Honeywell Design and Application Technical Reference Manual page 14

Section 1 - Ventilation
The IAQP method is used for spaces where
the designers target a specific contaminant
and control the concentration level of the
contaminant. This method has two
requirements: Maintain concentration of
specific contaminant(s) below target
concentration limits and achieve a design
target of perceived indoor air quality
acceptability. The IAQP method allows
ventilation rates to be lower than the rates
required by the VRP method if it can be
demonstrated the resulting air quality can
meet the required criteria.
The IAQP procedure has 4 steps:
• Identify the contaminants of concern.
• Determine acceptable concentration of
contaminant(s).
• Specify the perceived indoor air quality
criteria.
• Apply an acceptable design approach to
achieve the performance criteria.
Additional information on ventilation and the
two methods used to determine the ventilation
rates can be found in ANSI/ASHRAE Standard
62.1 and in the User's manual for ANSI/
ASHRAE Standard 62.1. Both documents are
available on the ASHRAE website at
http://resourcecenter.ashrae.org/store/ashrae/
Example using the VRP method: Office space
of 6600 sq. feet with maximum occupancy of 7
2
persons per 1000 ft
V = R P + R A where
bz p z a z
R = 5 cfm per person
p
(Table 6-A ASHRAE 62.1 User's Manual)
P = 7 person per 1000 ft
z
2
R = 0.06 cfm per ft
a
(Table 6-A ASHRAE 62.1 User's Manual)
2
A = 6600 ft .
z
3
V = 5 ft / min/person x 7 persons/1000 ft
bz
2 3
6600 ft + 0.06 ft / min/ft
= 231 cfm + 396 cfm
=627 cfm
Honeywell Economizers 63-8594-02
.
2
x A
z
2 2
x 6600 ft
For a single zone system V
ventilation) is the same as V
zone systems a zone air distribution system
effectiveness (E) factor needs to be used in
the calculation of the V
Standard 62.1 for method.
In our example during maximum occupancy
the ventilation is 627 cfm. When the
occupancy rate is less than the maximum
occupancy, the ventilation rate can be
adjusted to a lower occupancy and the
ventilation increased as the CO
space increases. This can be done following
these steps:
• Calculate the V
• Use V = R
bz
is the new ventilation rate V
building based component).
• Add a CO
2
• Adjust the CO
maximum occupancy).
• Adjust the minimum position for occupancy
for V .
a
In our example the V
and the minimum position (V
Using a CO
2
Ventilation, the new minimum position is set
for 396 cfm and the maximum damper position
for occupancy ventilation is 627 cfm. When
one person enters the space or the
commercial thermostat goes into occupancy
mode, the outdoor air dampers will open to
bring in 396 cfm of outdoor air. As space
occupancy increases, the CO
increase and the outdoor air dampers will
modulate open to the maximum of 627 cfm of
outdoor air.
NOTE: When the commercial thermostat calls
for free cooling using an economizer,
the dampers are still allowed to
override the DCV maximum position
2
x
for ventilation and open the damper
100% open for maximum free cooling.
8
(outdoor
OT
. For multiple
bz
. See ASHRAE
OT
level in the
2
.
OT
P + R A , where P
p z a z
(the area
at
sensor to the space.
maximum to the V
2
ventilation is 627 cfm
bz
) is 396 cfm.
a
sensor for Demand Control
level will
2
= 0. This
z
(for
bz