There are more and more companies making fan coil units with VFD motors, automatic variable supply air control rather than traditional 3-speed control, which gives them variable air volume capability similar to the typical VAV system (VAV box/terminal unit). So can variable speed FCUs be treated as VAV systems in the energy model?
Under 90.1, our system should be compared with System 8 VAV with PFP box, but I think it would be unfair to us if we just model it as a constant volume system.
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5906 thumbs up
November 15, 2011 - 9:58 am
Not sure I understand the question. Model the Proposed as designed and the Baseline according to Appendix G. The Appendix G Baseline system does not change based on the details of the Proposed system.
James Chueh
93 thumbs up
November 15, 2011 - 9:58 pm
Well, What I meant is can we call these "variable speed FCUs" a VAV system then?
Because normally when you say VAV it means constant SA air temp fitted with "VAV box", not a hydronic system such as FCUs.........
James Chueh
93 thumbs up
November 15, 2011 - 10:19 pm
Normally you would treat FCU as a constant speed CAV system, and it would be disadvantageous to us if this is compared to, in the case of our baseline, a VAV system in the energy model.
So I need to know if we can call our proposed system as a VAV system.
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5906 thumbs up
November 16, 2011 - 8:59 am
You should model what you have designed in the proposed. How you model it depends on the simulation program. They are all different. In general you cannot model a FCU as a VAV as there tend to be significant differences between the two.
Sounds like you are asking if modeling the variable FCU as a VAV would be an acceptable workaround in the software you are using. If that is correct I would suggest you post your question on one of the simulation software discussion groups at onebuilding.org.