eQuest - Campus Steam

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I've inherited an energy model that was done over 3 years ago by someone no longer at our firm.
I'm an eQuest novice and have a question about a system that uses campus steam for heating.
The original model was set up with two gas fired boilers. (I see this in the Component Tree tab in the Water-Side HVAC section)
How do I tell eQuest that the heating is from a campus/purchased steam system so that it complies with ASHRAE 90.1-2004 item G3.1.1.1, Purchased Heat which requires the campus utility rate to be used?

Jim Paulino, P.E., CxA, LEED ? AP

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Hi Jim,

Just FYI if this is a LEED model you should check out the District Energy Modelling Requirements from the USGBC (http://www.usgbc.org/ShowFile.aspx?DocumentID=7671). By modelling as purchased steam you are limiting the number of EAc1 points available.

Cheers,
Dan

?
Daniel Knapp, PhD, LEED? AP O+M

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Hi Daniel,

Thanks for the reply on the LEED requirements. You confirm an issue with having a campus system in that it can limit the potential energy points, but that is another topic...

What I'm not familiar with is how to change the "on-site" boilers that were modeled with a campus steam supply (I have been given a cost per lb of steam by the university), a steam to water heat exchanger and pumps. If anyone can walk me through this or point me in the right direction, I would appreciate that.

Thanks for any help,

Jim

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You could just apply a steam meter.

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Under the Water-Side HVAC Tab, right-click the Project: ?xxx? at the top of your component tree, choose ?Steam Meter? and apply it to your Hot Water Loop. Then delete your boilers.

Brad Huff, EIT, LEED Green Associate, Mechanical Engineer

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Daniel, that is curious that purchased steam would limit the number of EACr.1 points. Is that in your theory or from something more concrete? Or does it relate to DES modeling? I had this issue with a cogeneration project that was inaccurately sized for the demand and resulted in (according to calcs) less efficient operation than the minimum required baseline. Unfortunately the project was unable to meet the prerequisites for energy performance.

Kevin

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Kevin,

You should read the DES modeling guidelines that Daniel referenced. There
are two options on how you choose to model the district utility system. If
you choose to model it as a simple purchased steam meter, then you are
limited to a maximum amount of points under EAc1. Conversely, if you choose
to model the entire steam plant from source to site, you have to show a
minimum of 6 points.

Refer to Table 1 on page 10 of the DES guidelines.

Robby Oylear, LEED AP

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Jim,

Remove the boilers, and apply a steam meter to the heating hot water loop under the ?plant? tab just like you would add any other piece of equipment.

The use of district energy does not necessarily limit the amount of points you can get, but district energy does add some caveats within LEED. Per Table 1 of ?Treatment of District of Campus Thermal Energy in LEED v2 and LEED 2009 ? Design and Construction? issued August 13, 2010; Option 1 limits you to 10 points for New Construction or Option 2 does not limit your maximum point score beyond the credit maximum.

Option 2 requires that you model the central plant, which can be very challenging if insufficient information is available. Also, Option 2 comes with a 6 point minimum per Table 1. In other words, your building has to achieve at least 6 points with your building and your plant to use Option 2. If it doesn?t achieve 6 points, you need to use Option 1.

Hope that makes sense.

Fred

Fred Betz PhD., LEED AP

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