Emerson E2 Manuel D’Utilisation

adjustment.

As the value of the reset sensor varies within the mini-

mum and maximum range, an equivalent portion of the 
maximum setpoint adjustment will be added or subtracted 
from the heating or cooling setpoint. When the reset sen-
sor value is directly in between the minimum and maxi-
mum range values, nothing will be added or subtracted 
from the setpoint. Between the halfway point and the min-
imum value, part of the setpoint adjustment will be sub-
tracted from the setpoint. Between the halfway point and 
the maximum value, part of the setpoint adjustment will be 
added to the setpoint. An example of this is shown in Fig-
ure 11-28.

 

MIN

RANGE

MIDPOINT

MAX

RANGE

AD

D

SUBT

RA

CT

+0

MAX
CHANGE

MAX
CHANGE

A Heat/Cool application may be linked with another 

Heat/Cool application in what is called a “Lead/Lag” 
arrangement. In this arrangement, one Heat/Cool is desig-
nated as the Lead loop and used as the primary space tem-
perature control device. The other Heat/Cool, the Lag 
loop, becomes active only to support the Lead loop when 
it is unable to keep the space temperature within a certain 
proximity of the setpoint (called the setpoint delta).

Figure 11-29 shows how a pair of Heat/Cool applica-

tions using a Lead/Lag arrangement would operate in 
Cooling mode. When the temperature is in between the 

setpoint and the setpoint delta, the Lead loop alone will 
control cooling. However, when the temperature is above 
the setpoint delta, the Lag loop will come on-line, and 
both Lead and Lag loops will work to bring the tempera-
ture down.

The Lead/Lag arrangement works similarly in Heating 

mode, except that the setpoint delta is below the Heating 
setpoint, and Lead and Lag are both on when the tempera-
ture is below the setpoint delta.

SETPT
DELTA

LEAD AND 

LAG ON

LEAD AND

LAG ON

LEAD ON ONLY

LEAD ON ONLY

TEMPERA

T

URE

TIME

26512037

Heat/Cools in a Lead/Lag arrangement take turns act-

ing as the Lead loop. The user designates the maximum 
amount of time a Heat/Cool will act as a Lead loop; after 
this duration, the current Lead loop will switch places with 
its Lag loop.

Lead/Lag arrangements only work when both Heat/

Cools are in Occupied mode.

Dehumidification control uses the AHU’s existing cool 

stages (and a separate dehumidification device such as a 
desiccant wheel, if available) to remove moisture from the 
air. 

The dehumidification setpoint is placed at the 0% end 

of the dehumidification PID throttling range. In other 
words, the dehumidification output will start at 0% when 
the humidity is equal to the setpoint and increase to 100% 
when the humidity is equal to or above the setpoint plus 
the throttling range. 

The dehumidification output percentage is used much 

like a heating or cooling output percentage is used in Tem-
perature Control. The percentage represents the percent-
age of total dehumidification capacity available to the 
AHU (including cool stages and other dehumidification 
devices). 

Instead of using a single output source as an applica-

tion input, you may use a combination of up to sixteen 
input sources. To use multiple inputs, a Multiple Input cell