Carrier 30XA, XW Chiller Water Flow sensor / Switch How does it work & How to Troubleshoot Explained

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Hi Welcome back to UA Technical solutions, today we will discuss most common water flow sensor used in carrier chillers, water flow sensors used in carrier 30gx , 30xa , 30xw are completely digital based there are 2 types of sensors, In older models of carrier chiller 4 pin water flow sensor were used , but it changed to 5 pin with the release of 30xa and 30xw models.
Water flow Sensor operates at 24 volt ac which is supplied by the main processor board via port number J1 B at sensor wire 1 and 3 ,
Wire 2 and 4 are from sensor relay and connected on the main base board at port number j 5 B
Wire 2 is to supply 24-volt ac from the main processer board to the relay common contact, and wire 4 is the feedback to the main processor board. When there is water flow this relay closes the contact and send 24-volt signal to the main processor board as confirmation of water flow.
Wire 5 is used for remote contact purpose only. And it is connected at port c33
Now we understand the sensor working principal and wiring lets learn how to troubleshoot the water flow sensor and water flow alarm,
First make sure chilled water pump is running and chilled water line valves are open also make sure there is pressure as per design,
Step 2 is to confirm 24-volt power supplied on wires 1 and 3 using a multi meter,
Step 3 is to check wire 2 and 4 have 24 volt each, you can use negative of transformer and positive on wire 2 and 4 as shown, if there is absence of 24 volt at wire 4 It means sensor is faulty replace the sensor.