Seasonal Change Over of your HVAC systems

Despite the fact that we have just had our fourth Nor’easter in the last three weeks, the time to change you’re HVAC systems from heating to cooling is close at hand. How you perform the winter layup of the heating system or the startup of cooling system can have a dramatic effect on how your equipment will perform when you need these systems to heat or cool.

In the case of boilers, this is the time to properly clean both the fireside and waterside for the summer layup. If you have had reports of high chlorides or dirty water in the sight glass of your steam boiler, it probably makes sense to boil-out the boiler with a chemical cleaner. When this is completed the steam boiler should be drained, refilled and corrosion inhibitor should be added. If you have a closed water heating system that has had a high level of suspended solids or has a bad odor it should be chemically flushed with chlorinated chemical cleaner. After the cleaner has circulated for 24-48 hours the system should be drained, refilled, and re-inhibited.

Because the seasons in New England often seem to go from winter to summer with no spring in between, cooling towers are often put online without proper preparation and cleaning. A true cooling tower cleaning “is not simply washing the mud and debris out of the sump”. Cooling towers should be filled and circulated with a chlorinated cleaner or hydrogen peroxide to loosen the corrosion or bacterial growth that occurred during the winter layup. After circulation for 24 hours the tower system should be completely drained, pump strainers should be cleaned, and the tower should be power-washed and vacuum until it is completely cleaned. When this is completed the cooling tower should be refilled and a startup dose of biocide and corrosion inhibitor should be added. At this point your chemical feed and bleed system can be serviced and activated.

The biggest problem we face in the water treatment industry in the Northeast is glycol contamination of closed water systems (chilled water, closed condenser water, and dual temperature systems). If you have winterized a coil, chiller, heat exchanger, or piping system with glycol for freeze protection, it is imperative that this glycol be completely removed from these components. Failure to do this will activate normally dormant strains of bacteria that will feed off the trace amounts of glycol. This will eventually lead to bio-fouling, corrosion, and foul odors in these closed systems.

If you take the time and effort to properly prepare for the seasonal change over you will avoid many unnecessary problems during your cooling and subsequent heating season. If you have questions or need help with any aspect of the procedures that I have recommended, feel free to call our office for advice at 781.932.9911.

Brian R. Cusick, CWT LEED GA

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