RH-Combo-Duct-Balco

Supported Applications

The ACI Relative Humidity Duct with Balco Sensor series is a relative humidity transmitter designed for commercial heating and cooling building management systems. The unit features a thermoset polymer capacitive sensing element with a factory-fitted hydrophobic filter, providing resistance to dust, dirt, oils, and common environmental chemicals found in duct environments.

Operating Conditions & Performance

The series measures relative humidity across a 0-100% range within an operating environment of -40 to 140 °F (-40 to 60 °C). Storage temperature ranges from -40 to 149 °F (-40 to 65 °C), and the device operates in non-condensing conditions up to 95% RH. Accuracy specifications vary by selected range: +/- 1% over a 20% RH Range between 20 to 90%, or +/- 2% from 10 to 95%. The Balco RTD temperature sensor provides an accuracy of +/- 1.0% at 70 °F (21.1 °C). Response time is typically 20 seconds for humidity and 10 seconds nominal for the temperature sensor, with long-term stability listed as less than 2% drift over 5 years.

Power & Signal Specifications

• Supply Voltage: Configurable by output type. For 4-20 mA: 15 - 40 VDC / 18 - 28 VAC (with 250 Ω load) or 18 - 40 VDC / 18 - 28 VAC (with 500 Ω load). For 0-5 VDC: 12 - 40 VDC / 18 - 28 VAC. For 0-10 VDC: 18 - 40 VDC / 18 - 28 VAC.
• Output Signal: Factory default is 2-wire 4 to 20 mA; field-selectable via DIP switches for 3-wire 0-5 or 0-10 VDC and 4 to 20 mA.
• Load Resistance: Maximum 700 Ω for 4-20 mA output; minimum 4K Ω for voltage outputs (0-5 VDC or 0-10 VDC).

Installation Requirements

Sensors must be mounted in the middle of the duct where air circulation is well mixed, away from bends or obstructions. The probe should be placed three to four duct segments down from any bend and not on 90° bends. Mounting on the top or sides of ductwork is required; mounting on the bottom risks damage due to moisture.

Configuration Options

The series supports multiple enclosure configurations, wetted materials, and output options tailored for specific installation environments.

Housing & Enclosure Options

• Euro (-EH) Enclosure: ABS Plastic with UV Protectant (UL94-VO), rated NEMA 4X (IP 66). Features a gasketed cover and conformally coated boards.
• NEMA 4X (-4X) Enclosure: Polystyrene Plastic (100% V2, UL94-V2).
• D-BB Enclosure: Aluminum housing, Plenum Rated, NEMA 3R.

Sensing Tube & Filter Materials

• -EH Models: 304 Series Stainless Steel sensing tube with a stainless-steel sintered filter (optional accessory available).
• -4X and -BB Models: Schedule 40 PVC (White) sensing tube with slotted PVC without filter.

Sensor & Calibration Features

• Balco RTD Output: 1 KΩ nominal at 70 °F (21.1 °C), Orange/Yellow wire colors, with a temperature coefficient of 4618 ppm/°C.
• DIP Switch Configuration: On-board switches allow field selection of output signal and calibration adjustments without replacing the sensing element.
• NIST Certification: Three-point NIST Calibration Certificates are available (20%, 50% & 80%).
• Test Points: Includes built-in options to verify operation at 0%, 50%, and 100% RH.

Electrical Connections

The unit utilizes screw terminal blocks (polarity sensitive) accepting wire sizes from 16 AWG (1.31 mm²) to 26 AWG (0.129 mm²). Terminal block torque rating is specified at 4.43 to 5.31 lb-in (0.5 to 0.6 Nm).

Key Product Differences

The series distinguishes itself through specific enclosure materials and sensing tube constructions that dictate environmental suitability.

• -EH Configuration: Designed for weatherproof applications with a Euro-style ABS plastic housing, 304 Series Stainless Steel probe (7.75" length x 0.75" diameter), and sintered filter protection.
• -4X Configuration: Utilizes a Polystyrene Plastic NEMA 4X enclosure with a Schedule 40 PVC sensing tube (7.20" length x 0.840" diameter) featuring slotted PVC without a sintered filter.
• -D-BB Configuration: Features an Aluminum Plenum Rated NEMA 3R housing, also utilizing the Schedule 40 PVC sensing tube (7.20" length x 0.840" diameter) with slotted PVC without a sintered filter.

Accuracy options are selectable at order: RH1 for +/-1% over a specified 20% range, or RH2/RH3 for wider ranges of +/-2% or +/-3%. The series includes agency approvals UKCA, CE, RoHS, and WEEE.