CONTEMPORARY CONTROLS BAST-221C-B2 BACnet MS and TP Thermostat Installation Guide
- June 4, 2024
- CONTEMPORARY CONTROLS
Table of Contents
CONTEMPORARY CONTROLS BAST-221C-B2 BACnet MS and TP Thermostat
BACnet® MS/TP Thermostat
The BASstat series of BACnet-compliant wired communicating thermostats are
BTL listed to ensure effortless integration into BACnet MS/TP (EIA-485)
networks. These thermostats are suited for single or multi-stage heating,
cooling, and ventilation binary output control applications such as RTU or
AHU. Configurable control algorithm parameters allow adaptability to the
specific application. Adaptive control algorithm applied to multi-stage on/off
control saves energy and ensures seamless comfort for the occupants. Built-in
temperature sensor, input for remote temperature sensor, or temperature
override network command from Building Automation System. Occupancy status can
be set from thermostat buttons or over the BACnet network. Thermostat buttons
are optionally lockable to prevent unauthorized control. Digital display with
graphical icons is easy to read and understand. Several icons indicate
parameters such as: Active Mode, Cooling stage 1 or 2, Heating stage 1 or 2,
Ventilation Only, Fan Active, Occupied / Unoccupied state, and Clock icon to
indicate Short Cycle Delay or Max Cycles per hour active waiting state. Two
main control types are available: Cooling and Heating with Auto-changeover and
Cooling or Heating with Manual-changeover. These control types are selectable
from Engineering Menu (tyPE) or BACnet object MSV8.
Installation Guide
Electrical (Class 2 Circuits Only)
- INPUT AC only
- Voltage (±10%): 24 VAC
- Power: 5 VA
- Frequency: 47-63 Hz
Environmental
- Operating temperature: 0°C to 50°C
- Storage temperature: –10°C to +60°C
- Relative humidity: 5–95%, non-condensing
- Functional MS/TP
- Physical Layer: EIA-485
- Cable length limit: 4000 ft / 1200 m @76800 bps max
- MS/TP data rate (bps): 9600 – 76800 bps
- MS/TP node limit: 32 full-load devices max per segment
Installation
The BASstat requires 24 VAC while drawing no more than 5 VA of power. The recommended conductor size is 16–18 AWG or 1.5mm2 wires.
WARNING:
Internally, this device utilizes a half-wave rectifier and therefore can only
share the same AC power source with other half-wave rectified devices. Sharing
AC power with full-wave rectified devices is NOT recommended. Devices powered
from a common AC source could be damaged if a mix of half-wave and full-wave
rectified devices exists.
The BASstat does not provide End-of-Line termination. If the BASstat is the
first or last device on the MS/TP bus, a termination resistor (120Ω) must be
applied across pins 16 and 17 of the EIA-485 input terminal to avoid network
errors or failure.
BASstat mounts directly onto wall, panel, standard 65×65mm junction box (hole pitch 60 mm) or standard 2×4 inch vertical junction box (hole pitch 83.5 mm). To mount on electric box, separate back plate from the controller by loosening the screw. Align the mounting holes of the back plate to the screw holes of the electric box. Fix the back plate to the electric box using screws. Suggested screws for use are Phillips wide “truss head” or “washer head” screws #6-32 x ¾” (20mm). Wire the controller and mount on top of back plate. Secure by tightening the mount screw at the bottom.
WARNING:
DO NOT let the back-mount screw heads rise above the back plate or it may
touch the circuit board and cause a short.
BACnet MS/TP configuration requires setting the baud rate (9.6kbps – 76.8kbps) or using the default baud rate of 38.4kbps. A unique MS/TP MAC address is required to distinguish each thermostat from other MS/TP devices on the bus (default MAC address is 1). When more than one BASstat is installed at the same time on the same EIA-485 bus, their MAC addresses must be configured prior to communicating with all thermostats on the MS/TP bus, or communication will fail due to duplicate MAC addresses. The MAC address can be set from Engineering Menu item (Addr) with values of 1 – 127. The baud rate can be set from menu item (bAud) 9.6kbps – 76.8kbps. A unique Device Instance number throughout the entire BACnet internetwork is also required to distinguish the device from all other BACnet devices. Device instance can be modified in Engineering Menu items (dEVH) – high bytes and (dEVL) – low bytes; Device Instance = (dEVH)*1000+(dEVL). Max masters setting can be set from menu item (AdrH), default value is 127.
To enter the Engineering Menu, hold down the UP and DOWN buttons simultaneously for 5 seconds. Use the UP and DOWN buttons to navigate through the menu and change menu item values. Use the MODE button to enter a menu item and accept/confirm a selected value. To exit the Engineering Menu, navigate to menu item (End) and press MODE, or the menu will exit automatically when not used.
Mechanical Drawing
Operation Overview
The BASstat has a built-in space temperature sensor with provision for remote wired 3kΩ NTC thermistor sensor, or temperature value can be sent by another device over the BACnet network.
The default control type is Cooling and Heating with Auto-changeover. Two main control types are available: Cooling and Heating with Auto-changeover and Cooling or Heating with Manual-changeover. These control types are selectable from Engineering Menu (tyPE) or BACnet object MSV8. User-side comfort control is accomplished with six buttons – mode (Heat, Cool, or Ventilation – dependent on control type chosen from Engineering Menu (tyPE) or BACnet object MSV8), fan, raise, lower, set, and power. There are also options to lock select buttons or all buttons on the thermostat. A large LCD display indicates setpoint, space temperature, and current mode of operation using graphical icons. By default, the BASstat thermostat will not provide Fan output signal when in Heat Mode since most HVAC comfort systems provide their own Fan control signal based on a delay after a call for heating. This can be configured from Engineering Menu item (F-Ht) or BACnet object BV15 with a default value of 0. To enable Fan control signal output for heating, set this value to 1.
Reset settings can be performed from Engineering Menu item (rSt) which will reset all parameters including communication (MAC and Device Instance) and all control algorithm values back to factory-programmed defaults. For complete datasheet and details on BASstat, support, or compliance information, please download our BASstat User Manual and Data Sheet at: https://www.ccontrols.com/basautomation/basstat.php. Free BACnet Discovery Tool for configuration: https://www.ccontrols.com/sd/bdt.htm.
Contemporary Control Systems, Inc. reserves the right to make changes in the specifications of the product described within this manual at any time without notice and without obligation of Contemporary Control Systems, Inc. to notify any person of such revision or change.