Re: [EnergyPlus_Support] AirLoopHVAC has no air flow workaround?

Good point (about unmet loads).

What does â??indirectly conditionedâ?? mean? If there is some type of zone air conditioning, you will not have unmet loads.

Thinking about other modeling strategies:

Â· How about specifying a DX or heat pump system with COP = 10,000 and Delta pressure rise = 0? (E+ will accept these values; I have used them.) Approximately zero energy will result, but you will sacrifice correct heat transfer through walls which adjoin conditioned zones.

Â· What if you specify a specific airflow rate in Sizing:System and also make the coils unavailable during normal operations? (I think sizing and operation are calculated separately.)

Â· Let the unmet loads occur, report the hours which occur in the unconditioned zones, deduct those from the total and let the GBCI people know what you did in a narrative which explains it.

Â· If those donâ??t work, you could model the zones with heating and cooling, report the energy using a Meter:Custom and deduct that energy from the totals.

Â· When you figure this out or someone else offers a proven solution, let me know!

James V Dirkes II, PE, BEMP, LEED AP
www.buildingperformanceteam.com
Energy Analysis, Commissioning & Training Services
1631 Acacia Drive, Grand Rapids, MI 49504 USA
616 450 8653

From: EnergyPlus_Support@xxxxxxxxxxxxxxx [mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx] On Behalf Of Miroslav Bratanov
Sent: Thursday, December 06, 2012 8:21 AM
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
Subject: Re: [EnergyPlus_Support] AirLoopHVAC has no air flow workaround?

Hello James,

All the zones connected to this air loop have no loads. They are all indirectly conditioned.
I think that if I use normal setpoints with always off availability, it will result in hours with unmet setpoints.

On 6.12.2012 01:39, Jim Dirkes wrote:

Miroslav,
Iâ??m guessing that this is the only air loop? I have modeled other buildings wheere one or another zone had zero load, but always at least one zone had load ? with no fatal errors.
How about using normal setpoints and making the availability always OFF?

James V Dirkes II, PE, BEMP, LEED AP
www.buildingperformanceteam.com
Energy Analysis, Commissioning & Training Services
1631 Acacia Drive, Grand Rapids, MI 49504 USA
616 450 8653

From: EnergyPlus_Support@xxxxxxxxxxxxxxx [mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx] On Behalf Of Miroslav Bratanov
Sent: Wednesday, December 05, 2012 5:15 PM
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
Subject: Re: [EnergyPlus_Support] AirLoopHVAC has no air flow workaround?

James,
The program stops before the actual simulation. This is the full message from the .err file.

   ** Severe ** AirLoopHVAC AHU-RHT_BL has no air flow
   **   ~~~   ** Check flow rate inputs for components in this air loop and,
   **   ~~~   ** if autosized, check Sizing:Zone and Sizing:System objects and related inputs.
   ** Fatal ** Previous condition causes termination.
   ...Summary of Errors that led to program termination:
   ..... Reference severe error count=1
   ..... Last severe error=AirLoopHVAC AHU-RHT_BL has no air flow
   ************* Warning: Node connection errors not checked - most system input has not been read (see previous warning).
   ************* Fatal error -- final processing. Program exited before simulations began. See previous error messages.

On 6.12.2012 00:04, Jim Dirkes wrote:

Ignore the â??errorâ??. It does not prevent the simulation from running and, as you said, indicates a correct and proper condition.
E+ is just letting you know about an unusual condition.

James V Dirkes II, PE, BEMP, LEED AP
www.buildingperformanceteam.com
Energy Analysis, Commissioning & Training Services
1631 Acacia Drive, Grand Rapids, MI 49504 USA
616 450 8653

From: EnergyPlus_Support@xxxxxxxxxxxxxxx [mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx] On Behalf Of Miroslav Bratanov
Sent: Wednesday, December 05, 2012 4:46 PM
To: EnergyPlus Support
Subject: [EnergyPlus_Support] AirLoopHVAC has no air flow workaround?

Hello all,

I have a building with some indirectly conditioned spaces and I am
modeling a system (PVAV with reheat) just to satisfy the requirement of
Appendix G that all conditioned spaces should be simulated as both
heated and cooled. I set higher and lower setpoint temperatures for the
heating and cooling respectfully, so the system would never turn on. But
during the simulation I get a severe error which says that AirLoopHVAC
has no air flow. Of course this is absolutely correct since there are no
any loads.
I wonder if anyone has had such case and what's the way to deal with
this problem?

Any help is highly appreciated!

Thank you!
Miroslav