Checking of Refrigeration System with Manifold Gauge

This is a method in which the trouble is located by using a manifold gauge.

Read the manifold gauge pressure with the following established conditions:

(a) Temperature at the air inlet is 30 - 35°C (86 - 95*F)

(b) Engine running at 2,000 rpm

(c) Blower speed set at high

(e) Temperature control lever set at cool

NOTE: It should be noted that the gauge indications may vary slightly due to ambient temperature conditions.

1. NORMALLY FUNCTIONING REFRIGERATION SYSTEM

Gauge reading:

Low pressure side 1.5 - 2.0 kg/cm2

(21 — 28 psi, 147 - 196 kPa) High pressure side 14.5 — 15.0 kg/cm2

2. MOISTURE PRESENT IN REFRIGERATION SYSTEM Condition: Periodically cools and then fails to cool

Symptom seen in refrigeration system

Probable cause

Diagnosis

Remedy

During operation, pressure at low pressure side sometimes becomes a vacuum and sometimes normal

Moisture entered in refrigeration system freezes at expansion valve orifice and temporarily stops cycle, but normal state is restored after a time when the ice melts

Drier in oversaturated state i

Moisture in refrigeration system freezes at expansion valve orifice and blocks circulation of refrigerant

(1 ) Replace receiver and drier

(21 Remove moisture in cycle through repeated vacuum purging

(31 Charge new refrigerant to proper amount

3. INSUFFICIENT REFRIGERANT Condition: Insufficient cooling

Symptom seen in refrigeration system

Probable cause

Oiagnosis

Remedy

Pressure low at both low and high pressure sides

Bubbles seen in sight 9lass

Insufficient cooling performance

Gas leakaçe at some place in refrigeration system

Insufficient refrigerant in system

Refrigerant leaking

Check with leak tester and repair

Charge refrigerant to proper amount

4. POOR CIRCULATION OF REFRIGERANT Condition: Insufficient cooling

Symptom seen in refrigeration system

Probable cause

Diagnosis

Remedy

Pressure low at both low and high pressure sides

Frost on tubes from receiver to unit

Refrigerant flow obstructed by dirt in receiver

Receiver cloçged

Replace receiver

5. REFRIGERANT OVERCHARGE OR INSUFFICIENT COOLING OF CONDENSER

Condition: Does not cool sufficiently

Symptom seen in refrigeration system

Probable cause

Diagnosis

Remedy

Pressures too high at both low and high pressure sides

Unable to develop sufficient performance due to excessive refrigerant in system

Condenser cooling insufficient

Excessive refrigerant in cycle (1)

refrigerant overcharged

Condenser cooling insufficient condenser fins clogged or fan motor faulty

Clean condenser

Check fan motor operation

If (1) and (2) are in normal state, check refrigerant amount

Note: Vent out refrigerant through gauge manifold low pressure side by gradually opening valve.

6. EXPANSION VALVE IMPROPERLY MOUNTED/HEAT SENSING TUBE DEFECTIVE (OPENS TOO WIDE)

Condition: Insufficient cooling

Symptom seen in refrigeration system

Probable cause

Diagnosis

Remedy

Pressures too high at both low and high pressure sides

Frost or large amount of dew on piping at low pressure side

Trouble in expansion valve or heat sensing tube not installed correctly

Refrigerant flow out of adjustment

Excessive refrigerant in low pressure piping i

Expansion valve opened too wide

(1) Check heat sensing tube installed condition

(2) If (1) is normal, test expansion valve in unit form

Replace if defective

7. AIR PRESENT IN REFRIGERATION SYSTEM

Condition: Does not cool down sufficiently

NOTE: These gauge indications are shown when the refrigeration system has been opened and the refrigerant charged without vacuum purging.

Symptom seen in refrigeration system

Probable cause

Diagnosis

Remedy

Pressure too high at both low and high pressure sides

Air entered in refrigeration system

Air present in refrigeration system i

Insufficient vacuum purging

(1) Replace receiver and drier

(2) Check compressor oil to see if dirty or insufficient

<3) Vacuum purge and charge new refrigerant

8. REFRIGERANT DOES NOT CIRCULATE

Condition: Does not cool (Cools from time to time in some cases)

ac0is6

Symptom seen in refrigeration system

Probable cause

Diagnosis

Remedy

Vacuum indicated at low pressure side, very low pressure indicated at high pressure side

Frost or dew seen on piping before and after receiver and drier or expansion valve

Refrigerant flow obstructed by moisture or dirt in refrigerant freezingor adhering to expansion valve orifice

Refrigerant flow obstructed by gas leakage from expansion valve heat sensing tube

Expansion valve orifice clogged i

Refrigerant does not flow

Allow to stand for some time and then restart operation to determine if trouble is caused by moisture or dirt

If caused by moisture refer to step 2 on page AC-4

If caused by dirt, remove expansion valve and clean off dirt by blowing with air. If unable to remove dirt, replace valve

Vacuum purge and charge new refrigerant to proper amount

For gas leakage from heat sensing tube, replace expansion valve

ac0is6

9. INSUFFICIENT COMPRESSION Condition: Does not cool

Symptom seen in refrigeration system

Probable cause

Diagnosis

Remedy

Pressure too high at low pressure side

Pressure too low at high pressure side

Internal leak in compressor

Compression defective I

Valves leaking or broken, sliding parts

(piston, cylinder, gasket, connecting rod, etc.,) broken

Replace compressor

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