Re: [EnergyPlus_Support] one about vav system

["Michael J. Witte" <mjwitte@xxxxxxxx>]

This behavior indicates the coil is not large enough.  Suggestions:

1.  Make sure the OA flow rate and the supply air temperatures in teh ZONE 
SIZING and SYSTEM SIZING objects are consistent with the simulation OA flow and 
temperature setpoints.

2.  Use COIL:Water:DetailedFlatCooling, do not use COIL:Water:SimpleCooling.

If this does not fix the problem, please upload the input file to the files 
area in the Yahoo group or e-mail zipped idf to energyplus-support@xxxxxxxx.

Mike


On 24 Jun 2004, at 16:24, Xu H.T wrote:

>   Like the following email.
> 
>   I do a simulation for VAV system. The design day is used for sizing of zone,
>   system and plant. I set the supply air temperature to 19C. I find with the
>   design day simulation, the supply air temperature isn't 19 (20.5 actually) and
>   the air flowrate is constant. However, for the run period simulation, the
>   supply air temperature is actually 19 and the supply air flowrate is also
>   constant. Why? Any suggestion for this problem. Thanks.
> 
>   Xu 
> 
>   ----- Original Message ----- 
>     From: zhaicq98 
>     To: EnergyPlus_Support@xxxxxxxxxxxxxxx 
>     Sent: Thursday, June 24, 2004 8:51 AM
>     Subject: [EnergyPlus_Support] questions about dx vav system
> 
> 
>     I have two questions here.
> 
>     First, I am simulating a VAV system with no terminal reheat. I 
>     specify the supply air temperature to be 12.8oC in cooling season and 
>     35oC in heating season. According to results I got, it works well in 
>     cooling season, trying to keep the indoor temperature under 23oC by 
>     varing the supply air flow rate. While in winter, it keeps heating 
>     the space to a high temperature. In heating season, the supply air 
>     flow rate is always at its maximum value. I can not understand why 
>     the supply air flow rate in heating season does not vary.
> 
>     Second question is about the iteration. I am using a multispeed DX 
>     coil. The program terminates when simulating the system in May. There 
>     is a fatal error which says the iteration limit is exceeded when 
>     calculating the speed of the compressor. I have no idea how to 
>     resolve the problem.
> 
>     I have uploaded the file named BOX4_VAV.idf to the files area.
> 
>     Thanks.
> 
> 
> 
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========================================================
Michael J. Witte, GARD Analytics, Inc.
EnergyPlus Testing and Support      
EnergyPlus-Support@xxxxxxxx



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