PT MITRA DAYA INTI MAS
Addres :
Komplek Perkantoran Kota Grogol Permai , Jelambar Grogol Petamburan Kota Jakarta Barat.
BUSINESS FROFILE :
" Quicck , Realible and Professional Service With Efficient Lead Time "
OUR COMMITMENT IN QUALITY ASSURANCE :
" In line with our corporate vision and values , we are committed to continuously upgrade and improve on our products & services quality costomers “ satisfaction & at the same time maintaining a price competitive edge over our competitors , We will also , establish and maintain a quality management system that provides the review to ensure only quality products and services are delivered and Costomers services are constantly improved and enhanced "
OUR GENERAL DATA :
Address office :
Komplek Perkantoran Grogol Permai , Grogol , Jakarta Barat 11460
Phone :
( 62-21 ) 50182237
Fax :
( 62-21 ) 50182237
Work Shop :
Jln : Pintu Air , Jakarta 10710
Phone :
( 62-21 ) 50182237
Fax :
( 62-21 ) 3854267
Website :
OUR SERVICES :
ENGINEERING CONSULTANT
DESIGN AND BUILD
SUPPLY AND INSTAL
SERVICE MANAGEMENT :
Preventive & Correctiive Maintenance , Periodic Maintenance , Troubleshooting , Repair Replacement : Parts
PROJECT MANAGEMENT :
Heat , Ventilation & Air Conditioning Syntem , Mechanical Installation and Engineering , Electrical Installation and Engineering , Centralized / Chiller Air Conditioning System ( Air Cooled / Water Cooled ) Cold Storage , Air Handling Unit / Fan Coil Unit / Package Unit : Trane , MC Quay , Carrier , York , Hitachi , Dunham Bush , Daikin , Cooling Tower : Shinwa , Kuken , Liang Chi , Mesen , Pumps :
EB , Groundfos Etc .
PT MITRA DAYA INTI MAS
The Refrigeration Cycle :
The way your air conditioner pumps heat from inside to outside is through the refrigeration cycle, a thermodynamic cycle involving a special fluid - the refrigerant - that undergoes phase changes ( between liquid and vapor) , pressure changes, and temperature changes. The diagram below shows how the refrigerant flows through the air conditioning system and what' s happening along the way.
First, notice that the diagonal line shows which parts are inside the house and which parts are outside. If you have a split system, with the condensing unit sitting outside making noise and the air handler inside ( which could mean in the crawl space or attic) , the components are in different boxes. In a window AC or package unit, they' re all in the same box.
Now, let' s go through the four stages of the refrigeration cycle, one by one.
1. Evaporator Coil :
This is where the refrigerant picks up heat from inside the house. The evaporator coil is a copper tube, which carries the refrigerant, embedded in a framework of aluminum fins ( photo below) . Using this configuration, the refrigant is connected to a lot of surface area that makes contact with the air blowing over it, which aids heat trasfer from the air to the refrigerant. The most common geometry is the A-coil ( below) , but you also see flat coils and N-coils in some units.
The refrigerant comes into the evaporator coil as a liquid at a low temperature and low pressure. The air handler' s fan ( aka the blower) blows air from the house across the coil. The evaporator coil is cold ( about 40° F) , and the air from the house is warm ( about 75° F, depending on where you set your thermostat) . Heat flows from warmer to cooler, so the air temperature drops, and the refrigerant picks up the heat lost by the air. This is the second law of thermodynamics in action.
In addition to getting warmer, the refrigerant also changes phase here. It' s called the evaporator coil, after all, so the cold liquid refrigerant coming in evaporates and becomes a vapor. Phase changes are a great way to transfer heat because it takes a lot more heat to cause a phase change ( especially between liquid an vapor) than it does to change the temperature of a material. Thus, when the refrigerant starts boiling, it really sucks up the Btu' s ( British Thermal Units) .
One aspect of the flow may be confusing when you look at your air conditioner and try to figure out how the refrigerant flows from inside to outside. If you have a split system, the inside and outside pieces are connected by the refrigerant lines. These are two copper tubes, one larger and insulated tube ( the suction line) running parallel to another smaller and uninsulated tube ( the liquid line) . When the vaporized refrigerant leaves the evaporator coil, it' s still fairly cold. Hence, the refrigerant going to the compressor outside is in the larger, insulated copper tube, not the smaller, warmer tube. As paradoxical as it seems, the colder tube is the one carrying the most heat. You can see this in the photo at right because the suction line even has frost on it, which is not normal and indicates a problem.
2. Compressor :
When the refrigerant reaches the outdoor part of your air conditioner ( photo at top) , the compressor does exactly what its name suggests - it squishes the refrigerant down to a smaller volume, thus increasing the pressure and the temperature. Why? Because heat flows from warmer to cooler. You can' t get rid of heat from a cold refrigerant to 95° F air. The refrigerant has to be warmer than the outside air. That' s one reason why we need the compressor. The other is that the compressor is the pump that moves the refrigerant through the system.
3. Condenser coil :
When the high pressure, high temperature, vaporized refrigerant leaves the compressor, it enters the condenser coil. Again, it' s a copper tube embedded in aluminum fins that allows for efficient heat transfer. A fan inside the condensing unit pulls outdoor air through the sides of the coil and blows it out the top of the unit. Because of the work the compressor did, the refrigerant is hotter than the outdoor air. The second law of thermodynamics kicks in here, and heat flows from the warmer refrigerant to the cooler outdoor air blowing over the condenser coil.
In the evaporator coil, refrigerant changes from liquid to vapor at a relatively low temperature. Now we' re dealing with higher temperatures, and the phase change reverses. If you' re confused by the phase change happening at different temperatures, think about what happens when you go to high altitudes. The air pressure is lower, and water boils at less than 212° F. Pressure changes affect the boiling/ condensation point temperature, which is why boiling happens at a low temperature in the evaporator coil and a high temperature in the condenser coil.
After returning to the liquid state, the refrigerant travels through the liquid line ( the hot, uninsulated copper tube) back to the indoor part of the air conditioner.
4. Expansion Valve - Where the Magic Happens!
Once the refrigerant gets back to the indoor unit, it passes through the expansion valve, and the magic of the refrigeration cycle happens here. The high pressure, relatively warm liquid runs into a constriction that doesn' t allow the refrigerant to pass through easily. As a result, when the liquid does get through to the other side, it finds itself in a much lower pressure. When the pressure drops like this, so does the temperature - a lot! This is what makes air conditioning possible. Without being able to get the refrigerant down to temperatures below the air in your home, an air conditioner wouldn' t be able to work. Why? Because heat flows from warmer to cooler, the old second law of thermodynamics again.
After passing through the expansion valve, the refrigerant goes directly into the evaporator coil, and the cycle begins anew
Introduction
Troubleshooting and servicing refrigeration and air conditioning systems can be a challenging process for both the entry level and experienced HVAC/ R technician. Regardless of your experience, size of the equipment, or location, to troubleshoot the system it is essential that you have a solid understanding of the fundamentals of refrigeration— including the principles of superheat and subcooling. You also need to have the right tools and know-how to apply these principles to use the tool quickly and efficiently.
Troubleshooting techniques often require simultaneous knowledge of temperature, pressure, voltage, and current values in a system, which means that a single-function meter won’ t permit a complete analysis of the system. Frequently, multiple tools are required.
This application note provides information on troubleshooting the refrigeration system while applying the principles of superheat and subcooling to HVAC/ R equipment. It will also teach you the proper methods to tackle some typical troubleshooting tasks using thermometers, digital multimeters, pressure/ vacuum modules, and HVAC/ R accessories. Basic refrigeration principles are provided solely to illustrate how digital thermometers, multimeters, and accessories can make servicing and maintaining HVAC/ R systems straightforward, fast, and accurate.
The refrigeration cycle
Based on the principle that heat flows naturally from warmer areas to cooler areas, the refrigeration cycle consists of seven stages:
1. Compression of hot gas
2. Cooling
3. Condensing
4. Subcooling
5. Expansion
6. Evaporation
7. Super heating
A basic vapor compression refrigeration system consists of four primary components: a metering device ( e.g. a capillary tube, fixed orifice/ piston, or a thermostatic expansion valve) , evaporator, compressor, and condenser.
Superheat and its measurement
In the system’ s evaporator, conversion of liquid to vapor involves adding heat to the liquid at its boiling temperature, commonly referred to as the saturation temperature. After all of the refrigerant has boiled to a vapor, any additional temperature increase above the boiling point is called superheat.
Finding suction line superheat requires finding the suction pressure and two temperatures— the evaporator boiling temperature at a given pressure and the temperature of the refrigerant at the outlet of the evaporator on the suction line, commonly referred to as the superheat temperature/ pressure method.
On newer refrigerant blends, the temperature changes during the boiling or saturation phase. This is referred to as glide. Modern refrigerants with a temperature glide of 10 ° F ( 5 ° C) or higher use dew point ( DP) temperature. This is the temperature of the refrigerant when the last of the liquid has boiled into a vapor. Any vapor temperature increase above the dewpoint temperature is called superheat.
The best method to determine superheat using Fluke products is to use the 80 PK-8 Pipe Clamp Temperature Probe and a PV350 Pressure/ Vacuum Module in conjunction with a suitable Fluke digital multimeter with type K thermocouple measurement and a mV input. The pipe clamp allows pipe temperature measurements to be made more quickly and accurately because it clamps directly to the pipe without the need to add insulation or tape, as in the case of a bead thermocouple. The pressure/ vacuum module allows accurate and quick pressure measurements.
When measuring for superheat, remember to allow the system to run long enough for temperatures and pressures to stabilize while verifying normal airflow cross the evaporator. Using the pipe clamp or a Velcro pipe probe, find the suction line temperature by attaching the probe around a bare section of the pipe, at the outlet of the evaporator. Pipe temperature can be read at the inlet of the compressor on the suction line if the pipe is less than 15’ from the evaporator and there is a minimum pressure drop between the two points.
Subcooling and its measurement
In the system’ s condenser, conversion of vapor to liquid involves removing heat from the refrigerant at its saturation condensing temperature. Any additional temperature decrease is called subcooling. Finding liquid line subcooling requires determining the condensing pressure and two temperatures— the condensing temperature at the measured condensing pressure and the temperature of the refrigerant at the outlet of the condenser on the liquid line. The liquid line temperature involves measuring the surface temperature of the pipe at the outlet of the condenser. ( ( Note: Condensing temperature is derived from using the PT Mitra Daya Inti Mas . On new refrigerant blends with high temperature glide, this is called the bubble point ( BP) temperature.
To measure subcooling with a pipe clamp, or a Velcro pipe probe, allow the system to run long enough for temperatures and pressures to stabilize. Verify normal airflow and then find the liquid line temperature by clamping the pipe clamp around the liquid line. Attach the pressure/ vacuum module to a service port on the liquid line ( or discharge line at the compressor if a liquid line service valve port is not available) . Make a note of the liquid line temperature and pressure. Convert the liquid line pressure to temperature using a PT Mitra Daya Inti Mas for the refrigerant type being used. The difference of the two temperatures is the subcooling value.
Trouble diagnosis
Data from superheat and subcooling measurements can be useful for determining various conditions within the HVAC/ R system, including the amount of refrigerant charge and verifying the operating condition of the metering device.
These measurements can also be used to determine the efficiency of the condenser, evaporator, and compressor.
Before making conclusions from the measured data, it is important to check external conditions that influence system performance. In particular, you should inspect and verify the proper air flow in cubic feet per minute ( CFM) across coil surfaces and line voltage to the compressor motor and associated electrical loads. Remember to look for obvious problems at the coil surfaces such as dirty air filters upstream of the evaporator, or leaves and outside debris restricting airflow on the condenser.
Using superheat to troubleshoot
The superheat value can indicate various system problems including a clogged filter drier, undercharge, overcharge, faulty metering device, restricted airflow, or improper fan motor or blower direction. Suction line superheat is a good place to start diagnosis because a low reading suggests that liquid refrigerant may be reaching the compressor. In normal operation, the refrigerant entering the compressor is sufficiently superheated above the evaporator boiling temperature to ensure the compressor draws only vapor and no liquid refrigerant. On traditional HVAC/ R systems, which utilize mechanical metering devices such as a TXV or cap tube, the superheat heating will vary between 8 ° F to 20 ° F. On newer systems, which use electronic expansion valves and solid state controllers, it is possible to see the superheat setting as low as 5 ° F to 10 ° F.
A low or zero superheat reading indicates that the refrigerant did not pick up enough heat in the evaporator to completely boil into a vapor. Liquid refrigerant drawn into the compressor typically causes slugging, which can damage the compressor valves and/ or internal mechanical components. Additionally, liquid refrigerant in the compressor, when mixed with oil, reduces lubrication and increases wear, causing premature failure.
On the other hand, if the superheat reading is excessive— above 20 ° F to 30 ° F— it indicates that the refrigerant has picked up more heat than normal, or that the evaporator is being starved of refrigerant.
Possible causes of this condition include a metering device that is underfeeding, improperly adjusted, or simply broken. Additional problems with high superheat could indicate a system undercharge, a refrigerant restriction, moisture in the system, a blocked filter drier, or excessive evaporator heat loads.
Using subcooling to troubleshoot
An improper subcooling value can indicate various system problems including overcharge, undercharge, liquid line restriction, or insufficient condenser airflow ( or water flow when using water-cooled condensers) . The refrigerant is typically subcooled between 10 ° F to 20 ° F at the outlet of the condenser, however, some modern equipment may have subcooling values as low as 4 degrees in order to meet minimum efficiency standards.
For example, a very low reading between zero to 10 ° F subcooling indicates that the refrigerant did not lose the normal amount of heat in its travel through the condenser. Possible causes for this condition include insufficient airflow over the condenser, metering device problems such as overfeeding, misadjustment, or being stuck too far open, or the system may be undercharged. Often times, the problem is simply that the condenser coil surface needs to be cleaned thoroughly to eliminate airflow restriction.
Excessive subcooling means the refrigerant was cooled more than normal. Possible explanations include an overcharged system, a restriction in the metering device, misadjusted ( underfeeding) , or faulty head pressure control during low ambient conditions.
Principles of the refrigeration cycle and troubleshooting summary
The next time you are called upon to service or maintain any HVAC/ R equipment, remember to be patient and apply the principles you have learned in this application note.
Check the superheat and subcooling at the unit.
Be sure to do a visual inspection of the equipment to verify that all coil surfaces are clean and that fans are running in the right direction.
You need to have the right tools and know-how to apply these principles to use the tool as it was designed. Fluke thermometers, digital multimeters, pressure/ vacuum modules, and Fluke HVAC/ R accessories will help you solve the problem and repair the equipment correctly the first time.
Chillers:
The above systems are all considered Direct Expansion ( DX) systems because the units provide for direct expansion of the refrigerant in the air cooling coils. Chillers, on the other hand, make cold water that gets distributed by pipes to air cooling coils. Chiller systems also require boilers to make hot water for the heating cycle. A two pipe system either cools or heats and a system changeover must occur to go from cooling to heating. In the cooling cycle, the one pipe supplies the cold water while the other pipe returns the warmed water ( warmed by passing through the cooling coils with air blowing over the coils) . A four pipe system doesn' t need a system changeover, as each cooling coil unit has both a hot water supply and return and a cold water supply and return piped to it.
The energy efficiency of these systems and the excellent control options are the biggest benefits, while initial cost and maintenance complexity are the drawbacks.
Heaters: Hot air furnaces may burn gas, oil, coal, wood, etc. Radiant heaters, which produce infrared radiation which heats objects rather than the air adjacent to the heater, can be fueled by gas or electric. Electric resistance heaters are also common. Direct fired gas heaters, which use 100% fresh air and innovative fan distribution can also be an excellent heating solution for large spaces.
Fans and Ventilation : The use of fans to ventilate a space for cooling and/ or expulsion of indoor pollutants can be done in many ways. From a simple toilet exhaust fan to huge wall fans interconnected with wall louvers used for summer cooling, there are many ways to ventilate.
Air Conditioning and Refrigeration ( HVAC)
Gives you the knowledge to work with and understand HVAC systems. Helps you communicate intelligently with HVAC contractors.
Never again will your company be at the mercy of outside contractors to service and repair your cooling and refrigeration systems found in industrial and commercial applications. You’ ll be able to complete most common tasks associated with the repair of these complex systems, or at least, be able to understand those outside contractors and regulate what they are doing. You’ ll know if they are overcharging you, or better yet, ripping you off! This is a must for every maintenance person in an air-conditioned or refrigerated facility!
Keep your HVAC running cool… The end .
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