In engineering fieldwork, we often encounter a very real problem:

Even when using the same type of DDC or PLC, some systems develop constant issues within 3-5 years, while others run stably for a decade.

Many people's first reaction is:

“Is it because of different brands?”

“Is it because of differences in equipment quality?”

But those who have actually disassembled cabinets and modified programs know—

The gap isn't usually about brands, but about design and details.

I. Cabinet Design: Looks Similar, Performs Very Differently

When control cabinets are newly installed, most look “pretty neat.”

But after a few years of operation, the differences start to show.

Some cabinets feature clear wiring that remains understandable even years later;

Others have tangled, unlabeled cables that make logic changes hair-raising.

What truly impacts lifespan isn't cabinet size, but whether three critical aspects were considered during design:

•    Are high-voltage and low-voltage circuits physically segregated from the start?

•    Do terminal blocks allow space for future maintenance?

•    Does component layout account for heat dissipation, inspection, and replacement pathways?

Good cabinet design isn't about aesthetics—it's about considering the future maintenance technician.

When you stand at the site five years later and open that cabinet door, the answer will be crystal clear.

II. Whether there's “reserve capacity” determines if the system can grow

Many systems are designed with only one goal in mind:

“Functioning now and passing inspection.”

Thus you'll see:

•    Exactly the right number of points

•    Modules filled to capacity

•    Power supply capacity stretched to the limit

Short-term, no issues arise;

But adding a single device or function requires forced expansion.

Systems built to endure assume one fundamental truth from the outset:

Buildings evolve—systems must adapt.

Therefore, design phases incorporate:

•      I/O point redundancy

•    Communication port reserves

•    Scalable program architecture

Whether these reserves exist isn't about “saving money now,”

but whether the system can be upgraded later or must be completely rebuilt.

III. Program Clarity Determines the Courage to Modify

Many “short-lived systems” fail not because of hardware, but because of programming:

•      All logic crammed into a single program block

•    Start/stop, interlocks, and alarms tangled together

•    Changing one point affects a whole cluster

The result:

Whoever inherits it dares not touch it.

Programs that run stably for a decade often make structural trade-offs:

•    Clearly segmented functional blocks (start/stop, protection, interlocks, manual/auto)

•    Consistent naming conventions, not reliant on memory

•      Clear hierarchical logic for step-by-step troubleshooting

Programs aren't written for machines—they're written for the “next person to take over.”

This fundamental premise is often overlooked from the start.

IV. Commenting Standards: The Most Underestimated “Longevity Factor”

Many engineers avoid comments, thinking:

“It's fine if I understand it now.”

But the harsh reality on the engineering frontline is:

•    Three years later, you might not be the one maintaining it

•      Five years later, even you may forget why you wrote it that way

Code without comments is like equipment without manuals:

It runs, but no one dares touch it.

Truly mature systems consistently achieve:

•    Purpose documentation for each functional block

•    Source and significance annotations for critical parameters

•    Timestamps and rationale for every modification

Comments aren't formalities—they're the foundation of long-term maintainability.

V. Truly enduring systems share one common trait

Reviewing these items reveals a clear commonality:

They weren't “built for acceptance testing,” but “designed for long-term operation.”

From cabinet layout and point reservations to program structure and comment standards,

every detail minimizes future pitfalls and rework.

Systems plagued by frequent issues within three to five years,

often treat “working for now” as the ultimate goal.

Conclusion

The lifespan of a DDC/PLC system

is never determined solely by the equipment itself.

What matters more is the underlying set of engineering practices and systems thinking.

Equipment will age,

but systems designed for long-term operation become more stable over time.

This is the true difference.

                        If you have any other selection questions,please feel free to contact us!