450Ton Carrier Centrifugal Chiller

wot on erth R U talkin bout?

If there is no water flow, the refrigerant side of the chiller will continue to pump down, possibly freezing the stagnant water in the chiller. (It depends on the relative sizes of system parts, so this may or may not happen.)

Whoever does not understand this needs to explain to you, not you to them.

GA TORNADO and a good explanation of the most important characteristic to consider. I would also add that a 450ton unit has enough of a piping system attached, that just from an operating point..... I would much prefer to bypass some chilled water at the decks, or vav, or whatever exchangers ... than to start and stop water flow, thereby picking up a lot of sediments and redistributing them in the valve passages.

What sediments are you talking about?? Have you ever worked on a chiller in your entire life? If you did, does it still run after you got your hands on it?

Dear Fedski, Welcome my Polish friend. You have asked some ridiculous questions, but in all fairness you have sparked me to ask myself, why I seek anonymity here(klearzen). My reasoning....A throwback to days gone by when, in the wild west of the internet, you really could be anyone you wanted to be. Who am I ? I am turning 50 years old this month... have been a sailor, a contractor, and engineer....a father, a brother, and son. I was born here in Saint Louis. My family roots lead back to Ireland and Germany. Who are you FREDSKI? Smiles, Ray

I'm a 30 year HVAC commercial service contractor is So Calif. If you're concerned about sediment, try looking in the strainer.

Over 5000 posts? Is this your life, to sit on this blog all day and berate people asking questions?

You don't need your pump to stop from running when your air conditioned space are functional or with load.

Your chiller stops and the chilled water pump is running-when the load of the air conditioned space had decreased making the temperature of the incoming chilled water to chiller equal to the preset temperature (stop) of the chiller evaporator. The pump will continue running in order to absorbed the heat of the conditioned space, until such time the preset room temperature is achieved, the pump will stop running.

This is just like the thermostat of a window type air conditioning unit. The compressor stops when a preset temperature is attained-an increase of temperature will make the compressor turn on again, while the fan can not stop, not unless you want to turn all the unit off.

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If you do not know the complex, then get back with the basics

450 TR capacity is a big chilling a machine. It has its own control panel and system to operate the chiller based on the settings . You need not and cannot shut down the pump.

In all air-conditioning applications whether used for comfort or process cooling, the Chiller's Controls are designed to acheive the desired Chilled water temperature set-point, once this is acheived the Chiller is automatically shut down by its Controller, this is called a 'cycling' shutdown. The Chilled water pump has to continue to run to supply the cold water to whatever downstream equipment it supplies to and returns back to the chiller, this is the complete loop or circuit, eventually the water will pick up heat, its temperature will rise beyond a certain range and the Chiller's Controller will re-start the Chiller. This is how the system is set-up, irrespective whether it is a 450 TR Chiller or a 2500TR Chiller.

Hi Guest,

There have been some good answers to your query re the chilled water pump operation with regards to a centrifugal chiller.

On initial startup the chilled water pump is normally operated for a period (say 10 mins) to achieve a mixing of the chilled water in the system so that a representative temperature can be measured to determine whether there is a demand for cooling. If so the chiller is then enabled and the chiller's own control system begins the startup sequence i.e. oil pump and condenser pump before enabling a start of the drive motor.

Cyclng on and off as a function of temperature control

Depending on the system load the chiller may cycle off when the temperature of the chilled water goes beneath setpoint (normally set ± 6ºC) and the chiller will then be held off by the recycle timer (± 20 mins). During this cycling on and off as a function of temperature control the chilled water pump must be kept running in order to supply water to the connected loads plus equalise the pressures within the chiller. The condenser pump and the oil pump will be shut down by the chillers control system during this recycle period.

Once the chillers recycle time has elapsed and if the temperature of the chilled water has risen above set deadband temperature (normally ± 4 to 5ºC above the setpoint) the chiller will go through it's startup sequence and restart.

Shut down of the chiller

When the chiller is required to be shutdown (cooling no longer required) then the chiller control is disabled and the chiller goes into the shutdown sequence i.e. the drive motor is disabled, the load control vanes are closed (sometimes referred to as pre-whirl vanes) and the oil pump and condenser pump time out. The chilled water pump however should be kept operating on a run down timer (delay off timer) for a period of 3 to 5 minutes before switching off. This run down time is to stabilise/equalise the pressures within the chiller (ensuring no risks of freezing during any refrigerant boiloff in the evaporator) and also mix the chilled water in the system to ensure the water is all basically the same temperature.

The manual supplied by Carrier for your chiller should give you a full description of the recommended operation sequences and parameters and I suggest you refer to this manual as well.

The above noted sequences are good practice in the operation of centrifugal chillers but it has been my experience that some people, when using a temperature control system other than that included by the manufacturer, just switch off everything when either cycling or shutting down the chiller. My experience, gained over many years of experience installing, servicing and repairing centrifugal chillers (all makes but especially Carrier), has been that although the chillers are designed to handle a sudden interruption (oil headers to enable lubrication of the impeller gearbox during pump failure etc) this practice increases the risk of damage.

Hope the above info is of assistance in answering your query!

The chilled water pump needs to keep feeding the building and or process. When the return water temperature rises above the set point then the chiller will start back up.

This is S.O.P.