Draw Thru vs Blow Thru Air Handler
Draw Thru vs Blow Thru Air Handler
(OP)
Any recommendations or pros and cons for draw thru vs blow thru configuration?
Auditorium
20,000 cfm @ approx 3.0"
Cooling Coil w/Reheat Coil
VFD Fan
Office / Classrooms
15,000 CFM @ aaprox. 2.5"
Cooling Coil
VAV w/Reheat
VFD Fan
Thanks
Auditorium
20,000 cfm @ approx 3.0"
Cooling Coil w/Reheat Coil
VFD Fan
Office / Classrooms
15,000 CFM @ aaprox. 2.5"
Cooling Coil
VAV w/Reheat
VFD Fan
Thanks





RE: Draw Thru vs Blow Thru Air Handler
RE: Draw Thru vs Blow Thru Air Handler
I'm not a real engineer, but I play one on T.V.
A.J. Gest, York Int./JCI
RE: Draw Thru vs Blow Thru Air Handler
RE: Draw Thru vs Blow Thru Air Handler
RE: Draw Thru vs Blow Thru Air Handler
Thanks
RE: Draw Thru vs Blow Thru Air Handler
I'm not a real engineer, but I play one on T.V.
A.J. Gest, York Int./JCI
RE: Draw Thru vs Blow Thru Air Handler
If the load is highly sensible you may prefer blow through, as it allows the coil to remove the fan/motor heat. More heat for a coil to grab, easier to remove the fan heat.
With draw through, the air has to be overcooled to compensate for the reheat of the fan/motor. Sometimes the overcooling will end up on the saturation curve, and to get the air cool enough, you are forced to dehumidify air more than needed. Another option is to use more airflow but then this only adds to the static.
So sometimes it is possible that you may want a blow through coil on a load that is highly sensible.
RE: Draw Thru vs Blow Thru Air Handler
RE: Draw Thru vs Blow Thru Air Handler
I'm don't agree with you on the issue of blow through versus draw through and how one is going to affect the air density any differently than the other. The density or specific volume of the air is a function of its temperature and relative humidity, not whether the fan is a draw through or a blow through. The problem that you cited sounds like the air balancer did not adjust the fan properly.
Typically the air side CFM should be balanced to the design CFM with an active wet cooling coil. If the CFM is adjusted to design in the heating mode, when the system is in cooling mode the CFM delivered will be short.
I'm not a real engineer, but I play one on T.V.
A.J. Gest, York Int./JCI