AUTOOL LM120/LM120+ Digital Manifold Gauge User Manual

Product Introduction

Overview

The AUTOOL LM120/LM120+ is an intelligent electronic refrigerant manifold gauge instrument designed as an auxiliary tool for the installation, testing, and maintenance of refrigeration equipment, including air conditioners and cold storage systems. The instrument features double pressure testing, dual temperature testing, digital readout, multi-unit switching, multi-mode functionality, and a built-in refrigerant database.

The instrument is constructed with high-strength engineering plastics and a flexible non-slip silicone design, making it solid and comfortable to hold. It incorporates a 32-bit digital processing unit and a high-precision data acquisition unit for stable and accurate data. The large liquid crystal display (LCD) with backlight support ensures clear readability and convenient operation. A long-life valve switch and a 1/4-inch standard interface design contribute to the instrument's durability and versatility.

It can measure double pressure (gauge pressure) and perform dual temperature measurements simultaneously. It offers automatic multi-unit pressure conversion and automatic conversion of temperature between Celsius and Fahrenheit. The built-in database contains 89 kinds of refrigerants, enabling calculations for subcooling and superheat for direct reading of operating process data. It also tests vacuum measurement percentages, pressure leak measurements, and records leak time speed.

International Electrical Symbols

Specifications

Build-in 89 kinds of Refrigerant NIST:

* According to American NIST Standard.

R11, R113, R114, R115, R116, R12, R123, R124, R125, R1270, R13, R134A, R14, R141B, R142B, R143A, R152A, R170, R21, R218, R22, R227EA, R23, R236EA, R245CA, R245FA, R290, R32, R401A, R401B, R401C, R402A, R402B, R403A, R403B, R404A, R405A, R406A, R407A, R407B, R407C, R407D, R407E, R408A, R409A, R409B, R41, R410A, R410B, R411A, R411B, R412A, R413A, R414A, R414B, R415A, R415B, R416A, R417A, R418A, R419A, R420A, R421A, R421B, R422A, R422B, R422C, R422D, R423A, R424A, R425A, R426A, R427A, R428A, R50, R500, R501, R502, R503, R504, R507A, R508A, R508B, R509A, R600, R600A, R717, R744 (CO2), R1234.

Product Structure

Structure Diagram

The device features a front panel with an LCD display and control buttons, and a bottom section with pressure valves and inlets. The main components are labeled as follows:

• A: Clamp-on temperature probe socket
• B: LCD display
• C: Run / Stop button (In Leak Test Mode, Test Control Button)
• D: Function button (test function mode switch button)
• E: R+/R- Refrigerant type selection buttons (Switch to select different types of working refrigerants)
• F: Unit button (pressure unit switch button)
• G: °C/°F button (temperature unit switch button)
• H: Zero button (pressure display zero button)
• I: Backlit button
• J: Power button
• K: Refrigerant observation window
• L: Low pressure valve (blue)
• M: High pressure valve (red)
• N: 1/4 inch low pressure inlet
• O: 1/4 inch high pressure inlet
• P: Pressure release valve
• Q: Refrigerant inlet / Vacuum pump inlet

Function Instructions

1. Refrigerant Filling And Pressure Inspection

A- Turn off the blue (Low) and red (High) valves.

B- Power on the instrument. Ensure the LCD displays the pressure test status. If not, press the Function button to switch modes.

LCD Display Example (Pressure Test Status):

The display shows sensor temperatures (T1 Sensor, T2 Sensor), refrigerant type (e.g., R 134A), Evaporation Temperature (Ev), Condensation Temperature (Co), and pressure readings for both high and low sides (e.g., 2500 kPa).

C- If temperature probe accessories are connected, the real-time temperature will be displayed. Otherwise, no temperature will be shown.

D- Use the R+/R- buttons, Unit button, and °C/°F button to select the tested refrigerant and adjust the display units.

E- When the instrument is turned on, the high and low pressure display areas might show 10 digits. Press and hold the zero button until the display returns to zero.

F- Connect the instrument to the refrigeration system, paying attention to the direction of refrigerant flow. The diagram shows the connection between the Compressor, Condenser, Manifold Gauge, and Evaporator, with arrows indicating refrigerant flowing from Compressor to Condenser, then through the Manifold Gauge, and to the Evaporator.

G- Turn on the refrigerant valve and gently press the pressure release valve to vent air from the connecting hose.

H- When the refrigeration system is stopped, turn on the high pressure valve (red valve), fill with a certain amount of refrigerant, and then quickly shut the valve.

I- Run the refrigeration system, turn on the low pressure valve (blue valve), and fill the system with refrigerant. Vacuum operation is required if filling initially or completely. Refer to the vacuum operation section.

J- After filling, shut the low pressure valve (blue valve) and the refrigerant valve. Allow the refrigeration system to run.

K- Shut down the refrigeration system. Ensure all valves are turned off, then disconnect the instrument from the refrigeration system and source. Do not remove the high pressure valve connection until the pressure drops to a safe level. Then, turn off the instrument.

LCD Display Example (Evaporation/Condensation Temperature):

The instrument can display the corresponding Evaporation Temperature (EV) and Condensation Temperature (CO) during refrigerant pressure testing. The display shows refrigerant type (e.g., R 134A), Evaporation Temperature (Ev), Condensation Temperature (Co), and pressure readings (e.g., 2500 kPa).

LCD Display Example (Superheat/Subcooling Calculation):

The instrument can calculate Superheat (SH) and Subcooling (SC) when the tested refrigerant is preset and clamp-on temperature probes are connected correctly. The display shows refrigerant type (e.g., R 134A), SH, SC, and pressure readings (e.g., 2500 kPa).

2. Vacuum Operation

A- Turn off the blue and red valves.

B- Power on the instrument. Ensure the LCD displays the vacuum test status. If not, press the Function button to switch modes.

LCD Display Example (Vacuum Test Status):

The display shows percentage (%) and pressure (kPa) readings, typically starting at 0% and 0 kPa.

C- Press the Unit button to adjust the reading unit.

D- When the instrument is turned on, the high and low pressure display areas might show 10 digits. Press and hold the zero button until it returns to zero.

E- Connect the instrument to the refrigeration system according to the chart. Pay attention to the direction of refrigerant flow. Connected clamp-on temperature probes will not affect the operation.

The diagram shows the connection between the Compressor, Condenser, Manifold Gauge, Vacuum Pump, and Evaporator, with arrows indicating refrigerant flow and vacuum pump operation.

F- Turn on the blue and red valves, and start the vacuum pump.

G- After the vacuum operation is completed, turn off the blue and red valves, then shut off the vacuum pump.

H- At this point, the pressure leak test mode can be used to check for system leakage. Refer to section 3, Pressure Leak Test.

3. Pressure Leak Test

A- The instrument is powered on with the blue and red valves turned off.

B- Press the Function button to enter the pressure leak test mode. The current pressure value is displayed at the lower right corner of the LCD.

LCD Display Example (Pressure Leak Test - Initial):

The display shows time (hh:mm), a symbol (e.g., 'O'), temperature (°C), and pressure difference (ΔP) along with current pressure (e.g., 600 kPa).

C- Press the Run / Stop button to start the leak test.

LCD Display Example (Pressure Leak Test - During Test):

The display shows elapsed time (e.g., 00:45), initial pressure (e.g., 600 kPa), instantaneous pressure (e.g., 499 kPa), and the pressure difference (ΔP, e.g., 111 kPa).

At this time, the lower left corner records the initial pressure value; the lower right corner shows the instantaneous pressure value; the “ΔP” display area shows the difference between the initial pressure value and the instantaneous pressure value.

The time display area shows how long the leak test lasts in the format of Hour:Minute (HH:MM). All pressure units on the screen are the same. You can switch different pressure units by pressing the Unit button.

Common Problems

1. Low Battery Power Supply

The instrument displays a low power sign when the battery power is insufficient. The battery should be replaced as required to avoid affecting normal use.

2. Damaged Refrigerant Hose Or Valve Stem

Check the pipe fittings and hoses before testing. If any damage is found, replace them immediately to avoid improper use or accidents.

3. Failure Of Refrigerant Filling

There is a valve core in the refrigerant inlet of the refrigeration system. When connecting the instrument, pay attention to the two terminals of the hoses. Connect one terminal with a core to the refrigeration system, and the other terminal without a core to the instrument.

4. Potential Leak Points

Every hose terminal comes with a nylon pad that has a limited lifespan. Overuse or other situations can make it defective, leading to leakage. The instrument's refrigerant inlet (middle port) has a port with a valve core used to vent air after connecting the refrigerant. This port is equipped with a copper plug screw that must be tightened before or after each operation. Check the refrigeration system's pipes and connectors for leaks.

Glossary

Saturation

The state of saturation is the coexistence of a refrigerant in a liquid and gas state.

Condensation Temperature

In the condenser, the refrigerant is condensed by the high-temperature gaseous refrigerant to the temperature of the liquid refrigerant, which is the saturation temperature under condensing pressure.

Evaporation Temperature

In the evaporator, the refrigerant evaporates from the liquid refrigerant to the temperature of the gaseous refrigerant, which is the saturation temperature under evaporation pressure.

Degree Of Subcooling And Superheat

Subcooling: Condensing temperature - condensing outlet temperature.

Superheat: Evaporation outlet temperature - evaporation temperature.

Lower subcooling can improve the refrigeration capacity of the system. Adding a subcooling loop and economizer in the refrigeration system aims to increase subcooling for refrigerant enhancement.

Every hose terminal comes with a nylon pad that has a limited lifespan. Overuse or other situations can make it defective, leading to leakage.

The degree of expansion of the expansion valve (refrigerant charge) affects the degree of superheat. The greater the degree of superheat, the smaller the opening of the expansion valve can be determined (indicating less refrigerant charge).

Sensible Heat And Latent Heat

The amount of heat required to raise water temperature from 0 to 100 degrees is sensible heat. When water is heated to 100 degrees and becomes water vapor at the same temperature, the heat required for this process is called latent heat.

Gauge Pressure And Absolute Pressure

Gauge pressure: Refers to the pipeline pressure, or the pressure measured by pressure gauges, vacuum gauges, U-shaped tubes, etc. It is also known as relative pressure. The "table pressure" starts with atmospheric pressure, and the symbol is Pg.

Absolute pressure: The pressure directly acting on the surface of a container or object. The absolute pressure value uses absolute vacuum as a starting point. The symbol is PABS (ABS is a subscript). Absolute pressure is atmospheric pressure + gauge pressure.

At atmospheric pressure, the gauge pressure is 0 and the absolute pressure is 1.013bar.

Dry Bulb Temperature, Wet Bulb Temperature And Black Ball Temperature

Dry bulb temperature: The temperature measured by ordinary thermometers.

Wet bulb temperature: A wet cloth is wrapped around the thermometer, and the temperature indicates a drop due to the evaporation of water. The temperature at this time is called the wet-bulb temperature.

The device that has both the dry bulb thermometer and the wet bulb thermometer is called the dry humidimeter, which can be used to measure the relative humidity in the atmosphere.

Black ball temperature: Also called actual temperature, it indicates the actual sensory temperature expressed by temperature when a person or an object is combined with radiant heat and convective heat in a radiant heat environment. The black ball temperature measured is generally higher than the ambient temperature, which is the air temperature.

Maintenance Service

Maintenance

To maintain the performance and appearance of the product, it is recommended to follow these product care guidelines:

• Be careful not to rub the product against rough surfaces or wear the product, especially the sheet metal housing.
• Regularly check product parts that need to be tightened and connected. If found loose, tighten them in time to ensure safe operation. External and internal parts in contact with chemical media should be treated with anti-corrosion treatment (e.g., rust removal and painting) to improve corrosion resistance and extend service life.
• Comply with safe operating procedures and do not overload the equipment. Ensure safety guards are complete and reliable.
• Eliminate unsafe factors promptly. The circuit part should be checked thoroughly, and aging wires should be replaced in time. Adjust clearances of various parts and replace worn (broken) parts. Avoid contact with corrosive liquids.
• When not in use, store the product in a dry place. Do not store the product in hot, humid, or non-ventilated places.

Warranty

From the date of receipt, AUTOOL provides a three-year warranty for the main unit and a one-year warranty for all included accessories.

Warranty Access

The repair or replacement of products is determined by the actual breakdown situation. AUTOOL guarantees the use of brand-new components, accessories, or devices for repairs or replacements. If the product fails within 90 days of receipt, the buyer should provide video and pictures; AUTOOL will bear shipping costs and provide accessories for free replacement. For failures after 90 days, the customer will bear appropriate costs, while AUTOOL will provide parts for replacement free of charge.

Conditions Not Covered by Warranty

• The product is not purchased through official or authorized channels.
• Product breakdown caused by the user not following product instructions for use or maintenance.

AUTOOL prides itself on superb design and excellent service. It would be our pleasure to provide you with any further support or services.

Disclaimer

All information, illustrations, and specifications in this manual are subject to modification by AUTOOL without prior notice. Physical appearance and color may differ from what is shown; refer to the actual product. While every effort has been made to ensure accuracy, inevitable inaccuracies may exist. If in doubt, contact your dealer or AUTOOL after-service center. AUTOOL is not responsible for any consequences arising from misunderstandings.

Return & Exchange Service

If you are not satisfied with AUTOOL products purchased from authorized platforms or dealers, you may return them within seven days from the date of receipt, or exchange for a product of the same value within 30 days from the date of delivery.

Returned and exchanged products must be in fully saleable condition with the bill of sale, all relevant accessories, and original packaging.

AUTOOL will inspect returned items to ensure they are in good condition and eligible. Items not passing inspection will be returned to you without a refund.

You can exchange products through the customer service center or authorized distributors. Returns should be made to the place of purchase. For difficulties or problems with returns or exchanges, please contact AUTOOL Customer Service.

Contact Information