8/14/2014

COMPRESSOR TROUBLESHOOTING CHARGING A SYSTEM

COMPRESSOR TROUBLESHOOTING
CHARGING A SYSTEM


 
CHARGING A SYSTEM




3. CHARGING A SYSTEM:
 
Charging a system can be somewhat tricky when you take into consideration capillary tubes,
head master valves and fan cycle controls and suction pressure regulators.


EVACUATING A CHARGED SYSTEM

It is necessary before charging any system to remove air and any non-condensable that is ion
the system. If they are not removed, they will become trapped at the top of the condenser
taking up space and robbing the system of its ability to remove heat.
The length of time it takes to evacuate a system is only as long as it takes to reach as 25 – 28” of
vacuum. Then break the system by adding a small amount of refrigerant to the longest end of
the system and allowing it to reach 25 – 28” of vacuum again. Now you are ready to charge the
system in the discharge line before turning the system on. The only reason to evacuate a
system for a long period of time, such as overnight, is if you feel that the system has water in it.
If it does, you better have a real good pump to get the water to boil off in a vacuum otherwise
this process can be done usually in 30 minutes or less.
 
CHARGING AN EMPTY SYSTEM

Step one is to evacuate the system to remove all non-condensable form the system and clean
the condenser. This will allow you to get a good idea of when you have enough refrigerant in
the system if you don’t know the factory charge. The condenser is designed to remove a certain
amount of heat (BTU’s) from the Box or Room usually at 90 deg F of ambient. So if your
condenser is clean and you charge the system until the liquid line or drier gets good and warm
you are now removing all the heat from the box or room that it is designed to remove your
charge should be very close to being correct. Never let the liquid line get Hot!!!! Check your
Super Heat after the Box or Room comes down to the desired temperature.
 
ADDING REFRIGERANT

Adding refrigerant to a system that has a partial charge has usually three rules of Thumb:
1. Clear the sight glass
2. A Warm the liquid line
3. And, most important, is suction pressure.
With the 100+ refrigerants on the market, always consult your Pressure Chart for the correct
suction pressure. If your suction pressure gets too high, you can flood the evaporator with
liquid. The correct charge is to have 6 – 10 deg Super Heat at the end of the Evaporator.
Remember, the refrigerant needs to be at least 10 deg F colder than the box or the room in
order to remove the heat.
 We have not discussed Discharging Pressures. This is because there are so many refrigerants
that discharge pressure could be as little as 100lbs and as much as 350lbs. Discharge
temperature is what is important.

CHARGING A SYSTEM WITH A SUCTION LINE REGULATOR


This is a somewhat slow and usually wait and see process because, until the box reaches
temperature a true suction pressure is unknown. Smaller systems with capillary tubes should
be weighed in and the OEM charge needs to be known first.
Larger systems with receivers & TEV valves are tough. If the system is empty, look at the
receiver to get a good feeling for an amount. If the box is short of refrigerant slowly clear the
sight glass.

Either way, you must check the Super Heat after the box has reached its temperature.
For a Head Master Valve, this is where the tricky part starts. This is a Valve that allows the
discharge gas to bypass the condenser in cold ambient (outdoor) conditions. The manufacturer
of the equipment usually will give you a certain amount of refrigerant to add to the system after
you get a clear sight glass. Not knowing this will allow the equipment to work great just after
you fix the leak and charge the system to a full sight glass only to stop or lose temperature when
the conditions outside change with a new season. My advice is that if the OEM amount is
unknown to charge the system to a clear sight glass or a good warm liquid line and add about
10 – 20% extra for a full charge. The next step is very important. Close the Liquid line and
pump the system down watching the high pressure gauge to make sure that the receiver will
hold all the refrigerant. If it won’t, the next step is obvious--- Remove some of the refrigerant.
EVAPORATOR PULLEYS AND BELTS ------- A/C SYSTEMS
One of the most missed A/C problems that can harm a compressor, cause low suction
pressure, trap oil in the evaporator, flood the compressor and always cause you to over
charge a system is a worn pulley on the Blower Motor.
When the belts become loose, don’t just move the motor. Most systems have an adjustable
pulley. Adjust the pulley and bring the motor amps to almost full load amps with the motor
cover on. This will allow you to maximize the air flow across the coil, bring the suction
pressure up and cause the system to function properly.

nota:
EVAPORATOR PULLEYS AND BELTS ------- A/C SYSTEMS
One of the most missed A/C problems that can harm a compressor, cause low suction
pressure, trap oil in the evaporator, flood the compressor and always cause you to over
charge a system is a worn pulley on the Blower Motor.
When the belts become loose, don’t just move the motor. Most systems have an adjustable
pulley. Adjust the pulley and bring the motor amps to almost full load amps with the motor
cover on. This will allow you to maximize the air flow across the coil, bring the suction
pressure up and cause the system to function properly.

                             abo bahaa eddine

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