[Bldg-sim] System 1 vs System 3 Fan Power Consumption - ASHRAE 90.1 Appendix G

Ben Hollon bhollon at antella-inc.com
Thu Feb 6 06:35:36 PST 2014


Hi,



This question may have been discussed in length somewhere else but I was
not able to find it.



I am working on a mixed use dormitory. There is a restaurant, coffee shop
and university store/gift shop on the first few floors and private rooms
and suites on the upper floors. The building is DX cooling and gas heating.
Based on these conditions I have system 1 and system 3 for the baseline,
system one for the private rooms, system 3 for the other spaces.



Looking at section G3.1.2.9 in ASHRAE 90.1 there are two different
equations for fan power consumption. For systems 1 & 2, it's CFM * 0.3, for
systems 3-8, it's a slightly more complicated equation. However, after
performing the calculations I'm getting roughly CFM * 0.9. If I'm
interpreting this right it means that fan power consumption for systems 1 &
2 is 3 times less than that for systems 3-8.



It's not impossible that a split system, or system 1 type system, could be
installed in the other areas of the building, the mechanical contractor has
proposed as much for budgetary reasons. This would mean that the baseline
system could potentially use as much as 3 times as much energy as the
proposed system, and only because of the ASHRAE fan power consumption
equations.



Is there a reason why there is such a large difference between the two
equations? Or is my classification of the spaces and interpretation of the
equations off?



Thanks!



[image: cid:image003.png at 01CDAB78.6524ACE0]

*Ben Hollon, EIT, LEED*(R)* AP BD+C, MBA*

email:  bhollon at antella-inc.com <xxxxxx at antella-inc.com>

Cell (816) 536-3434 * Tele:  (816) 421-0950 ext. 104

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