Support on Coriolis Mass Flow meter

Model: CMF025M320N0A2EZZZ

Transmitter: 2400SIA11B2EZZZ which gives 4-20mA output.

I am using above Corriolis mass flow meter for R410A refrigerant flow measurement.

Flowmeter is connected in-between the liquid line between Condenser outlet and Evaporator Inlet.

Condenser ------ Flowmeter ------ Evaporator. (/resized-image/__size/304x406/__key/communityserver-discussions-components-files/39/MicrosoftTeams_2D00_image-_2800_13_2900_.png

Observed that my Condenser outlet pressure is constant when Unit is operated in steady state condition  , Flow meter values are varying by 4.5% of range and the Evaporator inlet pressure also varying continuously.

Pressure drop between Condenser outlet and Evaporator inlet pressure is 10Psia.

We have installed a sight glass before flow meter which is indicates clear refrigerant flow without any bubbles.

Other Observations: 

  • Initial Status light of flowmeter is Amber before unit is turned on and showing negative flow in the display -2 to -3 lb/min
  • Once unit starts Status light changes to Green.
  • Unit is running and when it is turned off status light is green and there is no amber light flashing. Also flow is 0lb/min.
  • After some time unit is turned off ,  approx. one hour status light changes to amber and flow is again showing negative in the display.

Also found the other pressures of our air conditioning systems are constant in steady state except evaporator inlet pressure i.e.   Flowmeter outlet pressure

Could you please suggest what are all the mounting and other precautions has to be done while installing Coriolis mass flow meter in our setup

2 Replies

  • What is the flow range that is configured?
    What are you measuring (lb/hr, lb/min, g/min)?
    What size is the tubing that is connected to the flowmeter?
    How long is the tubing run from condenser outlet to the flowmeter and from the flowmeter to the evaporator?
    Are there any bends in the tubing run?
    What flow is the flow meter showing when in steady state?
    What do you see in the sight glass one hour after the unit is turned off?
    Do you have access to a HART communicator to be able to connect to and configure / monitor the flow meter / transmitter status and error messages?

    Concerning flowmeter installation:
    Looking at the picture that was provided, it looks like you had to add several fittings before and after the flowmeter to connect it to the tubing between the evaporator and the condenser.
    It also looks like the tubing really cannot hold the weight of the flowmeter. It seems to be sagging on on side.
    It really is not necessary for measurement accuracy, but I would recommend to get 1/2" threaded tubing or better pipe that fits in the process connections on the flowmeter and extend that on both sides until it rests on the metal frame that is shown in the picture. If possible, install some clamps on the frame to hold the new tubing or pipe in place, then reduce to the tubing size you need.

    Concerning the flow variability:
    Without seeing the configuration of the transmitter, I can only guess. My theory is that with the installation of the flowmeter, you have introduced a pressure drop that is big enough to drop the pressure in the flowmeter low enough that the R-410A starts to evaporate in the line and is forming bubbles at the outlet. This could explain the flow variability and the varying evap inlet pressure. You could check that by checking the temperature of the line before and after the flowmeter. If the line temperature is considerably lower after the flowmeter, this could support this theory.
    I do not know if it is possible for you to introduce some back pressure after the flowmeter before the evaporator by using a globe valve to throttle the flow. But this would cause the R-410A to evaporate maybe right after the globe valve.
    It might also be necessary to add insulation to the tubing and the flowmeter to eliminate the temperature of R-410A changing and to ensure it stays in liquid from (I do not know how much of an effect this would have, I just speak from my experience with my home HVAC system).

    Concerning the amber light:
    My guess is, that when you shut down the system, you loose pressure in the system which causes the R-410A to evaporate in the flowmeter after some time and the flowmeter showing an error because the density of the R-410A gets too low or the transmitter detects dual phase in the flow meter. This can be confirmed with a HART communicator.

    I hope this gives you some helpful ideas to try.

  • Hello Prithvisaran,  

    This type of troubleshooting would best be handled by contacting our Micro Motion technical support team at  My initial guess is that the fluid is warming and flashing during stoppages.  Here are a few other comments:

    1) In order to achieve the best measurement performance, the meter should be zeroed at process conditions (bring the meter to operating temperature and pressure, block it in, and calibrate zero).  However, if flow is stopped and the conditions change, the meter may report a small flow rate (positive or negative).  An appropriate low flow cutoff should effectively negate seeing these readings.  If the fluid is flashing or has bubbles in it, the flow readings can be erratic, but especially at no flow.

    2) If the status light is not green, it means there are informational alerts present.  Which alerts are indicated?  I would look for A102 (Drive Overrange) or A105 (Slug Flow) if the fluid is outgassing.  Refer to Section 7.5 in the 2400S manual for instructions on viewing and acknowledging alerts:

    3) Also, additional diagnostic variables can be viewed from the display (such as Drive Gain and Density) - which can confirm the presence of gas in your liquid.

    Let us know if there's anything else we can do to help,