Emerson E2 User Manual

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CONTROL INPUT

OUTPUT AT
SETPOINT
(shown here as 50%)

0%

100%

THROTTLING

RANGE

Therefore, as the input value gradually drops below the 

setpoint, the Proportional Mode of PID will gradually 
bring the output percentage down. When the input drops 
below the low end of the throttling range, the output will 
be zero. 

The opposite happens with the input value begins to 

rise above the setpoint. The output percentage is gradually 
brought up from 50% until, when the input is at or above 
the throttling range, Proportional Mode will bring the out-
put to 100%.

For Condenser and HVAC PID Control, the Output at 

Setpoint defaults to 0%. This places the 0% end of the 
Throttling Range at the setpoint value, and it generally 
means Proportional Mode will strive to pull the input back 
down below the setpoint and attain a 0% output percent-
age. As the input climbs from the setpoint to the top of the 
Throttling Range, Proportional Mode likewise increases 
the output percentage to 100%.

The differences between the two PIDs can be seen by 

observing the throttling ranges. For non-Condenser Con-
trol applications, PID reacts to error that exists on either 
side of the setpoint. If the input goes lower than the set-

point, the output percentage is dropped from 50% (it is 
assumed this will result in the input rising back to the set-
point). Likewise, when the input is higher than the set-
point, the output percentage is raised. For Condenser 
Control PID, no reaction is made to an input that is lower 
than the setpoint, since the output percentage is already 
0%.

Advanced users may wish to change the Output at Set-

point in order to change the stabilization characteristics of 
their system(s). In most cases, the default values of the 
Output at Setpoint (0% for Condenser Control and HVAC, 
50% for all others) are appropriate and recommended. 
Changing the value of the Output at Setpoint may have 
some beneficial results, but at the same time it may also 
hamper the system’s ability to react to changing condi-
tions, and it may also result in decreased energy efficiency.

The following section lists other PID-related constants 

or control structures that are a part of some PID control 
algorithms. Many of these features are advanced features 
that are accessible only by service personnel or advanced 
users. As a general rule, it is best to contact Emerson 
Retail Solutions before changing any of these values.

The Output at Minimum and Output at Maximum val-

ues are used to change the range of possible output per-
centages. The default values (0% for minimum, 100% for 
maximum) allow the output to vary from fully off to fully 
on; changing these values, therefore, would only be neces-
sary if you desire a limited output range.

Two things occur when the Output at Minimum or 

Output at Maximum values are changed:

1.

The throttling range is shortened as dictated by 
the new values. For example, if you specified a 
20% minimum, the portion of the throttling range 
that would usually represent the range of outputs 
from 0% to 20% is cut off. Any input value that 
falls within the previous 0% to 20% portion of 
the throttling range will cause the Proportional 
Mode to move the output towards 20%.

2.

The Output at Minimum or Output at Maximum 
value replaces any calculated adjustment that 
would normally call for the output to be outside 
of the specified range. In other words, if the Out-
put at Minimum and Output at Maximum values