RE: [EnergyPlus_Support] Problem with results of a simulation

Richard,

Can you have a look whether you can modify the CBVAV to work with a variable fan. I find that the problem user are having with VAV without reheat is that the variable fan without a bypass of the return air to the OA mixer cannot keep the reference node temperature steady while the fan speed is waiting for the zone damper to move.

Without increase the fan flow volume the return air cannot be cooled to the reference node set point temperature.   With the bypass path, the return air can be recycled through the cooling coil and be cooled independent of the zone air flow rate.
=======================
Setting the reference temperature at the zone setpoint temperature would drive all the dampers to fully open.   Setting the reference lower, would over cool. Without the reheat, the zone thormstat must be set to zero as minimum. Then the zone temperature will just float to the low set point temperature. When all the zones are below the zone setpoint, then the cooling is shut off.

I am still experimenting with different conditions, because I do not know how the program is coded. I am trying to observe the system node conditions with different external and internal load level to find the program algorithm.

Dr. Li

To: EnergyPlus_Support@xxxxxxxxxxxxxxx
From: RRaustad@xxxxxxxxxxxx
Date: Thu, 10 Nov 2011 10:50:07 -0500
Subject: Re: [EnergyPlus_Support] Problem with results of a simulation

You are seeing the energy required to pull the zone temperature from setback to setup temp. The ideal loads air system provides the energy instantaneously. This is why you see the heating peaks. Increase the setback temperature in heating mode to reduce the peak. In V7, the ideal loads air system will have a maximum cooling/heating capacity input to better model correctly sized systems.

On 11/10/2011 9:34 AM, Ignacio wrote:

Hi,
I'm having some strange results from a simulation in Energy+.
The building is composed by 2 zones,each one of 50X15(m)and a height of 5 meters.
//////////////////
/ / /
/ / /
/ 750m2 / 750m2 /
/ / /
/ / /
//////////////////
The results of "Ideal Loads Air Heating Rate" are very high,the peak is almost 750000W for each zone.The peak value occurs at 6:00am when the thermostat change the temperature target.(Almost all the days I have this peak).
The results of "Ideal Loads Air Cooling Rate" are normal, the peak is near 25000W for each zone.
I can send the files if someone needs it to help me.
Thanks
P.S.:The simulation is for Malaga(Spain)

-- 
Richard A. Raustad
Senior Research Engineer
Florida Solar Energy Center
University of Central Florida
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