Welcome to Controls Traders, located in Adelaide, South Australia. We are a supplier of quality building automation controls and peripheral products for the HVAC industry. We stock a full range of controllers, sensors, valves and actuators, damper actuators and accessories to suit any application. Our aim is to provide our customers with the highest level of service, from sales to delivery and after sales support. With our extensive in-house knowledge and expertise in the industry, we can advise you on selection and application of our wide range of controls products.
Backed by 40 years industry experience. When you just need to be sure.
No, we’re serious. Anywhere. Anytime.
We stock all major global brands. And if we don’t have it, we’ll find it.
We warehouse the stock so you don’t have to wait.
$150.00 ex GST
Maximizing Accuracy with DP Sensors and Air Gauge Accessory Kits
In the realm of building automation, while temperature sensors dictate comfort, pressure sensors dictate safety and mechanical efficiency.
Differential Pressure (DP) sensors are the silent workhorses of the plant room. They allow the Building Management System (BMS) to "feel" the resistance in the ductwork, providing the critical data needed to ramp up Variable Speed Drives (VSDs) or trigger maintenance alarms.
At Controls Traders, we stock high-accuracy air pressure sensors from brands like BAPI and Schneider Electric, alongside the necessary hardware to install them. Here is a guide on maximizing your airside accuracy.
Why Monitor Differential Pressure?
An air DP sensor measures the difference in pressure between two distinct points and outputs an electrical signal (like 0-10V) to the BMS. There are two primary applications in HVAC:
1. Filter Monitoring: As Air Handling Unit (AHU) filters accumulate dust, the pressure drops significantly across the filter bank. By placing the "High" port of the sensor before the filter and the "Low" port after the filter, the BMS can monitor this resistance. Once it hits a critical threshold (e.g., 150 Pascals), the system flags a "Dirty Filter" alarm, ensuring maintenance is driven by actual data rather than a calendar.
2. Duct Static Pressure Control: In a VAV (Variable Air Volume) system, as terminal boxes open and close, the pressure in the main supply duct fluctuates. A static pressure sensor—typically installed two-thirds of the way down the main duct—monitors this. If pressure drops, the BMS tells the supply fan to speed up; if it rises, the fan slows down, saving massive amounts of fan energy.
The Role of Air Gauge Accessory Kits
A high-quality sensor is useless if it cannot properly interface with the air stream. This is where the Air Gauge Accessory Kit comes into play.
These kits typically include the clear pneumatic tubing, mounting brackets, and the static pressure probes required to cleanly penetrate the ductwork.
Selecting the Right Sensor
When sourcing a DP sensor, ensure you select the correct pressure range.
Fast Delivery Across Australia
Don't let a missing accessory kit or a faulty pressure sensor delay your commissioning. Controls Traders warehouses a full range of Sensors & Transducers, including high-grade DP sensors and accessory kits, in our Adelaide facility.
Browse our catalog online or call our team on 1300 740 140 for expert selection advice and fast Australia-wide shipping.
What is the difference between an air DP sensor and a liquid DP sensor?
Air DP sensors (dry media) measure pressure differences in ductwork — typically in Pascals (Pa) — and are used for filter monitoring and duct static pressure control. Liquid DP sensors (wet media) measure pressure drops across pumps, chillers, and valves in hydronic systems, usually reading in kPa or Bar. The two types are not interchangeable — using a dry media sensor on a liquid application will damage or destroy it.
What pressure range should I select for a filter monitoring DP sensor?
For standard AHU filter banks, a 0–250 Pa sensor is typically sufficient. A clean filter will read close to 0 Pa, and you would set the BMS alarm threshold at around 150–200 Pa to flag a dirty filter before it causes significant airflow restriction. If your filters are coarser or your system runs at higher face velocities, a 0–500 Pa range may be more appropriate.
Where should a duct static pressure sensor be installed?
The standard practice is to install the static pressure sensor approximately two-thirds of the way down the longest main supply duct run, downstream of the main branch take-offs. This location represents the most challenging point for the fan to maintain pressure. Installing it too close to the fan will cause the BMS to react to local turbulence rather than true system pressure, leading to unstable fan speed control.
What is a Magnehelic gauge and how does it work alongside a BMS sensor?
A Magnehelic is an analog visual differential pressure gauge that uses a diaphragm and a magnetically linked pointer to display pressure. In critical environments like hospitals and cleanrooms, a Magnehelic is mounted on the outside of the AHU alongside the digital BMS sensor, giving technicians an instant visual pressure reading during walk-arounds without needing to log into the BMS. It serves as both a verification tool and a backup indicator.
Can a single DP sensor be used for both filter monitoring and duct static control?
No — these are two separate measurement points requiring separate sensors. Filter monitoring measures the pressure drop across the filter bank (between the dirty and clean sides of the filter). Duct static pressure control measures the pressure in the supply duct downstream of the fan and coils. Both are important, both require their own sensor and pneumatic connections, and both are typically wired to separate BMS inputs.
Read more
In commercial HVAC control panels, the Building Management System (BMS) relies on two critical functions to operate mechanical equipment safely: command (telling a device to start) and feedback (confirming it is actually running).
To achieve this, panel builders rely heavily on relays and current switches. At Controls Traders, we supply premium electrical components, including the highly sought-after Automated Components Inc (ACI) current switches and Schneider Electric relays.
Here is a practical guide on how these two essential components work together in a typical HVAC panel and best practices for wiring them.
The Role of the Schneider 24VAC Relay (The Command)
A BMS controller typically outputs a low-voltage (24VAC or 24VDC) signal. However, the exhaust fan or pump you want to start likely requires 240VAC or 415VAC. You cannot wire a high-voltage fan directly to a low-voltage controller without destroying it.
The Schneider 24VAC 2-Pole Relay acts as the isolation bridge.
The Role of the ACI Current Switch (The Feedback)
Just because the BMS commanded the relay to close does not mean the fan is moving air. A belt could be snapped, or a local isolator could be turned off. This is where "Proof of Flow" is required.
The ACI Solid Core Adjustable Current Switch provides this proof.
Best Practices for Panel Builders
Source Your Electrical Controls Locally
Sourcing reliable control panel parts shouldn't hold up your manufacturing schedule. Controls Traders, based in Stepney, South Australia, warehouses a massive range of Switches & Electrical components.
Whether you need a box of Schneider relays or ACI adjustable current switches, we offer fast, Australia-wide delivery. Browse our range online or call us on 1300 740 140 for project pricing.
What is the difference between a relay and a contactor in HVAC control panels?
A relay is a smaller switching device typically used for low-to-medium current loads — such as starting a single fan or signalling a control circuit. A contactor is a heavier-duty switching device designed for high-current loads like large motors, chillers, or three-phase pump starters. In BMS panels, relays handle the command interface between the low-voltage controller and the high-voltage field circuit, while contactors are usually found in the motor control centre (MCC).
Why use an adjustable current switch instead of a fixed one?
An adjustable current switch lets you set the exact amperage trip point to match the motor’s normal operating load. This is critical for detecting broken belts — a fan motor with a snapped belt still spins and draws current, but at a lower level than normal. A fixed switch may not detect this subtle drop, whereas an ACI adjustable current switch can be calibrated to trip below the unloaded motor current, triggering an alarm immediately.
Can I use the same relay for both 24VAC and 24VDC?
Not necessarily — relay coils are rated for specific voltage types. A relay rated for 24VAC may not pick up reliably on 24VDC, and vice versa. Always check the coil voltage specification on the relay datasheet before wiring. Controls Traders stocks both AC and DC variants of common HVAC relays — call 1300 740 140 to confirm the correct model for your application.
How do I loop a wire through an ACI current switch for low-amperage motors?
If the motor draws less current than the minimum sensing threshold of the ACI switch, simply loop the live supply wire through the solid core multiple times. Each additional loop effectively multiplies the sensed current by the number of passes. For example, three loops through the core triples the apparent current reading, allowing the switch to detect very small motors reliably.
Where can I buy ACI current switches and Schneider relays in Australia?
Controls Traders stocks ACI adjustable current switches and Schneider Electric relays from our Adelaide warehouse for fast Australia-wide delivery. Browse our Switches & Electrical range online or call 1300 740 140 for bulk project pricing.
Read more
.png)
The Complete Guide to BAPI 10K-2 Sensors: Room, Duct, and Immersion
In the world of Building Management Systems (BMS), the 10k Type 2 thermistor is the undisputed industry standard. And when Australian integrators look for reliable, high-quality 10k-2 sensors, they overwhelmingly turn to BAPI.
A thermistor is an NTC (Negative Temperature Coefficient) device, meaning that as the temperature in the room or duct rises, the electrical resistance of the sensor drops. This provides a highly sensitive, cost-effective signal that almost every BMS controller on the market can read natively.
At Controls Traders, BAPI 10K-2 sensors are consistently among our top-performing products. Here is a complete guide to the three most critical BAPI 10K-2 form factors and where to apply them.
1. BAPI 10K-2 Quantum Room Sensor
The Quantum Room Sensor is designed for the occupied space. It features a modern, clean aesthetic that blends into high-end office environments while providing rapid response to changing heat loads.
Best Application: Standard office VAV zones, meeting rooms, and corridors. Because room sensors are exposed to the ambient environment, the BAPI Quantum housing is designed to allow excellent airflow over the 10k-2 thermistor bead, ensuring the BMS doesn't lag behind the actual room temperature.
2. BAPI 10K-2 Duct Temperature Sensor
Monitoring the air inside your ductwork is critical for controlling Air Handling Units (AHUs). BAPI provides robust Duct Sensors equipped with the 10k-2 thermistor.
Best Application:
3. BAPI 10K-2 Immersion Temperature Sensor
Water is the lifeblood of central HVAC plants. The BAPI Immersion Sensor is built to sit directly in the fluid flow to measure chilled or heating water.
Best Application: Chiller supplies, boiler returns, and condenser water loops. These sensors are inserted into a stainless steel or brass thermowell. Pro Tip: Always use thermal paste when inserting the BAPI sensor into the well to eliminate insulating air gaps and ensure a lightning-fast response time.
Why Buy BAPI from Controls Traders?
Using an incorrect sensor curve (like wiring a 10k-2 sensor into a controller programmed for a 10k-3) will result in massive temperature offsets and system failure. Standardization is key.
By standardizing your site on the BAPI 10K-2 range, you ensure uniform accuracy from the chiller plant to the boardroom.
Controls Traders warehouses a massive inventory of Sensors & Transducers, including the full BAPI 10K-2 Quantum, Duct, and Immersion lines. Located in Adelaide, we provide fast, Australia-wide shipping so you can keep your commissioning schedule on track.
Browse our BAPI range online today or call 1300 740 140 for technical selection advice.
Frequently Asked Questions
What is a 10k Type 2 thermistor?
A 10k Type 2 (10k-2) thermistor is an NTC (Negative Temperature Coefficient) resistive temperature sensor with a nominal resistance of 10,000 ohms at 25°C. As temperature increases, resistance decreases. It is the most widely used thermistor curve in building automation, natively supported by virtually all major BMS controller brands. The "Type 2" refers to the specific resistance-temperature curve — it is not interchangeable with Type 3 without reconfiguring the controller software.
What happens if I wire a 10k-2 sensor into a controller configured for 10k-3?
The BMS will still receive a signal, but the temperature reading will be significantly offset — often by 5°C or more depending on the operating range. This will cause the controller to over-cool or over-heat the space, wasting energy and generating comfort complaints. Always verify the thermistor curve in the controller configuration matches the sensor you are installing.
What is the difference between a BAPI rigid probe and an averaging duct sensor?
A rigid probe inserts into the duct at a single point and is best used in small, well-mixed ducts like supply air branches. An averaging sensor stretches across the full width of the duct, measuring at multiple points simultaneously. Averaging sensors are essential in large AHU mixed-air plenums where cold outside air and warm return air can create significant temperature stratification — a single-point probe in that environment will give a misleading reading.
Why use thermal paste with an immersion sensor thermowell?
Without thermal paste, an air gap forms between the sensor tip and the inside of the thermowell. Air is a poor conductor of heat, which creates thermal lag — the water temperature changes, but the sensor takes many minutes to register the shift. This delay causes the controller to overreact and hunt. Filling the gap with thermal conductive paste ensures the sensor responds almost instantaneously to changes in fluid temperature.
Where can I buy BAPI sensors in Australia?
Controls Traders stocks the full BAPI 10K-2 sensor range — including Quantum room sensors, duct probes, averaging elements, and immersion sensors — from our Adelaide warehouse with fast Australia-wide delivery. Call 1300 740 140 for technical advice and project pricing.
Read more
In a Building Management System (BMS), your mechanical plant is only as smart as the data it receives. If a chiller plant receives bad data from a faulty return water sensor, it will operate inefficiently—no matter how advanced the controller logic is.
When building occupants complain about stuffy rooms or freezing drafts, the mechanical equipment is often blamed first. However, the root cause is frequently sensor failure.
At Controls Traders, we supply premium Sensors & Transducers across Australia. Drawing on our 40 years of experience, here is an advanced troubleshooting guide to identifying the symptoms of faulty HVAC sensors.
Symptom 1: Massive Temperature Offsets (-40°C or +120°C)
If your BMS is suddenly reading an impossible temperature (like -40°C in an office or +120°C in a chilled water line), the issue is almost certainly electrical, not environmental.
The Cause:
Symptom 2: Sluggish or "Hunting" Control Loops
If the room temperature swings wildly from hot to cold, or the chilled water supply temperature oscillates, the sensor may be suffering from thermal lag.
The Cause:
Symptom 3: CO₂ and Humidity "Drift"
Unlike standard thermistors (which rarely drift), Indoor Air Quality (IAQ) sensors—like CO₂ and Humidity transducers—contain active sensing elements that can degrade or drift over time.
The Cause:
What to Do When a Sensor Fails
If a sensor has drifted beyond repair or suffered water ingress, it must be replaced to restore building efficiency.
Standardizing your site with reliable, high-quality sensors from reputable brands reduces the frequency of these service calls. Controls Traders warehouses a massive inventory of Sensors & Transducers locally in Adelaide.
Whether you need a replacement duct probe or a highly accurate room unit, we offer fast shipping Australia-wide. Call our support team on 1300 740 140 for cross-referencing and technical advice.
How do I know if my HVAC temperature sensor has an open circuit or short circuit?
For a 10k thermistor, use a multimeter set to resistance (ohms). At room temperature (~25°C), a healthy 10k-2 sensor will read approximately 10,000 ohms. A reading of OL (overload/infinite resistance) indicates an open circuit — the wire or sensor element is broken. A reading of near 0 ohms indicates a short circuit — the wires are touching. Both faults produce extreme temperature readings on the BMS (typically -40°C or maximum scale).
What is Automatic Background Calibration (ABC) in CO₂ sensors?
ABC is a self-calibration feature in CO₂ sensors that assumes the lowest CO₂ reading recorded over a rolling period (typically 1–2 weeks) represents clean outdoor air (~400 ppm). The sensor uses this baseline to correct for drift. ABC works well in buildings that are regularly unoccupied overnight. However, in buildings occupied 24/7 — like hospitals or data centres — CO₂ never drops to baseline, and ABC logic will gradually drift the calibration upward, requiring manual recalibration or replacement.
Why does my room temperature sensor read correctly at times but drift at others?
Intermittent readings usually point to a loose connection or a partially broken wire that makes and breaks contact with vibration or temperature changes. Check terminal screws at both the sensor and controller ends first. If wiring checks out, the thermistor bead itself may have a hairline fracture — common in older sensors that have experienced physical shock — and the sensor will need replacing.
Can a humidity sensor be repaired after moisture or chemical contamination?
Generally no. Humidity sensors use a polymer film that absorbs and releases moisture to measure relative humidity. Chemical contamination or prolonged exposure to saturated air (RH > 95%) permanently alters the polymer, skewing the reading. Some manufacturers offer a bake-out recovery process for mild contamination, but in most cases, a contaminated humidity sensor must be replaced. Controls Traders stocks replacement room sensors with integrated humidity sensing for fast dispatch from Adelaide.
How often should HVAC sensors be recalibrated or replaced?
Standard thermistors (10k-2) rarely need recalibration and can last 15+ years if installed correctly. CO₂ sensors typically require recalibration every 2–3 years and replacement every 5–7 years depending on the environment. Humidity sensors in clean indoor environments can last 7–10 years, but those exposed to outdoor air, pool environments, or chemical fumes may need replacement every 2–3 years. Differential pressure sensors should be verified annually against a calibrated reference.
Read more
