Basic Documentation
Table Of Contents
- About this Application Guide
- Chapter 1–Introduction
- Chapter 2–Goals of the Laboratory Environment
- Chapter 3–Unique Ventilation Needs of a Laboratory Facility
- Chapter 4–Ventilation Systems Classification
- Chapter 5–Laboratory Facility Exhaust Systems
- Chapter 6–Laboratory Containment Units - Ventilation
- Chapter 7–Room Ventilation, Makeup Air, and Pressurization Control Systems
- Chapter 8–Laboratory Temperature and Humidity Control Systems
- Chapter 9–Laboratory Emergencies - Ventilation System Response
- Chapter 10–Laboratory Ventilation System - Validation
- Chapter 11–Laboratory Ventilation System - Commissioning
- Glossary
- Index
Chapter 8–Laboratory Temperature and Humidity Control Systems
Variable Air Volume Room Temperature Control
When a room is served by a variable air volume system, the room controller has the
option of modulating the hot water flow through the reheat coil as well as increasing
the room supply airflow above that necessary to maintain the minimum required
room ventilation (ACH) rate. Although this arrangement provides greater control
flexibility, there are some instances when this type of temperature control
arrangement will not provide satisfactory results. In particular, this control
arrangement is not suitable for small chemical laboratory rooms (for example, two
person module type rooms) that can undergo large changes in the exhaust and
supply airflow due to VAV fume hood sash movements.
SUPPLY
TERMINAL
ROOM
CONTROLLER
FUME HOODS
EXHAUST
TEMP
ROOM
TEMPERATURE
SENSOR
REHEAT COIL
Figure 15. Basic Control Arrangement for Laboratory Room Temperature Control.
The problem can be best explained by considering a typical scenario of events. Let’s
consider the case of a two-person laboratory room height served by a VAV system.
Two-person labs are typically limited in size, frequently being about 12-feet wide, 25-
feet long and perhaps 9-feet in height. Assume this laboratory room is equipped with
a six-foot VAV chemical fume hood with a single vertical sash. Based upon good
laboratory ventilation practice, the room should always maintain a minimum
ventilation rate of 10 air changes per hour (ACH).
74 Siemens Building Technologies, Inc.