It’s Not Always the Contractor’s Fault.

Although the time has come when warmer weather is upon us, the effects of this past winter are still being felt.  Recently, we were involved in an investigation that focused on the cause of damage to a water cooling coil located inside of a cooling tower (see photo below).  This might seem strange to some but, it is possible to require the cooling of a building during the winter.  In the investigation we were performing, the system was comprised of a water cooled water chiller.  This might not mean anything to most people but to those familiar with chiller operation, water was the fluid used to both cool the air and remove the heat absorbed by the refrigerant.  On the condenser side, water was circulated through a shell and tube heat exchanger and then pumped to another coil type heat exchanger located inside the cooling tower.  The problem arose when the local air temperature began to drop below freezing.  As the water temperature dropped below 40 F, water flow between the condenser and water coil was stopped (as part of the automatic control sequence).  As the air temperature continued to drop, the water temperature also dropped until the water froze inside the coil and caused it to burst in several places.  Since this was new construction, it was the engineer’s position that the mechanical contractor had erred and was negligent in their responsibility to protect the equipment.  However, it was later determined that the building had been turned over to the building owner under the substantial completion part of the contract.  As a result, the building owner was responsible for the protection of the building as well as the building’s mechanical systems.  Regardless of the positions taken by the various parties, the design of the HVAC system including the incorporation of freeze protection, was the responsibility of the mechanical engineer.  This responsibility is not an arbitrary assignment.  It has been long recognized by engineers and specifically, those engineers that are involved in HVAC design.  Although freeze protection had been designed into other parts of the system, no provision for freeze protection was made for the cooling coil located inside the cooling tower.  When all was said and done, the engineer failed to incorporate an adequate way to protect the coil and blamed the contractor in order to avoid the appearance of failure on their part.

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