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[EnergyPlus_Support] size boiler and chiller using air and operative temperature.

Hi all,

I try to size HVAC system by using air temperature and operative temperature for an air-conditioned campus building with fully glazed north and south facades in the UK. The results are,
Using air temperature: boiler 1355 kW, chiller 523 kW
Using operative temperature: boiler 2279 kW, chiller 785 kW
It makes sense that the HVAC capacity may be larger by using operative temperature. But it seems the boiler capacity with operative temperature control is too high, almost two times higher than capacity by using air temperature. These results are still reasonable or I should check which input parameters in the models?

Another problem is that the hours for heating or cooling setpoint not met are also larger than those with air temperature control although the capacity of HVAC becomes larger with operative temperature control. According to ASHRAE 90.1, the unmet hours shall not exceed 300 hours for the whole building. In EE4 (canada software based on Doe2.1E), the unmet hours for heating and cooling should be less than 100 hours for one zone although any unmet hours for cooling are acceptable.  Apart from these two sources, would you please let me know whether there are any general rules for unmet hours (or other different metric to evaluate unmet conditions) in air-conditioned buildings?

Thanks,

Ming 



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