Duuh!hii kali ebu isome kidogo

Pure nomaa · Dec 16, 2011

Kuna mzee mmoja alikuwa anashangaa sana maana kila akiweka whisky yake kwenye fridge akija kuiangalia baadaye anaikuta imepungua,siku moja akiwa pamoja na mkewe akaamua kumuuliza house boy wao ambaye alikuwa jikoni anapika;mzee akauliza nani anayekunywa whisky yangu humu ndani house boy akajibu sisikii,mzee akaita tena hb,hb akaitika naam mzee akauliza tena nani anayekunywa whisky yangu humu ndani ,hb akajibu sisikii,mke akaingilia kati hb mbona mzee anakuuliza swali hutaki kujibu,hb akajibu ukiwa jikoni halafu mtu akauliza swali humsikii kama mnabisha mmoja wenu aende jikoni halafu mi niulize swali nione kama atanisikia,basi mzee akaamua aende yeye jikoni,hb akaita mzee ,mzee akaitika naam,hb akauliza nani anatembea na house girl humu ndani mzee akajibu sisikii,hb akaita tena mzee akaitika naam akauliza swali lile lile tena mzee akajibu sisikii,basi mzee akatoka jikoni huku akisema kweli nimeamini mtu ukiulizwa swali ukiwa jikoni huwezi kulisikia.
ukiwa jikoni

Wa kusoma · Dec 16, 2011

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Water Chiller System

What is the difference between a water chiller system and a window air conditioner?

In a window air conditioner, refrigerant is flowing through the coil that cools the room's air.

In a chilled water air conditioning system, cold water is flowing through the coil that cools the room's air.

The air conditioning machine that cools the water is called a chiller, and it will be located in a dedicated machinery area somewhere in the building, on the roof, or outside.

In the chiller, refrigerant flows through the coil that cools the chilled water.
The chilled water is pumped through a piping loop to air handlers in the spaces to be cooled, where it absorbs heat from the air that flows over the air handling coil.

The warmed up water then returns through the piping loop back to the chiller, where the heat it absorbed is released to the refrigerant flowing through the chiller's evaporator coil.

The chilled water circuit of a typical water chiller system will consist of a pump, cooling coils, expansion tank, and piping valves and controls, in a closed loop.

The temperature of the chilled water supplied to the loop will depend on the set point of the chiller.

The temperature in the spaces being cooled will be controlled by thermostats.

They will sense room temperature, and keep the room at the set temperature by controlling water flow and/or air flow through the air handler.

The compressor in the chiller unit might be a reciprocating type, a screw type, a scroll type, or it might be a centrifugal compressor.

On a water cooled chiller, water flows through the condenser to cool the hot discharge gas to condensing temperature.

On an air cooled chiller, air flows through the condenser coils to cool the hot discharge gas to condensing temperature.

An air cooled water chiller system with a reciprocating compressor will operate at pressures and temperatures very similar to those of a window air conditioner that's running in the same outdoor climate, with the same indoor room temperature.

The normal temperature for the chilled water leaving the chiller is about 44°or 45°, so the low side pressure should be equivalent to about 35° to 38° when the water is near 44° to 45°, which is only a few degrees below the design evaporating temperature for a window air conditioner.

Superheat will depend on the manufacturer's specifications, but I would expect a water chiller system with a reciprocating compressor to have 20° to 30° of superheat at the compressor inlet.

You'd look for much the same conditions in a window air conditioner.

The design chilled water temperature drop through the chiller is normally 10°, so when the supply chilled water temperature is at or near 44° to 45°, look for the chilled water to be returning to the chiller at about 54° to 55°.

Condensing pressure should be equivalent to 20° to 35° above ambient temperature.
Look for the air temperature to rise 20° to 30° through the condenser coil.
A rise of over 30° is too high.

Similar to what you'd look for in a window air conditioner.

Look for 10° to 15° of subcooling, unless the manufacturer specifies otherwise.

Once again, similar to what you'd find in a window air conditioner.

Are you troubleshooting the solid state controls on a large water chiller system?
If so, you're going to have to get a copy of the manufacturers troubleshooting guide for the controls, or else bring in a professional technician who has the manuals and knows how to use them.

With regard to water chiller system operating pressures and temperatures, you might find our Chiller Evaluation Manual helpful.
It has cycle diagrams for air cooled and water cooled chillers, and guidance about evaluating a chiller's pressure and temperature readings.

With regards to maintenance, a water chiller system requires more maintenance than a standard air conditioning system, and our Chiller Maintenance page will introduce you to some important maintenance procedures.

If you're an equipment owner considering cutting maintenance costs, you might be interested in the comments on our Reduce Chiller Maintenance page, and there's a brief discussion of several proven ways to help your chiller run more efficiently on our Improve Chiller Efficiency page.

I hope this page has helped, and please feel free to contact us with any specific HVAC questions you might have, including questions about air conditioning on Guam, or refrigeration on Guam.

Are you learning the HVAC Trade "on the job"?
If you would be interested in the possibility of studying at home to develop your potential to become the finest HVAC Technician you possibly can; we highly recommend that you contact Penn Foster Career School

and request the free, no-obligation information brochure about their complete, accredited HVAC Technician course.
It won't take even 5 minutes, and might change your whole future.
You'll find a brief review of the course on our HVAC Training page.

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HVAC-02, Air Conditioning Troubleshooting and Repair

Acrobat Printable Version

Introduction
Since I'm constantly receiving questions on 944 air conditioning systems, I figured it's time to come up with come helpful troubleshooting tips. Working on the 944 A/C system is no different than working on any other automotive A/C system. They have all the same components which function in the same manner as any other A/C system.
First, if you're having a problem with the A/C system on your 944, there are two ways you can approach solving the problem. The first is to just start replacing components and hope you get lucky by replacing the faulty component the first time. The other method involves doing some actual testing to narrow down the cause of the problem. In order to properly test the A/C system and narrow down the possible causes of your problem, you're going to have to invest in a set of A/C gauges.
Before we begin with the actual troubleshooting, to properly troubleshoot the A/C system, it's extremely helpful to understand how the automobile A/C cycle works. So, we'll begin by discussing automotive air conditioning theory of operation.
There are two basic types of automotive air conditioning systems. The type of system is determined by the device used to control the expansion of the high pressure, high temperature liquid to a low pressure, low temperature liquid. One system uses and expansion valve while the other uses an orifice tube. 944s use an expansion valve system. We'll discuss the operation of both.
The first component in the A/C cycle is the compressor. The compressor takes low temperature refrigerant gas and compresses it into a high pressure, high temperature gas. The refrigerant is then sent to the condenser which sits in front of the radiator. The condenser removes some of the heat from the refrigerant which causes the refrigerant to change phase from a hot gas to a warm liquid.
In the expansion valve A/C system, the warm liquid is then passed through a receiver-drier which removes moisture (via a desiccant in the drier) from the refrigerant to maximize the efficiency of the heat exchange capability of the refrigerant. On 944s, the receiver-drier is a small canister (probably with a sightglass on top) located near behind the driver's side headlight (LHD cars). No phase change occurs as the refrigerant passes through the receiver-drier. From there, the refrigerant is then passed through the expansion valve. The expansion valve has a sensing line that is attached to the suction of the A/C compressor. The expansion valve senses the pressure at the suction of the A/C compressor and modulates to maintain the pressure at the compressor suction. On 944s, the expansion valve is located near in the passenger's footwell (LHD cars) near the center console next to the firewall.
In the orifice tube system, the warm liquid refrigerant passes directly from the condenser to the orifice tube. The orifice tube is a fixed expansion device. The pressure drop across the orifice tube is proportional to the pressure into the orifice tube. So, the orifice tube system maintains the pressure at the suction of the A/C compressor by cycling the compressor on and off via a clutch. This is the type of system typically used by GM vehicles.
The expansion of the warm liquid through the expansion valve or orifice tube causes a pressure drop and hence a temperature drop in the refrigerant. So, out of the expansion device we get a low temperature liquid refrigerant.
The next component in the A/C system is the evaporator. Air from the passenger's compartment passes across one side of the coils in the evaporator. The low temperature liquid refrigerant passes through the other side of the coils. The refrigerant removes heat from the air in the passenger's compartment and returns to the A/C compressor suction as a low temperature gas (phase change).
In the orifice tube system, there is an accumulator located between the evaporator and the A/C compressor suction. The accumulator has moisture removal desiccant just like the receiver-drier used in the expansion valve system. However, it also collects any un-evaporated refrigerant to prevent liquid lock of the compressor. This can occur due to the cycling action of the compressor. The diagrams below show the two different A/C system cycles.

Tools

A/C Gauges and hose set

A/C System Troubleshooting
The following is an general A/C system troubleshooting guide. Realize that it is generic and many of the things listed here may not apply to the 944.

Symptom / Possible Cause	Solutions
Low Compressor Discharge Pressure 1. Leak in system 2. Defective expansion valve 3. Suction valve closed 4. Freon shortage 5. Plugged receiver drier 6. Compressor suction valve leaking 7. Bad reed valves in compressor	Repair 1. Repair leak in system 2. Replace valve 3. Open valve 4. Add freon 5. Replace drier 6. Replace valve 7. Replace reed valves
High Compressor Discharge Pressure 1. Air in system 2. Clogged condenser 3. Discharge valve closed 4. Overcharged system 5. Insufficient condenser air 6. Loose fan belt 7. Condenser not centered on fan or too far from radiator	Repair 1. Recharge system 2. Clean condenser 3. Open valve 4. Remove some refrigerant 5. Install large fan 6. Tighten fan belt 7. Center and check distance
Low Suction Pressure 1. Refrigerant shortage 2. Worn compressor piston 3. Compressor head gasket leaking 4. Kinked or flattened hose 5. Compressor suction valve leaking 6. Moisture in system 7. Trash in expansion valve or screen	Repair 1. Add refrigerant 2. Replace compressor 3. Replace head gasket 4. Replace hose 5. Change valve plate 6. Replace drier 7. Replace drier
High Suction Pressure 1. Loose expansion valve 2. Overcharged system 3. Expansion valve stuck open 4. Compressor reed valves 5. Leaking head gasket on compressor	Repair 1. Tighten valve 2. Remove some refrigerant 3. Replace expansion valve 4. Replace reed valves 5. Replace head gasket
Compressor Not Working 1. Broken belt 2. Broken clutch wire or no 12v power 3. Broken compressor piston 4. Bad thermostat 5. Bad clutch coil 6. Low Refrigerant - low pressure switch has cut off clutch power	Repair 1. Replace belt 2. Repair wire or check for power 3. Replace compressor 4. Replace thermostat 5. Replace clutch coil 6. Add refrigerant
Evaporator Not Cooling 1. Frozen coil, switch set too high 2. Drive belt slipping 3. Hot air leaks into car 4. Plugged receiver drier 5. Capillary tube broken 6. Shortage of refrigerant 7. High head pressure 8. Low suction pressure 9. High suction pressure 10. Defective expansion valve 11. Frozen expansion valve	Repair 1. Turn thermostat switch back 2. Tighten belt 3. Check for holes or open vents 4. Replace drier 5. Replace expansion valve 6. Add refrigerant 7. See problem #2 8. See problem #3 9. See problem #4 10. Replace expansion valve 11. Evacuate and replace drier
Frozen Evaporator Coil 1. Faulty thermostat 2. Thermostat not set properly 3. Insufficient evaporator air	Repair 1. Replace thermostat 2. Set to driving condition 3. Check for excessive duct hose length, kink or bend.

AC System Gauge Readings
The following table is a general guideline for A/C system pressures and temperatures based on ambient outside temperature. Remember that these are a guideline and your actual temperatures and pressures will vary depending on humidity in the air and the condition of your system.

A/C System Pressure Readings
Ambient Temperature	Low Side Pressure	High Side Pressure	Center Vent Temperature
60 °F	28-38 psi	130-190 psi	44-46 °F
70 °F	30-40 psi	190-220 psi	44-48 °F
80 °F	30-40 psi	190-220 psi	43-48 °F
90 °F	35-40 psi	190-225 psi	44-50 °F
100 °F	40-50 psi	200-250 psi	52-60 °F
110 °F	50-60 psi	250-300 psi	68-74 °F
120 °F	55-65 psi	320-350 psi	70-75 °F

Duuh!hii kali ebu isome kidogo

Pure nomaa

JF-Expert Member

Wa kusoma

JF-Expert Member

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