Why replace a perfectly good PDU when only the energy metering is outdated?

In many established data centres, power distribution has evolved over years or even decades.

Different generations of racks coexist. Different PDU manufacturers may be installed across the facility. In colocation environments, customers may also have selected or supplied their own PDUs.

Technically, there may be absolutely nothing wrong with them.

A well-built PDU can continue distributing power reliably for many years. The challenge arises when requirements for energy metering, monitoring, reporting, power quality and DCIM integration develop faster than the electrical infrastructure itself.

This raises an important question:

Do you really need to replace hundreds or thousands of functioning PDUs simply to gain modern energy monitoring?

Not necessarily.

The PDU itself is not always the problem

When modernising a data centre, replacing existing PDUs with newer intelligent rack PDUs can seem like the obvious approach.

For new-build facilities or equipment that has reached end of life, that makes perfect sense.

Existing operational environments are different.

The electrical distribution may still perform exactly as intended, while the monitoring technology around it has become outdated. Older installations may lack sufficiently detailed measurements, modern communications, centralised management or integration with current monitoring platforms.

Replacing the complete PDU means replacing the part that still works simply to modernise the part that does not.

And replacing a PDU in a live data centre is not comparable to swapping an ordinary IT component.

A and B feeds, connected equipment, redundancy, cabling, change windows, commissioning procedures and the risk of service interruption all have to be considered.

Multiply that across hundreds or thousands of racks and a metering upgrade can quickly become a major infrastructure project.

Colocation makes the challenge even more interesting

The situation becomes particularly relevant in colocation environments.

A data centre operator may be responsible for power availability, capacity management, energy reporting and potentially customer billing, while the infrastructure beyond a particular point belongs to or is managed by the customer.

That creates an interesting technical challenge.

The operator may want better energy data without wanting, or being permitted, to replace the customer’s existing rack PDU.

This is where metering upstream of the PDU becomes particularly interesting.

Instead of requiring the intelligence to reside inside the rack PDU, the metering layer can be installed before it.

The Schleifenbauer Inline Meter 5.0 is designed around this principle. It is installed between the power source and the existing PDU, providing modern energy measurements while allowing the downstream power distribution infrastructure to remain in place.

Retrofit: keep the power distribution, modernise the metering layer

This changes the way a data centre modernisation project can be approached.

Instead of:

old PDU → replacement intelligent PDU

the architecture becomes:

existing PDU → retained
metering and communications → modernised

The Inline Meter is positioned upstream of the existing PDU in the power chain. Depending on the electrical design of the facility, this also creates opportunities to position the metering point outside the rack.

For existing data centres, this can be a significant advantage.

There is no need to make the metering capability dependent on the electronics inside the existing rack PDU. The power distribution infrastructure can remain in service while a new measurement layer is introduced.

This makes the retrofit approach particularly relevant for:

• established data centres with a large installed base of PDUs;
• colocation environments with customer-specific PDUs;
• basic PDUs without energy metering;
• older intelligent PDUs with outdated metering or communication technology;
• mixed PDU estates involving multiple manufacturers and generations;
• phased modernisation projects where all racks cannot be upgraded simultaneously.

The important distinction is that power distribution and energy intelligence no longer have to be replaced at the same time.

More than a kWh meter

Modern data centre energy monitoring requires considerably more information than a cumulative kWh reading.

Depending on its configuration, the Schleifenbauer Inline Meter can provide measurements including voltage, current, active power, apparent power, reactive power, energy, frequency, power factor, crest factor and Total Harmonic Distortion (THD).

The 5.0 architecture also supports modern communication and integration technologies including 1 Gbps Ethernet, REST API, Modbus/TCP and SNMP.

That distinction matters.

You are not simply adding another electricity meter.

You are adding a modern digital measurement and communication layer to existing electrical infrastructure.

And that creates opportunities far beyond basic energy consumption monitoring.

One meter provides data. Thousands provide insight.

A single meter can tell you what one feed is doing.

Hundreds or thousands of meters can tell you what is happening across the data centre.

This is where EnerTree DCEM becomes an important part of the retrofit proposition.

EnerTree is Schleifenbauer’s Data Centre Energy Management software platform. It can centralise information from the metering infrastructure rather than requiring operators to manage individual devices separately.

EnerTree provides capabilities including real-time monitoring, historical data and trending, centralised configuration, reporting, role-based access control and power quality analysis.

Through open interfaces, energy data can also be made available to existing DCIM, BMS and other data centre management platforms.

This changes the scale of the retrofit discussion.

It is no longer simply:

“How do we read these older PDUs?”

The more interesting question becomes:

“How do we create one modern energy monitoring architecture across an existing, heterogeneous power distribution estate?”

And then there is software licensing

Hardware cost is an obvious consideration when evaluating a PDU retrofit project.

At scale, however, the Total Cost of Ownership of the monitoring platform can become just as important.

If hundreds or thousands of measurement points are deployed, recurring software licences, subscriptions or device-based monitoring fees can have a significant impact on the long-term business case.

Schleifenbauer takes a different approach with EnerTree.

EnerTree DCEM is provided licence-free with the relevant Schleifenbauer hardware.

That means an Inline Meter project is not simply an investment in additional measurement hardware. With the appropriate Gateway architecture, the infrastructure can also be connected to a central DCEM platform without introducing a separate recurring software subscription for that functionality.

For large estates, that distinction becomes increasingly relevant.

The number of measurement points can grow without automatically creating a corresponding increase in software licence costs simply to access and manage the energy data generated by the infrastructure.

Retrofit becomes particularly interesting at scale

Consider an existing data centre with hundreds of racks.

Across the facility there may be a combination of basic PDUs, older intelligent PDUs and products from several manufacturers.

Electrically, the infrastructure continues to perform reliably.

Operationally, however, the data centre wants a modern and consistent monitoring layer for energy, capacity, reporting, analysis and power quality.

A traditional modernisation programme could involve replacing a significant proportion of the installed PDU estate.

A retrofit strategy allows the question to be turned around:

Which components actually need replacing, and which simply need better intelligence?

If an existing PDU still performs its primary function reliably, distributing power, an Inline Meter can provide the missing measurement and communication functionality upstream.

That allows more of the existing investment to remain in service.

It can also reduce the amount of hardware being replaced and minimise the need for work inside operational racks purely because the monitoring electronics have become outdated.

Connectivity matters too

Once hundreds of measurement points are introduced, another practical challenge appears: network connectivity.

A meter only creates operational value when its data can be collected and managed reliably.

The Inline Meter 5.0 uses Schleifenbauer’s modular communication architecture, with Gateway, Controller and Daisy Chain options available depending on the application.

This is particularly relevant for retrofit projects.

A solution that requires a separate network connection, switch port and IP configuration for every additional measurement point can simply replace one infrastructure challenge with another.

A successful retrofit strategy therefore needs to consider both sides of the equation:

power and data.

Why metering outside the rack can be an advantage

The assumption that rack-level energy measurement must always be integrated into the rack PDU itself is worth reconsidering.

If the objective is to measure the total energy consumption of a rack, feed or customer, positioning a controlled measurement point upstream of the PDU can make considerable sense.

Particularly in colocation.

The customer can retain the existing rack configuration while the operator can introduce a standardised measurement point on the supply side.

This creates a clear separation of responsibilities:

the PDU distributes the power; the Inline Meter provides the data.

That separation becomes especially valuable when different customers use different PDU manufacturers, generations or configurations.

Instead of attempting to make every downstream PDU equally intelligent, the operator can create a more consistent measurement architecture independently of the rack PDU behind it.

Modernisation does not have to mean replacement

Data centres are long-life assets.

It is inevitable that infrastructure from different technological generations will coexist.

The important question is therefore not whether every component is equally new.

The question is whether operators have the information they need to manage that infrastructure effectively.

If an existing PDU remains electrically fit for purpose but no longer meets today’s requirements for energy metering, communication and analysis, complete replacement does not necessarily need to be the first option.

Retrofit allows the intelligence to be modernised while the existing power distribution remains intact.

With the Schleifenbauer Inline Meter 5.0, modern energy metering can be introduced upstream of the existing PDU. With EnerTree DCEM, that information can then be centrally collected, analysed and integrated without a separate recurring software licence for the platform.

For established data centres, that can provide a very different approach to infrastructure modernisation.

Keep what works. Modernise what has become outdated.

Inline Meter models

GM 47A7VIP1101 Inline Meter vertical single phase 16 A 

GM 8BCFDIP1101 Inline Meter double horizontal single phase 16 A 

GM 681DVIP1301 Inline Meter vertical single phase 32 A

GM ED23DIP1301 Inline Meter double horizontal single phase 32 A 

GM 373AVIP3101 Inline Meter vertical three phase 16 A 

GM BA4EDIP3101 Inline Meter double horizontal three phase 16 A 

GM B295VIP3301 Inline Meter vertical three phase 32 A 

GM 0A1DDIP3301 Inline Meter double horizontal three phase 32 A 

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Bron: https://www.schleifenbauer.eu/en/pdu-retrofit-energy-metering-without-replacement/