Turbulence in cold water inlet pipe when recirculation pump is running
Turbulence in cold water inlet pipe when recirculation pump is running
(OP)
Hello,
The diagram below is a simplified version of a product we are developing.
I cannot get into my lab until September, and I am trying to work out if the flow meter will detect turbulence in the pipe when the recirculation pipe is running (when there is no flow through the system)
the Flow meter is a simple turbine
I can add another one way valve before the flow meter if necessary but I am trying to avoid additional parts unless necessary.
When the flow meter detects flow, it stops the recirculation pump from running.
We need a one way valve at the start of the system as shown so I cannot just move the flow meter behind the existing one way valve.
thank-you
The diagram below is a simplified version of a product we are developing.
I cannot get into my lab until September, and I am trying to work out if the flow meter will detect turbulence in the pipe when the recirculation pipe is running (when there is no flow through the system)
the Flow meter is a simple turbine

I can add another one way valve before the flow meter if necessary but I am trying to avoid additional parts unless necessary.
When the flow meter detects flow, it stops the recirculation pump from running.
We need a one way valve at the start of the system as shown so I cannot just move the flow meter behind the existing one way valve.
thank-you
RE: Turbulence in cold water inlet pipe when recirculation pump is running
You may need to play around a bit to prevent the recirculation pump starting and stopping to often.
But what fkie is the recirculation compared to full flow? 10%? Then why turn it off?
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: Turbulence in cold water inlet pipe when recirculation pump is running
that is very sensible
I will ask the PCB designer to make it a configurable parameter what the flow rate should be before the system considers the tap to be open.
That way I can test to determine what we can consider turbulence from the recirculation pump
RE: Turbulence in cold water inlet pipe when recirculation pump is running
Moving the flow meter directly to the line to the tap would eliminate the effect.
RE: Turbulence in cold water inlet pipe when recirculation pump is running
the next 100 machines I have to build need the flow meter positioned as shown as we have ordered flow meters with temperature sensors in the same brass piece (to measure cold water temp).
in future machines I will do as you suggest.
thank-you
RE: Turbulence in cold water inlet pipe when recirculation pump is running
Also turbine meters need min 5 to 10D upstream from a valve or tee to reduce swirl and give false readings.
Or fit flow straighteners or even flow discs.
How big is this pipe?
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: Turbulence in cold water inlet pipe when recirculation pump is running
In the short term i will add another one way valve before the flow meter.
In the future i will move the flow meter to after where there might be turbulence in the water.
thank-you all for your help
RE: Turbulence in cold water inlet pipe when recirculation pump is running
RE: Turbulence in cold water inlet pipe when recirculation pump is running
RE: Turbulence in cold water inlet pipe when recirculation pump is running
one of the parameters i have been given is that there needs to be a non-return valve where our device connects to the incoming water.
the outgoing CTO told me that this is regulations in France, but I have no idea if its true.
If it is not necessary then your solution is perfect
georgeverghese - again thank-you for your comment. i will check with the flow meter supplier.
This is what we are using: https://www.chnsensor.com/2ProductsShow.asp?id=224...
RE: Turbulence in cold water inlet pipe when recirculation pump is running
Usually they want two...
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.