RE: [EnergyPlus_Support] No heating occured when VAV with reheat is used

When you are using EPlus for simulation, you need to know what you are going to simulate as found in your real operating system.

So far you have not really descibed your system. Chiller and boiler are water plant system. Do you really have that with your roof top VAV system?

In your .csv file you did not display the OD temperature, the VAV duct temperature, the zone set point temperature, the damper position, the reheat heater flow rate.

It is very diffucult to verify the conditions of simulation using the following result.

THERMAL ZONE 19:Zone Mean Air Temperature [C](Hourly)

THERMAL ZONE 19:Zone Air Relative Humidity [%](Hourly)

CHILLER ELECTRIC EIR 1:Chiller Electric Consumption [J](Hourly)

BOILER HOT WATER 1:Boiler Heating Output Energy [J](Hourly)

NODE 51:System Node MassFlowRate[kg/s](Hourly)

Your csv showed that the boiler did not come on until February in the annual simulation.

You may have errors in your schedules.

The output from the IDF is different from the above, and do not have the boiler. Because the name of the zones and nodes are all in numbers, it is difficult to tell where they are.

Only two DesignDay objects are required for sizing simulation. One for Winter (99.6%) and one for SUmmer (0.4%). The others are for diferrent optins, and down sizing, to 1% and 2% data range exclusions.

For your questions:

Wen the damper is set to zero, the minimum value is zero and therefore no reheat air flow. Try closing to 0.01 instead. It is not a desirable setting, but may turn on the reheat heater.

The boiler is not controlled by the zone thermostat or damper position. You may have schedule errors, as I do not recognize some of the setpoint manager usauage in you IDF.

You are confused, because you have not match the simulation objects to your real system, and did not display the correct variable output data.

There were 51 warnings on the Design Day simulation run. The err file is attached.

Dr. Li

To: EnergyPlus_Support@xxxxxxxxxxxxxxx
From: wanghaojie630@xxxxxxxxx
Date: Thu, 1 Nov 2012 17:43:26 -0400
Subject: [EnergyPlus_Support] No heating occured when VAV with reheat is used

Hi all,

I use packaged rooftop VAV with reheat for my system. Since I need to
use natural ventilation for sometime, I set the zone minimum air flow
rate at AirTerminal:SingleDuct:VAV:Reheat to be zero to make sure no
mechanical cooling is used when natural ventilation can satisfy the
cooling load. However, by making this number to zero, the boiler stops
working even when the zone air temperature is below the heating setpoint
temperature. But when I change zero to 0.3, heating will work normally.
I am quite confused about this output, and would appreciate your help.
I also attached my idf file and spreadsheet here.

Thanks,

HJ

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