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Home > Blackcomb > Troubleshooting > Blackcomb - Low UV Intensity Alarm
Blackcomb - Low UV Intensity Alarm
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A low UV output alarm can only be displayed if a UV sensor is installed in a UV system. Many different factors can cause the UV intensity reading to be low when a UV sensor is installed. If low UV intensity is detected, one of the following screens will be displayed.




When determining the cause of a UV alarm, the first step is to perform a water quality test. It is important that water quality parameters fall within the specifications below.


Hardness:                        <7 gpg (120 mg/L)

Iron (Fe):                          <0.3 ppm (0.3 mg/L)

Manganese (Mn):          <0.05 ppm (0.05 mg/L)

Turbidity:                         < 1 NTU

Tannins (organics):        <0.1 ppm (0.1 mg/L)

UVT (transmittance):    >85%


If the water quality falls outside the requirements, pre-filtration must be installed to resolve the issue. If the water quality falls within the requirements above, a dry test should be performed following the directions below.

Dry Test Procedure

  • Shut off the water source.
  • Unplug the controller from the power source.
  • De-pressurize the chamber and drain water.
  • Clean and dry the sensor and reinstall.  How to Clean a UV Sensor
  • Clean and dry the quartz sleeve and reinstall. How to Clean a Quartz Sleeve
  • With the water still shut-off, plug the controller into the power source.
  • Check the UV intensity. If 100%, the UV sensor is operating normally.

If the dry test shows a good result, other possible causes of low UV alarms are:

  • Air bubbles in water.
    • This can be tested by taking a water sample after the UV system in a clear glass. Look to see if bubbles form. If they do, there are air bubbles in the water. This must be purged from the water supply before the UV system.
  • High water temperatures.
    • This is seen when water is not flowing through the chamber for long periods of time. A flowmeter or a temperature relief valve can be installed to mitigate this issue.  



If the UV sensor is displaying a low UV intensity during a dry test, or if the cause for the alarm is undetermined after troubleshooting, please submit a ticket for support. New Ticket


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