25% Difference Between Identical Equipment
Two identical air-conditioning units provided cooling at a technical site and alternated operation in cycles. However, the measurement data clearly showed that one unit was drawing approximately 25% more electrical power during operation than the other.
A targeted on-site inspection eventually revealed a refrigerant shortage. After the leak was repaired and the system recharged, the two units once again showed very similar energy-performance characteristics.
The starting point
Energy consumption at a technical site was higher than at comparable locations, and the cause needed to be identified.
Cooling was provided by two identical air-conditioning units.
The units alternated in operation, so under normal conditions their electrical consumption profiles should have been very similar.
At first glance, both units appeared to be operating normally and the required cooling was being provided.
However, comparison of the submetering data revealed a clear difference.
What did we measure?
We measured the site’s main consumption groups separately, including:
the technical equipment;
the air-conditioning units;
the total incoming electrical supply.
The submetering system allowed us to monitor the electrical power consumption of each air-conditioning unit separately.
Because the two units were identical and performed the same function, their operation could be compared directly.
The measurement profiles showed that the second air-conditioning unit was drawing approximately 25% more power during operation than the other unit.
The difference was significant enough to justify a targeted technical investigation.
What did submetering reveal?
25% higher air-conditioning power consumption revealed by submetering – OMS24 Zrt.
The first chart compares the operating cycles of the two identical air-conditioning units.
Although the units operate alternately, it is clearly visible that one of them draws more electrical power during its operating periods.
The difference is not a one-off spike. It appears repeatedly and consistently, indicating that it is not simply measurement noise or an occasional operating condition.
The second chart shows daily energy consumption. Here, it can also be seen that the higher power draw resulted in increased daily electricity consumption.
25% higher air-conditioning power consumption revealed by submetering – OMS24 Zrt.
Comparing two identical pieces of equipment can often reveal more than analysing the consumption of a single unit in isolation.
What was causing the unnecessary consumption?
Based on the measurement data, a targeted on-site maintenance inspection was carried out.
The investigation found that the air-conditioning unit with the higher power consumption had insufficient refrigerant.
In other words, the increased energy use was not caused by operating behaviour or different settings.
It was caused by a technical fault.
The unit was still operating — but not efficiently.
What did we change?
During maintenance:
the refrigerant charge was restored;
and after the intervention, we compared the measurement data of the two units again.
Following the repair, the two air-conditioning units once again operated with similar energy-performance characteristics.
However, approximately one week later, the abnormal operating condition appeared again.
The technician was therefore sent back to the site. This time, the refrigerant leak itself was repaired, after which the correct refrigerant charge was restored once again.
This also demonstrates that submetering can be used to verify the effectiveness and quality of maintenance work.
The result
The technical fault became identifiable through the measurement data.
Following the corrective action:
the significant difference between the two identical units was eliminated;
unnecessary energy consumption was reduced;
the air-conditioning unit returned to normal operation.
Based on the original measurement data, the difference in electrical power consumption was approximately 25%.
What does this case show?
A piece of equipment can be operating without necessarily operating correctly or efficiently.
A fault can remain unnoticed for a long time if the equipment continues to perform its basic function, no alarm is generated and it does not shut down.
Energy consumption data, however, may still reveal that something has changed.
Submetering can therefore provide not only energy-management information, but also valuable operational and maintenance insight.
This can be particularly valuable when the performance of several identical or similar pieces of equipment can be compared with one another.
Do you have identical pieces of equipment that appear to operate in the same way?
Comparing their consumption data can reveal differences that may not become apparent during a conventional on-site inspection.