How to Fix a Faulty Expansion Valve in a Constant Temperature and Humidity Test Chamber

Source：LINPIN Time：2025-04-27 Category：Industry News

A constant temperature and humidity test chamber consists of multiple components, and any malfunction can disrupt testing. Previously, we discussed troubleshooting methods for other issues. Today, we focus on expansion valve failures.

To resolve expansion valve problems, first identify the root cause. Common issues include:

Irregular refrigerant supply (fluctuating flow)
Excessive subcooling or superheating

constant temperature and humidity test chamber
These problems are often related to the thermal bulb, primarily due to two reasons:

1. Broken Capillary Tube in the Thermal Bulb
If the capillary tube is damaged, the refrigerant charge inside leaks, preventing accurate signal transmission to the expansion valve’s actuator.

2. Incorrect Thermal Bulb Installation
Improper positioning during assembly can lead to malfunction.

Solutions
① For a Damaged Capillary Tube
Repair or replace the thermal bulb (requires professional servicing).
② For Incorrect Thermal Bulb Installation
Correct the installation position:
The thermal bulb head should face downward or horizontally.
It must be installed below the valve diaphragm’s upper chamber, close to the evaporator and away from the compressor suction port.
Avoid vertical installation—it should be mounted on the horizontal section of the evaporator’s outlet pipe.
Additional Guidelines:

If the thermal bulb is installed higher than the diaphragm chamber, bend the capillary tube into a U-shape to prevent liquid refrigerant from entering the chamber.
For horizontal pipes with a diameter > 7/8″:
Install the bulb below the pipe’s centerline, at a 45° angle (3 o’clock position).
For pipes < 7/8″:
Install it at the top (1 o’clock position).
Avoid mounting at the bottom—this reduces sensitivity, causing excessive refrigerant flow and unstable supply.
By following these steps, you can effectively troubleshoot and resolve expansion valve issues in your test chamber. Regular maintenance ensures optimal performance and extends equipment lifespan.

Previous article: Moving Forward Together to Achieve Greater Heights: Linpin Instruments Renews Partnership with Siemens

Next article: Summary of the 9 Test Levels for Rain Test Chambers

News Recommendation

25.05

5 Operation Pitfalls to Avoid in Thermal Shock Testing—Prevent Test Failure or Equipment Damage

Thermal shock test chambers are essential tools for verifying a product’s ability to withstand extreme temperature changes. However, in practical applications, neglecting operational details can lead to inaccurate test results, sample damage, and even equipment failure.

25.03

What Should Be Considered to Ensure the Smooth Operation of a Constant Temperature and Humidity Test Chamber?

By subjecting products to various temperature environments—such as high temperature, low temperature, and alternating humidity—constant temperature and humidity test chambers can evaluate the heat resistance, cold resistance, dryness resistance, and moisture resistance of materials under different climatic conditions.

24.07

How the cryogenic test chamber achieves a stable low-temperature environment

Cold and thermal shock test chamber on the market is divided into two categories, a two-compartment type, including high-temperature region and low-temperature region, the test object were tested in two different temperatures in the area of the test, alternating hot and cold test; the other is a three-compartment type, in addition to high-temperature and low-temperature areas, there is also a test area, and the difference between the two-compartment is that the three-compartment type does not need to be tested directly in the test area.

25.06

Testing the performance and reliability of products under extreme temperature changes: Cold and Hot Shock Test Chamber

A cold and hot shock test chamber is an environmental test equipment used to evaluate the performance and reliability of products under extreme temperature changes.

25.07

Ozone Aging Test Chamber

The ozone aging test chamber, also known as the ozone aging test machine, is used for rubber products such as vulcanized rubber, thermoplastic rubber, cable insulation sheaths, etc.