Series-CDTR

Supported Applications

The Dwyer Series CDTR Carbon Dioxide, Relative Humidity & Temperature Transmitters are designed to accurately monitor CO2 concentration and temperature in indoor environments. Documented applications include schools, office buildings, hospitals, and other facilities requiring demand control ventilation or energy savings support for LEED® certification.

The series supports specific regulatory compliance needs:

• Schools (K-12): DSA-compliant option (-S) available with a front-facing LED that illuminates when CO2 exceeds 1100 PPM, addressing requirements under Public Utilities Code 1625 (Assembly Bill 841).
• Ventilation Control: Optional relay output allows control of exhaust fans, windows, dampers, or signaling lights/horns based on user-adjustable set points.

Operating Conditions & Performance

The Series CDTR utilizes a single-beam dual-wavelength non-dispersive infrared (NDIR) sensor with an expected life of 15 years. The transmitters feature digital barometric pressure adjustment to maintain accuracy at various elevations and include Automated CO2 Baseline Correction (ABC) for maintenance-free operation in intermittently occupied spaces.

Measurement Ranges:

• CO2: 0 to 2000 PPM or 0 to 5000 PPM (depending on model).
• Temperature: 32 to 122°F (0 to 50°C).
• Relative Humidity: 0 to 85% RH or 0 to 100% RH (non-condensing, for units configured with humidity output).

Accuracy Specifications:

• CO2: ±40 PPM + 3% of reading at 2000 PPM; ±50 PPM + 5% of reading at 5000 PPM. (Note: Specified CO2 accuracy is guaranteed after three weeks of continuous operation in intermittently occupied environments).
• Temperature: ±1°C @ 25°C.
• RH: ±2% for units configured with humidity output (measured at 10 to 90% RH or 0 to 85% RH depending on source).

The response time is documented as 2 minutes for a 90% step change. A warm-up period of 30 minutes is required upon powering the transmitter.

Configuration Options

The series offers configurable mounting styles, output signals, and display options to accommodate diverse installation requirements while maintaining consistent sensor performance.

• Housing & Mounting: Available in North American style wall mount or duct mount configurations. Duct mount probes feature a diameter of 1-15/64" [31.35] and an overall length of 11-49/64" [298.85]. Wall mount units measure approximately 4-1/2" height x 2-51/64" width.
• Power Supply: Universal input supporting 16-35 VDC or 19-28 VAC.
• Output Signals (Selectable via DIP Switches):
• Current: 4-20 mA (max. load resistance 500 Ω).
• Voltage: 0-5 VDC or 0-10 VDC (min. load resistance 500 Ω). Other ranges include 0-20 mA, 2-10 mA, 0-5 mA, and various voltage spans.
• Relay: SPST NO rated 2A @ 30 VDC with user-adjustable set points (RON/ROF).
• Sensor Output: RTD or thermistor per r-t curves on page 4 of the manual (depending on model).
• Display Options: Integral LCD display available; remote indication supported via Model A-449. Remote calibration and validation are supported via Model A-449A.
• Compliance & Approvals: CE marked. DSA-compliant option (-S) for school environments.

Key Product Differences

The Series CDTR encompasses both wall mount and duct mount form factors, distinguished by their physical dimensions and installation method (wall plate vs. cut hole into duct). The series title indicates the inclusion of Relative Humidity measurement in the "CDTR" designation.

• Wall Mount: Designed for indoor room monitoring with a compact housing profile suitable for standard wall installations.
• Duct Mount: Features an extended probe design (overall length 11-49/64") intended for insertion into HVAC ductwork to monitor air quality within the distribution system.

Variants differ by CO2 range selection (0–2000 PPM vs. 0–5000 PPM) and output configuration, which is set via internal DIP switches for current or voltage ranges. The DSA-compliant option (-S) adds a front-facing LED indicator specific to school monitoring requirements.