LCBS CONNECT SOLUTION
13
31-00118EFS—01
HVAC professionals like this method as it's probably the simplest strategy to deploy and understand. This technique was
widely used before humidity sensing technology became cost effective. As with all economizer limit and changeover
strategies, LCBS Connect remote services alerting and analytics can help you fine tune setting to maximize customer
energy savings and maintain comfort.
How does it work? If there is a call for cooling and outdoor air temperature is less than outdoor air temperature is below
high limit, changeover set point, outdoor air will be used to cool your customer's building.
Temperature hysteresis is adjustable to make sure that you don't experience excessive enabling and disabling of the
economizer cycle potentially overusing the economizer actuator. It is advised that you don't change this value unless you
talk to a Honeywell distributor or customer support professional.
Low Limit Temperature Override Control
HVAC coil protection is offered as a feature as part of integrated economizer control. Please note that this feature does
not work with the "simple" digital input, digital output economizer control sequence described above.
How it works. The low limit control overrides the economizer damper position to prevent the economizer control sensor,
mixed air temperature or discharge air temperature from falling below the low temperature override limit by closing the
economizer, outdoor air damper. The low limit temperature override control is disabled when DCV is enabled as heating
will allow to cycle on.
Freeze Stat Operation
The capability to apply and install an electromechanical freeze stat as an ultimate redundant control is available. Simply
select freeze stat function by configuring the appropriate digital input on the LCBS Connect controller. A freeze stat
contact must be installed and an output from the device needs to be terminated to the LCBS controller. If the freeze stat is
configured and the LCBS Connect controller input is closed, the CVAHU system will be shut down.
The freeze stat
function can also be used to shut down the CVAHU system for smoke or fire alert, alarm.
Economizer Control Summary
LCBS Connect controllers feature an "ASHRAE Complete" range of economizer control, changeover, and
high limit options. If you are attempting to commission a "direct drive" economizer system, read this
description carefully. LCBS Connect remote services will be a great help to you as you fine tune economizer
control.
ADVANCED TEMPERATURE CONTROL FUNDAMENTALS
If you would like to learn how to "fine tune" control loops, you may want to take some time to learn about more advanced
control fundamentals. This will also be important for you if you chose to construct "Accessory Loops" as part of your
control business. Please read the following about proportional, integral, and derivative control operation. Contact your
Honeywell LCBS Connect professional for assistance.
Proportional Control and the Concept of Differential and Throttling Range
Let's start with basic control. Feedback control uses the "error", defined as the sensed value minus the set point, to
determine how to drive the output. Proportional Control commands the output as a direct proportion of the current error.
This is typically configured with a "Proportional Band" or a "Throttling Range" that defines the value of the error that will
result in the control output going to 100%. These terms are typical when we are describing modulating output. If we are
driving a digital output, the difference that is observed between the controlled load being energized and de-energized is
typically referred to as Differential.
So, if we are driving a modulating output, then the output is set to the percent calculated from the ratio of the error to the
Throttling Range (TR, e.g. if the error is ½ the TR, the output would be 50%, and if the error is equal to the TR then it would
be 100%).
Proportional Control
Proportional control is the function that determines the output setting required to meet the load conditions.