Hi all,

So, here's a scenario. Not the first time I've had to deal with this but I'd like to know if there's a better/alternative approach:

* A VAVS system serves hundreds of zones. Limited humidity control in this system accomplishes maintaining a minimum of 20% RH in the return airstream.

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* For a selection (minority) of zones under the large VAVS system, humidity is further controlled to a tighter band of 40-60% by localized electric humidification units (representative example: http://www.carnes.com/humidifiers.phtml).
* Because the VAVS runs 24/7, supplies mostly OA, and the spaces of concern have relatively light occupancy profiles being the only substantive contributor to moisture in the space, the RH measured in the field for these select spaces is determined primarily as a function of the air supplied by the VAVS system.

How should one go about accurately simulating the energies associated with localized humidification equipment?

I cannot simply add the more stringent humidity range of 40-60 to the central unit - this results in way more humidification and active dehumidification than is actually happening./

Presently, I'm making a copy of the VAVS, assigning only those critical spaces to the copy, and applying the following system level humidification inputs to the (smaller) copied system only:
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The main perceived problem with this approach is that the separate SYSTEM will not during the simulation observe the actual RH conditions caused by the larger (actual) VAVS system, which is determined as a combination of effects due to OA conditions, RA conditions, and active humidification at the central unit.

Secondary problems (seemingly easier to address) include:

* Ensuring the (smaller) copied system is not over/undersized in airflow/coil capacities
* Introducing the effects of the localized active humidification/dehumidification on the RA stream of the main unit requires transposing "free" latent loads to other zones

... Is there a better way to skin this cat? Can localized humidification equipment be more explicitly included in our doe2/eQuest simulations? Also interested to learn of any 3rd party tools or spreadsheet based calculations others are used to performing for such situations.

Thanks in advance!

~Nick

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Nick Caton, P.E., BEMP
Senior Energy Engineer
Regional Energy Engineering Manager
Energy and Sustainability Services
Schneider Electric

D 913.564.6361
M 785.410.3317
F 913.564.6380
E nicholas.caton at schneider-electric.com

15200 Santa Fe Trail Drive
Suite 204
Lenexa, KS 66219
United States

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