how to check the charge of an air conditioner/

[kimberlite]

how to check the charge of an air conditioner.
i have only onr schrager ( bicycle type) valve on each compressor.
fair winds,
eric

[GordMay]

Testing refrigerant levels & pressures requires knowledge, equipment, and a licence.
I don’t recommend this as a Do-It-Yourself project.
Refrigerants can be extremely dangerous! . At atmospheric pressure, most refrigerants boil at or near zero deg.F, some even colder than that. Inadvertently spilling a drop of liquid refrigerant on your skin results in instant frostbite - splash a drop in your eye and it could mean instant blindness.

Basic (incomplete) Procedure:
You’ll need a manifold gauge/hose set. There are two gauges on that manifold one for low pressure (also known as suction) one for high pressure (also known as head). By using these gauges you can tell a lot about how your system is working, but the gauges will not tell all you need to interpret them as well as monitor other things like the temperature of the refrigerant lines.

Start the air-conditioner, and allow the unit to run & stabilize.

Identify the high pressure side and low pressure (suction) side of the system, and connect the gauge hoses:.
- The Blue hose from your manifold gauges goes on the low (suction) side.
- The Red hose goes on the high (head) side.
- The Yellow hose (centre) is the service line.

The Suction pressure is a reflection of how well the evaporator portion is picking up heat (higher) and how well the compressor is removing it (lower). The Head pressure is a reflection of how well the condensing coil is getting rid of the heat (lower) and how much load the system is putting on it (higher).

In general you want the suction pressure to be as high as possible without it being caused by an over charged condition, and the head pressure to be as low as possible and still maintain a full liquid line. High efficiency units will have higher suction pressure and lower head pressure than an older unit depending on the size of the coil and the airflow.

A LOW Refrigerant Charge will be indicated by lower than specified Discharge & Suction Pressures.
A HIGH Charge will be indicated by higher pressures.

HTH,
Gord

[ozskip]

You need to know which refrigerant is in the system and the relative pressure/temperture values for that refrigerant.If your asking this question then you you should getting someone that is licenced to do the job.(NOTE: in australia there is a fine of up to$240,000 if you are caught selling,buying,TESTING or working on a system without the appropriate licences.) Greg.

[GordMay]

From Richard L. Kollmann
Author of “DIY Refrigeration & 12-24 Volt Refrigeration”
Website: http://kollmann-marine.com/
Forum: http://www.kollmann-marine.com/phpBB/

Richard's Website & Forum are replete with excellent (detailed) Refer' info' - not to mention his excellent book.

”Save from $50 to $2000 on refrigeration repairs”

Boat refrigeration repair costs are now very expensive because the ground rules regarding refrigerants have changed and there are few qualified service techs. In most cruising areas it is impossible to find a one who is familiar with your type of refrigeration system. A knowledge of what questions to ask when contacting a service tech will pay big dividends. A service technician today will cost from $60 to $80 per hour plus travel time. An average service call can cost $250 or much more if he has to make a repeat visit.
If you can perform a few simple checks of the system yourself before looking for help, you might be able to solve the problem yourself. When checking your refrigeration system, you should look for the following:.

• The condensing unit located on the outside of the box disposes of the process heat of refrigeration by a fan coil, a static air coil or a water tube coil. For a refrigerator to perform correctly the cooling medium air or water must lower the temperature collected in these coils. By touching a condenser coil you will be able to see if they are being cooled. They will feel warmer than body temperature but not hot. Air cooled condenser coils do become restricted with dust and water cooled condensers collect sea growth and require an annual cleaning. Static air condenser coils may require an additional fan in warm climates to remove the excess heat.
• The part of the refrigeration unit that is inside the refrigerator that gets cold is called the evaporator. There are two types of evaporators used in boat refrigerators: a thin plate, generally aluminum and painted white, or a tank type filled with a solution that is know as a holding plate evaporator. The exterior surface of the thin plate evaporator is the best indicator of how the system is performing:
• If the evaporator stays warm in the box there is an electrical problem or a refrigerant problem. If the compressor is running and there is no cooling, then the trouble will be a lack of refrigerant flow. If the thin plate evaporator has a coating of frost covering 100% of the service area, this would indicate that there is enough refrigerant in the system. If the thin plate evaporator is only partially covered with frost then the system is low on refrigerant.

• Large holding plate boat refrigeration systems use a different type of refrigerant flow device with a storage tank to store extra liquid called a receiver. On these systems the refrigerant charge of a system can be monitored by viewing the liquid flowing through a sight glass. Reading the sight glass correctly takes experience especially with some of the new blended refrigerants. It is not necessary for the glass to be full of liquid for the system to work properly. When you see the glass half liquid and half gas, the amount of the refrigerant charge is not causing a performance problem.
• Most of the larger systems use low pressure switches. This means when the refrigerant is low the compressor will cycle off and on repeatedly.
If all of the above items check OK but the box does not get cold enough, the thermostat control may be stopping the compressor too soon.

If you don’t feel confident in doing the above checks or checks don’t show the problem then you might have to ask for help but there are some things you should know about your refrigeration system before seeking help:

• Who manufactured the refrigerator system?
• The approximate age of the system.
• Type of compressor and the model number.
• What type of refrigerant is in the system; R12, 134a, 409B, 404A, R502, R414B, Hot Shot, or some other type refrigerant?
• Current history of problems and corrective action.

1. Questions you should ask a repairman before hiring him.
Do you have _____ refrigerant which is the type refrigerant in the system today?
Do you have experience with a _____________ refrigerator?

Do you have an electronic leak detector?
2. Be careful of a repairman if he gives these types of a comment.

You can’t find leaks with electronic units they only work some of the time.
Not True, if you know how to use them and they are properly maintained they do work.

This refrigerant can be mixed with the present refrigerant.
Not true.
This refrigerant is approved by the EPA for use in your system.
Wrong not true, EPA does not approve refrigerants they accept them for air quality and health hazards. The compressor manufacturers approve the types of refrigerant and oil to be used in their compressors and no one else.

Your system is very low on refrigerant so all it needs is to be recharged. Wrong, most refrigerators do not leak refrigerants, as they are tightly sealed. Open shaft driven compressors and systems with hoses instead of metal tubing are the exception and may need topped off with refrigerant occasionally.
When a system has lost refrigerant there is a leak, if the leak is not found and repaired a repeat service call will be required.

By doing a check of the system yourself and knowing what questions to ask can save you those huge repair bills.

R.L. Kollmann
***

To which, I'd add:
In cases of slow loss of refrigerant, the first thing you can do is to carefully tighten all the compression fittings that you can identify. Do this after the unit has reached ambient temperature and with the power off.

Also, if you find an oily film around a connection or joint, this may be the source of the leak, since the refrigerant normally contains oil for compressor lubrication.

If that doesn’t work, make a solution of fresh water and dish washing soap and put it over the joints. If you see bubbling, you have a leak.

HTH,
Gord