Application

Room Functions
Room Coordination Functions for HVAC
48
Siemens Industry, Inc.
Application Note
A6V11692055
Smart Infrastructure – Building Products
2019-04-01
NOTE:
The VAV with hot water or electric heating coil application has been pre-loaded to
support the Supply air VAV damper and the heating coil valve or stages of electric
heat.
If the default application does not meet job requirements, an application can be
configured and modified to job specifications in ABT Site.
This application function works in collaboration with a room segment temperature
control AF. The heating room temperature PID or staged controller is enabled
based on a signal that is read via the grouping function (from equipment in the
room segment) indicating whether heating is available.
Temperature sequence order: 1) Radiator, 2) Heating ceiling, 3) Heating coil, 4)
VAV heating (only for VAV serial fan operation).
Warm-up
When the room operating mode is Economy the central system scheduler can
initiate warm-up mode. To do so the scheduler commands the VAV supply
changeover condition point (VavSuChovrCnd) to Heating and the warm-up request
point (WarmUpReq) to Active. When this happens the following occurs:
1. Plant operating mode goes go to 6:Warm-up and Room operating mode goes to
4:Comfort
2. Room temperature setpoint for heating returns to Comfort heating setpoint
(SpHCmf, default = 70°F)
3. Radiator modulates to full-open
4. Heating coil is activated
5. Vav supply damper positioned to provide min heating airflow (e.g., 100 CFM)
6. Vav supply damper modulates to full-open, max heating airflow (e.g., 1200
CFM)
Due to length of sequencing/interlock times between the HVAC devices, it takes
several minutes before the box is able to provide maximum airflow for heating (e.g.,
1200 CFM).
Alternative Methods for Implementing Warm-up
Option 1
To avoid the sequencing/interlock delay times, the application can be configured
using ABT-Site. The values for two Boolean parameters in the room application
function for VAV heating can be changed as follows:
⚫ Coil: controller mode by warm-up (CoilWarmUp) must be set to 2-position
⚫ Radiant devices: ctr.mode by warm-up (RadDevWarmUp) must be set to 2-
position
These parameters belong to the room application function for VAV heating
(VavTRCtlH11 or VavTCasCtlH11).
Option 2
To avoid the sequencing/interlock delay times, the following can be commanded
from the central workstation (e.g., Desigo CC using the scheduler) to place the
room into warm-up mode:
1. VavSuChovrCnd = Heating
2. WarmUpReq = Active
3. VavSuDevMod = 3:Max. air volume flow
4. HclDevMod = 3:Full Open