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IF TWO FANS ARE IN PARALLEL INSTALLATION, IS IT NECESSARY TO PRIVIDE BACKDRAFT DAMPERS ON THE DISCHARGE SIDE OF EACH FAN IF THEY ARE START UP AND SHUT DOWN AT THE SAME TIME? IF NOT,DO THE FAN CAN BE DEMAGED WHEN THEY ARE START UP OR SHUT DOWN IN SERIES? THANK YOU

in a 6 story office building project, people sugest we could put a water to water heat pump on the interior zone system, therefor trnasfer the waster heat to the air handling units serving the exterior zones in winter and off season. Is the hot water generate by the heat pump at 105 to 110 deg F...

The winter design temperature is -12deg. F in my case, some people suggested that we should us 50% propylene glycol for roofrop make-up air units, but I am so hesitate with this figure. Except increasing pressure loss and risk of corrision of the water loop system, decreasing equipment...

The winter design temperature is -12deg. F in my case, since there is a dry cooler in the system which need not function in winter, some people saying that we should us 50% propylene glycol, without the experience of glycol concertation in hudraulic system, besides the increasing of pressure...

I currently have a project which recoverys heat from condensers to preheat make-up air. My question is how much glycol concentration is proper for make-up air roof top unit? my concenption is that even at night the unit is shutdown, the water loop still keep on runing, therefor, it is not...

Both Trane and Carrier water source heat pump roof top unit do not have preheat coil option, is this type of unit a good application in cold climats like Canada? What's the advantage and risks using water source heat pump roof top units instead of interior installed water source heat pumps?

I am confused by the water source heat pump operating conditions. in 2000 Ashrae system and equipment handbook, chapter 8, it mentions that in order to operating satisfactorily, the air entering the water source heat pumps should be above 60 deg. F. Therefore, the ventilation air must be...