Manual Pump down on an A/C system.

This method is applied to store the refrigerant in a system of air conditioning using the compressor. The main reason is to avoid a system from lost the refrigerant charge when perform repairing job services or to relocated the unit.

We can save the cost for refill a refrigerant stored charge and help to reduce the air pollution. Why we must throw out the refrigerant if we can stored it and save money?

Imagine if the system used a lot of amount of refrigerant but we do not store it to recycle later? We waste the gas and cost for refill it back and deplete the ozone layer.

Why pump down method is important when we perform a task that require open or dismantle a pipe line or a/c system. All maintenance hvac technicians must know how to perform pump down on an air conditioning system.

We must setup for the tool and equipment needed.

Tools and Equipment

A. Manifold gauge.B. Ratchet Offset Wrench.C. Two jaws jumper cable.A. Adjustable wrench.B. Safety glass.C. Gloves.D. Digital Multimeter.E. Workshop Cleaning wipe.

 

Manual Pump down method step by step

A. Check the disconnecting switch to ensure the air conditioning unit is shut down by the main switch. Use a Digital Multimeter to confirm it have no power supply.

B. Be sure the king and suction valves are back seated.C. Remove the service port cap and valve stem cap. Open the end cap of the service valves

for suction and king valve using an adjustable wrench.D. Verify the closed position in the manifold gauge. E. Install the manifold gauge. Use the blue hose (Low pressure meter in the left side) and

connect it to the suction valve in the compressor. (This is the big tubing). Use the red hose (high pressure meter in the right side) and connect it to the king valve in the liquid line. (This is the small tubing).

F. Mid seat the king service valve (located downstream from the condenser in the liquid line. The small tubing) using a Ratchet Offset Wrench. Turn it around four times with clockwise rotation, to ensure we have refrigerant in the hoses. Open the high side gauge manifold (the red in the right side).

G. Open the low side gauge manifold (the blue in the left side) and purge the suction line hose to evacuate the air in the gauge hoses.

H. Front seat the king valve. Using a Ratchet Offset Wrench. Turn it around with clockwise rotation until it reaches the end. (by turning the valve stem outwards as far as it will go.

I. Mid seat the suction service valve in the compressor.J. Jump the low pressure control automatic reset switch that open on Pressure Fall to

prevent the compressor shut down at 30 psi when is in operation.K. Turn on the main switch, turn on the unit by the thermostat and check the process until

the low side gauge reading should drop to a lower suction pressure on the gauge. This indicates the low pressure gauge readings reaches between 0 to -10 psi. All of refrigerant in the system goes through the compressor and we have stored it temporarily between the compressor and the condenser.

L. Back seat the suction service valve, turn it around with counterclockwise rotation until it reaches the end. (by turning the valve stem inwards as far as it will go)

M. Turn off the unit. Close both (the low and high side gauge manifold); check your gauges readings to ensure you have MANUAL PUMP DOWN in the system. The low pressure gauge readings should be between 0 to -10 psi.

N. Turn off the unit by the thermostat.

REMOVING THE GAUGES

A. Be sure that you have closed both (the low and high side gauge manifold)B. Back seat the king service valve.C. Mid seat the suction service valve.D. Start the unit by the thermostat.E. Open the high side gauge manifold and slowly open the low side to ensure we are

equalizing the pressure between the two hose and the system. When done back seat the suction service valve in the compressor.

F. Remove the manifold gauge and attach the hoses in the back side.G. Replace the service port cap and the valve stem caps.H. Turn off the unit by the thermostat.I. Clean the manifold gauge, the hoses and the service port valves with workshop cleaning

wipe.J. Remove the jumper from the low pressure control automatic reset switch.

What is a king valve in an air conditioning system?

When referring to the "king" valve, most air conditioning technicians are referring to the valve which is found downstream from a liquid line receiver. It is also commonly referred to as a liquid line service valve or an isolation valve. This valve is not as common as other valve types in residential units. It is called a "king" valve perhaps because it can be closed to permit the pump down of an air conditioning system in order to trap the refrigerant in the receiver and condenser; in that sense, it rules the system.

Working With Compressor Service Valves

Many refrigeration compressors incorporate a suction service valve and a discharge service valve. These are used to allow refrigeration gauges to be attached to the system; and, if needed, they are used to isolate the compressor from the rest of the system.

Working with these valves is not difficult, but there are some finer points to remember.

Service Valve Parts

A typical compressor service valve is composed of four essential parts:

1. Line connection.

2. Compressor connection.

3. Valve stem.

4. Gauge port.

There are three positions in which the valve can be oriented. If the valve stem is all the way out, the valve is considered to be in the back seated position. The gauge port is closed and the valve is open, allowing refrigerant to flow through the system.

If the valve stem is all the way in, the valve is considered to be in the front-seated position. The gauge port is open to the compressor connection and the refrigerant line (suction or discharge) connection is closed.

If the valve stem is between the front-seated and back seated position, it is considered to be in the mid-seated position. In this position all three connections — the gauge port, line, and compressor — are open. This allows the refrigerant to flow through the system and the system pressure to be read through the gauge port.

When placing the valve in its mid-seated position, be sure to turn the valve in its back seated position first and then turn the valve stem only one or two complete turns into the mid-seated position.

Points of useWhen opening a service valve, make sure it is secured by placing it in a vise or attaching it to the compressor.

Also, look to see if the service valve has a packing gland nut. Many service valves will have this. The packing gland nut helps to ensure a leak-free seal. It is typically made of brass and is found at the base of the valve stem. It must be loosened by a quarter turn to a full turn before opening the valve stem.

Not loosening the gland packing prior to turning the valve stem may cause the valve to leak. In addition, make sure you tighten the nut when you are finished manipulating the valve stem.

When opening and closing compressor service valves, make sure to use the right tools, such as an appropriately sized service wrench. Do not attempt to open a service valve with an adjustable wrench. You can easily round the valve stem edges, rendering the valve useless.

If the valve stem is difficult to open and appears to be stuck, lightly tap the end of the valve stem with a hammer. This should open the valve. (Remember to loosen that packing gland nut before attempting to open the valve stem!)

Remember to replace the service port cap and valve stem cap after closing the valve port and removing your refrigeration gauges. These caps serve two purposes:

1. They help prevent a refrigerant leak; and

2. They prevent the threads on the service valve from being rusted over or otherwise damaged.

When brazing either a suction or discharge service valve, make sure the valve is mid-seated before brazing. If left in either the front-seated or back seated position, heat from brazing can cause the inside plunger to “weld” to the seating area on the inside of the valve body.

When brazing, it’s best to wrap the service valve in a wet rag. This prevents the valve from being overheated and damaged. Be sure not to allow water to enter the system.

Working with these valves is very simple. Just remember some basic rules for trouble-free operation.