Francesco,
Comments interspersed below
James V Dirkes II, PE, BEMP, LEED AP
The Building Performance Team Inc
1631 Acacia Drive, Grand Rapids, MI 49504
616 450 8653
From: EnergyPlus_Support@xxxxxxxxxxxxxxx [mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx] On Behalf Of FrancescoP
Sent: Thursday, August 16, 2012 8:49 AM
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
Subject: [EnergyPlus_Support] Sizing according to ASHRAE 90.1
I have some doubts concerning the sizing of baseline equipment according to APPENDIX G of ASHRAE 90.1.
1) Paragraph G3.1.2.8 of ASHRAE 90.1 states: "System design supply airflow rates for the baseline buildings design shall be based on a supply-air-to-room-air temperature difference of 11°C". I interpret that statement in the following way: if the internal set-point temperature during the winter season is Twin then system design supply airflow rates have to be calculated considering a design supply airflow temperature of Twin + 11°C and if the internal set-point temperature during the summer season is Tsum then system design supply airflow rates have to be calculated considering a design supply airflow temperature of Tsum - 11°C. Is my interpretation correct?
This is correct.
Does the procedure of paragraph G3.1.2.8 of ASHRAE 90.1 regard only the sizing run or even the simulation with the test reference year?
The HVAC system of the baseline is "Packaged VAV with reheat".
E+ performs sizing coincident with simulation. If you elect to make a separate “sizing” run, the same criteria, including “Autosize”, must be used for both.
In EnergyPlus can I satisfy the request of paragraph G3.1.2.8 using Controller:WaterCoil?
This object does not affect sizing at all. The criteria that E+ uses are contained in the Sizing:System and Sizing:Zone objects.
2) In order to calculate the baseline fan motor power I have to calculate the parameter A according to tables 6.5.3.1.1A and 6.5.3.1.1B. Shall I model "fully ducted return and/or exhaust air systems" for every return or relief fan? In the IP edition it is specified that the adjustment is valid only for WCs, but that specification is not present in the SI edition. I don't understand why.
The Baseline model must use the power adjustments consistent with the Proposed model. E.g., if the Proposed model is fully ducted, the Baseline fan power should include that adjustment.
p.s., I am guessing that “WC” is a “water closet”, but I am not sure ….
Shall I consider a pressure drop adjustment equal to
125 Pa (0.5 in IP units)
for every "fully ducted return and/or exhaust air system" (see table 6.5.3.1.1B)?
If on one floor there are three WCs where there is a mechanical extraction system. In the baseline model I modelled those WCs as connected to a AHU having both supply and exhaust fans. Shall I consider a total pressure drop adjustment equal to 375 Pa (= 3 x 125 Pa)?
The rooms which have mechanical extract systems should be modeled as having a Fan:ZoneExhaust. The pressure adjustments do not normally apply to these. (A pressure adjustment would apply to something like a laboratory extract system which has mechanized dampers for flow control.)
With Regards
Francesco Passerini
__._,_.___
Primary EnergyPlus support is found at:
http://energyplus.helpserve.com or send a message to energyplus-support@xxxxxxxx
The primary EnergyPlus web site is found at:
http://www.energyplus.gov
The group web site is:
http://groups.yahoo.com/group/EnergyPlus_Support/
Attachments are currently allowed but be mindful that not everyone has a high speed connection. Limit attachments to small files.
EnergyPlus Documentation is searchable. Open EPlusMainMenu.pdf under the Documentation link and press the "search" button.
Change settings via the Web (Yahoo! ID required)
Change settings via email: Switch delivery to Daily Digest | Switch to Fully Featured
Visit Your Group | Yahoo! Groups Terms of Use | Unsubscribe
__,_._,___