Emerson E2 - Manual (Page 187)

Anti-Sweat Setup Software Overview • 11 - 45
11.16 Anti-Sweat Setup
An anti-sweat application controls one anti-sweat
zone. An anti-sweat zone is defined as one or more anti-
sweat heaters that use the same dewpoint (or RH and tem-
perature) sensors and the same control setpoints. If all the
outputs on a 20-channel PMAC panel are going to use the
same setpoints and dewpoint device(s), then all the heaters
may be set up in a single zone.
Zones are set up in a single screen called the Anti-
Sweat Control Setup screen.
11.16.1 How Anti-Sweat Works
Anti-sweat applications control anti-sweat heaters by
monitoring the dewpoint. A dewpoint value may come
from a dewpoint probe mounted within the Zone, or it may
be calculated automatically by the E2 using a combination
of a relative humidity sensor and a temperature sensor.
The dewpoint value is used to pulse the heaters ON for
a certain percentage of a user-defined time interval. The
dewpoint is compared to the anti-sweat application’s con-
trol setpoints (the Full ON Dewpoint and the Full OFF
Dewpoint). Based on this comparison, the anti-sweat heat-
ers will do one of three things:
• If the dewpoint is equal to or above the Full ON
Dewpoint, the heaters remain ON 100% of the time.
• If the dewpoint is equal to or below the Full OFF
Dewpoint, the heaters will be ON 0% of the time
(fully OFF).
• If the dewpoint is between the Full ON and Full
OFF Dewpoint, the heaters will be pulsed ON for a
percentage of the specified time interval. The per-
centage is determined by proportionately measuring
where the dewpoint falls between the range of val-
ues formed by the two setpoints.
Figure 11-6 shows an example of an anti-sweat appli-
cation. The setpoints (Full ON = 80°F, Full OFF = 20°F)
form the range of dewpoints across which the heaters will
be pulsed. When the measured dewpoint is 45°F (directly
in between both setpoints), the percentage will be 50%,
and the heaters will be pulsed ON for five seconds of the
defined 10-second interval. If the dewpoint drops to 30°F,
the percentage will lower to 20%, and the heaters will be
on only two seconds out of every 10.
11.17 Heat/Cool Control
Heat/Cool Control is a special kind of sensor control
that applies to heating and cooling devices. Heat/Cool
Control applications use PID control to vary the amount of
heating and cooling based on the current temperature and
its relation to the heating or cooling setpoint. Both staged
and modulated (0-100%) heating and cooling outputs are
supported by Heat/Cool Control.
Heat/Cool controls are available in RX units, allowing
small installations with simple HVAC systems to use one
controller for all refrigeration and HVAC systems.
11.17.1 Temperature Control
Heat/Cool applications use PID control to vary the out-
put of heating and cooling devices. As is the case with all
applications that use PID control, Heat/Cool control
makes use of a PID setpoint and a throttling range. Refer
to Appendix D: PID Control for more information.
Unlike normal PID loops that assume a 50% output is
required to keep the temperature stabilized on the setpoint,
Heat/Cools strive to stabilize the temperature on the set-
point with the output at 0%. Thus, when the temperature
goes below a heating setpoint or above a cooling setpoint,
the heating or cooling outputs climb from 0% to 100% as
determined by the throttling range (see Figure 11-25).
By default, only the proportional and integral modes of
PID control are enabled for Heat/Cools. The user may
choose to add the Derivative mode or to get rid of the Inte-
gral mode and use strictly Proportional control.
11.17.2 Unoccupied Hysteresis
When the Heat/Cool receives an indication that the
building is unoccupied, the control mode changes from the
PID method described previously, and uses simple ON/
OFF control of the heating and cooling outputs.
The Heat/Cool application in unoccupied mode makes
use of a hysteresis value to form a range of temperature
values across which the heating and/or cooling will be
applied. As shown in Figure 11-26, when the temperature
Figure 11-25 - Example of Heat/Cool PID Control
Lighting Control Command Cells
Input Value
1 - 4
In 1
In 2
In 3
In 4
Use Alt Comb
Out
DVCOMBINER SCHEDIF
Out
Comb Type
Alt Comb
Invert Output
Alt Combiner
DV
Logic In
Sched In
Use Alt Sch
Occupied
DV
Comb Type
Alt Comb
Invert Output
MIN ON/OFF
In Out
ONESHOT
Trigger Out In Out
OVERRIDE
Command
(on, off, normal)
Type
(timed, fixed)
OV time
Pulse Width
Timer
Alt Schedule
DV
DV
Min On/Off Times
Min On/Off Delays
LIGHTS
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