Minimum Outside Air Reset -IAQ
If either IAQV or IAQ mA is selected as the Min OA Type,
the Minimum OA Position is calculated based on a 0-10V or
0-20 mA CO
2
sensor input. The CO
2
level is expressed as
Parts Per Million. The minimum and maximum sensor input
values (0-10V or 0-20 mA) and the corresponding minimum
and maximum PPM values are user dened. This calculated
Minimum OA Position varies linearly from the Demand Control
Ventilation Limit at the “PPM @ DCV Limit” to the Ventilation
Limit at the “PPM @ VentLimit”. The “PPM @ DCV Limit” is not
allow to be set equal to or greater than the “PPM @ VentLimit”
Examples of typical Min OA reset schedules.
If IAQ VDC is selected as the Min OA Type, the Minimum OA
Position is calculated based on a 0-10V CO
2
sensor input.
The CO
2
level is expressed as PPM (Parts Per Million). The
minimum and maximum sensor input values (0-10V) and the
corresponding minimum and maximum PPM values are user
changeable. This calculated Minimum OA Position varies
linearly from the Demand Control Ventilation Limit at the value
labeled “PPM @ DCV Limit” to the Ventilation Limit at the value
labeled “PPM @ VentLimit”. The “PPM @ DCV Limit” is not
allow to be set equal to or greater than the “PPM @ VentLimit”
Example #1 Min OA reset type = IAQ VDC
If the requirement is to have the OA damper be at its minimum
(Demand Control Ventilation Limit) when the CO
2
levels are
less than 800PPM and to be at its maximum (Ventilation Limit)
when the CO
2
levels are greater than 1000PPM, the controller
would be set up as follow:
• Vent Limit= 100%
• Lo Flow Vent Limit= 100%
• DCV Limit= 0%
• Min OA reset type= IAQ VDC
• PPM@DCV Limit= 800
• PPM@Vent Limit= 1000
• IAQ PPM= Current PPM
• Min PPM= 0 (From CO2 transducer)
• Max PPM= 2000 (From CO2 transducer)
• V/A @ Min PPM= 0 VDC
• V/A @ Max PPM= 10 VDC
In this example the Minimum OA Position would vary linearly
from 0% outside air at 800PPM or less to 100% outside air at
1000PPM or greater.
Examples of typical Min OA reset schedules.
If EXT VDC is selected as the Min OA Type, the Minimum OA
Position is calculated based on an external 0-10 VDC signal.
This calculated Minimum OA Position varies linearly from zero
% at the changeable minimum external signal to 100% at the
changeable maximum external signal, but it is set no lower
than the Demand Control Ventilation Limit and no higher than
the Ventilation Limit.
Example #2 Min OA reset type = EXT VDC
If the requirement is to have the OA damper be at its minimum
(Demand Control Ventilation Limit) when the eld supplied
signal is at its minimum (0VDC) and to be at its maximum
(Ventilation Limit) when the eld supplied signal is at its
maximum (10VDC), the controller would be set up as follow:
• Vent Limit= 100%
• Lo Flow Vent Limit= 100%
• DCV Limit= 10%
• Min OA reset type= EXT VDC
• OA@MinV/mA= 0%
• OA@MaxV/mA= 100%
• Min V/mA= 0 VDC
• Max V/mA= 10 VDC
In this example the Minimum OA Position would vary linearly
from 0% outside air at 0 VDC to 100% outside air at 10 VDC.
Reset Temperature Limit
The user has the option of setting a low temperature limit that
will override all the outdoor air reset functions described in this
section except the Return Fan Capacity Override function if the
discharge air temperature or entering fan temperature gets too
cold as a result of the reset. The user can choose the override
sensor by setting the Reset Temperature Limit to None, DAT or
EFT. When set to None the Reset Temperature Limit function
is disabled. A Reset Temperature Limit PI_Loop will be used
to reset the minimum outside air damper setpoint downward
when the selected temperature input drops below the Reset
Temperature Limit.
operator’s guIde
www.DaikinApplied.com 105 OM 1141-3 • MICROTECH UNIT CONTROLLER
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