Enhancing Interpretability of Data-Driven Fault Detection and Diagnosis Methodology with Maintainability Rules in Smart Building Management

Table 4

HVAC System - Cooling Towers.

Problem	Design	Construction	Maintenance
Biological fouling of cooling tower; Foaming in cooling tower basin; Scale and dirt build-up in fouled fills	Provide a suitable cooling tower design to prevent dirt accumulation and stagnation.; Minimise tower fan power and size of towers for close approach in accordance with SS 564-1 or equivalent.; Provide automatic chemical dosing system to ensure acess hatches, level indicators mixers, pump etc. can be easily reached by personnel for maintenance and operation.; Provide adequate reach to all parts of the cooling tower for cleaning so as to prevent bacterial growth.; Specify locally green certified cooling tower water treatment system [8], but not limited to automated non-dispersant, non-chemical treatment etc. as it will minimise the downstream maintenance issues. The automated system with the capability of checking of the conductivity and other recommended parameters can be also linked to the building management system (BMS).	Prepare and submit an operation and maintenance (O&M) manual; For the chemical dosing system after the successful commissioning of the system.; Install equipment to routinely observe chemical tank levels and the tank condition of the automated dosing system. During installation, ensure that access hatches, level indicators, mixers, pumps, etc. can be easily reached by personnel for maintenance in the operation phase.	Perform frequent overall visual inspection and cooling tower sequencing. Clean tower fill, basin and drift eliminators. Conduct weekly check on fan motor; clean screen; make up water float and water sampling.; Carry out monthly check of motor supports, fan blades, motor alignment.; Check on condition of bearings and motor, as well as for nozzle clogging, annually. Clean cooling tower at least once a year.; Perform monthly checks for legionnaire, scaling and corrosion in/of the condenser system. Disinfect and manually de-sludge cooling towers if required.; Monitor water usage in cooling towers and review the efficiency.; Ensure optimum scheduling of temporary shutdown and standby of cooling towers.; Discharge used water from cooling owners into a sewerage system.
Water efficiency	Consider collection of condensates for re-use.; Take into consideration the cycles of concentration of the cooling owner used in order to reduce blow-down frequencies.; Avoid uncontrolled water losses due to drift, splash, overflow etc.	Ensure proper installation of float operated inlet valve to reduce frequencies of overflow.; Link cooling towers in order to maintain water balance.; Consider using solenoid operated inlet valves for cooling towers.
Legionella outbreak; Outbreak on air-water surfaces of cooling tower; Cooling tower air intake blocked by organic matter; Testing the water for legionella	Avoid redundant pipework, bends, and loops for cooling system design. Allow easy access to all parts of the system for maintenance [9].; Minimise drift by enclosing cooling tower pond.; Take the wind direction/distribution and the surrounding environment into account when designing the cooling system.; Use non-corrosive, chemical-resistant, non- porous, smooth, opaque (to block sunlight) material to inhibit growth and proliferation of microorganisms.; Design of cooling towers must be capable for preventing dirt accumulation and water stagnation.; Accommodate suitable and efficient water treatment methods in the system’s design.	Perform proper commissioning to ensure safe operation of cooling towers. Develop cooling tower maintenance manual including cleaning/water treatment/decontamination procedures and handover during commissioning.; Ensure system is clear of dirt/debris/organic matter and clean before operation.; It is presupposed that the control of legionella bacteria in cooling towers is in compliance with applicable statutory and regulatory requirements.	Cooling tower’s water temperature should be monitored since elevated temperatures and moisture at air-water surfaces provide ideal conditions that may serve as a nutrient source for legionella growth.; The chemical concentration limits of cooling tower effluents should be checked and in compliance with the relevant local standard.; If cooling tower is not in use, it should be kept drained and dry. If not in use for more than 5 days, it should be drained, cleaned and disinfected before operating. Regular testing for legionella bacteria should be carried out and get water samples from the cooling tower pond in accordance with ASHRAE 12-2000, ANSI/ASHRAE; 188 or equivalent.