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Old 08-12-2019, 15:12   #1
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flow sensor switch recommendation

Hi All,

I'm installing an aquisense Aquapearl UV sterilizer for my freshwater system on our liveaboard sailboat.

I am looking for a type of inline flow sensor switch that will detect flow up to 4gpm that will detect flow and close a switch that will turn on a UV sterilizer and then shut it off when the faucet is closed and flow is stopped.

It should be 3/8" or 1/2" inch. I'm also looking for a backflow preventer to put in line as well.

Any recommendations or thoughts would be appreciated.

Cheers!
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Old 08-12-2019, 16:07   #2
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Re: flow sensor switch recommendation

From the website tanninglamps4less.com: “The output of any fluorescent ultraviolet lamp is never constant in a given time cycle. If you turn the lamp on, it WILL produce less ultraviolet in the first five minutes than it will in the next five minutes, as temperature also affects the UV output.”

I remember having read somewhere (can’t find it back) that UV lamp lifetime is greatly reduced with regular on and off switching. And as UV intensity diminishes with hours burned it is recommended to replace the lamps after 8000-9000 hours or once a year.

So I don’t think UV sterilisation of the tankwater with a lamp is a great idea.

BTW, why don’t you use a pressure switch instead of a flow switch?
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Old 08-12-2019, 16:14   #3
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Re: flow sensor switch recommendation

Hi Sailormed,
This is a new style UV LED sterilizer. I've discussed this with the manufacturer.
They don't see a problem with on and off.
It's just important to keep water flowing over the UV LED to keep the LED cool according to them.

I'm not that familiar with pressure switches.
How would you see that working?
Thanks for the feedback.
Cheers!
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Old 08-12-2019, 17:02   #4
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Re: flow sensor switch recommendation

These will last forever:


Gems Sensors FS-200 Series Bronze Flow Switch, Inline, Shuttle Type, 0.5 gpm Flow Setting, 1" NPT Female https://www.amazon.com/dp/B006UKOGM2..._m7y7DbG35RQHM
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Old 09-12-2019, 03:57   #5
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Re: flow sensor switch recommendation

According to AquiSense Technologies, the PearlAqua is self-contained, without the requirement for a separate control box. You shouldn’t need a separate flow switch.
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Old 09-12-2019, 05:22   #6
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Re: flow sensor switch recommendation

Ill tell you what I tell my swimming pool customers.

Dont waste your money.
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Old 09-12-2019, 12:05   #7
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Re: flow sensor switch recommendation

Quote:
Originally Posted by samoorelex View Post
...................
I'm not that familiar with pressure switches.
How would you see that working?
Thanks for the feedback.
Cheers!
On my boat if I open the tap, water flows, the pressure drops, the pressure switch detects the pressure drop and activates the water pump. Water flow out of the tap continues.
I understand you want to activate the UV lamp with water flow.
Just piggyback on the pump pressure switch (probably use a relais) for the activation of the UV lamp.
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Old 09-12-2019, 19:45   #8
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Re: flow sensor switch recommendation

Sam,
You know that bad things can happen if the lamp goes out or the lense gets dirty.
Can you fit an alarm to alert you if the lamp does go out?
There is a reason that many states don't allow UV for potable water on Comercial installation.
But I am sure you already considered that.
Cheers!
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Old 14-12-2019, 08:59   #9
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Re: flow sensor switch recommendation

Sailormed is on target by suggesting that you just piggyback off of the pressure pump's switch. Using the same switch will provide proof that the UV system is getting power since your water will also be off if it isn't. LED's draw very little power, I wouldn't worry about the need for relays. Just wire it up to the pump side of the pressure switch.

I always questioned whether water flowing past a UV lamp has enough exposure time to be effective. In a contained system where the water is constantly flowing, the water gets many passes by the lamp, so it aggregates the exposure, adding up over all the passes and may be effective for the system as a whole.

If you are just exposing the water to UV for just the brief time it is passing the LED in a pipe, would this be enough time to be effective? I think of it like tanning. You can be exposed to the sun for short periods with no noticeable effect. It is the long duration of exposure that kills the skin cells. I would think that in order to kill any biologics, you'd need more dwell time or multiple passes.
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Old 14-12-2019, 22:57   #10
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Re: flow sensor switch recommendation

When making water I run a UV sanitizer light (not LED) after my membranes, before the tanks. The bulb lasts a couple years depending on hours. Glass tube never seems to get dirty. Water coming out of the membranes is very clean.
UV light needs to be sized to flow.
Lots of flow switches on eBay.
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