Overlapping User limits Interactivity

| Overview

The Overlapping User Limits is a feature introduced in the 75F BMS space. With this, the building limits and the user limits in the scheduling space (Building, Zone, Named, & Special Schedules) permit overlapping of cooling and heating user limits.

This solves very complex building environment cases, where multiple CCUs get deployed, with the option for multilevel user limits across the system.

| Overlapping User Limits

The overlapping user limit feature enables the master controller user limits for cooling and heating to overlap with each other, to achieve the desired user limits.

It uses a criterion to allow the limits to overlap.

Below are the conditions that favor the overlapping of user limits.

• Heating Limit Max + deadband (heating + cooling) should be less than or equal to Cooling Limit Max.
• Cooling Limit min - deadband (heating + cooling) should be greater than or equal to Heating Limit Min.

Example:

For the same case discussed above,

Where the:

When the user tries to increase the heating max user limit above 72, to overlap with the cooling limits, now the system permits the user limit to overlap with colling limits as below

And when the user tries to decrease the cooling min user limit below 72, to overlap with the heating limits, now the system permits the user limit to overlap with cooling limits as below.

This feature caters to complex scenarios in buildings that demand more CCUs, to meet their requirements of varying user limits for zones. These user limits fall within a wide range of heating or cooling limits of the building.

Note: The above actions are applicable from the installer options in the internal portal as well.

| Criterion

From the above examples, it's evident that overlapping user limits are possible now.

But we were not able to increase the heating max user limit above 73 and decrease the cooling min user limit below 71.

It is because the values 73 and 71 only meet the criterion set.

• Heating Limit Max + deadband (heating + cooling) should be less than or equal to Cooling Limit Max.
• Cooling Limit min - deadband (heating + cooling) should be greater than or equal to Heating Limit Min.

For the above scenario, the deadbands for heating and cooling are 2 and 2 as below.

Hence For Heating Max limit value, 73:

• Heating Limit Max + deadband (heating + cooling) should be less than or equal to Cooling Limit Max.
• 73+4=77, which is less than or equal to the Cooling Limit Max 77. The value meets the criterion; hence the overlapping was permitted.

And For Cooling Min limit value 71:

• Cooling Limit min - deadband (heating + cooling) should be greater than or equal to Heating Limit Min.
• 71-4=67, greater than or equal to Heating Limit Min 67, value meets the criterion hence the overlapping was permitted.

For any value above 73 as the Heating max limit:

• 74+4=78, which is not less than or equal to Cooling Limit Max, value does not meet the criterion hence the overlapping is not permitted.

For any value below 71 as the Heating max limit:

• 70-4=66, which is not greater than or equal to Heating Limit Min, value does not meet the criterion hence the overlapping is not permitted.

| Effect at the Zone Level

The Overlapping user limits implementation at the master control level affects the Zone Level, Named, and Special Scheduling user limits.

Scheduling changes or user intent changes to the user limits at the zone level the following criterion is followed.

When the set cooling desired temp - heating desired temp >=deadband, then the desired temperatures can be within the overlapping limits.

Note: The set desired temperatures can overlap without varying the other (the Heating Desired Temperature can be increased without varying the Cooling Desired Temperature, and the Cooling Desired Temperature can be decreased without varying the Heating Desired Temperature)

For Example:

In the below case

The desired temperature setpoints are 76 for cooling and 70 for Heating.

When the user tries to decrease the desired cooling setpoint to 75 as below.

As per the criterion, the desired Cooling setpoint - The desired heating setpoint, 75-70=5 > the Deadband, hence the desired cooling setpoint, or the desired heating setpoint can be decreased/increased without increasing/decreasing the other.

When the user tries to decrease the desired cooling setpoint to some value below 74 as below:

The desired cooling setpoint - The desired heating setpoint, 73-70=3 < the Deadband,  increasing/decreasing the heating/cooling desired setpoint will alter the other and vice versa.

The above cases are applicable for the Building, Zone, Named, and Special Schedules as well, during the user limits set for the schedules.

| Advantage

This feature implementation has helped

• To curb the requirement of multiple CCUs getting deployed, providing an option to provide multilevel user limits across the system.
• To set user limits as per space needs.
• Enable the building to operate in a larger range for both heating and cooling limits respectively without the limiting factor.
• Enables the user to increase the maximum heating temperature desired limit to the minimum cooling user limit.
• Enables the user to set the cooling desired setpoint away from the heating desired setpoint by the difference of the deadband limit.