Hi, I'm Patricia Bleckman with KE2 Therm solutions. In this video, we'll cover how to troubleshoot
a suction line pressure transducer. To ensure the pressure transducer is reading
correctly, first verify the pressure transducer is correct for the application. The model number as well as range should be
marked on the unit. For most refrigerants, the controllers use
a zero to one hundred fifty psia or absolute transducer, for R-410A the controllers use
a zero to three hundred psig or gage transducer, and finally CO2 uses a zero to five hundred
psig also a gage pressure transducer. Once the transducer is confirmed to be matched
to the refrigerant selected, the next step is to verify the sensor's reading. Many times this can be done by simply attaching
a calibrated gage set to the same suction line and verifying the readings are similar.
If this is not possible or the readings do
not match, the sensor reading can be verified using a multi-meter. The first step, and I know this can sound
silly, is identify the cable from the pressure transducer. It contains 3 wires: Red, Black, and Green. Valiate the sensor's connection to the controller,
And that the cable between the sensor and the controller has not been damaged. You'd be surprised how many times we catch
the problem here. Once the integrity of the cable and connection
are verified, identify confirm each wire is connect to the
correct position on the controller. Now that the sensor model and wiring are confirmed,
it is time to verify the pressure reading itself. To do this you will need to have your multi-meter
ready and set to read DC volts. With the Red probe to the red wire and the
black probe to the black wire, confirm the voltage is reading positive, or +5 Volts.
If this reading is correct, proceed to the
next step. If not, determine why you're not getting the
correct reading. Next, move the Red probe to the green wire's
position and measure the voltage. NOTE THIS READING as it will be used to calculate
the pressure read by the controller. Now's the part where we have to use math … And
we know for many of you this may not be your favorite part, but trust us it looks worse
than it is. Use the voltage reading taken between the
green and black wires into the following equation: As you can see in the equation, the first
thing you need to do is subtract 0.5 volts, or a half a volt from the reading.
Next divide the new number by 4, since this
is the range of the transducer. Finally multiply this number by the range
of the transducer, so for most refrigerants this is 150. If you find your result is about 14.7 pounds
below what you thought it should be, don't worry. This is because it is an absolute transducer. The controller automatically converts the
pressure to gage since that's what we're used to seeing. The engineers used an absolute transducer
for those of you that need really cold saturation temperature to meet your customer needs. So it's that simple. In a few steps you are able to go from a DC
voltage reading, to what the controller is reading.
For more information visit our website or
contact our technical support line..
