Filter
Top Products
56
Adjust the minimum position potentiometer to a llow the
minimum amount of outdoor air, as required by local
codes, to enter the building. Make minimum position
adjustments with at least 10_F temperature difference
betwee n the outdoor and return-air temperatures.
To determine the minimum position setting, perform the
following procedure :
1. Calculate the appropriate mixed air temperature
using the following formula:
(T
Ox
OA
)
+(TR
x
RA
)=T
M
100 100
T
O
= Outdoor-Air Temperature
OA = Perce nt of Outdoor Air
T
R
= Return-Air Temperature
RA = Percent of Return Air
T
M
= Mixed-Air Temperature
As an example, if local codes require 10% outdoor
air during occupi ed conditions, outdoor-air
temperature is 60_F, and return-air temperature is
75_F.
(60 x .10) + (75 x .90) = 73.5_F
2. Disconnect the supply air sensor from terminals T
and T1.
3. Ensure that the factory-installed jumper is in place
across terminals P and P1. If remote damper
positioning is being used, make sure that the
terminals are wired according to Fig. 62 and that the
minimum position potentiometer is turned fully
cloc kwise.
4. Connect 24 vac across terminals TR and TR1.
5. Carefully adjust the minimum position
potentiometer until the measured mixed air
temperature matches the calculated value.
6. Reconnect the supply air sensor to terminals T and
T1.
Remote control of the EconoMi$er IV damper is desirable
when requiring additional temporary ventilation. If a
field-supplied remote potentiometer (Honeywell part
number S963B1128) is wired to the EconoMi$e r IV
controller, the minimum position of the damper can be
controlled from a remote location.
To control the minimum damper position remotely,
remove the factory-installed jumper on the P and P1
terminals on the EconoMi$er IV controller. Wire the
field-supplied potentiometer to the P and P1 terminals on
the EconoMi$e r IV controller. (See Fig. 62.)
Damper Movement
Damper movement from full open to full closed (or vice
versa) takes 2-
1
/
2
minutes.
Thermostats
The E conoMi$er IV control works with conventional
thermostats that have a Y1 (cool stage 1), Y2 (cool stage
2), W1 (heat stage 1), W2 (heat stage 2), and G (fan). The
EconoMi$er IV control does not support space
temperature sensors. Connections are made at the
thermostat terminal connection board located in the main
control box.
Dema nd Control Ventilation (DCV)
When using the EconoMi$er IV for demand controlled
ventilation, there are some equipment selection criteria
which should be considered. When selecting the heat
capacity and cool capacity of the e quipment, the
maximum ventilation rate must be evaluated for design
conditions. The maximum damper position must be
calculated to provide the desired fresh air.
Typically the maximum ventilation rate will be about 5 to
10% more than the typical cfm required per person, using
normal outside air design criteria.
A proportional anticipatory strategy should be taken with
the following conditions: a zone with a large area, varied
occupancy, and equipment that cannot exceed the required
ventilation rate at design conditions. Exceeding the
required ventilation rate means the equipment can
condition air at a maximum ventilation rate that is greater
than the required ventilation rate for maximum
occupa ncy. A proportional-anticipatory strategy will cause
the fresh air supplied to increase as the room CO
2
leve l
incre ases eve n though t he CO
2
setpoint has not been
reached. By the time the CO
2
level reaches the setpoint,
the damper will be at maximum ventilation and should
maintain the setpoint.
In order to have the CO
2
sensor control the economizer
damper in this manner, first determine the damper voltage
output for minimum or base ventilation. Base ventilation
is the ventilation required to remove contaminants during
unoccupi ed periods. The following equation may be used
to determine the percent of outside air entering the
building for a given damper position. For best results there
should be at l east a 10 degree differenc e in outside and
return-air temperatures.
(T
Ox
OA
)
+(TR
x
RA
)=T
M
100 100
T
O
= Outdoor-Air Temperature
OA = Perce nt of Outdoor Air
T
R
= Return-Air Temperature
RA = Percent of Return Air
T
M
= Mixed-Air Temperature
Once base ventilation has been determined, set the
minimum damper position potentiometer to the correct
position.
580J