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Due to the split nature of the HRM-V™ system, a complete factory installation into an air handling unit is not always practical or feasible. More often the heat pipe coils are installed into air handling units, at HPT or at a manufacturer’s facility, and then shipped to the project location where the remaining work is completed on site. Therefore, provisions should be made for field work by Heat Pipe Technology technicians and by a local mechanical contractor. Heat pipe coil installation is usually by the equipment vendor at the manufacturer’s facility when systems are installed in air handling units. If practical, the air handling units can ship to HPT for factory coil installation at HPT’s facility. Installation in duct work is typically by a local mechanical contractor. Below are guidelines for a standard scope of work involved for an HRM-V™ split passive heat pipe system installation.

Heat Pipe Technology - HPT will custom manufacture coils according to the design engineer’s plans and specifications. Parts included shall be the exhaust and supply heat pipe coils, modulating stepper valves, and control box. Once the system has been installed and the air handlers are operational, a Heat Pipe Technology technician will travel to the project location and perform the following; verification of pressure test, evacuation of circuits, and charging. The HPT technician will inspect the system and installation to ensure there are no problems with the installation. HPT technicians will verify the pressure test that shall be left on the system by the mechanical contractor. Once verified to be leak free, each circuit will be evacuated and charged by the Heat Pipe Technology technicians with an amount of refrigerant to be calculated based on actual pipe lengths measured by Heat Pipe Technology technician. Due to variance from the estimated length the mechanical contractor may be required to supply additional refrigerant over the amount estimated.

Equipment Vendor - The equipment vendor may be required to provide space and/or install the heat pipe coils within their air handling units. The equipment vendor shall be responsible for providing mounting hardware as well as drain pans and drain connections for removing condensate.

Equipment Vendor or Mechanical Contractor - The equipment vendor or mechanical contractor shall be responsible for the installation of the heat pipe coils in the supply and exhaust air streams and/or the placement of air handling equipment containing heat pipe coils in a mechanical room according to the engineer’s plan. The equipment vendor or mechanical contractor shall provide and install type L, ACR copper piping, fittings and valves between the coils, insulation for all exposed piping, condensate drains including appropriate traps for both coils, brazing equipment, and nitrogen for purge and pressure test per Heat Pipe Technology’s specified pipe sizes and guidelines. The equipment vendor or mechanical contractor shall also provide the refrigerant to charge the system per Heat Pipe Technology’s estimate amount plus any extra that may be needed due to changes in estimated piping lengths. Piping between the coils shall be run overhead and properly supported without creating traps as per Heat Pipe Technology drawings and guidelines.  Brazing of the joints shall be with suitable silver brazing rod while purging the pipe with nitrogen. When the assembly of the piping is complete, the equipment vendor or mechanical contractor shall provide a pressure test with nitrogen of each circuit to 200 PSI. The pressure shall hold on the system for a period of at least 48 continuous hours before being read again. Pressure readings shall be made at a time of day and recorded to provide the same temperature on the system. After pressure testing, the access valves shall be shut and capped and the system left under pressure until verified by Heat Pipe Technology. The equipment vendor or mechanical contractor shall be responsible for repair of any leaks found by Heat Pipe Technology. The connecting piping shall not be insulated until the leak test is complete and approved by HPT. The equipment vendor or mechanical contractor shall have the refrigerant for charging available during the scheduled field work for use by Heat Pipe Technology.

Drain Pans

A drain pan is required to retrieve moisture from both supply and exhaust sides of the heat pipe coils.  Intermediate drain pans are also required when heat pipes are installed in stackable sections. Due to the vertical orientation of the tubes, the fins are horizontal. Condensate does not drain to the bottom of the coil as it does with a conventional coil. The condensate can build on each fin until it is pushed away at the leaving face by airflow. Therefore, condensate management must be taken into account during the initial layout of the system. An extended drain pan that continues at least 3 feet past the leaving face of the coil is suitable for capturing condensate. For some applications where significant condensate is present, the coils may be tilted at an angle from the horizontal plane to help with condensate management.


To ensure a clean fin surface and optimal performance, suitable filters should be installed. Filter racks should be placed upstream of the supply and exhaust coils even if the exhaust is from clean indoor air. The types of filters should be compatible with the specific environmental conditions for a given application. It is recommended that inspection doors be installed adjacent to the heat pipe on both supply and exhaust sections.