8
Parallel
Fan-Powered
VAV-SLM005-EN CONFIDENTIAL DOCUMENT. FOR INTERAL USE ONLY.
Feature
Evaluation
Hanger Brackets/Air Filter/Filter Frame/Fan Disconnect
Trane provides hanger brackets, air filter, filter frame, and a fan disconnect as
standard. When Trane is in control of the specifications, make sure that we are making
our competition provide these options in their bill of materials!
Metal Encapsulated Edges
All VariTrane units are complete with metal encapsulated insulation edges. This
encapsulated design arrests cut fibers and prevents erosion of the fibers into the
airstream. As a standard, our competition “butters” the edges of the exposed
insulation with an adhesive spray intended to hold the fibers together. After being
handled, and over time, the adhesive breaks down and allows fibers to escape into the
airstream. Edge spray is clearly not equivalent! Specifying VariTrane metal
encapsulated edges will force the competition to add additional dollars to their units.
Whether or not Trane is basis of design, make sure the consultant understands the
significance of metal encapsulated edges.
Suggested Spec
I
NSULATION EDGE TREATMENT—All cut edges of insulation shall completely en-
closed by metal to arrest cut fibers and prevent erosion into the airstream.
Number of Measuring Points on our Flow Ring (How low can
you go?)
The accuracy of a flow-measuring device is determined by the lowest allowable
minimum cfm setting. Below this cfm, the VAV units will change from pressure-
independent (PI) to pressure-dependent (PD) control. Because VariTrane units are
designed to integrate into a DDC control system the UCM, flow ring, and pressure
transducer create a flow measurement “system” which provides unmatched flow
performance in the VAV industry. Accuracy is +/- 5% from maximum to minimum
cfm.
See pp. 11 for a comparison of Trane vs. the competition.
Given:
A consultant is designing a space that requires 800 cfm maximum airflow. Ventilation
is determined by minimum occupancy = 8 persons. 15 cfm/person equates to 120
minimum cfm.
Using the VariTrane Quick Select (VAV-SLP001-EN), the consultant chooses an
8” inlet.
The 8" VariTrane air valve can have a minimum set as low as 110 cfm. Thus, the
120 cfm minimum is available. Competitor “N” has a minimum that stops at
150 cfm and can be no lower. Let’s look at the system/cost impact:
Find:
The efficiency impact by having a higher minimum cfm setting.
Assume:
Unit operates for 3000 hours per year
Unit is providing reheat 50% of the time.
Room setpoint (winter) = 70°F
Supply Air = 55°F
Solution:
When in reheat, the VAV unit operates at its minimum airflow. VAV systems typically
have 55°F primary air temperature. Let’s see how this 30 cfm can impact operating
costs:
Qs = 1.085 x cfm x DT
The additional energy required by competitor “N” is
1.085 x 30 cfm x (70 – 55) = 488 Btuh
This equates to 732,375 Btu per year, per 8” valve, which is an increase of 25% in
energy required to reheat the air up to room temperature.
