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Flow switch!

Flow switch!

Flow switch!

(OP)
I have been having a really hard time with a problem on site.  We presently use a paddle wheel style flow switch for HVAC/ventalation low flow indication.  I strongly dislike these unreliable and hard to set up switches.

I have been tempted to go toa 3/4 four wire velocity/flow transmitter, but know that the costy of this will get squashed.  Instead, I have been looking into thermal switches.  There are many of these on the market at decent prices, but it appears they are all 3/4 wire devices.  

Needless to say, I do not want to spend a small fortune running new cable for 100 switches.  I really want to get away from switches with moving parts, and thought thermal was the answer.

Does anybody know of such a 2 wire device?  Are there any other suggestions?  


Any input on this one would be extremely welcome.  I have been doing a lot of diffing on this, all to no avail!

RE: Flow switch!

Hi, some time ago I made a PIC based airflow sensor. It could be made into a 4-20mA device I guess.

RE: Flow switch!

There are "no moving parts" anemometers that are heated wires or ultrasonic whistle based.

Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com

RE: Flow switch!

What type of paddle wheel switch are you using? I know of a company that specializes in custom thermal flow measurement. try intekflow.com

Dr. Tim and Dr. Joe
Flow Measurement and Steam Surface Condenser Professionals

RE: Flow switch!

(OP)
I realise a thermistor is the way to go, but am trying to stay with a 2 wire device, as I do not really want to spend 160k rewiring these installs

thanks for the feedback though

RE: Flow switch!

Re "this site wont allow me to send you the details."
I have never had that problem. You can put net url links in with no problem.
What is the problem that stops you?

RE: Flow switch!

Hi Francist, the information doesn't have a URL.

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