UC Los Angeles Campus & Medical Center Strategic Energy Plan ...

The project involves installing DDC dampers on outside air intake, return air and exhaust air to
control percentage of outside air and return air in supply air to vary according to the load and
outside conditions. In addition, a retrofit kit (damper actuator, flow measuring station, outside air
temperature and humidity monitoring station, mixed air temperature sensor) is installed on each
of the air handler. This kit includes direct digital controls, which increases the cost but greatly
increases the functionality. Enthalpy changeover control strategy will be adapted to use outside
air in the most economical way without use of energy required to dehumidify additional outside
air. Enthalpy is a measure of the total heat in the air, which is calculated by measuring both the
dry bulb temperature and the relative humidity. Outside air will be used for cooling when the
enthalpy of outside air is lower than the enthalpy of return air. Outside air and return air
dampers are modulated to admit enough outside air to minimize cooling energy use. When
outside air enthalpy is greater than the return air enthalpy, minimum outside air required for
ventilation is brought into the space.
8.2.10 Laboratory Air Handler Project 1. Convert Laboratory Air Handlers and Fume Hoods to
Variable Air Volume
The intention of this project is to convert laboratories to variable air volume systems and reduce
the large outside air heating, cooling and fan power loads. Many existing labs are constant
volume reheat systems, with a fixed air flow coming from the air handlers being reheated at the
laboratory and exhausted through the constant volume hoods or room general exhaust. Most
new laboratories utilize VAV air handlers and fume hoods. The intention of this project is to
update the configuration of the existing labs so that they can operate as efficiently as the new
labs. The UC EH&S Laboratory Safety Design Guide Second Edition September 2007 states
“All laboratories should contain a fully integrated laboratory variable air volume (VAV)
airflow/pressure control system to control room temperature, ventilation rate and room
pressurization.”
This project starts with a review of the air balance requirements of the facility. The air flow
needs of each room are determined according to the function of the room, the number of hoods
and the internal and external heat loads. This air balance may be significantly reduced from the
existing design because of better understanding of actual loads or better design parameters.
The minimum air changes typically needed in a laboratory are 6 air changes per hour for a room
with a 10 foot ceiling, per the EH&S Design Guide. A given lab may need higher minimums,
depending upon the density of hoods.
The mechanical work includes converting the air handlers to VAV with the addition of VFDs to
the supply fans. This may be appropriate for the exhaust fans as well, depending upon how
they are ducted together. The hoods are converted to variable flow through the addition of an
exhaust flow control valve and the sealing off of the sash bypass. If there are a small number of
hoods in a larger room, these do not need to be converted to VAV, where the general exhaust
requirements for the room are great enough that it makes no difference whether the air leaves
through the hood or the general exhaust duct. The room supply air and general exhaust
typically require new flow control valves or dampers as well to allow pressure control of each
room. The exhaust fans may need stepping control and/or VFDs to maintain proper exhaust
pressure in the duct and proper discharge velocity on the roof. The control systems should
include supply temperature reset, utilizing either a DDC sequence or a controller such as DART,
described above.
2413.01/Reports/UC SEP Final Report – UCLA.doc 8-10 December 31, 2008
Newcomb | Anderson | McCormick