Hi,

I am modeling a mixed-use building using ASHRAE 90.1 2010. The building uses four Heat pump water heater connected to Geothermal loop. The Heat pump is connected to three storage tanks of 850gal each. Now, since it has huge storage tank, the EF calculated will be negative value. I am missing anything? Do we have to consider the separate tank volume for the calculation or something else?

Thanks,

Pramod