T Series Legionella - Self Install Guide
Learn how to install the Invisible Systems T Series Legionella monitor. This guide covers pipe mounting, daisy chaining, temperature offsets, and connecting to the Live Platform.
Table of Contents
Use the below links to navigate to the section you need:
Introduction

Thank you for purchasing a T Series Legionella monitoring device. This manual explains how to install and set up the product.
Before the installation and use of the product, carefully read the supplied instructions.
The T Series Legionella monitor measures the temperature of water pipes, detecting any fluctuations or hot spots that may indicate the presence of legionella bacteria.
Specifications
| Measurement Range | Accuracy | Notes | |
|---|---|---|---|
| Temperature | -40°C to +105°C | ±0.3°C | |
| Operating Range | -20°C - +50°C | - | Battery must not be exposed to temperatures higher than +50°C |
Note: This product can have up to four datapoints, using daisy chained probes.
Limitations & Responsibility
- This guide provides instructions for installing Invisible Systems equipment only.
- It does not replace site-specific risk assessments or safe working procedures.
- Invisible Systems accepts no responsibility for installation work carried out by third parties outside the scope of this guide.
- Use of the Invisible Systems platform is subject to the applicable customer agreement and platform terms.
- Damage resulting from incorrect installation or use outside the scope of this guide may not be covered under warranty.
Safety
Warning
Keep batteries out of reach of children. Swallowing a lithium battery can cause serious injury.
Caution
If the battery becomes hot, swollen, leaks, or emits an unusual smell:
- Stop using the device immediately
- Remove the battery if safe to do so
- Move it away from flammable materials
- Contact Invisible Systems support
This product is intended for indoor installation only.
Caution - Ensure the pipework is cool or that protective gloves are worn before attaching the sensor.
Caution
This product uses a replaceable AA Cell Battery
- Use only the specified battery type
- Do not mix old and new batteries
- Do not use damaged or leaking batteries
- Do not short-circuit battery terminals
- Do not crush, puncture, or incinerate the battery
Caution
- Do not dispose of lithium batteries with general waste.
- Used batteries must be disposed of in accordance with local regulations.
What's in the Box
Note: As standard the sensor is sent with a 250mm probe cable. Longer cables are available on request.
The battery is supplied pre-installed.
| Item | Quantity |
|---|---|
| T Series Legionella Sensor | 1 |
| Sticker | 1 |
| Additional Probes | As Specified |
Options
Available probe configurations and cable lengths.
| Item |
|---|
| Single Probe |
| Dual Probe |
| Triple Probe |
| Quad Probe |
| 1 Meter Probe Cables |
| 2 Meter Probe Cables |
Before You Start
Prerequisites
Note: An active gateway must be installed and active before proceeding with sensor installation.
Before installing this device, ensure the following:
- You have an active account and login access to the Invisible Systems Live platform
- The monitoring location has been checked and agreed
- The installation location provides suitable signal coverage
- The device asset ID / label has been recorded or is visible
- You have safe access to the installation location
- The environment is within the normal operating conditions for the product
Tools Required
- Cable Ties
- Pipe Insulation
- Thermometer



Installation Steps
Record the Device ID
-
Note the 16-digit Device ID from the sticker on the rear of the device.
The ID will begin with 70B

Mount Transmitter
The legionella transmitter (white box) can be mounted on any cold or insulated pipe near the monitoring location.
- Using the mounting plate on the rear of the sensor thread two cable ties through the mount


-
Place on pipe and secure

Mount Sensor
Caution - Ensure that the pipework is cool or protective gloves are being worn before attaching sensor to hot pipes.
Sensors should be installed directly onto the pipe you are monitoring. The sensor has a flat side which should be placed against the pipe.
Follow your legionella risk assessment to determine the temperatures that need to be monitored.
Securing points are indicated on the sensor as ‘Cable Tie’

Single Sensor
-
Mount the sensor and secure in place.

-
Apply pipe insulation around the sensor

Multiple Sensors

Dependant on the requirements, you may have multiple sensors which are daisy chained together. This is useful if you are monitoring hot and cold pipes which are next to each other.
You can have up to four sensors daisy chained.
These may arrive pre connected. Refer to the Daisy Chain section.
Mounting instructions are the same as a single sensor installation.
Activate the Sensor
Before applying the front sticker, the device must be reset.
-
Using a small flat object, press the reset button as indicated below.

-
Observe the LED indicator:
- 1 green flash — device powered on
- After at least 30 seconds, 2 further green flashes — device successfully connected to the gateway
-
If the additional green flashes are not observed, repeat the reset procedure once.
If the device still does not connect, check that the gateway is online, as described in the Common Issues section.
Confirm Device Start-Up
-
1 green flash - device powered on
-
2 further green flashes - device successfully connected to the gateway
If the additional green flashes are not observed, refer to the Common Issues section.
Note: Do not proceed with installation if you have not seen the successfully connected flashes, refer to the Common Issues section.
Add the Sensor to the Live Platform
- Log in to the Invisible Systems Live Platform
- Navigate to Sensor Setup
- Select Add New Sensor
- Enter the 16-digit Device ID recorded earlier
For full platform instructions, refer to the Live Platform User Guide.
Verify Data Is Being Received
- In the Live platform, navigate to Sensor Diagnostics
- Confirm the sensor status is online
- Verify that data readings are being received
- If data is not visible, refer to the Common Issues section
Note: It may take up to 10 minutes after activation for data to appear.
Installation and commissioning are complete once data is visible in the Live platform.
Daisy Chains
Multiple sensors can be connected together in a daisy chain when monitoring more than one pipe (for example, hot and cold pipes in close proximity).
- Up to four sensors can be connected in a single daisy chain
- Each sensor is identified by a unique colour (Blue, Red, Black, Green)
- Each sensor is also marked with an address number (1, 2, 3, or 4)
- Do not use duplicate colours or address numbers within the same chain
Make a note of the sensor colour, address number, and the pipe it is installed on, as this information is required during system setup.
Connecting Sensors in a Daisy Chain
- Sensors may arrive pre-connected
- Once connected, sensors cannot be separated by hand
- To disconnect sensors, use a Picoflex (Micro Ribbon) connector extraction tool or a suitable non-metallic pry tool
If sensors are not pre-connected:
- Connect one sensor to the transmitter
- Connect the next sensor to the free port on the first sensor
- Continue connecting sensors end-to-end
You should only ever have one free port at each end of the chain. Do not create loops or branches. Daisy chains must be linear.
The order of sensors does not matter, provided there are no duplicate colours or address numbers.

Offsets
Temperature offsets may be required to align the sensor reading with the actual water temperature at the outlet.
When to Take an Offset Reading
Offsets should be determined after the sensor has been installed and activated, once the device is online and reporting data.
Determining the Offset Using a Handheld Thermometer
-
Complete installation and activation
Install the sensor and confirm successful activation (green LED flashes as described earlier).
-
Record the time
Make a note of the time at which the sensor was activated.
-
Identify the monitored supply
- If the sensor is installed on a hot water pipe, test the hot tap
- If the sensor is installed on a cold water pipe, test the cold tap
-
Run the tap
Open the tap and allow the water to run for at least 30 seconds to stabilise the temperature.
-
Measure the water temperature
Using a calibrated handheld thermometer, measure the water temperature and record the reading.

-
Record the sensor reading
Check the corresponding temperature reading from the sensor in the Live platform.
-
Calculate the offset
The difference between the handheld thermometer reading and the sensor reading should be used to determine the required offset, which can then be applied within the system.
If an Actual Water Temperature Cannot Be Measured
If it is not possible to take a direct water temperature measurement (for example, where no suitable outlet is available), use the offset values provided in the table below.
These values are based on typical temperature differences for common pipe materials and should be used as an alternative where direct measurement is not feasible.
| Water Temperature | Copper Pipe | ABS Pipe | UPVC Pipe | Galvanised Pipe |
|---|---|---|---|---|
| 10°C | -1.5 | -4 | -4.5 | -2 |
| 20°C | -1 | -1.5 | -1.5 | -1 |
| 30°C | 0 | +1 | +1.5 | 0 |
| 40°C | +0.5 | +4 | +4 | +1 |
| 50°C | +1 | +6.5 | +7 | +1.5 |
| 60°C | +2 | +10 | +10 | +2.5 |
Source: BSRIA AG4-94 Guide to Legionellosis
Values shown are temperature offsets in °C
Important Notes
- Offsets should only be applied after installation and commissioning are complete
- Ensure offsets are applied to the correct sensor and datapoint
- Any applied offset should be recorded for future reference
- Offsets should not be used to compensate for incorrect sensor placement
Common Issues
| Issue | Likely Cause | Action |
|---|---|---|
| No LED flashes after battery activation | Battery not seated | Recheck battery position and ensure the pull tab has been fully removed. Press the reset button. |
| Only one green LED flash observed | Device powered but not yet connected | Wait 60 seconds, then press the reset button. If still unresolved, check the gateway is online and move the sensor closer. |
| No data visible in Live platform | Device has not sent a data packet | Wait up to 10 minutes, then refresh the page. If the sensor shows online but no data is received, contact Invisible Systems Support. |
| Sensor shows offline in diagnostics | Battery issue or gateway connection | Press the reset button and refresh the page. If still offline, check the gateway is online and reposition the sensor closer, if 24 hours have passed contact Invisible Systems Support. |
| Incorrect readings displayed after 24 hours | Unsuitable mounting location | Relocate the sensor. If readings remain incorrect, contact Invisible Systems Support. |
Resetting the Sensor
-
Peel the sticker from the bottom right corner until you expose the second hole

-
Press the Reset Button
Using a small flat, non-metallic object, gently press the sunken reset button.
-
Observe the LED Indicator
Confirm the LED flashes as described in the installation steps.
Battery Replacement
Caution
- Do not use damaged, leaking, or swollen batteries
- Do not mix old and new batteries
- Do not short-circuit, crush, puncture, or incinerate batteries
- Keep batteries out of reach of children
-
Remove the Front Cover
Carefully remove the screw cover from the centre of the device.
Remove the single screw, then lift off the front cover.

-
Remove the Battery
Gently pull the battery out of the holder.

-
Insert the New Battery
Insert the new battery into the holder, ensuring the correct polarity is observed.
Note: The battery terminals may not hold the battery tightly after battery removal. Battery terminals may be gently bent inwards using finger pressure only.
-
Confirm Device Start-Up
Observe the LED indicator to confirm the device powers on.
-
Re-fit the Front Cover
Replace the front cover and secure it using the two security screws.
Support
For the fastest resolution, please use the Support options below.
- Visit www.invisible-systems.com
- Select Support from the main menu
- Access the Help Centre or Raise a Support Ticket
When raising a support ticket, please provide:
- Device ID
- Site name
- Description of the issue