Hevacomp software, a building is set up by tracing around the internal perimeter of each room, adjacent surfaces are automatically detected as partitions. Databases of constructional elements are used. An extensive roof and floor modelling program is available, which enables simple or complex roofs to be traced from DXF files. Walls and partitions are automatically trimmed vertically to fit the roof, rooms above and below target rooms are detected. This enables a full 3D model to be produced for little more effort than a simple 2D tracing.
Once the building has been set up, building simulation, linking to EnergyPlus, can be carried out to examine room heat losses and gains, summer overheating, peak design months, overheating frequency and building energy. The package will also produce 3D external shading graphics and internal solar penetration graphics, showing moving sunshine patches within rooms.
Summer overheating frequency can be simulated using CIBSE summer design weather data (available from CIBSE) and hours of overheating can be obtained from cumulative frequency results to check against UK PartL code requirements. Natural infiltration can be examined by defining flowpaths and opening windows, this enables quite complex natural and mixed mode ventilation systems to be examined, including controlled opening of windows.
A large amount of weather data for annual energy simulation is provided. Hevacomp provide an extensive Meteonorm weather database of over 7000 locations world-wide. A detailed profiling and scheduling module is available so that you can set up any required plant, gains, occupancy and temperature schedules. Typical schedules for a large range of building are provided, compatible with UK PartL requirements.
As well as building simulation, a plant simulation module enables engineers to simply define HVAC systems such as radiators, warm air, constant volume a/c, VAV, fan coils, room a/c units, etc. Central plant items such as boilers, chillers and cooling towers can also be defined. Databases of common plant and equipment are provided. From a brief HVAC set of data, the package will automatically set up all the required HVAC components, water and air networks and central plant. Although simple to set up, complex systems can be defined, which are not limited to Compact HVAC components.
With plant simulation, plant sizing can be carried out, using summer and winter design days, plant and equipment sizing schedules are produced. Annual energy consumption can be computed, together with fuel cost and CO2 consumption.
Hevacomp has an alliance with CHAM (UK) so that results from Design Simulation can automatically be used to carry out CFD analysis, enabling room air movement and temperature studies to be carried out. Hevacomp provides an extensive object library so that you can place items such as furniture and people in rooms to see the effect on air movement.
Please click this link http://www.hevacomp.com/



















Sunday, December 21, 2008

FIRE SYSTEM

Fire System
The fire systems in a building are many. There are equipment and systems for monitoring, communication, fighting fire, indication, raising alarm, diverting smoke and many others. Generally they can be classified into two categories:
. Fire Protection System
. Fire Fighting System
Fire systems fall under the fire codes for buildings. As fire codes may vary in different countries, no attempt is made to specify the fire codes.
Sometimes, there is an overlap of functions - the systems may contain elements of both fire protection and fire fighting.


Fire Protection System
Fire protection systems are used to alert people that a small fire or some overheating has occurred, and that there is a danger of fire happening soon. Smoke detectors, and heat detectors are used to detect such incidents before a big fire occurred. Persons detecting a fire need to sound the alarm to get more assistance. The break glass is the easiest way to sound the alarm. All the fire alarm panels, sub-control panels, bells, break-glass, smoke detector, heat detectors can be grouped into this area.


Fire Fighting System
The fire fighting system will be used when a big fire has already started. There is a need to extinguish it. Sprinkler systems, and hose reel systems are some of the systems used for fire fighting. Wet risers are pipes which distribute large volumes of water to canvas hoses.
The fire fighting systems contain pumps, tanks, and their own distribution piping. Motors or diesel engines drive the pumps. Hose reels and canvas hoses are terminated with nozzles for spray or jet. Sprinkler systems have special glass bulbs and sprinkler rose. Flow switches are installed to cause bells to ring when the sprinkler systems are activated. The systems can also contain gongs activated by water flow.
Automatic CO2 flooding system will discharge CO2 gas into electrical rooms to stop any fire.
Portable fire extinguishers are installed at strategic locations so that they can be used to put out small fires. Fire intercom systems are used by fire fighters to communicate with fire control room personnel.
Fire escape doors are indicated with Exit signs, and emergency lights are installed to give a bit of light if the main electrical supply has been cut off. Firemen who have to fight fires will face the danger of electrocution if they use hoses and water. The fireman switch can be switched off to avoid this problem.
Smoke spill fans and exhaust fans are sometimes installed for controlling smoke in a burning building.

Saturday, December 13, 2008

INSULATING MATERIALS

Why Insulation Is Used?

All insulating material used in the manufacture of electrical motors perform one or more the folllowing functions:-
1. Act as a dielectric medium to prevent occurrences of an electrical breakdown.
2. To protect the conducting parts from moisture, abrasion, corrosion, etc.
3. To provide mechanical support to conducting parts.
4. To withstand heat which is present at their point of use during operation of the motor. It is essential that the insulating properties of the materials used remain unaffected at the operating temperature.

Where To Insulate?

Listed below are four principal areas where a potential difference occurs and where, therefore, insulation must be aplly;

1) Between turns in a coil (turn-to-turn)
2) Between coils of the same phase (coil-to-coil)
3) Between coils of different phases (phase-to-phase)
2) Between coils and ground (phase-to-ground)

2 Way Switch Diagram














2 Way Switch Wiring Diagram

- Above is a simple schematic diagram of how the wiring for a two way switch should be installed.
-As mentioned, a two way switch has three terminals, as seen in the diagram, S1 and S2 represents the two switches.

- In S1 you will notice that the live wire goes to a and then connected to c in the switch.

- In this case, the b terminal and the c terminal are the common terminals connected by two common wires to the common terminals of S2.
-The diagram demonstrate a state where the light are now being switched OFF.

- Now for example, S1 is installed at one end of the corridor and S2 at the far end.

- When you enter the corridor, you will switch on the lights using S1.

-Inside the S1, the terminals are closed via a and c.

-What happens when you toggle the switch is the copper strip connecting a and c will be pushed to connect to b.

-That means a and b now forms a closed circuit.

-Now look at the diagram again.
-The live wire from the mains will now go to a connected to c where it is again connected by common wire 2 to b2 of S2 which is the switch at the end of the corridor.

- This live supply then passes through to b2 to a2 and onwards to the light, thus completing the full loop to light up the light.

- All this while, S2 has never been touched.
-When you walk right to the end of the corridor and you want to switch OFF the light, the switch will toggle the terminal from b2 to c2, breaking the circuit, thereby switching OFF the lights.

- The switch will stay that way for the whole duration until someone else switches the lights ON again at either end. When that happens the reverse order happens

Friday, December 12, 2008

Contactor

3 Type in Contactor;

1. Normally Open (NO)


2. Normally Close (NC)


3. Coil (etc. A1 and A2)

- sample one of AC Contactor.......






Thursday, December 11, 2008

Electrical Part (Safety)


FUSES



New appliances have to be supplied with a plug that is fused in accordance with manufacturers' instructions.

Always follow manufacturers' recommendations for fuses, or seek expert advice.

If a fuse blows for no obvious reason or an appliance is not working properly, switch off the appliance at the socket and unplug it before trying to find out why. If the fault can't be found or you are uncertain how to find the fault, get expert advice.

The same principles apply to fuse boxes or circuit breakers-always switch off at the mains before you investigate and remember to replace the cover before switcing back on. If you need to change a main fuse, check the correct rating for that circuit-the blown fuse might have been incorrect in the first place. Using a thicker fuse wire than the correct rating is dangerous.

DIY Ductwork Installation

Typical Leak Search and Repair on Commercial A/C - Part I