Honeywell LCBS Applications Manual page 16

LCBS CONNECT SOLUTION
When the proportional error equals 0 the calculated integral error is 0 and no change is made to the output.
When the proportional error is less than 0 the integral error is calculated as a negative value resulting in decrease in the
integral error.
The integral time value is set in seconds based on the lag time of the controlled process. A slow process such as space
temperature control requires a long integral time (600 seconds or more) while a fast process such as static pressure
control requires a short integral time. An integral time value of 0 (default) eliminates implementation the integral
function.
P+I control can decrease stability of a control loop. Stability of the control loop is a balance of the throttling range and the
integral time. If a P+I control loop is unstable it is necessary to increase the throttling range and/or increase the integral
time. In general, the throttling range required for P+I control is greater than that for proportional only.
NOTICE
A bit of good news. Honeywell has utilized "proportional plus integral control" in analog and digital temperature
control devices for residential and commercial customers for 40 years. LCBS Connect controllers are
preconfigured with proper settings as they have been for 40 years. You simply don't have to do a thing to take
advantage of this sophisticated control.
If you decide to use LCBS Connect controller "accessory loop" function, you may want to ask your Honeywell LCBS
Connect distributor for a hand. If you decide to control something other than temperature with the accessory loop
function, you may need to provide integration timing factor. For example, if you want to control outdoor lights, the
integration feature doesn't add to the quality of control and the integration timer should be set to zero (0). Simple set
point and differential are the only parameters that need to be set.
Do You Want to Know More about Integral Control?
As a starting point, the LCBS Connect controller uses the dependent gains form of the PID equation. This means that you
specify an integral time and the actual integration gain is dependent on the Throttling Range (TR). Specifically the
integral time is the time in seconds that it should take for the integration result to be 100% if the error is held constant at
the TR. For room control integral time typically ranges from 1,000 to 2,500 seconds given the standard throttling range
used. Note that the LCBS Connect controller integral gain for the thermostat function is predefined for optimal
performance and should generally not be changed! The purpose of integral action is to reduce the offset from set point
during steady state control that can be experienced using proportional only control. Again, as general information,
control action is impacted by throttling range selection and adjustment. It's a good idea to adjust the throttling range first
before making any adjustment to integral time. It's a good idea to adjust throttling range to be as wide as possible
because this will provide the most stable control. Remember that the integral will eliminate the steady state error so you
do not need to have a small throttling range to have accurate control. Integral action allows for controlling to set point
even with a wide throttling range.
31-00118EFS—01
80°F
INPUT
SENSOR 75°F
DEGREES F
70°F
100%
80%
OUTPUT
60%
%
40%
20%
0%
T0 T1
PROPORTIONAL PLUS INTEGRAL CONTROL
EI = INTEGRAL ERROR
EP = PROPORTIONAL ERROR
V=TOTAL ERROR IMPACT, P PLUS I
Fig. 7.
16
THROTTLING
RANGE
SETPOINT
V=E + E
I P
E
I
E
P
T2 T3 T4
MCR36701