Amana ASH13018 Service Manual download pdf (Page 61)

SERVICING

S-111 FIXED ORIFICE RESTRICTOR DEVICES

The fixed orifice restrictor device (flowrator) used in conjunc-

tion with the indoor coil is a predetermined bore (I.D.). It is

designed to control the rate of liquid refrigerant flow into an

evaporator coil.

The amount of refrigerant that flows through the fixed orifice

restrictor device is regulated by the pressure difference

between the high and low sides of the system. In the cooling

cycle when the outdoor air temperature rises, the high side

condensing pressure rises. At the same time, the cooling

load on the indoor coil increases, causing the low side

pressure to rise, but at a slower rate.

Since the high side pressure rises faster when the tempera-

ture increases, more refrigerant flows to the evaporator,

increasing the cooling capacity of the system.

When the outdoor temperature falls, the reverse takes place.

The condensing pressure falls, and the cooling loads on the

indoor coil decreases, causing less refrigerant flow.

If a restriction should become evident, proceed as follows:

1. Recover refrigerant charge.

2. Remove the orifice assembly clean or replace.

3. Replace liquid line drier, evacuate and recharge.

Capillary Tubes/Orifice Assembly

CHECKING EQUALIZATION TIME

During the “OFF” cycle, the high side pressure bleeds to the

low side through the fixed orifice restriction device. Check

equalization time as follows:

1. Attach a gauge manifold to the suction and liquid line dill

valves.

2. Start the system and allow the pressures to stabilize.

3. Stop the system and check the time it takes for the high

and low pressure gauge readings to equalize.

If it takes more than seven (7) minutes to equalize, the

restrictor device is inoperative. Replace, install a liquid line

drier, evacuate and recharge.

S-112 CHECKING RESTRICTED LIQUID LINE

When the system is operating, the liquid line is warm to the

touch. If the liquid line is restricted, a definite temperature

drop will be noticed at the point of restriction. In severe cases,

frost will form at the restriction and extend down the line in the

direction of the flow.

Discharge and suction pressures will be low, giving the

appearance of an undercharged unit. However, the unit will

have normal to high subcooling.

Locate the restriction, replace the restricted part, replace

drier, evacuate and recharge.

S-113 OVERCHARGE OF REFRIGERANT

An overcharge of refrigerant is normally indicated by an

excessively high head pressure.

An evaporator coil, using an expansion valve metering device,

will basically modulate and control a flooded evaporator and

prevent liquid return to the compressor.

An evaporator coil, using a capillary tube metering device,

could allow refrigerant to return to the compressor under

extreme overcharge conditions. Also with a capillary tube

metering device, extreme cases of insufficient indoor air can

cause icing of the indoor coil and liquid return to the compres-

sor, but the head pressure would be lower.

There are other causes for high head pressure which may be

found in the "Service Problem Analysis Guide."

If other causes check out normal, an overcharge or a system

containing non-condensables would be indicated.

If this system is observed:

1. Start the system.

2. Remove and capture small quantities of gas from the

suction line dill valve until the head pressure is reduced to

normal.

3. Observe the system while running a cooling performance

test. If a shortage of refrigerant is indicated, then the

system contains non-condensables.

S-114 NON-CONDENSABLES

If non-condensables are suspected, shut down the system

and allow the pressures to equalize. Wait at least 15

minutes. Compare the pressure to the temperature of the

coldest coil since this is where most of the refrigerant will be.

If the pressure indicates a higher temperature than that of the

coil temperature, non-condensables are present.

Non-condensables are removed from the system by first

removing the refrigerant charge, replacing and/or installing

liquid line drier, evacuating and recharging.

S-115 COMPRESSOR BURNOUT

When a compressor burns out, high temperature develops

causing the refrigerant, oil and motor insulation to decom-

pose forming acids and sludge.

If a compressor is suspected of being burned-out, attach a

refrigerant hose to the liquid line dill valve and properly remove

and dispose of the refrigerant.

NOTICE

Violation of EPA regulations may result in fines

or other penalties.

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Amana ASH13018 Service Manual Page 61

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