[bldg-sim] DOE2.2-How to link two different systems to the same thermal zone?

[Mike Tillou]

I think Justins approach is the way to go in this situation.  DOE 2.2 can't model what you want to do exactly so you have to get creative.  Just remember to calibrate the model carefully and be sure the results match what you see in the field.

The newest version of equest, v3.54, has changed how the OA-FROM-SYSTEM keyword works so that OA flowrates can be based on hourly zone requirements (variable OA) rather than simply providing a fixed volume of OA.

As far as determining how to model the fan coils, try doing some data logging to create a load profile of when and how the various FC operate.  If there is a central elec panel that all the fan coils  are served from you could monitor how the load on the panel changes throughout the day.  That should give you a good indication of the percentage of fans that run at any given time.    
  

Good luck,

Mike Tillou, PE
etc Group, Inc


-----Original Message-----
From: postman at gard.com [mailto:postman at gard.com] On Behalf Of Justin Harrell
Sent: Monday, March 28, 2005 11:02 AM
To: bldg-sim at gard.com
Cc: pedromanuelrc at yahoo.es
Subject: [bldg-sim] DOE2.2-How to link two different systems to the same thermal zone?


I have recently modeled (in eQUEST) a building with a similar situation in which laboratory zones with fume hood exhaust had a central make-up air system in addition to multiple water-loop heat pump units.  The make-up air was 100% OA and conditioned to a neutral temperature by a chilled water coil and gas furnace.  In order to simulate this I created a dummy zone, maintained at 75F supplied by the make-up air system.  The laboratory zones were specified with their own water-loop heat pumps and zone thermostats.  In the WLHP systems I specified OA-FROM-SYSTEM to come from the make-up air system with a fixed CFM because the make-up air had a constant volume supply.  This forced the WLHPs to have their fans ON at all times, so I moved the WLHP fan energy into the cooling and heating EIRs so that the fans could run for free for the OA.  In the real building, the WLHP fans run only when the compressor is running. This may not have been the best solution, but it gave pretty good results.

Perhaps you could do something similar by moving the reheat coil energy either into the central system, or into the FC systems, and using the OA-FROM-SYSTEM keyword.  As far as I know, there is no way to simulate this situation directly.  The best work-around will depend on how your systems are controlled and what ECMs you want to simulate.

Justin Harrell
Southern Illinois University Carbondale

---------Included Message----------
>Date: 28-Mar-2005 05:48:25 -0600
>From: "Pedro Rodrigo" <pedromanuelrc at yahoo.es>
>Reply-To: <pedromanuelrc at yahoo.es>
>To: <bldg-sim at gard.com>
>Subject: [bldg-sim] DOE2.2-How to link two different systems to the 
>same thermal zone?
>
>Hello all!
>I belong to a team of researchers in the University of
>Jaen, Spain. It would be very useful for us if you
>could
>tell us your opinion about a little DOE2-related
>question.
>We are simulating a real (yet existing) multi-zone
>building in eQuest. The problem is that we have two
>kinds of terminal units operating together in each
>zone: i) a two-pipe air handler unit (with outside air
>dampers) and ii) several two-pipe fan-coils. The AHU
>provides a primary flow of 21ºC set conditioned air.
>Users in different rooms served by the same AHU,
>operate on/off and set room temperature via the
>individual fan-coils.
>We have realized that it´s not possible to link two
>different systems (i.e. SZR + FC) to the same thermal
>zone in DOE2 (only one is allowed). How could we model
>this building without increasing too much the number
>of thermal zones? And how could we schedule the
>operation of the individual fancoils, for example
>20%-On, 40%-On, 60$-On,...? (We have up to 50 fan-coil
>units working together with a single AHU).
>Thanks in advance,
>Regards,
>Pedro Rodrigo
>University of Jaen
>
>
>		
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