Does coil cleaning save energy? This was the first question that we asked before agreeing to promote Steril-Aire as a manufacturer. We knew that the technology worked; that you could clean a coil to a nearly new condition by using UVC lights. That we knew. We also new that a clean coil would save energy. But we didn’t know whether you could save enough to make it worthwhile.
The short answer is yes, coil cleaning does save energy and it is worthwhile. I have included an article published in the November 2006 ASHRAE Journal; “Coil Cleaning Saves Energy”. This study looked at air handling units (AHUs) before and after coil cleaning to see what impacts coil cleaning had on energy savings.
Three key variables that added credibility to the study:
- The AHUs were large enough to provide substantial data (both units over 30,000 CFM).
- The AHUs were constant volume (not easy to find these days). It would have been difficult to quantify energy savings on Variable Air Volume (VAV) units.
- The weather data was constant during reporting periods.
The study looked at a huge building in downtown NYC. See the following results and conclusions:
- Cleaning the AHU SF-9 coil resulted in a decrease in the pressure drop across the coil, of approximately 14%. This resulted in a corresponding increase in airflow.
- Cleaning the cooling coil in AHU SF-9 resulted in an increase of 25.3% tons of cooling (on prior 81 tons of cooling). They estimated that 100 tons (352 kW) of cooling capacity would be added to the building once all four AHUs coils were cleaned. (Building had a total of 1,800 [6330 kW] tons available capacity.)
- Cleaning the cooling coil increased the thermal efficiency of the cooling coil 25% with respect to its ability to transfer its energy to its sensible loads (10% with respect to latent loads).
- Cleaning the cooling coil would continue to save energy by decreasing the load on the chiller plant, and making the heat transfer of this loading more efficient. It reduced the time of multiple chiller operation and its associated pumps, cooling towers, chemical costs, wear and tear, etc.
It is worthwhile to note that the coils in these units were 30 years old and its last cleaning was nearly a year before the study.
Conclusion: Good maintenance practices, including coil cleaning, can significantly improve energy efficiency (by as much as 10% to 15% as in this case).
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