Energy Refurbishment Issues
AHU Cases
AHU cases are subject to corrosion over a long period of time, along with poor maintenance. Water damage at the intake, and leaking coils and water carryover from cooling coils often cause damage to the case. Faulty access panel fasteners can result in the panel being levered off or not properly refitted. The insulation in single skinned air handling units can be refitted or replaced. A thorough refurbishment can resolve these issues permanently.
Air Intake
High velocity louvred air intakes in an exposed location will invariably allow rainwater to enter. These can be replaced with cowls if necessary. Intake dampers are often corroded and seized, these can be replaced and new motors fitted.
Mixing Boxes
Two or three way mixing boxes are very economical to run if properly controlled. The dampers need to work efficiently, with the motors accurately controlled. This allows 100% recirculation overnight, and the correct amount of fresh air during building occupancy. Refurbishment may include damper repair or replacement, plus new actuators.
Filters
Filters near the intake can get wet and collapse, ultimately resulting in blocked heating and cooling coils. Upgraded filter sections will require new bulkhead and channels, this will result in lower resistance to airflow, with lower power consumption.
Heating and Cooling Coils
The heating coils near the intake can get blocked and deteriorate to the point where the fins rot and flake away. Coil leaks are common over time, including frost damage leaks and general corrosion. Water carryover from cooling coils can be due to insufficient depth of trap, undersized drain outlet, blocked drain pans, excessive airflow. All these problems can be resolved. Should coils need to be replaced they can be provided with corrosion resistant fins. Large coils can be flat pack installed on site if there are space limitations.
Plate Heat Exchangers
Plate heat exchangers are often not maintained at all. The critical component is the face and bypass damper, which automatically adjusts for heat recovery or free cooling. AHS can withdraw the plate heat exchanger for cleaning, with the damper refurbished and actuator checked and replaced if necessary. The sensors and controls will also be checked to ensure correct heat recovery function.
Thermal Wheels
Thermal wheels are also not generally maintained. If the small drive motor fails, or the drive belt fails, there will be no heat recovery. Also, if the brushes are not checked and maintained regularly the efficiency will fall off considerably. The wheel faced can become blocked over time leading to a reduction in airflow. All these items can be rectified by refurbishment.
Gas Burners
The new generation of gas burners have gas condensing energy modules with efficiencies in excess of 100%. The furnace and air/flue exchanger are manufactured from stainless steel. The output automatically modulates from 100% down to 20% capacity. The complete module can replace the old unit with some case modifications to the air handling unit or rooftop packaged unit.
Centrifugal Fans
Considerable energy savings can be made by replacing forward curved double inlet centrifugal fans with backward curved single inlet direct drive ‘plug’ fans with inverter speed control, or EC fans with electronic controller. AHS Specialist Services will advise on the best option in terms of duty, cost, and efficiency. Changing the fans alone will provide energy savings of 20% on the fan running cost. Large backward curved centrifugal fans can be refurbished with new bearings and high efficiency motors, or replaced with a bank of two, three or four direct drive ‘plug’ fans.
Motors
Old motors should be replaced with the latest IE3 premium efficiency motors. Old but functioning TASC drive motors can be replaced with the high efficiency motors with inverters. This provides the potential for demand control ventilation, including night set-back, humdity and CO 2 demand ventilation. At the same time the pulleys and belts should be checked for correct selection and adjustment, as this is a potential energy wasting component if not correctly set up and adjusted.
Silencers
Silencer pod infill collapses with time, and the silencer absorbent facing becomes very dirty and difficult to clean. This increases resistance to airflow and reduces the attenuation. The silencer can be completely replaced or new pods fitted with perforated steel facings.
Controls
Both the control system and the components fitted to the air handling unit, such as sensors and valves and dampers with actuators, are a major source of energy wastage in ventilation systems. AHS Specialist Services can check all these items, replace and re-commission as necessary.
