Loading and Unloading of chiller

[Sumit]

Dear Friends ,

As we already know that when we start the chiller , it takes sometime to come on full load i.e 100 % . Can you please tell me what are the main reasons due to which chiller is not initially started (put) at full load i.e 100 %. Why it usually starts with 10-20-40-50 % and so on.

[james10]

Power consumption, letting the compressor start efficiently,
Imagine starting your car and putting it in 5th gear and trying to pull away it wouldn't be easy

[Grizzly]

Good answer James!
Grizzly

[install monkey]

also to prevent short cycling and allow for better control

[Sumit]

Thanks james for your reply.

Hi Install Monkey ,

Can you please explain me how it can prevent short cycling.

Thanks for your cooperation

[NoNickName]

Lower inrush current

[Tesla]

Hi Sumit
If you start say a building on a cold morning and there is an initial heat load due to office and internal heat sources - all or most of the chilled water valves CHWVs will open at near 100% then they would close in about 1/2 an hour, this would mean the chiller goes to 100% for a short time and then there would be no load due to use of outside air as a first stage of cooling. Where the outside air cooling would be enough to bring the building down to temp in 1 hour. Considering most commercial buildings are charged for power on the highest 1/2kWh for the whole month where it is possible that the chiller may not be required for that month.
The chiller load on stage up is often controlled by deviation from CHW setpoint plus a time of say 20 mins (depending on the size of the system). If you had a load of 100kW and your chiller is 500kW at 100%loading it would start then shut down and start again in short periods of time.

[Sumit]

Thanks Tesla,

Good explanation, its clear to me now.