3 Minute Read
The Overlapping User Limits are a feature introduced in the 75F BMS space. With this, the building and 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.
A car dealership. Has 20VAVs served by a single AHU in the offices, 3 RTUs serving the show floor, and 14-unit heaters in the shop? For this job our BOM would intuitively list:
- 1 CCU
- 20 VAV Smart Nodes
- 3 Hyperstats
- 14 additional Hyperstat or Smart Nodes depending on local control preference
The offices require heating setpoints between 65-70 and cooling setpoints between 68-74
The show floor requires 70 at all times.
The shop heaters require heating setpoints between 58-62
With the overlapping user limits feature, the above example building requirement can be accommodated.
The requirements for the above scenario can be achieved to some extent by building user limits set, with the 75F defined paradigm, at a range of 63-70 for the Heating user limits and 68-75 for the Cooling user limits at the building level. with a deadband of 4 (2 for heating and 2 for cooling) as below.
And further tweaking the building limit min to 50 using the tuner as below
The requirement for the example building can be achieved as below.
Range of 58-70 for the Heating user limits and 68-75 for the Cooling user limits at the building level. with a deadband of 4 (2 for heating and 2 for cooling) as below.
Effects in Zones
With the above user limits for building in the master control of the BMS, we can achieve the varied ranges of desired temperatures as per the example below.
The Office Zones:
In the office zones, we can achieve the desired temperature of 67- 71 which are the midpoints of the heating setpoints 65-70 and cooling setpoints 68-74 as above.
The Show Zones:
In the show zones, we can achieve the desired temperature of 69- 73 which accommodates the required setpoint of 70 for the show zones as above.
The Shop Zones
In the shop zones, we can achieve the desired temperature of 60 for heating which is the midpoint of the required heating setpoints 58-62 as above.
With this, it's evident that the multilevel desired temperatures for the zones can be achieved, by utilizing the overlapping feature, without increasing the overall limits. for more information on the interactivity of user, limits refer to Overlapping User limits Interactivity