Table 2. Possible causes for maintenance...

Table 2.

Possible causes for maintenance issues caused by design defects

System component	Defect SN	Maintenance issue	Possible causes
Internal environment	1	Insufficient cooling level	Thermostat insensitivity owing to wrong location
			Improper selection of cooling coil valves
			Sensors are not recalibrated at regular intervals. It may be owing to poor accessibility or poor maintenance practices
	2	Fungal growth and stains on walls	Moisture entry from the fresh air inlet
			Infiltration of external warm air – short circuiting
			Moisture carry-over from cooling coil
	3	Noticeable noise from machines rooms	Location of AHU plant room within occupancy space
			Improper selection of the low-static FCU fan type
			Poor acoustical insulation of the mechanical room
	4	Users’ dissatisfaction or discomfort	Air from the cooling tower gets sucked by air intakes. It may cause legionella infection
			Mold growth in return air plenum
			Dumping of cold air or malfunction of VAV terminal/FCU
	5	Hygiene risk of infections or sick building syndrome (SBS)	When air intake sucks air from a cooling tower, legionella infection may be caused
			Mold growth in the return air plenum
			Cold air dumping at users or malfunction of VAV terminal/FCU
	6	Foul smell	Lack or inefficiency of exhaust fans, especially in the toilets and kitchen
	7	Thermal discomfort	Temperature instability resulting from the inadequacy of the HVAC system
	8	Static electricity	Insufficient humidification of outside air coming inside the facility
	9	Noise or pollution threat from maintenance crews’ movement across corridors	Several nonadjacent HVAC technical rooms will result in more trips between them
			Location selected for machinery rooms is ill-advised and very close to the patients’ area
			Insufficient acoustical insulation for machinery rooms
	10	Limited HVAC control over some unoccupied spots	Some unoccupied locations have a full operating mode
Air handling unit (AHU) and fan coil unit (FCU)	11	Fan motor noise	Improper selection of the low-static FCU fan type
	11	Fan motor noise	Inadequate, fatigued, or rusty vibration isolation
	12	Corrosion/scaling of cooling coils	Selection of coils and coats, especially in harsh weather locations
			A large volume of fresh water is added to refill substantial leaks and the different minerals piles of the coils
			The housing is not designed to be adequately sealed, which allows continuous contact with moist air and dampness
	13	Buildup or dust on coils affecting airflow	Insufficient or lack of cleaning because of the poor accessibility for maintenance
	13	Buildup or dust on coils affecting airflow	Improper filter selection or sizing in the design
	14	Water leakage	Condensate pan material’s poor selection, especially when the material is corrosion-resistant but with low-quality considerations
			Fine dust accumulations may block fins
			Poor accessibility to clean tubes
	15	Water retention and buildup on the drain pan	Undersized drain trap
	15	Water retention and buildup on the drain pan	Drain-off pipe damage because of insufficient pipe fittings design
	16	Condensation on the exterior of components	Poor specifications for the casing of the AHU/FCU, which provides insufficient insulation
	17	Air filter clogging causes air pressure drops	Mostly occur when the inlets are located nearby an exhaust outlet or a pollution source such as cooling towers and parking lots
			Poor accessibility for maintenance which causes inadequate cleaning for filters or late replacements
			When the pressure gauge location is at an inaccessible location or hidden, which inhibits adequate maintenance and calibration
			BMS-linked differential pressure (DP) is not added to AHU, which limits real-time monitoring
	18	Poor maintenance accessibility	Crowded layout of piping and ducting around AHU/FCU
			AHU/FCU location at very high levels
			Existence of structural obstructions that impede the accessibility
			Insufficient or wrong access panels that lead to the above-ceiling AHU/FCU
	19	Control valves not closing appropriately	Improper selection of balancing valves of coils
Air distribution and terminal systems	20	Condensation on air conduits and their components	Inadequate insulation
			The diffuser’s location is near an external air infiltration into the facility or near entry areas
			Lack of proper recalibration of sensors because of accessibility challenges
	21	Air leakage	Flanged joints are subject to air leakages because of their quality, material selection or sizing
	21	Air leakage	Avoidance of flexible duct connectors
	22	Corrosion	Rainwater-related moisture is transported from the fresh air into the ducts
			Especially in coastal areas, the wet exhaust inability to drain out the moisture
			Especially in coastal areas, AHU-related moisture carry-over into supply air ducts
			The lack of a heating coil may increase the chances of corrosion occurrences
	23	Dirt and stains on ducts	Inadequate or lack of cleaning of ducts because of poor accessibility for maintenance
	24	Noisy airflow	Turbulence occurrence because of under-sized ducts
			Air movement in the ducting system is not balanced
			Rapid air movement in the duct system because of insufficient or undersized diffusers
			Improper allocation of VAV dampers controls
			Unavailability of sound attenuator
	25	Dumping of cold air or poor air balance	Short-circuiting occurrence causing air to return before it is circulated. This case occurs if a diffuser location is near return air grilles
			Blockage of furniture, false ceiling, or equipment for diffusers
			Dirt accumulation because of maintenance inaccessibility
			Poor selection of diffusers and their layout, which aim cold air directly at users, especially in patient rooms
	26	Pneumatic controls inefficiency	Air compressor failure, especially the open type
	26	Pneumatic controls inefficiency	Lack of redundant systems since this system is obsolete and needs frequent maintenance
Chillers	27	Condenser scaling	The use of the open-loop design of condenser water, mainly in a large application
	28	Corrosion of inside parts of condenser; face plate and tubes	The tubing material is not resistant to all forms of corrosion
	28		Unaccounted factors of harsh conditions of dust, temperature and humidity
	29	Refrigerant leakage	Unavailability of the refrigerant leakage detection system
	30	Refrigerant contamination	Moisture occurrence around refrigerant because of leakages of condenser tubes
			Air and moisture leak into the chiller, which necessitates purging
			Improper selection of refrigerant, which may allow for mixing of metallic moving parts of compressor motor or lubricant
	31	Leakage from coils (Fins)	Fins become blocked with dust which is mainly a location issue
	32	Surging of the chiller	Operating the chiller under its load capacity lower than 25% of its handling capacity. The type of chillers may vary; thus, the effect of this cause varies
			Condenser pressure because of corroded tubes that may cause surging
			Non-condensable matter increases in the refrigerant, caused by either leakage in the evaporator or periodic purging. This noted for subatmospheric refrigerants
	33	Noise and noticeable vibration	Damaged or insufficient spring isolators
			Poor acoustical insulation around the machine’s locations and mechanical rooms
			Compressor aging because of continuous running or repeated start-stop.
	34	Poor access to maintenance	Insufficient access for system components for maintenance and replacement
	34	Poor access to maintenance	Limited space for routine maintenance around machines and parts, especially in mechanical rooms
	35	Condensation on chilled water pipes	Inadequate insulation causes the pipes to get cold
	36	Water is coming out from monitoring devices	Remotely installed, which makes it difficult to fit perfectly due to the accessibility challenge
Cooling tower	37	Biofouling	Occurs when the cooling tower is not perfectly designed to prevent dirt accumulation and stagnation. This consideration is more critical when treated water is used for cooling
	38	Corroded body and components	The materials of cooling tower components, such as louver and collection basin, are not corrosion resistant
	39	Condenser water foaming	Cleaning challenges because of inaccessibility to all parts
	40	Inadequate heat rejection	Obstruction of structures around, above or inside the cooling tower
			The cooling tower is located near heat exhausts allowing for short-circuiting
			Over supplying or undersupplying of condenser water pump, in which the flow rate is too high to reject heat perfectly
	41	Poor access to maintenance or replacement	Improper consideration for maintenance accessibility in the design

System component	Defect SN	Maintenance issue	Possible causes
Internal environment	1	Insufficient cooling level	Thermostat insensitivity owing to wrong location
			Improper selection of cooling coil valves
			Sensors are not recalibrated at regular intervals. It may be owing to poor accessibility or poor maintenance practices
	2	Fungal growth and stains on walls	Moisture entry from the fresh air inlet
			Infiltration of external warm air – short circuiting
			Moisture carry-over from cooling coil
	3	Noticeable noise from machines rooms	Location of AHU plant room within occupancy space
			Improper selection of the low-static FCU fan type
			Poor acoustical insulation of the mechanical room
	4	Users’ dissatisfaction or discomfort	Air from the cooling tower gets sucked by air intakes. It may cause legionella infection
			Mold growth in return air plenum
			Dumping of cold air or malfunction of VAV terminal/FCU
	5	Hygiene risk of infections or sick building syndrome (SBS)	When air intake sucks air from a cooling tower, legionella infection may be caused
			Mold growth in the return air plenum
			Cold air dumping at users or malfunction of VAV terminal/FCU
	6	Foul smell	Lack or inefficiency of exhaust fans, especially in the toilets and kitchen
	7	Thermal discomfort	Temperature instability resulting from the inadequacy of the HVAC system
	8	Static electricity	Insufficient humidification of outside air coming inside the facility
	9	Noise or pollution threat from maintenance crews’ movement across corridors	Several nonadjacent HVAC technical rooms will result in more trips between them
			Location selected for machinery rooms is ill-advised and very close to the patients’ area
			Insufficient acoustical insulation for machinery rooms
	10	Limited HVAC control over some unoccupied spots	Some unoccupied locations have a full operating mode
Air handling unit (AHU) and fan coil unit (FCU)	11	Fan motor noise	Improper selection of the low-static FCU fan type
	11	Fan motor noise	Inadequate, fatigued, or rusty vibration isolation
	12	Corrosion/scaling of cooling coils	Selection of coils and coats, especially in harsh weather locations
			A large volume of fresh water is added to refill substantial leaks and the different minerals piles of the coils
			The housing is not designed to be adequately sealed, which allows continuous contact with moist air and dampness
	13	Buildup or dust on coils affecting airflow	Insufficient or lack of cleaning because of the poor accessibility for maintenance
	13	Buildup or dust on coils affecting airflow	Improper filter selection or sizing in the design
	14	Water leakage	Condensate pan material’s poor selection, especially when the material is corrosion-resistant but with low-quality considerations
			Fine dust accumulations may block fins
			Poor accessibility to clean tubes
	15	Water retention and buildup on the drain pan	Undersized drain trap
	15	Water retention and buildup on the drain pan	Drain-off pipe damage because of insufficient pipe fittings design
	16	Condensation on the exterior of components	Poor specifications for the casing of the AHU/FCU, which provides insufficient insulation
	17	Air filter clogging causes air pressure drops	Mostly occur when the inlets are located nearby an exhaust outlet or a pollution source such as cooling towers and parking lots
			Poor accessibility for maintenance which causes inadequate cleaning for filters or late replacements
			When the pressure gauge location is at an inaccessible location or hidden, which inhibits adequate maintenance and calibration
			BMS-linked differential pressure (DP) is not added to AHU, which limits real-time monitoring
	18	Poor maintenance accessibility	Crowded layout of piping and ducting around AHU/FCU
			AHU/FCU location at very high levels
			Existence of structural obstructions that impede the accessibility
			Insufficient or wrong access panels that lead to the above-ceiling AHU/FCU
	19	Control valves not closing appropriately	Improper selection of balancing valves of coils
Air distribution and terminal systems	20	Condensation on air conduits and their components	Inadequate insulation
			The diffuser’s location is near an external air infiltration into the facility or near entry areas
			Lack of proper recalibration of sensors because of accessibility challenges
	21	Air leakage	Flanged joints are subject to air leakages because of their quality, material selection or sizing
	21	Air leakage	Avoidance of flexible duct connectors
	22	Corrosion	Rainwater-related moisture is transported from the fresh air into the ducts
			Especially in coastal areas, the wet exhaust inability to drain out the moisture
			Especially in coastal areas, AHU-related moisture carry-over into supply air ducts
			The lack of a heating coil may increase the chances of corrosion occurrences
	23	Dirt and stains on ducts	Inadequate or lack of cleaning of ducts because of poor accessibility for maintenance
	24	Noisy airflow	Turbulence occurrence because of under-sized ducts
			Air movement in the ducting system is not balanced
			Rapid air movement in the duct system because of insufficient or undersized diffusers
			Improper allocation of VAV dampers controls
			Unavailability of sound attenuator
	25	Dumping of cold air or poor air balance	Short-circuiting occurrence causing air to return before it is circulated. This case occurs if a diffuser location is near return air grilles
			Blockage of furniture, false ceiling, or equipment for diffusers
			Dirt accumulation because of maintenance inaccessibility
			Poor selection of diffusers and their layout, which aim cold air directly at users, especially in patient rooms
	26	Pneumatic controls inefficiency	Air compressor failure, especially the open type
	26	Pneumatic controls inefficiency	Lack of redundant systems since this system is obsolete and needs frequent maintenance
Chillers	27	Condenser scaling	The use of the open-loop design of condenser water, mainly in a large application
	28	Corrosion of inside parts of condenser; face plate and tubes	The tubing material is not resistant to all forms of corrosion
	28		Unaccounted factors of harsh conditions of dust, temperature and humidity
	29	Refrigerant leakage	Unavailability of the refrigerant leakage detection system
	30	Refrigerant contamination	Moisture occurrence around refrigerant because of leakages of condenser tubes
			Air and moisture leak into the chiller, which necessitates purging
			Improper selection of refrigerant, which may allow for mixing of metallic moving parts of compressor motor or lubricant
	31	Leakage from coils (Fins)	Fins become blocked with dust which is mainly a location issue
	32	Surging of the chiller	Operating the chiller under its load capacity lower than 25% of its handling capacity. The type of chillers may vary; thus, the effect of this cause varies
			Condenser pressure because of corroded tubes that may cause surging
			Non-condensable matter increases in the refrigerant, caused by either leakage in the evaporator or periodic purging. This noted for subatmospheric refrigerants
	33	Noise and noticeable vibration	Damaged or insufficient spring isolators
			Poor acoustical insulation around the machine’s locations and mechanical rooms
			Compressor aging because of continuous running or repeated start-stop.
	34	Poor access to maintenance	Insufficient access for system components for maintenance and replacement
	34	Poor access to maintenance	Limited space for routine maintenance around machines and parts, especially in mechanical rooms
	35	Condensation on chilled water pipes	Inadequate insulation causes the pipes to get cold
	36	Water is coming out from monitoring devices	Remotely installed, which makes it difficult to fit perfectly due to the accessibility challenge
Cooling tower	37	Biofouling	Occurs when the cooling tower is not perfectly designed to prevent dirt accumulation and stagnation. This consideration is more critical when treated water is used for cooling
	38	Corroded body and components	The materials of cooling tower components, such as louver and collection basin, are not corrosion resistant
	39	Condenser water foaming	Cleaning challenges because of inaccessibility to all parts
	40	Inadequate heat rejection	Obstruction of structures around, above or inside the cooling tower
			The cooling tower is located near heat exhausts allowing for short-circuiting
			Over supplying or undersupplying of condenser water pump, in which the flow rate is too high to reject heat perfectly
	41	Poor access to maintenance or replacement	Improper consideration for maintenance accessibility in the design

Source: Created by the authors

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