RE: [EnergyPlus_Support] Help with VAV to Constant Air Volume

To do the VAV conversion i converted Zone HVAC Air Loop Terminal Units to Constant Volume,

With VAV, the reheat does not come on until the damper is at the minimum. Do you still have reheat?

Fans to constant volume,

If you do not change the Ref.Node temperature and still running it below the zone termperature requirement, the zone reheat may be on all the time.

removed the damper.

When the damper is removed, it is replaced with a fixed one, which divide the AHU air according to your setting. The zone air volume is no longer zone load dependent. When the zone load is increased, the reheat is reduced, if the reheat is running.

My file is running without errors.

This is not a coding problem. It is a design problem. The file you have posted is still in VAV mode, I think. VAV usually does not reduce overall enerage usage, because the power used for the control equipment (VSD, sensors and drivers) are not included.

The main reason for the heavy energy usage is the low supply temperature and the use of reheat. The AHU is probably running all the time in Summer, because the ref node temperature is set below the OD temperature.

Dr. Li

To: EnergyPlus_Support@xxxxxxxxxxxxxxx
From: energyplus.1984@xxxxxxxxx
Date: Fri, 18 Nov 2011 15:15:02 +0000
Subject: [EnergyPlus_Support] Help with VAV to Constant Air Volume

Hi,

I converted my Variable Air Volume file to Constant Air Volume and my heating consumption has increased by almost 6 times. The weather file used is Chicago. What are the possible reasons that would lead to such a change?

To do the VAV conversion i converted Zone HVAC Air Loop Terminal Units to Constant Volume, Fans to constant volume, removed the damper. My file is running without errors.

Is my method of making it Constant Volume ok? Any help is appreciated.

Thanks,

J

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