Tandem Compressor Lubricant Equalization to Prevent Oil Dilution

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Solution Overview

Problem

In HVAC systems with tandem compressor assemblies, lubricant management is inadequate when one compressor is turned off, leading to refrigerant condensation in the oil sump, dilution of oil, and potential compressor failures upon restart, reducing reliability and efficiency.

Innovation Solution

A control system that manages lubricant levels by turning off both compressors temporarily to allow equalization between the two compressors during transitions from partial to full load, ensuring proper lubrication and preventing refrigerant condensation in the idle compressor's sump.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If one compressor is turned off while the other operates in a tandem assembly, then system efficiency is improved by reducing load, but refrigerant condenses in the idle compressor's oil sump causing oil dilution and potential compressor failure

Engineering Contradiction:

Improvesystem efficiencyVSAvoidcompressor reliability

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The controller temporarily shuts down both compressors before transitioning from partial to full load operation. This preliminary action allows refrigerant to evaporate from the oil sump and oil levels to equalize between compressors, preventing oil dilution and compressor damage when the idle compressor restarts

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system prevents refrigerant condensation in the idle compressor's oil sump by shutting down both compressors before load transition. This preliminary anti-action counteracts the harmful effect of refrigerant accumulation before it can cause oil dilution and compressor failure

Inventive Principle:

Principle #9Preliminary anti-action

2Reliability

If both compressors are turned off to allow lubricant equalization during load transition, then compressor reliability is improved by preventing oil dilution, but system productivity decreases due to temporary shutdown

Engineering Contradiction:

Improvecompressor reliabilityVSAvoidsystem productivity

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system implements periodic shutdowns during specific transition phases (from partial to full load) to allow oil equalization. This periodic action is applied only when necessary for reliability, minimizing impact on overall productivity while preventing compressor failures

Inventive Principle:

Principle #19Periodic action

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This approach enhances the reliability and efficiency of compressor assemblies by maintaining optimal lubricant levels, reducing downtime for maintenance, and extending the life of the compressor assembly.

Implementation Method 1

turns off both compressors to allow time for lubricant levels to equalize between the first and the second compressor when the tandem compressor assembly is transitioning from a partial load to a full load

Methodology Applied

Scientific EffectEvaporation: Evaporation

Implementation Method 2

oil used as a lubricant in the HVAC system is equalized between the compressors of the tandem assembly by an oil equalization system, such as piping between each compressor that maintains an equal oil level in the oil sumps

Methodology Applied

Scientific EffectFluid flow:

Data Source

PatentEP2960600B1System for managing lubricant levels in tandem compressor assemblies of an HVAC system

Publication Date: 2022.03.30 LENNOX IND INC

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AI summary

The present invention provides a control system for managing lubricant (11) levels in tandem compressor assemblies (100, 101, 102) of a heating, ventilation, and air conditioning (HVAC) system (1000, 1002). In transitioning from a partial load that operates a first compressor (101) but not a second compressor (102) of a tandem assembly to a full load that operates both the first and the second compressor (101, 102), a controller (128) of the HVAC system (1000, 1002) turns OFF both compressors of the tandem compressor assembly (100, 101, 102) to allow time for lubricant levels (11) to equalize between the first and the second compressor (101, 102).