Modern data centers generate thousands of infrastructure data points. Temperatures, breaker states, UPS loads, generator alarms, valve positions, fuel levels, rack capacity and environmental conditions all need to be visible to operations. Three platforms are commonly involved: the Building Management System (BMS), Electrical Power Monitoring System (EPMS) and Data Center Infrastructure Management (DCIM). Their functions overlap, but they are not the same system.
What the BMS does
The BMS is primarily responsible for monitoring and, where designed, controlling building and mechanical infrastructure. Typical points include chilled-water temperatures, pump and fan status, CRAH operation, valve positions, room temperature, humidity, water leak alarms and selected auxiliary systems.
Because cooling is a dynamic system, the BMS often includes real-time control sequences such as lead/lag rotation, pump staging and temperature or pressure control.
What the EPMS does
EPMS focuses on the electrical power chain. It typically collects data from utility incomers, switchgear, transformers, generators, UPS systems, PDUs, branch circuits and meters. Useful values include voltage, current, kW, kVA, power factor, frequency, breaker status, energy and power-quality data.
EPMS is especially valuable for electrical event analysis because high-resolution trends and sequence-of-events information can help determine exactly what happened during a power disturbance.
What DCIM does
DCIM generally provides a higher-level operational view that combines facility capacity and IT-space information. Depending on the product, it may manage racks, devices, floor plans, power capacity, cooling capacity, asset records, connectivity, alarms and change planning.
The strongest use of DCIM is not to duplicate every low-level control function, but to turn infrastructure data into operational information for capacity, planning and decision-making.
Integration should not create control ambiguity
It is common to integrate BMS and EPMS data into DCIM. The design should clearly define which system is the source of truth for each data point and which platform is allowed to issue control commands.
Duplicating control across multiple platforms can create risk. For example, a CRAH fan sequence should not be controlled independently by both BMS and DCIM unless the architecture has been specifically engineered for that purpose.
Use open protocols where practical
BACnet is widely used for building automation and is defined by ANSI/ASHRAE Standard 135. Modbus and SNMP are also commonly used in data-center infrastructure integrations. Protocol choice should consider reliability, cybersecurity, polling rate, data type and vendor support.
Alarm ownership
An alarm visible on three platforms still needs one accountable owner. Operations should define who receives each alarm, who investigates it, how it is escalated and when it is closed.
A monitoring system that collects alarms without clear response ownership can create the illusion of control while increasing operational confusion.
Practical architecture principles
- Keep real-time mechanical control within the approved control platform.
- Use EPMS for detailed electrical monitoring and event analysis.
- Use DCIM to combine infrastructure data with capacity, asset and planning information.
- Define a source of truth for every critical data point.
- Document protocol gateways and failure behavior.
- Avoid unnecessary duplication of commands across platforms.
- Assign every critical alarm to an operational owner.
Key takeaway
BMS, EPMS and DCIM should complement one another. BMS controls and monitors building systems, EPMS provides deep electrical visibility, and DCIM turns facility and IT data into operational intelligence. The objective is not to make all three systems do everything, but to create a clear architecture with defined ownership, reliable integration and useful information.
References and Further Reading
- ANSI/ASHRAE Standard 135, BACnet — A Data Communication Protocol for Building Automation and Control Networks.
- ASHRAE data center resources and TC 9.9 publications.
- ISO/IEC TS 22237-7:2018, data center management and operational processes.
