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Re: [EnergyPlus_Support] Re: unit ventilator woes
What is the zone return node flow rate compared to the zone supply node
and zone exhaust node flow rates? If there is any flow rate on the zone
return node, and you are bringing in 100% OA, then the relief air node
flow rate will equal the zone return node flow rate (for 1 zone models,
for multiple zone you will have to add up all the return node flow rates).
If your zone exhaust fan has a larger flow rate than the zone supply
node flow rate, then the return node flow rate will be zero and the zone
will be negatively pressurized, and you will see the warnings.
Report out all 3 zone nodes, Return, Supply, and Exhaust. Also report
out the outside air node and relief air node flow rates.
If (Zone Supply - Zone Exhaust) flow rate is <= 0 and the Zone Return
node flow rate is > 0, upload your file to the _Problem_Submittals
folder in the files area.
http://tech.groups.yahoo.com/group/EnergyPlus_Support/files/_Problem_Submittals/
and I'll check for a bug.
Here's the point, if you do see an outside air system relief air flow
rate (when you think you shouldn't) and it is equal to the zone supply
air flow rate. then just put in the zone exhaust fan at the same flow
rate and let E+ calculate the power for you. The extra exhaust flow
leaving the outside air system's relief node will not affect the heat
balance calculations. Even if E+ thinks the zone is at negative
pressure, the simulation will not add infiltration to compensate.
Josh K wrote:
>
> Hi Richard;
>
> Thanks for the reply. It's good to know that I can ignore the error,
> but it
> seems like this could possibly be a bug in the software. When a UNIT
> VENTILATOR is drawing 100% outside air, it doesn't seem like the zone
> exhaust node that it is connected to should be showing any flow...
>
> Also, I had a second issue that remains a problem: that of the UNIT
> VENTILATOR not running in a COOLING/NO COIL/FIXED AMOUNT scenario.
> Specifically: my UNIT VENTILATOR uses an outside air control type of FIXED
> AMOUNT, and has only a heating coil and no cooling coil. On the summer
> design day, when there is no heating load, the UNIT VENTILATOR in my model
> isn't turning on when its component availability schedule is > 0 as the
> documentation suggests that it should be. Can you think of a reason
> why this
> is happening?
>
> Thanks a lot for your help,
>
> Josh
>
--
Richard A. Raustad
Senior Research Engineer
Florida Solar Energy Center
University of Central Florida
1679 Clearlake Road
Cocoa, FL 32922-5703
Phone: (321) 638-1454
Fax: (321) 638-1439 or 1010
Visit our web site at: http://www.fsec.ucf.edu
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