The HVAC Air Handler Freeze Stat is a low temperature limit control and it is used mainly in commercial systems in the duct work on economizers or in air handlers just before any coil especially water coils. It is a safety and protection control to prevent extremely cold air from reaching the hot water or chilled water coils inside the air handler where the air enters from the economizer. Under ideal control set up if the freeze stat trips the economizer dampers close and the blower fan stops. This prevents coils from freezing. A frozen coil can bust open and will need to be replaced if it freezes thus the purpose of the freeze stat in HVAC air handler applications which utilize economizers for free cooling. Air Handler Freeze Stat
Air Handler Water Coil Freeze Stat – Freezing Protection Control
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This is a secondary chilled water pump in a large pump room designated for pumps and piping in a data center. After a few minor tweaks and corrections these pumps all operated flawlessly. There was very little issues with the secondary pump start-ups unlike the primary pumps where cavitation was encountered on the primary chilled water pumps and the condenser water pumps for the chiller. The diagnosis for the cavitation of the primary pumps and the condenser water pumps was that the loops were not properly purged of air and this caused those pumps to cavitate. The secondary pumps, pictured here, did not have that problem giving kudos to the team that purged the loops on this side of the chilled water system. 
Water towers maintain a ready limited supply of water for communities in the event the water main goes down. Many water towers are used for emergency situations for the fire department to have water for fighting fires and for water fire suppression systems to have a supply of water for the emergency if it should arise. 
This domestic hot water mixing valve offers a way to temper the hot water coming from a hot water loop and 
This is a hot water economizer and is a big preheater for domestic hot water use. This boiler plant serves a large community for heating and domestic hot water use. Domestic hot water is used for showers, washing dishes, laundry, ect, ect, ect…. The cold water supply from the city is routed through the economizer to be pre-heated before it goes through a heat exchangerand then the hot water storage tank. This system saves money because it uses the exhaust gases from the boiler to pre-heat the city water supply which is normally 50 degrees Fahrenheit. The exhaust gases from the boiler would otherwise be vented to the atmosphere and would be considered wasted heat. 
Cooling towers use the process of evaporation to cool or removes heat from the condenser water that was transferred to the water in the chiller condenser barrel. The heat is absorbed at the load in this case in a data center on a data center floor. The servers and electrical equipment produce a massive amount of sensible heat. The heat is absorbed by computer room air conditioners or computer room 
This is not a normal commercial boiler stack in this boiler room. It has a bypass stack for an commercial hot water economizer. All 
