[HLT] DATA HALL HEAT LOAD TESTING | A Guide

The fundamental purpose of a Heat Load Test [HLT] is to thoroughly test a data centre’s cooling and electrical infrastructure under different load conditions, operating conditions, and failure scenarios prior to allowing it into operation to ensure it meets the design objectives, uptime/redundancy expectations and intended overall reliability, minimizing downtime.

⚠️ Note that this article covers a project that is NOT using ‘Data Centre Levels’ as the process for delivering the overall testing and commissioning. It focuses on a ‘general’ delivery where Heat Load Testing forms the final verification and validation of the Mechanical Systems.

🔗 To read more about the Data Centre Levels and how to deploy them, see our article | DATA CENTER | 0, 1, 2, 3, 4, 5, 6 Levels of Commissioning

---

⬛ Key Take Away

This Article provides an in-depth exploration of heat load testing (HLT) for data centres, focusing on validating cooling and electrical systems before operational handover, with the key highlights being:

• Purpose: Emphasizes the necessity of HLT to ensure that cooling systems can handle maximum load conditions, maintain reliability, and prevent downtime,
• Testing Types: It categorizes HLT into three types: Full Infrastructure & Data Hall, ata Hall Only Equipment, Data Hall + Additional Infrastructure,
• Design Considerations: Discusses various data hall designs, including hot aisle containment and raised floor systems, which influence testing strategies’,
• Team Roles: Identifies key participants in the testing process, including the commissioning manager, general contractor, and facilities management,
• Documentation: Lists essential documents such as the Heat Load Test Plan and Heat Load Test Reports,
• Benefits: Highlights advantages like validating cooling capacity, proving system reliability, enhancing energy efficiency, and mitigating business risks.

---

🟩 Benefits of Heat Load Testing

Conducting heat load testing in a data centre can offer several benefits:

• ✅ Validating the Cooling System Capacity: Part of the test will simulate 100% load conditions to ensure the data hall’s cooling infrastructure can maintain the required ambient conditions in line with the overall designed conditions.
• ✅ Proving the CFD and Ensuring there are No Hot Spots: Usually, within the design documentation of the Data Hall will be a Computational Fluid Dynamic [CFD] Study. This study is a crucial tool used by the designer and commissioning team that shows simulation and analysis of the airflow, temperature, and other thermal characteristics within the space, ensuring that the server inlet temperatures are maintained within recommended ranges and there are no hot spots.
• ✅ Proving Reliability and Uptime: Proactively testing the load and various failure scenarios on the plant/equipment and overall chilled water cooling system helps to prove reliability and uptime, preventing unplanned future downtime.
• ✅ Enhancing Energy Efficiency: The data/trends captured from the heat load testing will allow further analysis of the plant/equipment and systems to ensure they run efficiently.
• ✅ Mitigates Business Risks: Conducting a comprehensive heat load test on a new data center helps mitigate business risk for the operators and owners by validating that the cooling infrastructure can manage the expected loads, maintain temperatures/humidity, and prevent equipment failures, service disruptions, and costly downtime.

---

---

🟩 When to Complete a Heat Load Test

Depending on the overall Commissioning Process being used, as noted in the below section ‘Different Types of HLT’, the Heat Load Test [HLT] will usually be completed at the end of the construction / site acceptance testing stage and before handover / occupancy and operations stage:

Type of Process	When to Complete
ASHRAE	Completed during Stage 3c—Commissioning after the site acceptance testing of the plant, equipment, and systems.
Levels 0-6	Completed during Level 4 – Functional Testing or on some projects Level 5 – Integrated Systems Testing, depending on the Client.

🔗 To read more about the ASHRAE Process, see our article | THE COMMISSIONING PROCESS | Explained

---

🟩 Different Types of HLT

Generally we will come across 3 different types of infrastructure when considering the testing and commissioning of a project:

• Full Infrastructure & Data Hall,
• Data Hall Only Equipment,
• Data Hall + Additional Infrastructure.

🟧 Full Infrastructure & Data Hall

When considering the data centre cooling system, ‘Full Critical Infrastructure’ would generally refer to the overall set of equipment, systems and components that are essential for ensuring effective and reliable cooling of the Data Hall Space from the heat rejection plant to the Data Hall Cooling Equipment, covering items such as:

• Cooling Towers
• Condenser Water Pumps
• Water / Air Cooled Chillers [inc Controls]
• Chilled Water Pumps
• CRAC / CRAH / Fan Wall Units
• Primary / Air Handling Unit [PAU / AHU]
• Building Management System etc…

🚀 This type of testing would usually be used / required when a new data centre is being constructed or a building being converted to a data centre.

🟧 Data Hall Only Equipment

These types of projects are quite common when a client/owner decides to fit out / extend an additional floor or space that can be supplied with Chilled Water from the existing system without needing to install any additional major equipment.

Usually there will be a ‘future’ chilled water flow and return connection close to the space, that will feed the data hall provided by the previous works / phase.

The focus of the testing will be on the equipment directly associated with the data hall covering:

• CRAC / CRAH / Fan Wall Units
• Primary / Air Handling Unit [PAU / AHU]
• Building Management System etc…

🚀 As noted this type installation would usually be an extension of an existing system where the client is adding space.

🟧 Data Hall + Additional Infrastructure

Within some projects, quite commonly, clients/owners will do projects that are a hybrid of the 2 above delivery models.

The projects will involve constructing an additional data hall within an existing building under a new phase of works. The equipment directly serving the data hall will usually be installed as per the ‘Data Hall Only’ Model – noted above.

The existing chilled water major plant and equipment may not have been sized and installed, under the previous phase of works, to accommodate the additional load of the new space, additional equipment will be installed and integrated into the existing system.

⚠️ This can bring a few issues, especially when completing the testing and commissioning on the new major plant and equipment due to the existing systems needing to be online.

Types of Equipment to be installed under this type of work would be:

• Cooling Towers
• Condenser Water Pumps
• Water / Air Cooled Chillers [inc Controls]
• Chilled Water Pumps
• CRAC / CRAH / Fan Wall Units
• Primary / Air Handling Unit [PAU / AHU]
• Building Management System etc…

---

🟩 Different Types of Data Hall Design

When conducting a heat load test consideration needs to be given to the type of cooling solution the data hall is designed to, as each will have a slight difference on how fully tested and what type of equipment is used.

Most commonly there are 3 types, hot aisle containment, cold aisle containment, and raised floor systems.

🟧Hot Aisle Containment

Features server racks arranged back-to-back, creating aisles where hot air is expelled. This design includes barriers to contain the warm air, directing it back to cooling units through ducts.

• Allows for higher server density,
• Improves airflow uniformity and reduces hotspots.

🟧Cold Aisle Containment

Involves racks facing each other across a cold aisle, with cold air delivered directly into this space. The cold aisle is enclosed to prevent cold air from mixing with warm air from the hot aisles.

• Ensures that cold air reaches the equipment directly.
• Allows for better control of specific temperature zones.

🟧Raised Floor Systems

Create a plenum space beneath the floor, allowing efficient airflow management with cool air being supplied through perforated tiles / grilles, while hot air can be returned through overhead ducts or by using the room as an open plenum

• This design offers flexibility for future changes in layout or equipment placement.
• It facilitates better cable management and airflow distribution.

---

---

🟩 How Long Does a Heat Load Test Take?

Depending on the specific project and scale, if we take the above types of Heat Load Testing, we would, from our experience expect the total testing time to be:

• 2-3 DAYS | Full Infrastructure & Data Hall
• 1-2 DAYS | Data Hall + Additional Infrastructure
• 1 DAY | Data Hall Only Equipment.

---

🟩 Cx Team, Roles and Responsibilities

For these works the Commissioning Team delivering and involved will usually consist of multiple parties, including:

1. Commissioning Manager [CxP, CxA] – main party involved coordinating the testing,
2. General Contractor – provides resources, equipment and support for the testing,
3. Contractors, Vendors, and Suppliers – support the general contractor,
4. MEP Designer – Provides support on design and operational items to the commissioning team,
5. Owner/Client/End User – General attendance and support,
6. Facilities Management – General attendance and support,
7. Project Manager – General attendance and support,

Each team member will have specific roles to ensure the testing is completed correctly and by all approved scripts, methods, and expectations, as noted below:

🟧 Commissioning Manager [CxP, CxA]

The CxP/CxA will be responsible for this stage of the works and testing, their responsibilities will usually include:

✅ Initially agree on the tests that are to be conducted,

✅ Write the Heat Load Test Script or Method Statement,

✅ Command the testing throughout,

✅ Provide update at the end of each day to the project and client team on progress and any issues, observations, and punch-list items,

✅ Write the Load Bank Plan/strategy document,

✅ Plan, oversee, coordinate, and manage the testing and resources,

✅ Coordinate the closeout and provide advice for any issues, observations and punch-list items,

✅ After the testing, prepare, write, and issue a full, detailed report

🟧 General Contractor

Once the Site Acceptance Testing/Level 3—Systems Startup Testing has been completed, the General Contractor will hand the system over to the CxP/CxA for them to conduct the Heat Load Testing.

During this time their usual responsibilities will be:

✅ Support the CxA/CxP in the overall delivery of the testing

✅ Supply all required resources to support the CxA/CxP management throughout the works. This will usually include contractors, vendors/manufacturers etc.

✅ Upon completion of the testing, obtain and provide all data from the equipment and instruments used. This will usually cover BMS Trends, Data Loggers, Alarm Logs, Screen Shots etc.

✅ Supply and install all temporary equipment and instruments required,

✅ Support in closing out of all issues, observations, and punch-list items,

🟧 Owner/Client/End User

The Owner/Client/End User will support and advise the overall project for the Heat Load Testing requirements and deployment.

✅ Approve the tests that are to be conducted,

✅ Approve the Heat Load Test Script or Method Statement,

✅ After the testing, approve the detailed report

✅ Approve the Load Bank Plan/strategy document,

✅ Attend the testing throughout,

🟧 Facilities Management / Building Operator

If the work involves working with live, existing systems, the facilities manager will generally advise and provide the relevant permits.

If no new systems are integrated with existing ones, they may observe the testing for knowledge and training.

✅ Provide advice and assistance on any tests if they interact with existing systems, including monitoring of systems and equipment,

✅ Approve and provide any permits that might be required,

✅ Attend testing for knowledge sharing and training.

🟧 Contractors, Vendors, and Suppliers

The contractors and vendors will support the General Contractor in documentation, temporary equipment, and onsite activities.

🟧 MEP Designer

The MEP Designer will be present to advise and inform the commissioning manager on the overall design and will also support the closure of any issues, observations, and punch-list items.

🟧 Project Manager

The Project Manager will have limited input into the Heat Load Testing. Generally, they will be overseeing the contract, etc.

---

🟩 Documentation Requirements

Five documents will typically be written, issued, and approved to facilitate and record the overall heat load testing, consisting of:

1. Heat Load Test Plan
2. Load Bank & Equipment Plan
3. Heat Load Test Script/Method Statement
4. End-of-Day Heat Load Testing Summary
5. Heat Load Test Report

🟧 Heat Load Test Plan

This document will serve as a roadmap for the testing, outlining the scope, objectives, methodologies, tests, and acceptance criteria. Once approved, it will ensure alignment among project team members.

✍️ Written by: Commissioning Manager [CxA/CxP] | ✅ Approved by: Owner/Client/End User

🟧 Load Bank, Equipment, and Instrument Plan

The load bank plan details the temporary equipment and instruments required for the test, such as artificial heat load banks, heaters, fans, and data loggers. It specifies their installation locations, connections, power sources, and control mechanisms.

✍️ Written by: Commissioning Manager [CxA/CxP] | ✅ Approved by: Owner/Client/End User

🟧 Heat Load Test Script

The Heat Load Test provides a detailed step-by-step guide for executing the heat load test. It will cover prerequisites, instruments and temporary equipment, the testing team, design parameters, logic, layouts, etc.

✍️ Written by: Commissioning Manager [CxA/CxP] | ✅ Approved by: Owner/Client/End User

🟧 End-of-Day Heat Load Testing Summary

The end-of-day summary is written and issued at the end of each day’s testing. It is intended to provide the overall project team with a concise update on the testing activities, progress, and observations.

✍️ Written by: Commissioning Manager [CxA/CxP] | ✅ Approved by: N/A

🟧 Heat Load Testing Report

The heat load test report is written to document the test activities and analyze results and findings.

It will form an official record, confirming whether the cooling system and infrastructure operate as designed.

✍️ Written by: Commissioning Manager [CxA/CxP] | ✅ Approved by: Owner/Client/End User

---

🟩 Temporary Equipment and Instruments

As noted in the previous sections, various types of equipment and instruments will be required to complete the testing successfully, as noted below.

🚀 The General Contractor and Vendors will generally supply and, where required, install, the instruments and equipment based upon the load bank and equipment plan.

🟧 Walkie-Talkies

Walkie-talkies will be used as a portable two-way radio device that can be used throughout the testing for quick communication between different parties who are located in different areas of the building / facility.

Walkie-talkies, also known as two-way radios, are portable communication devices that allow users to send and receive voice messages operating on specific radio frequencies, enabling instant communication without the need for dialling or waiting for connections.

Particularly beneficial as quick communication is essential for sending commands and receiving information from the field engineers.

#️⃣ Quantity, will depend on the quantity of people involved within the testing – we would use 10 as a baseline initially.

🟨 Reference

🔗 Walkie Talkies – MIDLAND

🟧 Temporary Data Logger [Temperature and Humidity]

The use of calibrated temporary temperature and humidity data loggers is a crucial to ensure accurate monitoring / reporting during the heat load testing of the cold aisle condition ensuring that it meets the overall design / service level agreement requirements.

ASHRAE guidelines recommend installing temperature and humidity data loggers, set to log at 1 minute intervals, at a height of 1.5 meters in various strategic locations within each cold asile, between 1 m and 9m [10 ft to 30 ft]. Ensure they are calibrated, powered, and connected to the Building Management System (BMS) for real-time monitoring, with data recorded at one-minute intervals.

⚠️ Ensure to allow for these in your costings as if not already have can be expensive, due to the quantity sometimes required.

✅ Will require calibration certificate before using

#️⃣ Quantity, will depend on the size of the data hall and quantity of cold aisles, plot on a drawing to understand the correct quantity needed.

🟨 Reference

🔗 ASHRAE Thermal Guidelines for Data Processing Environments

🔗 TESTO 174H – Mini temperature and humidity data logger

🟧 Digital Thermometer & Humidity Meter

A calibrated digital thermometer and humidity meter will can be used to cross reference live data and be used help measure accurately the temperature and humidity levels throughout the testing within the cold / hot aisle and any other required areas, where needed.

✅ Will require calibration certificate before using

#️⃣ Quantity, usually will require 1 or 2 meters for the period of testing

🟨 Reference

🔗 Fluke 971 Dual Display Temperature Humidity Meter

🟧 Thermographic Imaging Camera

Thermal cameras detect infrared radiation emitted by objects, converting it into a visible image, capturing heat signatures.

This allows visualization of temperature variations, by various colours, in real-time during the testing allowing a detailed pictorial evaluation where needed, identifying over / under cooling of components.

✅ Will require calibration certificate before using.

#️⃣ Quantity, usually will require 1 camera for the period of testing.

🟨 Reference

🔗 Flir Thermal Camera | FLIR E54

🟧 Vane Anemometer

A vane anemometer is an instrument that is used when accurately measuring the flow rate of grilles / floor grilles / terminals or air outlet, using a rotating vane that spins, measuring its speed.

✅ Will require calibration certificate before using.

#️⃣ Usually will require 1 to 2 vane anemometers for the period of testing.

🟨 Reference

🔗 Testo Vane Anemometer | Testo 440 Delta P

🟧 Pitot Tube + Micromanometer

A Pitot tube is used to measure the air flow velocity, consisting of a tube that measures total pressure [static + velocity pressure] at its open end and static pressure through side openings, with the difference between these pressures allowing for calculating the flow velocity.

They are used mainly for measuring the airflow within main ducts via a ‘duct traverse’ and the most accurate method.

✅ Will require calibration certificate before using.

#️⃣ Usually will require 1 pitot tube + micromanometer for the period of testing.

🟨 Reference

🔗 Dwyer Pitot Tube | 160E-02

🟧 Air Capture Hood [Balometer]

Air Capture Hoods, commonly known as a Balometers, are an electronic instrument used to measure air volume flow rates at diffusers and grilles, including floor grilles. It consists of a hood that captures air and a micromanometer that measures the air pressure and flow.

For this testing they are usually used if there is a raised floor with floor grilles.

✅ Will require calibration certificate before using.

#️⃣ Usually will require 1 Air Capture Hood for the period of testing.

🟨 Reference

🔗 ITM Instruments Inc | Balometer

🟧 Temporary Load Banks / Emulators

Temporary load banks or Emulators [3KW to 100KW] are usually used in the heat load testing of data halls to simulate the electrical and thermal loads that servers will produce during normal operation, helping verify the performance of cooling systems under controlled conditions.

⚠️ Ensure to allow for these in your costings as can be expensive, and plan for delivery time in your programme as can be issue to source at short notice.

#️⃣ Quantity, will depend on the size of the data hall, quantity of cold / hot aisles and IT load, plot on a drawing to understand the correct quantity needed.

🟨 Reference

🔗 [3KW] Rata | AC/DC Rack Mounted Load Bank

🔗 [100KW] Rata | 100KW Load Bank

🟧 Tap Off Boxes

In some projects where the heaters are directly connecting to the bus bar, tap-off boxes will be needed to connect to the electrical bus bar trunking system in the data hall to allow power supply for the temporary load banks / emulators.

⚠️ Ensure to allow for these in your costings as can be expensive, and plan for manufacture time in your programme.

#️⃣ Quantity, will depend on the size of the data hall, quantity of heaters and IT load, plot on a drawing to understand the correct quantity needed.

🟨 Reference

🔗 EAE Electric | Tap Off Box

🟧 Temporary Cables

Various temporary cables will be required to connect the temporary heaters to the Power Distribution Unit [PDU] or Bus Bar Tap Off Box to allow routing of power.

⚠️ Ensure to allow for these in your costings as the quantity of cables can make expensive.

#️⃣ Quantity, will depend on the size of the data hall, quantity of heaters and IT load, plot on a drawing to understand the correct quantity needed.

🟧 Hand Held Fire Extinguishers

Due to the Fire Alarm and Suppression Systems usually being isolated during the testing, portable fire extinguishers will be placed at locations within the testing area / data hall incase needed during the testing.

Generally they are not used but there is risk of issues with the temporary heaters that can sometimes catch fire, and better to be prepared.

⚠️ Ensure to use correct extinguishers for Electrical Fire [Class C – Carbon Dioxide or Dry Powder].

#️⃣ Quantity, will depend on the size of the data hall, quantity of heaters and IT load, plot on a drawing to understand the correct quantity needed.

🟨 Reference

🔗 American Fire Extinguishers | Co2 Fire Extinguisher

---

🟩 Pre-Requisites before Conducting the HLT

Before performing a heat load test, it is essential to ensure that several prerequisites are in place to ensure that the testing has been planned and is ready to commence:

🟨System Setup and Configuration

• BMS Configuration: Ensure that a networked, permanent, or temporary Building Management System (BMS) is in place, including remote screens or projectors.
• Software Backups: Confirm that software backups for the BMS are available.
• Power Supplies: Resilient / backup power supplies must be set up for all necessary equipment – including the BMS.
• Data Logging Equipment: A thumb USB drive should be ready to download testing data.
• Folder / File Structure: Folder structure should be provided to allow capture of all screen shots and
• Consolidated Screens: To allow efficient review and capture of BMS information, screens that consolidate data are a good thing to have created and use.
• Data Trending: Ensure that all data, that is needed to be captured is trending and available to be viewed live at the BMS.

🟨 Documentation Availability

• Heat Load Layout and Data Logger Drawings: Ensure that both the heat load layout drawing and data logger layout are issued and accessible.
• As-Built Drawings: Confirm availability of as-built drawings for electrical, mechanical, BMS, P&D, and fire alarm systems.
• Heat Load Script: Ensure that the Heat Load Script is fully approved.

🟨 Safety and Compliance

• Permit to Work: Implement a Permit to Work system for safety compliance.
• Signage: Install necessary signage for emergency exits and designate key areas .
• Fire Safety Measures: Fire extinguishers must be in place, and a designated operative should act as ‘Fire Watch’ during the testing. Additionally, fire systems need to be isolated.

🟨 Operational Readiness

• Clean Environment: Ensure that the testing areas are fully cleaned and free of debris.
• Plant Setup: All equipment or plant should be labelled appropriately and set up with correct timings, alarms, and settings based on design requirements and approved construction information.
• UPS and Fuel Preparations: Ensure UPS batteries are fully charged, and sufficient oil and fuel are available for the entire duration of testing.

🟨 Data Monitoring and Equipment

• BMS Data Logging Setup: The BMS should be configured to log and capture vital information such as temperatures and humidity levels at specified intervals.
• Load Bank and Equipment Configuration: Install load banks on the appropriate supplies and make sure all equipment is set to the correct power supplies.
• Calibration and Balancing: Check that critical components, such as sensors, air balancing, water balancing, CRAC testing, and floor grille balancing, are all complete and calibrated.
• Equipment Calibration: Ensure that all tools and instruments used for the testing, where required have a current ‘Calibration Certificate’.

🟨 Final Checks and Approvals

• Completion and Sign-off: Verify that site acceptance testing and verification is complete and that all relevant documentation is signed off.
• Defect Resolution: Ensure all defects are addressed and nothing outstanding could impact the testing.

---

🟩 List of Common Tests

There are many types of tests that can be conducted during a heat load test, depending on your project and design, below is a high level list of what is usually covered:

---

🟩 Challenges & Considerations

There are many challenges and considerations needed prior to, planning for and running a heat load test, some are explained below:

Challenge / Consideration	Type	Description / Mitigation
Supply and Type of Equipment	Planning	Ensure that during the tender stage of the project, the Client agrees to the types of equipment that is to be used and who will supply / pay for them - especially types of temporary load banks and emulators.
Agreement of the scope for the General Contractor	Planning	Ensure it is clearly documented in the Contract documents what the expectation is relating to the works, tasks and responsibilities of the General Contractor. Especially what equipment is to be supplied and installed etc.
Understanding and Agreement of the Tests that are to be completed	Planning	Writing the heat load test script can take considerable effort and time, we can then issue the document for it to come back with many comments and changes - generally due to the types of test we expected to conduct. Before writing the Script - issue a ‘Heat Load Test List’ and have agreed by all relevant parties [Client, Facilities, Designer etc].
Time to have the script approved	Planning	Do not leave the approval of the Script until the last minute, aim to issue it at least 16 weeks prior to ensure it is ready.
Installation, testing and validation of the MEP Systems and Infrastructure	Construction	During the construction, review the onsite progress to ensure that the systems will be installed and validated ready for the heat load testing.
Completion of the Data Hall [especially if using hot aisle / cold aisle [containment]	Construction	Ensure that the project team understand when developing the construction programme, how critical the purchasing and installation of the containment or flooring / ceiling systems are to allow well planned testing.
Hunting of Cooling Valves serving the equipment in the Data Hall causing issues with controlling the stability of the temperature and humidity	HLT	Allow time in the programme prior to the heat load test for the equipment supplier to set up the valves and equipment, then testing at the different load levels to prove prior to official testing.
Issues with tests during the official heat load test	HLT	Ensure a ‘Pre Heat Load’ is conducted with the project team and contractors prior to Client Official one.
Hot Spots	HLT	We find that hot spots are most common when using a floor plenum and floor grilles. Ensure that the floor has been balanced inline with the design requirements and that there are no areas of ‘negative’ pressure that can be found at the grilles if to close to the cooling units.
Intermittent Hot Spot	HLT	Sometimes during certain tests we can get a hot area in the data hall, that is not constant. Check the action / operation of the cooling valves on the cooling units - usually can find that during tests that affect the operation of the valve [power failures etc] they can close and not be opened prior to fans restarting.
Cold Spots	HLT	Cold spots are not very common but can be found if the BMS sensors reporting data are located within the air supply of the cooling unit or floor grilles are not balanced properly.

---

⬛ Related Articles

⬛ Latest Articles

---

⬛ Author

If you would like to know more about the author, here is my Personal Linkedin Account