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VAV Thermal Comfort Issues

VAV Thermal Comfort Issues

VAV Thermal Comfort Issues

Hey All,

I'm troubleshooting an existing building where I have some internal and external zones where occupants are constantly complaining about being too cold. All Internal zones are fan powered boxes with no reheat, all external zones are fan powered boxes with hot water reheat. What are my options for increasing occupant comfort. The internal zones are more of a concern because I'm pretty limited in what I can do. Boxes are already set to minimum ventilation primary air so this cannot be reduced any further. Any troubleshooting tips would be helpful.

RE: VAV Thermal Comfort Issues

can you adjust the supply air temperature up without affecting the ability to dehumidify?

RE: VAV Thermal Comfort Issues

Are the fan-powered boxes parallel or series?
where do they draw air from? You maybe able to reduce the minimum flow setting. Most designs I 've seen don't calculate min. flow, they always use 30%. Obviously just using a rule of thumb is not good design.

In conference rooms you can use CO2 sensors to re-set minimum airflow. In most offices you can use motion sensors to reduce minimum flow to 0. All these will limit the amount of cold air going into spaces with little internal heat gain.

And implement discharge air temperature reset at AHU.

RE: VAV Thermal Comfort Issues

You can add reheat coils to the interior zones and/or reset air temperature.

RE: VAV Thermal Comfort Issues

A heat load simulation for the day in question will help eliminate the possibility of over-design in interior zones.How is the off- coil temperature at the AHU controlled?How is the ventilation air treated?

RE: VAV Thermal Comfort Issues

Had the same issue in our property.
First we adjusted the air supply temp, but being located in a sub-tropical climate, it had a very detrimental effect on the humidity levels inside the property.
The we had to go with dehumidification cycles, which improved immensely the overall confort levels.
This strategy doesn't come cheap though because our electricity bills ramp up pretty fast.

RE: VAV Thermal Comfort Issues

Can you find any pattern on how spaces in which occupant complain differ from others or how they are different from others?

RE: VAV Thermal Comfort Issues

Check also placement of each box temperature sensor. Make sure each is not over a heat producing appliance or the sun. Ideal position would be near return air intake.

RE: VAV Thermal Comfort Issues

It is not just temperature that causes complaints. Drafts are another important factor and everyone will perceive these differently.

RE: VAV Thermal Comfort Issues

Champchops, Are you still there? I think EnergyProfessional's question is the most important to helping you remedy the situation. Series or parallel boxes on the interior zones? If parallel, the solution may be simple.

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