[Bldg-rate] ASHRAE 90.1 - VAV Fan Part-Load Power Limitation

[Dan Russell]

My question regards Section 6.5.3.2.1 Part-Load Fan Power Limitation
from ASHRAE Standard 90.1-2004, which states:

 

6.5.3.2.1 Part-Load Fan Power Limitation. Individual

VAV fans with motors 15 hp and larger shall meet one of

the following:

(a) The fan shall be driven by a mechanical or electrical variable-

speed drive.

(b) The fan shall be a vane-axial fan with variable-pitch

blades.

(c) The fan shall have other controls and devices that will

result in fan motor demand of no more than 30% of

design wattage at 50% of design air volume when static

pressure setpoint equals one-third of the total design static

pressure, based on manufacturer's certified fan data.

 

I have a project that is using Fanwall technology in the air handlers
that serve the VAV system.  The air handler has 3 rows of 8 fans each of
them only 7.5 hp each (at total of 24 - 7.5 hp fans for a total of 180
hp).  When the Standard here says "Individual VAV fans..." is it saying
that for this type of air handler where no individual fan exceeds 15 hp
that part-load control is not required?  Certainly, if this is true,
using this technology would be great for demonstrating energy points
(aka LEED), but I'm having a hard time justifying this in my mind.

 

Does anyone know if this Section applies to "fanwall" technology or if
it is simply intended to make distinction between supply, return,
relief, and exhaust fans?

 

Thanks,

 

 Dan Russell, EIT 

 

 

 

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