Time-Based Safe Mode for Freecooling Chiller Under Sensor Failure

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Solution Overview

Problem

Multi-mode chiller systems in data centers fail to switch to freecooling effectively when temperature sensors malfunction, leading to inefficient operation and increased energy consumption.

Innovation Solution

A controller device for a multi-mode chiller system that monitors ambient and return water temperatures, engaging a time-based safe mode to alternate between direct refrigeration and freecooling based on user-configurable time parameters, ensuring efficient operation even with sensor failures.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If temperature sensors (NTC thermistors) are used to determine switching conditions between direct refrigeration and freecooling, then the system can automatically optimize cooling efficiency, but the system becomes unreliable when sensors fail and must default to less efficient direct refrigeration

Engineering Contradiction:

Improvesystem operation reliabilityVSAvoidenergy consumption

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The controller stores configuration time parameters in advance that define safe mode operation durations. When sensor failure is detected, these pre-stored parameters enable immediate transition to time-based safe mode without requiring real-time sensor data, allowing the system to maintain energy-efficient freecooling operation despite sensor failure

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system uses its own internal clock and stored configuration parameters to autonomously manage safe mode operation. The controller automatically alternates between freecooling and direct refrigeration modes based on elapsed time since safe mode activation, without requiring external intervention or functional temperature sensors

Inventive Principle:

Principle #25Self-service

2Ease of operation

If the system defaults to direct refrigeration when sensor failure is detected, then operational simplicity is maintained, but energy efficiency is significantly reduced

Engineering Contradiction:

Improveoperation simplicityVSAvoidenergy waste

Core Design Contradiction:

Ease of operationVSLoss of energy

Solution Approach 1:

The controller implements periodic alternation between freecooling mode and direct refrigeration mode during safe mode operation. Based on configuration time parameters, the system cycles through different cooling modes at predetermined intervals, allowing energy-efficient freecooling to operate periodically while maintaining simple automated control through the internal clock

Inventive Principle:

Principle #19Periodic action

3Productivity

If automatic mode switching based on temperature sensors is implemented, then cooling efficiency is optimized, but the system loses operational flexibility when sensors malfunction

Engineering Contradiction:

Improvecooling efficiencyVSAvoidoperational flexibility

Core Design Contradiction:

ProductivityVSAdaptability or versatility

Solution Approach 1:

The controller is designed to perform multiple functions: normal automatic mode switching using temperature sensors, safe mode operation using time-based parameters, and hybrid operation combining both approaches. This multi-functionality allows the system to adapt to different operational conditions and sensor states while maintaining cooling efficiency through configuration time parameters that define safe mode durations

Inventive Principle:

Principle #6Universality (Multi-functionality)

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

Preserves energy-efficient cooling functionality by automatically switching to a hybrid or freecooling mode based on time-based parameters, reducing electricity and water consumption when temperature sensors fail.

Implementation Method 1

The FC directs ambient air over the water loop via a fan, without mechanical refrigeration

Methodology Applied

Scientific EffectHeat transfer: Convection

Implementation Method 2

The DX system may be the default chiller subsystem, cooling the water loop via a full refrigeration cycle

Methodology Applied

Scientific EffectRefrigeration cycle: Heat Exchanger

Data Source

PatentUS12455093B2Time-based energy efficient safe mode for freecooling unit

Publication Date: 2025.10.28 VERTIV CORP

AI summary

A system and method for time-based safe mode operation of a multi-mode chiller device incorporating a freecooling system and a direct refrigeration system (e.g., wherein a fluid loop is circulated between the chiller device and a data center or similarly sensitive environment, from which the chilled water transfers heat before returning to the chiller device) senses ambient air temperatures outside the data center environment and return water (RW) temperatures (e.g., of water returning to the chiller from the environment) and engages the freecooling system based on a difference or delta between ambient and RW temperatures. If either the RW or ambient temperature sensors fail, preventing the freecooling system from engaging automatically, time-based safe mode is engaged wherein the freecooling and direct refrigeration systems are alternately engaged according to configuration time parameters adjustable by a user.