Chilled Water SystemTypical Operational Overview

Training Overview

Purpose of a chilled water system

Parts of a chilled water system

Plate frame for cooling

Plate frame for reheat

System pumps

Multi pump / chiller systems

Chilled water system sequence of operation Condenser sequence of operation

Purpose of a chilled water system

The purpose of a chilled water system is to provide cold water to air-handler equipment for the purpose of cooling supply air to control space temperature.

Water is cooled to a predetermined set-point that is set within the chiller itself.

Parts of the chilled water system

Evaporator Area of the chiller that cools the water

Condenser Area of the system that pulls heat off the machine

Cooling Tower Cools water from the condenser by dissipating it into the air.

Tower Bypass Valve Controls condenser water flow either over the cooling tower

or recirculates it through the machine.

Parts of the chilled water system

Plate frame for cooling

A system that has a plate frame heat exchanger configured for cooling will provide chilled water to air-handlers by using cooler outside air temperatures to cool the water.

Condenser water flows over cooling tower to be cooled by outside air.

Cold condenser water flows through plate frame heat exchanger to cool the chilled water.

Plate Frame for cooling

Plate frame for reheat

A plate frame heat exchanger that is configured for reheat uses the heat generated by the chiller to provide heat for the hot water system.

Heat that isn’t pulled off the machine by the plate frame is pulled off by the cooling tower.

Plate frame for reheat

System pumps

Single pump systems only have one chilled water pump that moves water through the chiller and air handlers.

Multi pump systems have primary chilled water pumps and secondary chilled water pumps. Primary chilled water pump flows water through the

evaporator side of the chiller.

Secondary pumps flow water through AHU’s

Condenser pumps flow water over the cooling tower to remove heat from the machine.

System Pumps

Multi pump / chiller systems

Some systems have a total of four chilled water pumps and four condenser water pumps as well as two chillers.

Lead Lag Systems Allow for either pump combination to run with any chiller

Fixed pump systems Allow only for a specific pump to run with a specific chiller.

Chilled Water System Sequence of Operation

Chilled water system lockout set-point Common set-point for economizer disable and chilled water

system lockout.

System enable Chilled water and condenser water pumps start BEFORE the

chiller startup

System disable Chilled water and condenser pumps run for a period of time

AFTER chiller is disabled.

Condenser Sequence of operation

When condenser water reaches a specific temperature the system reacts to keep temperature from getting too hot. A high condenser temperature can damage the machine. Most chillers will trip on high head pressure.

Cooling tower bypass valve (where equipped) allows condenser water to flow over the tower or recirculate through the machine.

Cooling tower fans help push air through the tower to cool condenser water.

The Plate Frame heat exchanger (where equipped) will also pull heat from the condenser loop.

Questions?