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WOJCIESZAK & ASSOCIATES, INC.CONSULTING ENGINEERS833 EAST 5TH STREETSTUART, FLORIDA 34994(772) 286-8696TECHNICAL BULLETINNO.DATEREVISION20204/25/062CHILLED-WATER, FOUR-PIPE (CHW) SYSTEMConstraints1. House square footage2. Smallest zoneEstimated Costs10,000 SQ. FT. or more250 SQ. FT.System DescriptionChilled-water systems can be installed in residencesover 10,000 square feet, however, because of the highinitial cost, they are commonly found in residences30,000 square feet and above. This system providesthe most flexibility and has been described as providinga high level of comfort. The high level of comfort isachieved because of the system’s ability to maintainnearly constant temperature and humidity levels withinthe house. Artwork, decorations and interior finishesare well preserved in this type of indoor climate andcould be the reason some residences under 30,000square feet have chilled-water systems.The chilled water is produced by large compressorsinside a chiller. One or two chilled-water pumps pumpthe 45 F chilled-water to the air handling units that sit inmechanical closets. The air handling units consist of afan, a chilled water coil, and a hot water coil. The fanblows the room air over the chilled-water coil anddelivers cold air to the room. This process warms upthe chilled-water to about 55 F. The chilled-water ispumped back to the chiller.A cooling tower is used, like in the water-cooled heatpump system, to provide cooling for the chiller’scompressors. Condenser water is pumped to thecooling tower. The cooling tower has a fan that blowsair across this water and cools the water before itreturns back to the compressor.The hot water coil inside the air handler has 140 F to160 F water circulating through it. The fan blows roomair over the coil and delivers the warmed air to theroom. The hot water is cooled by about 10 F and it ispumped back to the boiler where it is heated back up.The hot water coil also serves to dehumidify the spaceas needed.Obtain from an HVAC contractor.Notes:1. Equipment Replacement FrequencyCooling tower fan motor(every 4-5 years)Cooling tower(every 10-15 years)Chilled water pumps inside(every 10-15 years)Condenser water pumps outside (every 5-7 years)Boiler outside(every 5-10 years)Boiler pumps outside(every 5-7 years)Air Handling Units(every 15-20 years)Chiller(every 20 years)Indoor Equipment1. Air Handling Unit (AHU)a. Typical mechanical closet/room size2-ton48” x 42”3-ton48” x 56”4-ton49” x 56”5-ton49” x 62”b. Since there is only a fan and hot and chilledwater coils, the chilled-water AHU is relativelyquiet.c. Location of equipment should be in areaswhere service personnel can easily access theequipment, via hallways in lieu of bedroomclosets, for example. Filter changing and coilcleaning are routine maintenance.d. For added comfort, two speed fans can beused for the AHU fan. The slow speed willprovide a comfortable environment while thespace is below maximum capacity; whereasthe high speed can provide adequate coolingfor maximum capacity.2. Chiller and Chilled-Water Pumpsa. The chiller and pumps should be locatedinside a room far away from the mainliving/sleeping areas.Particular attentionshould be given to sound-proofing this room.
WOJCIESZAK & ASSOCIATES, INC.TECHNICAL BULLETINCONSULTING ENGINEERS833 EAST 5TH STREETSTUART, FLORIDA 34994(772) 286-8696NO.DATEREVISION20204/25/062CHILLED-WATER, FOUR-PIPE (CHW) SYSTEMb. Indoor mechanical room dimensions:SQ. 2’8’70,00022’12’9’3. It is best to locate the pumps for condenser waterinside the building. This shelters the equipmentfrom the harsh outdoor environment, thusextending its useful life.The pumps runcontinuously, therefore it makes it important tocarefully locate this equipment and sound proof theroom. Pumps may be located outside if no interiorspace is available.4. A boiler is used to heat the condenser water andprovide heating on cool days. It too may be locatedinside to be protected from the weather, but air forcombustion has to be provided as well as flueventing for the flue gases. If no room is availableinside, it may be located outside.Outdoor Equipment1. Cooling Towera. Typical cooling tower sizeSQ. ��-7”6’-7”6’-7”6’-7”6’-7”b. Because of the size of the cooling tower, alarge space on the property is necessary.Although there are several optionsavailable for noise reduction, the towershould be located far away from theresidence or sound sensitive outdoorareas of the property. Local codes maylimit the noise levels at adjacent propertylines.2. Overall Outdoor Equipment Pad ��12’7’70,00019’12’7’PipingChilled water piping is typically copper insulated with2-inch thick foamglass insulation. Care should bemade to locate piping in accessible locations abovethe ceiling where the insulation can be repaired whenit wears out (15-20 years). The piping can also be rununder ground and under the slab when welded steel isused.Condenser water piping is generally PVC undergroundand copper above ground and does not requireinsulation. It is usually run above the ceiling.Humidity ControlHumidity control is available through the hot water coilon the air handling unit. The hot and chilled watercoils work together to dry out the air.Energy ConsumptionEnergy consumption is quite low in systems of 100tons or more. However, in the smaller systems, thereis not much difference between the chilled-water andwater-cooled heat pump systems.
The chilled water is produced by large compressors inside a chiller. One or two chilled-water pumps pump the 45 F chilled-water to the air handling units that sit in mechanical closets. The air handling units consist of a fan, a chilled water coil, and a hot water coil. The fan blows the room air over the chilled-water coil and
