Restrictions on Flow Switch Location?

6/18/2019

I've seen floor control assemblies (isolation valve, sometimes a check valve, waterflow switch, test & drain) in many different configurations as far as spacing of each of the components. I also understand that several manufacturers make an "all in one" valve assembly that can have all of these components.

Is there any benefit to the operation of the waterflow switch by spacing out these components? I'm wondering if a steady stream from the test and drain that is further from the switch allows the waterflow switch to operate more consistently?

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2 Comments

PJD

6/18/2019 10:48:22 am

Sir or Ma'am,

The requirement comes from the listing-cut sheets for the System Sensor, Potter, et al. require 2'-0" from any outlet or fitting on either side of the flow switch. The reason is that the paddle (vane type) switches are designed to function in laminar flow conditions (Re < 2100). The outlets and fittings make turbulence in the flow.

Anonymous

6/18/2019 11:20:33 am

The conservative distances in the flow switch literature have been there ever since I remember. The manufactured risers (like the Reliable CR of Vic 747M) are listed with tighter distances. I still have contractor who insists on fabricating the devices 3 or 4 inches apart, which I consider an unnecessary liability. However at least for Potter, you Potter rep can provide a latter where the claim the distances are just recommendations. They state, "If the device passes the flow test it can be considered an acceptable installation." When I started in the industry we would just maintain 12" distance. If fabricating myself, I still try to provided the distance recommended in the literature to ensure operation and reduce the liability risk. The "all in one" devices seem to pencil-out these days however.

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