Settings For Co 2 -Based Demand Controlled Ventilation - Trane Tracer UC400 Installation, Operation And Maintenance Manual

Settings for CO
The CO
the ASHRAE Standard 62.1 User Manual, Appendix A.
N N o o t t e e : : This sequence is intended for a fan-coil, blower-coil, and unit ventilator product that is
The following describes how to determine the appropriate OA damper and CO
DCV sequence:
•
•
•
BAS-SVX48H-EN
-Based Demand Controlled Ventilation
2
-based DCV sequence used in UC400 Controller is based on the sequence suggested in
2
applied as a single-zone ventilation system. That is to say, outdoor air enters through an
intake and is delivered to a single ventilation zone, which would be typical of a terminal
unit that is equipped with its own OA damper.
Calculate the required outdoor airflow (V
2- and 6-3 from ASHRAE Standard 62.1
V = R × P + R × A (Equation 6-1)
bz p z a z
V = V / E (Equation 6-2)
oz bz z
V = V (Equation 6-3, for single-zone ventilation systems), where
ot oz
V = minimum outdoor airflow required in the breathing zone, cfm
bz
R = outdoor airflow required per person (from Table 6-1 in ASHRAE Standard 62.1), cfm/
p
person
R = outdoor airflow required per unit of floor area (from Table 6-1 in ASHRAE Standard 62.1),
a
cfm/ft2
P = zone population, number of people
z
A = zone floor area, ft 2
z
V = zone outdoor airflow required, cfm
oz
E = zone air distribution effectiveness (from Table 6-2 in ASHRAE Standard 62.1)
z
V = outdoor air intake flow required, cfm
ot
E E x x a a m m p p l l e e : : Consider an example K-12 classroom with a design population (P
and a floor area (A ) of 1000 ft2. Table 6-1 in ASHRAE Standard 62.1-2010 requires 10 cfm of
z
outdoor air per person (R
this type of space. The zone air-distribution effectiveness (from Table 6-2in Standard 62.1) is
determined to be 1.0 for this system configuration.
V = 10 cfm/p x 35 people + 0.12 cfm/ft
bz-Design
V = 470 cfm / 1.0 = 470 cfm
oz-Design
V = 470 cfm
ot-Design
Use the same equations to calculate the required outdoor airflow (V
are currently present in the zone (P
N N o o t t e e : : This setpoint may need to be increased if the zone requires makeup air to replace air
that is exhausted directly from the zone (for example in a kitchen, a laboratory, an art
or science classroom, or any space with a restroom connected to it). In this case, the
V setpoint may need to be adjusted so that it is slightly above the local exhaust
ot-DCVmin
airflow to ensure positive building pressurization.
E E x x a a m m p p l l e e : :
V = 10 cfm/p x 0 people + 0.12 cfm/ft
bz-DCVmin
V = 120 cfm / 1.0 = 120 cfm
oz-DCVmin
V = 120 cfm
ot-DCVmin
Use Equation A-J from the ASHRAE Standard 62.1-2010 User's Manual to calculate the
steady-state indoor CO
2
its design outdoor airflow rate (V
CO = CO + [1,000,000 x N / (V
2space 2outdoors
CO = concentration of CO
2space
) at design occupancy using Equations 6-1, 6-
ot-Design
) plus 0.12 cfm of outdoor air per square foot of floor area (R
p
2 x 1000 ft
= 0).
z
2 x 1000 ft
concentration (CO
2
space-Design
).
bz-Design
/ P )] (rearrangement of Equation A-J) where,
bz z
in the breathing zone, ppm
2
setpoints for this
2
) of 35 people
z
2 = 470 cfm
) if no occupants
ot-DCVmin
2 = 120 cfm
) when the zone is fully occupied and at
) for
a
63