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

25.04

Have You Mastered the Correct Usage of the Temperature Test Chamber?

The temperature test chamber is a widely used testing equipment in industrial enterprises. If your company has newly purchased a temperature test chamber, you must understand the precautions during its operation to avoid deviations in test results or equipment damage caused by improper usage.

25.06

How to test satellite components using a thermal vacuum chamber?

In order to verify the ability of satellite components to withstand vacuum thermal environments, a thermal vacuum chamber is used for testing. The purpose is to validate the rationality of the design and identify defects in the components, materials, and manufacturing processes.

25.09

Standardized Operating Instruction for Constant Temperature and Humidity Test Chambers (Applicable to R&D, Quality Inspection, and Third-Party Laboratories)

To ensure the electrical, mechanical and thermodynamic integrity of constant temperature and humidity test chambers (hereafter “the chamber”), to standardize operating procedures, and to reduce failure and accident rates, this instruction is established. It applies to all programmable, single-point and walk-in chambers that are newly purchased, in service or relocated.

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.

25.04

How to Choose the Right Damp Heat Test for Your Temperature & Humidity Test Chamber

When using a high-low temperature alternating damp heat test chamber, the appropriate damp heat test method should be selected based on the material characteristics and testing requirements.