chiller plant operation sequence

[bundy]

hi All,

Can someone advise me what is the normal operating sequence of the cooling tower, condenser Pump, Chiller water pump, chiller and AHU.
Which equipment should start first ?

thanks

 

[quark]

Condenser Pump--->Cooling Tower Fan---->Chilled Water Primary Pump---->Chiller----->Chilled Water Secondary Pump---->AHU

My philosophy

Wet the fills first by starting circulation pump of cooling water and then start fan. Secondly, you will come to any irregularities in water flow through cooling tower.

Chilled water primary pump will take care of the higher pressure in the chiller if you start it first.

To reduce initial cooling down time (even though it is marginal)chilled water pump should be started prior to AHU.

Regards,

 

[bundy]

i was told that the Air handling unit will need to start first before the starting of the CHiller. As there could be a possible surge/trip if the chiller experience no loading ?

Anyone got experience in the control of chiller starting sequence using bAS software ?

 

[briand2]

Bundy,

Provided the volume of the chilled water system is sufficient to suit the type/capacity of your chiller(s), there should be no problem with "surge/trip" if you start or run the chiller with no load. Typical figures range from 5 litres to 10 litres (or more) per kW of cooling (this needs to be in the primary loop, as water in the secondary loop is not available to the chiller unless there is some flow through the loads (or perhaps through three-port valves).

By the way, I would slightly amend quark's start-up procedure; I wouldn't start the cooling tower fan second - I'd just make sure it was enabled and then it will start / stop as required depending upon requirements (to control cooling tower leaving water temperature).

Brian

 

[TEGGER]

Using a BAS system our chiller starts when one of four air handlers are calling for mechanical cooling due to 'recirc' not satisfying space temps from VAV box. Sequence: Air handler 'On' - Chiller call to run-cooling tower pump 'on'-chill water pump'on'- bypass valve modulating to tower flow. Water treatment controls monitoring PH, Biocides etc....