[TRNSYS-users] Chiller performance limiting

[Marcus <jones.0bj3@gmail.com>]

Hi All, 

I'm using TESS type 655 to model an air cooled chiller. Similar to many other types I've seen, it has the COP and Capacity at rated conditions as input parameters. Even the Type text shows that rated conditions are i.e. "typical 35 C (95 F) ambient and 7 C (44 F) chilled water set point temperature". 

However, in the mathematical description and the behaviour of the chiller, "If the calculated PLR is greater than unity, Type655 automaticall limits the load met by the chiller to the capacity of the machine". 

Isn't this a misunderstanding between "Rated Capacity" and "Maximimum Capacity"? In my chiller data sheet, the chiller can of course operate above rated capacity to meet a higher load. 

For example, my chiller is rated 198 kW over 9.5 l/s, at ARI . But the data sheet still has a point for 242 kW chilled capacity at 11.6 l/s. Doesn't this limiting cut out these extreme points, which might occur at i.e. startup? Clearly the chiller can operate above rated conditions. 

I am just starting to model a monitored system with real data, could this be an issue? 

Cheers,

Marcus
-- 
Marcus Jones,  M.Sc., LEED®AP BD+C
Freelance energy consultant
Vienna, Austria