The cooling load of my project is 500 ton, I would like to use 2 chillers for my baseline case in OS1.7 so that each chiller is less than 300 ton. However, if I autosize the chiller, the part load ratio show that only 1 chiller will be used whose size is 500 ton. How should I change the control mode so that the load could distributed evenly to each chiller?
In this case, only one chiller is being used because both chillers are probably sized to meet the full load of 500 tons.
Every chiller, boiler, etc. object has a field for "Sizing Factor" which is used to allocate the design load across multiple pieces of equipment. This defaults to 1.0, and the autosizing does not have a way to check if there are multiple chillers or boilers present. The detailed inputs for the chillers in OpenStudio should give you access to set the Sizing Factor for each one. For example, if you want 2 chillers of equal size, then set the sizing factor of both chillers to 0.5. If the total design chiller load is 500 tons, then this would result in 2 chillers of 250 tons.
If you set the chiller's sizing factor to 0.6, then a 500 ton size will come out as 300 tons.
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