ModPac II Heater Upgrade
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Marvair has determined that the original heater control system in the
ModPac II air conditioner units can, under some circumstances, allow a
heat strip to remain energized without air circulation through the unit.
Although this is an unlikely occurrence which requires multiple control
failures, it creates an unacceptable risk of fire, especially in an
unoccupied building. The reason this is primarily a risk for an
unoccupied building is because the process by which a control system
failure can result in a fire involves a gradual overheating of the HVAC
unit and the supply duct system. This process is accompanied by smoke
and odor, and it can initially be stopped simply by disconnecting the
power to the HVAC unit and requesting service assistance.
To reduce the possibility of a control system failure, we are offering a control system upgrade which involves replacing the entire heater assembly and the control relay. The new system adds another layer of control redundancy in the control circuit and incorporates components that are believed to be more reliable. This new control system was developed by General Electric and has already been installed by General Electric in the modular buildings in its fleet. Marvair is using the control system under license from General Electric. Marvair has inspected a number of the fire incidents involving the ModPac II units. None have involved personal injury and almost all have occurred in unoccupied buildings. We have consistently found that the units involved in fires were installed contrary to Marvair's installation instructions and not in compliance with the metal duct requirements contained in NFPA 90B. Many of the fire incidents also involved blocked or restricted return air systems, dirty filters, and/or improper field service (bypassed control components and improper parts substitutions.) It is believed that the new control system will be more tolerant of improper ductwork and of restrictions in return airflow. Because it replaces all existing control components, it will also eliminate any control bypasses or improper replacement parts that may currently exist in the original heater assemblies. The new heater assembly will be furnished without cost to the current owners of these ModPac II units. The owner will be responsible for the cost of installation and for the suggested inspection of the remainder of the HVAC system. Regardless of whether your modular buildings are leased or owned, we are asking that you contact the Marvair Parts Department for this product upgrade program for assistance in being sure your ModPac II units are upgraded. You may contact us by phone at 888-726-2734 or 229-273-3636, or by fax at 229-276-1479, or by email at kpate@airxcel.com. Direct correspondence to 156 Seedling Drive/Hwy 41 N., Cordele GA 31015 Thank you for your cooperation, David L. Shuford Vice President of Marketing |