In testing the impact of the HP EIR_fFlow curve (see 3453), it was found in CZ07 Retl models, increasing the economizer DB limit from 69F to 75F resulted in less cooling energy use. I have not looked into this deeply, but I suspect it may be because it is in combination with using proposed SZVAV. This may be something worth investigating further, i.e., should SZVAV have different prescribed economizer limits than those listed in Table 140.4-G… As JA pointed out, it is not uncommon for CZ07 to have cooler very humid days, so higher economizer DB limit may potentially come at the expense of comfort (high humidity) at certain times of the year. This suggests potentially expanding the thermal comfort criteria beyond just unmet load hours based on drybulb temperature, or alternatively, limiting user inputs on economizer lockout temp control limits. Again, a lower control limit may be acceptable in the context of SZVAV if the fan runs at 50% when economizing....
In testing the impact of the HP EIR_fFlow curve (see 3453), it was found in CZ07 Retl models, increasing the economizer DB limit from 69F to 75F resulted in less cooling energy use. I have not looked into this deeply, but I suspect it may be because it is in combination with using proposed SZVAV. This may be something worth investigating further, i.e., should SZVAV have different prescribed economizer limits than those listed in Table 140.4-G… As JA pointed out, it is not uncommon for CZ07 to have cooler very humid days, so higher economizer DB limit may potentially come at the expense of comfort (high humidity) at certain times of the year. This suggests potentially expanding the thermal comfort criteria beyond just unmet load hours based on drybulb temperature, or alternatively, limiting user inputs on economizer lockout temp control limits. Again, a lower control limit may be acceptable in the context of SZVAV if the fan runs at 50% when economizing....
Reported by: joesinger12
Original Ticket: cbecc-com/tickets/3474