Modeling Space with 2 Ventilation Sources

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Good Morning All,

I'm currently putting together and energy model of a hotel for LEED.  The guest rooms in the hotel receive ventilation air directly to the space through a rooftop MAU.  They also receive ventilation air via through-wall heat pump in each space.  I've got it set up now as a heat pump system with dedicated OA, however this isn't correct as the entire OA load is being handled by the MAU coil.  I've already tried to go through Trace for a solution to this, but they don't have one.  I was hoping someone here might have had to do this in the past.  Is there a proper workaround for this that someone may have had approved for LEED.

Any advice would be much appreciated!


Jason Dietterick

jdietterick's picture
Joined: 2013-04-23
Reputation: 0

The only way I have seen this done is by the same convention that you would do this in eQUEST. (use a dummy zone).

I'm guessing that one of the ventilation sources is 100% OA - so create a dummy zone (no walls, roofs, loads or anything) and just add the correct cfm of ventilation - then assign that dummy zone to the correct system. [you wouldn't be able to use the DOA option in TRACE, but instead of two systems: the heatpumps, and the MAU]
Of course, for LEED, you would need to keep the dummy zone in the baseline (so the reviewer doesn't get confused - because you have to have the same number of zones). However, in the baseline building, you would just assign the dummy zone to the same system as the actual zone.

I'm pretty sure that would be acceptable and work out thermodynamically (and is essentially how it is done in eQUEST).

Bob's picture
Joined: 2010-06-30
Reputation: 275