Duct Losses vs Static Pressure

[SWISGR8]

I am new to the HVAC realm and just visiting it at that. I have a system that I am designing which is probably most similar to a car's. I need to spec an Air Handler and my biggest concern as opposed to cooling power is the flow rate coming out at the end ports. When I run through calculations using Equal Friction, I get worst case losses of just under 6 in H2O. All the air handlers I come across have static friction ratings of .5 most commonly and with some changes that can get into the 1.x's but now where near my 6inH2O.

Does this mean if I use one of these AHU's with my system that I will not get the flow I need? I dont really understand the implications of the static pressure of the AHU. Is it strictly a "must supply more static pressure" than losses? Or is there another way to look at it that will mean my system could work afterall?

Thanks for any help,

Signed,
"GOTNOCLUE"

 

[SWISGR8]

I kind of hear you there, but I wasnt meaning equal "flow" but nearly equivelant losses. Again I'm a newbie here, so just saying my point from my understanding. I understand the field/real-world value of the dampers, but the balancing of losses makes sense to me in terms of the path of least resistance analogy. If something can go through a less resistant path, than it will do so until the optional paths all offer a relatively close level of resistance. And with respect to the design parameters, my understanding tells me that if you do not design to a balanced system then the numbers are really just arbitrary and the real system will not produce them without "fied" tweaking (which again I understand that is part of the whole game).

Please any and all correct my thought process if gone astray. Not challanging your point willard3, just trying to understand it.

Thanks for your help,
Mike

 

[willard3]

snip
I kind of hear you there, but I wasnt meaning equal "flow" but nearly equivelant losses.
snip

This is equal friction design and is the basis of the Trane and etc wheels.

There are always physical constraints for ductwork size and aspect ratio. Air has lousy specific heat and it takes lots of it in big pipes to heat or cool. Ventilation also takes high air volumes.

HVAC systems are contained within other structures and all systems compete for volume.

Given the above, it's not always possible to have equal friction ductwork and compromises are made. It's the Engineer's job to make sure it works.

 

[SWISGR8]

Gotchya ... thanks for all the patience and explanation

Appreciate it,
Mike