Temperature and hygiene

Legionella temperature monitoring

Wireless pipe probes on the calorifier flow and return, the end of each loop and the cold feed. Edge trends every point and raises an alarm when a temperature drops or a sensor goes quiet.

Build this system See the hardware
TES-22 Probe Temperature Sensor
TES-22Pipe probes
ZGW-20 Gateway
ZGW-20Gateway with Edge
Measure
Calorifier flow and return, the return leg of each loop, the cold-water supply
Rule
Calorifier flow 60 °C, return not below 50 °C HSG274
Sensors
TES-22 pipe probes, ±0.2 °C from 0 to 70 °C TES-2X datasheet (PDF, opens in a new tab)
On site
ZGW-20 Gateway, up to 250 wireless devices ZGW-20 datasheet (PDF, opens in a new tab)

Hardware for hot water temperature monitoring

One TES-22 reads a calorifier's flow and return. Each other pipe you watch takes a TES-21, and one Gateway serves the site.

If the plant has a controller with a register map

TES-22 and ZMB-31 share one enclosure with different terminals inside, so the ordering code is what you specify.

Sensor positions on a calorifier loop

Start from the risk assessment and the water-system schematic. The competent person names the sentinel points, and each probe answers a question about one of them.

Sensor positions on a calorifier loopEvery sensor reports wirelessly to the Gateway. The two probes of a TES-22 share one transmitter, so the flow and return pipes must both be within reach of its 2 m leads. Cold-water supply Calorifier Flow Nearest outlet Furthest outlet Return pump Return ZGW-20 GatewayEdge on site TES-22 · flow TES-22 · return TES-21 · loop end TES-21 · feed Sensor positions on a calorifier loopEvery sensor reports wirelessly to the Gateway. The two probes of a TES-22 share one transmitter, so the flow and return pipes must both be within reach of its 2 m leads. Flow Return pump Furthest outlet Nearest outlet Calorifier Cold-water supply ZGW-20 GatewayEdge on site TES-22 · flow TES-22 · return TES-21 · loop end TES-21 · feed
Every sensor reports wirelessly to the Gateway. The two probes of a TES-22 share one transmitter, so the flow and return pipes must both be within reach of its 2 m leads.
Sensor positions for sensor positions on a calorifier loop
PositionWhat it tells youReferenceSensor
Calorifier flow Whether water leaves storage hot enough 60 °C or above HSG274 TES-22 (on this page), probe 1
Calorifier return Whether the circuit loses too much heat on the way round Not below 50 °C HSG274 TES-22 (on this page), probe 2
End of each loop The far sentinel: the return leg towards the end of each circulating loop At least 50 °C, 55 °C in healthcare premises HSG274 TES-21 (on this page), one per loop
Cold-water supply Heat gained by the cold feed before it reaches the calorifier Below 20 °C where possible HSE TES-21 (on this page)

  • A pipe probe reads the pipe. HSG274 accepts surface readings on metallic return legs. Insulate over the probe so it follows the water, not the plant room.

  • Disinfection runs outside the accurate range. The pipe probe holds ±0.2 °C from 0 to 70 °C and ±0.5 °C up to 105 °C.

  • Keep the transmitter off hot metal. The sensor enclosure is rated to operate up to 55 °C. Mount it on a cooler surface and run the lead to the pipe.

Calorifier return temperature monitoring in Edge

Rules run on the Gateway itself and watch every probe at once.

A return below its limit
A limit rule on each return probe. Agree the limit and how long it must hold with the responsible person, so a short draw-off does not raise an alarm.
A sensor that stops reporting
A no-data rule fires when a probe has been silent for a set time, from one minute to a day, so a missing reading is never taken for a good one.
Who is told
Email, SMS, a webhook to the BMS or helpdesk, or an alert in Edge. Email and SMS need the Gateway's mail and SMS settings, and a connection to reach them.
A record through an outage
Each TES stores up to 70,000 readings in its own memory, so a radio outage does not lose the readings taken during it.

Commissioning checks

Do these before anyone relies on the trends, and repeat the last one when the system changes.

  • Every probe is on the schematic

    Name each sensor in Edge after its point on the water-system schematic, and photograph the fitted probe under its insulation.

    Pass when every sensor name matches a point on the current schematic.

  • Each probe agrees with a reference

    With the loop at temperature, read a calibrated contact thermometer on the same pipe beside each probe.

    Pass when each difference is inside the tolerance agreed with the responsible person, and recorded.

  • An alarm reaches a person

    Add a test rule on one probe with a limit its live reading already breaches, then delete the rule.

    Pass when the named recipient receives the message and acknowledges it.

  • A silent sensor is reported

    Take the battery out of one TES for longer than the no-data rule's time.

    Pass when the no-data alarm arrives and names that sensor.

  • Trends match the monthly checks

    Compare a month of trends with the manual monthly temperature checks at the same points.

    Pass when any consistent difference is explained and written into the record.

What monitoring does not replace

Temperature monitoring shows how the system behaves between manual checks. It does not assess every Legionella risk.

  • The risk assessment, the written control scheme and the responsible person.
  • Water sampling and microbiological testing.
  • Outlet checks. A probe on a pipe does not measure the water at a tap after one minute of running.
  • Flushing of little-used outlets, cleaning and disinfection, and the records of that work.
  • Scald protection. HSE sets separate requirements for thermostatic mixing valves in healthcare premises.

Sources and related guides

Sources

Related

Reviewed by EpiSensor Engineering on . Revision 5.

Put sensors where the risk assessment says they belong

We will propose sensor positions against the risk assessment and size the sensors and Gateway for the site.

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