Watermaker

[privileged]

Does anyone know the best way to install an alarm on the feed line line to an r/o unit .Would it be pressure , flow or air to activate. I sucked in a jelly fish and luckily noticed a different sound and had a look and the feed line was sucked flat. It got through the first weed strainer then blocked the 20micron filter . Any thoughts appreciated.

[goboatingnow]

negative pressure or vacum gauge. or whats better is a electronic flowmeter

[H2O Guy]

You can install a low pressure switch on the suction side of the H.P. pump and wire it to the contactor control. This will allow the pump to turn off when the inlet pressure gets to low (filters are dirty). You can get a simple normally open pressure switch from most hardware or electronic supply stores. There are even adjustable switches that let you adjust the pressure that the switch will open on.

[privileged]

would you have a link to a switch that would do . I rang around today and they dont seem very common here , and also would you know what pressure is on the feed side, it has a boost pump then three 10inch filters 60 mic -20mic-5mic thanks Mick

[H2O Guy]

I did a google search for "Low Pressure Switches" and came up with many options. You will want the H.P. pump to turn off around 6 to 0 psi inlet pressure. The pressure will vary on the inlet side to the pre-filters depending on boost pump size. This is of no concern, you are mor interested on the pressure being delivered to the H.P. pump. Your switch will be best utilized installing it between the 5 micron pre-filter and the H.P. pump.

[privileged]

thanks h20guy the manufacturers recomend a flow switch in the discharge line to activate at 1.5gpm would tell if there was a blockage . The guys at Omega recomend an fsw 530 switch . Do you think that is the best way to go ? thanks Mick
http://www.omega.com/Green/pdf/FSW530_series.pdf

[H2O Guy]

I don't think it is a good idea. It will only turn off the unit when you have a blockage in the discharge. What happens when you suck something into the thru hull or the filter gets clogged? You want the unit to turn off when it's not receiving enouph water. The low pressure switch accomplishes this.