Multi-Story Office Buildings - Air Source

Air Sourced Design 

If you are working with an Air source design and you have RTUs with single thermostats and no VAV, please check out the Single Story Office Article as the concepts will be the same.

Thinking of an air sourced design you will be thinking of an AHU, VAV boxes, reheats, and potentially boilers for the reheats. 

Read about the importance of the CCU here

Air Handling Unit (AHU)

There are a few different AHU design types to consider:

1. Staged conditioning 
2. Fully modulating conditioning
3. Staged conditioning with a VFD 

Regardless of which type of control you have, 75F has a solution. The next question would be whether the AHU has any sort of economizer. If it has an economizer an OAO will be necessary. 

Variable Air Volume (VAV) box

Multi-story office buildings often use a single AHU to serve multiple zones with varying loads. To counteract this VAV boxes are introduced to help redirect air to where it is needed or reduce the airflow for a reheat call. 

The VAVs often come equipped with one of two types of reheat:

1. Electric
2. Modulating (Hot Water)

No matter what the control type, the VAV w/ Reheat Application will be able to control. 

Boilers

For an office building where there are water source reheats a modulating analog valve can be used to modulate the flow of hot water through the reheats. In this application it is typical for the boilers to internally control the loop temperature at ~140F. When this is the case, in a 75F implementation all we would add is a temperature monitoring device to monitor and alert on loop temperature.