Question-and-Answer Resource for the Building Energy Modeling Community
Get started with the Help page
Ask Your Question

Modeling Fans for LEED

asked 2015-06-17 06:44:04 -0600

hugopft gravatar image

updated 2015-07-10 13:46:14 -0600

I have been modeling a building to submit it to LEED certification and I have some issues Regarding to how to set Correctly fan parameters for the baseline model . I am aware que ASHRAE 90.1 provides a table regarding to BASELINE FAN MOTOR POWER, but I am not find the relation between them and the values ​​found in OpenStudio to configurate the fans. In OpenStudio we have as a fan input The Following items:


I would like to know which one of them I have to set, and where I can get the values ​​to set them correctly. I know, for instance, that TRACE 700 when is dealing with a BASELINE model of its own calculations. I do not need to set such parameters in there, only for the proposed model.

edit retag flag offensive close merge delete


@hugopft this may be a duplicate of this question. If so, I will close this one.

MatthewSteen gravatar imageMatthewSteen ( 2015-06-17 07:33:23 -0600 )edit

3 Answers

Sort by » oldest newest most voted

answered 2015-06-17 13:31:32 -0600

updated 2015-06-19 10:27:16 -0600

I built my spreadsheet based off the calculator below. It gives a good overview of how exactly to reverse engineer that fan power. Careful when switching between units.

Credit to the Integrated Design Lab (University of Idaho)


UPDATE: Not that this is really relevant to the original question (more so at the title of the question), but for any of those looking on how to complete the calculation for compliance modeling, GBCI's Table 1.4 spreadsheet >link< to track your inputs is a great tool to deconstruct for really understanding to how to model according to Appendix G of ASHRAE 90.1. Un-hide all the mechanical fan tabs and swim through all the references.

edit flag offensive delete link more


I really appreciate the answer. I am going throught it in the next weeks and all of this stuff will be very helpfull .

hugopft gravatar imagehugopft ( 2015-06-19 07:49:31 -0600 )edit

No problem. I also found this a big change coming from eQuest and Trace 700. After you distill that IDL tool down to the essential inputs and outputs, it actually becomes a much easier task to ensure compliance IMO.

nfonner gravatar imagenfonner ( 2015-06-19 10:30:39 -0600 )edit

I used the spreadsheet, @nfonner. For these inputs : 2.76 m³ / s, Fan efficiency of 0.7 , the motor efficiecy of 0.88 , an A = 0 ( Been conservative ) . Then , I am getting the delta pressure output of 1188.54 Pa . I checked the values ​​as suggested in the spredsheet , and everything is all right . But , thinking about real project, I know que about 600 Pa is a reasonable delta pressure to be considered, and I am thinking that this value for the baseline is to high. Did you guys get high values ​​like this one? Is it right?

hugopft gravatar imagehugopft ( 2015-07-03 09:47:17 -0600 )edit

All other inputs remaining unchanged, the Pressure Rise will decrease with more realistic Tot Fan Effs. I'm working on a project now ranging from 42.3% - 61.4%. (Packaged Rooftops - some CV and some VAV) While 70% is really quite high in my opinion, it is only a default that I choose to keep since I am not complying with Pressure Rise and Tot Fan Eff from an energy code point of view.

...and yes. I have a few in that 1200 Pa range. (PSZ-AC Sys 3 - 90.1 with ~ 2,398 cfm (1.13 m3/s), 70% Tot Fan Eff, 87.5% Mtr Eff. & a marginal increase (0.14 bhp) due to filtration credits.)

nfonner gravatar imagenfonner ( 2015-07-07 09:17:29 -0600 )edit

Hi @nfonner , just to be sure that I understood it right: this range of 42.3 % - 61.3 % is the Tot Fan Effs?

hugopft gravatar imagehugopft ( 2015-07-07 10:14:32 -0600 )edit

answered 2015-06-17 12:15:17 -0600

Hello. I am not sure but I think you have to calculate manually the fans for the baseline. After you have the power you have to do some reverse calculation to convert the kW to pressure. Power= Q x P.

edit flag offensive delete link more


I really appreciate the answer. I am going throught it in the next weeks and all of this stuff will be very helpfull .

hugopft gravatar imagehugopft ( 2015-06-19 07:49:18 -0600 )edit

answered 2017-11-03 10:33:32 -0600

fp0417 gravatar image

Hi thanks for sharing the link to that fanpower calculator. I have a question, It seems to work well to generate the system fan power but when it comes to the energyplus - enduse output the demand (kW) does not match the system fanpower calculated from 90.1. Is it supposed to match? I can see in the equipment outputs the fan-power matches the calculator but not in the enduse. any thoughts?

edit flag offensive delete link more

Your Answer

Please start posting anonymously - your entry will be published after you log in or create a new account.

Add Answer


Question Tools



Asked: 2015-06-17 06:44:04 -0600

Seen: 492 times

Last updated: Jun 19 '15