The purpose of this procedure is to define the step by step method to implement the correct practices for the testing, pre-commissioning & commissioning of Fresh Air Handling Units FAHUs with Heat Recovery Wheel System through the guidelines contained herein so as to ensure that the job execution complies with the project requirements and serves the intended function to satisfactory level.
Precommissioning Procedure for FAHUs with Heat Wheels
- 7.1. Ensure that the Fresh Air Handling Unit (FAHU) installation is complete and mechanical completion is approved.
- Ensure that no damage has occurred between mechanical completion & pre-commissioning.
- Repair all damages to the equipment finish paint.
- Check FAHU installed as per the approved shop drawings and manufacturer’s instructions.
- Verify that proper thermal overload protection is installed in motors, starters and disconnects.
- Check all chilled water piping, connected to FAHU is with proper valve package, drain, air vents, instruments, etc as per the approved shop drawing.
- Lubricate bearings, pulleys, belts and other moving parts with factory recommended lubricants.
- Check all VCDs, BDs and fire dampers are open.
- Check all motorized dampers are installed & connected with power supply & controls properly.
- Check filters are clean and fixed properly.
- Check for proper electrical power, control panel and earthing connections as per manufacturer’s recommendations. Field wiring to be pre-tested for continuity and insulation resistance.
- Disconnect drive motor, verify proper rotation direction, free fan wheel rotation and smooth bearing operations. Reconnect fan drive system, align belts and install belt guards.
- Set earth leakage and overload relays as per motor nameplate rating.
- Check for proper drain of condensate.
- Check the air intake louvers are installed properly.
- BMS & Fire Alarm interface shall be checked in line with the procedures.
Heat Wheels
- Check for proper orientation of the unit. The labyrinth seal shall be located in the vertical direction across the FAHU.
- Check the unit is installed such that the purge sector is facing the conditioned air inside the building. This is the side where the return air enters & supply air leaves the unit.
- Check the rotor alignment at the top, bottom, left & right sides, there should be equal spacing on all sides & a minimum 1/4″ spacing from any metal parts for smooth & trouble free operation.
- Check all bearing collars & mounting screws for proper installation as per manufacturer’s recommendations.
- Check wheel flatness & seal clearance.
Commissioning Procedure for FAHUs with Heat Recovery Wheels
- Outdoor Intake air – Air entering the FAHU from atmosphere Supply air – Air leaving the FAHU to the building Extract air intake – Air entering the Heat Wheel from the building
exhaust system Extract air outgoing – Air leaving the Heat Wheel from the building exhaust system. - Ensure that all the pre-commissioning checks are carried out successfully.
- The precommissioning & commisiong of the exhaust fans shall be completed prior to commissioning of the FAHUs . The same shall be carried out in line with the approved procedure.
- Check for the correct direction of rotation of the fans.
- Start FAHU and run for 5 minutes.
- Check for proper rotation of the heat wheel.
- Measure air flow in the main supply air duct and adjust, if required to set design value.
- Measure outdoor intake air flow and adjust, if required to set design value.
- Set the fan RPM to provide total air quantity within acceptable limits and the required static pressure to operate the system.
- It shall be ensured that the fan speed does not exceed the maximum allowable RPM as established by the manufacturer.
- It shall be ensured that the final setting of fan speed does not overload the fan motor in any mode of operation.
- The total flow shall be measured & recorded by using the duct traverse method and the flow shall be set to 105% of the design value.
- Measure the intake & supply air temperature (DB/WB) & record it.
- Measure the extract air intake & outgoing temperature (DB/WB) & record it.
- Measure & record the supply & intake air relative humidity.
- Measure & record the supply & intake absolute relative humidity.
- Measure & record the chilled water flow across the FAHU coil.
- Calculate temperature efficiency & humidity efficiency.
- Measure & record voltage, current & speed of fan motor.
- The cooling performance shall be calculated & established using the following formula. Capacity (KW) = Flow (lps) X (Outlet CHW temp (oC)- Inlet CHW temp(oC)/0.239.
- The motorized valve shall be checked for proper operation based on the signal from the return air temperature sensor vide DDC controller.
- Check the condensate drains freely & the slope of the condensate drain pipes is from 1 to 3% & the drain trap is serviceable.
- Record all readings in the final performance check list.
ATTACHMENTS
- Pre-commissioning check sheet for Heat Recovery System
- Commissioning check sheet for Heat Recovery System
- Performance Test Record for Heat Recovery System
- Risk Assesment