What do you use to "sense" flow through your UV unit.

[BZOFIQ]

Per subject line.

I'm interested in solutions other than unreliable apex flow meters. I don't need to measure flow per se, just a device that would confirm there is flow.

Please let me know, thanks.

 

[ca1ore]

I guess it depends on how you have the UV configured. While I do use the apex flow sensor (and don't find them to be generally unreliable, though perhaps not the last word in accuracy), I also use float sensors in the sump to sense that the main pump is operating properly. If the pump is off, the water level in the sump rises and the float turns off the UV. Obviously that won't work if the UV is on a dedicated 'closed loop'.

 

[BZOFIQ]

I guess it depends on how you have the UV configured. While I do use the apex flow sensor (and don't find them to be generally unreliable, though perhaps not the last word in accuracy), I also use float sensors in the sump to sense that the main pump is operating properly. If the pump is off, the water level in the sump rises and the float turns off the UV. Obviously that won't work if the UV is on a dedicated 'closed loop'.

Thanks for your response. It's more of a dedicated loop as I'm planning the system to be run with 2 (maybe even 3) pumps. I need some sort of flow sensor that would simply close the loop so that I can wire it to B.O.B or own control relay.

I did find an ultrasonic flow meter, I actually think GHL literally uses these as their OEM but the control signal is 4-20ma and I haven't found a cheap solution that would close the relay when the flow is sensed. Before going deeper into finding a solution I figured I'd ask what everybody else is using.

Reading reviews I don't want to chance my UV unit with Neptune's flow meters - so that's definitely off the table.

 

[ca1ore]

Reading reviews I don't want to chance my UV unit with Neptune's flow meters - so that's definitely off the table.

Well .... I have 8 flow sensors (at last count). They DO periodically fail, though in all but one case the issue was simply debris and a quick clean returned them to proper operation. In ALL cases, however, failure means the sensor no longer reads flow; in other words flow = 0. If you set the outlet up to be UV off when flow falls below a certain level, then a sensor failure will simply turn the UV off. It will still reliably avoid the run dry scenario. Just food for thought .......

 

[BZOFIQ]

Well .... I have 8 flow sensors (at last count). They DO periodically fail, though in all but one case the issue was simply debris and a quick clean returned them to proper operation. In ALL cases, however, failure means the sensor no longer reads flow; in other words flow = 0. If you set the outlet up to be UV off when flow falls below a certain level, then a sensor failure will simply turn the UV off. It will still reliably avoid the run dry scenario. Just food for thought .......

Valid point, thank you.


Still want to see if there are better solutions.

 

[Bpp124987]

After going thru a similar search, I just put a 1 gallon bucket below the outlet and time how long it takes to fill up.

 

[Jeffcb]

I just go by what the pump say it does and forget it. It would be valuable to know exact flow and be able to adjust.

 

[Crashjack]

Though not a perfect failsafe, what I do is put my outlet tubing just under the surface of the sump. That way if the pump turns off, water does not siphon out of the UV due to backpressure. Though the bulb would remain on, at least the UV would still be filled with water albeit not running water.

 

[BZOFIQ]

Though not a perfect failsafe, what I do is put my outlet tubing just under the surface of the sump. That way if the pump turns off, water does not siphon out of the UV due to backpressure. Though the bulb would remain on, at least the UV would still be filled with water albeit not running water.

The 50W High Output unit I bought would definitely overheat if no flow was going through housing.

 

[BZOFIQ]

After going thru a similar search, I just put a 1 gallon bucket below the outlet and time how long it takes to fill up.

I just go by what the pump say it does and forget it. It would be valuable to know exact flow and be able to adjust.

My objective is not to measure how much water is flowing through but to install a failsafe device that would cut off power to the unit should there be no flow.

 

[Crashjack]

The 50W High Output unit I bought would definitely overheat if no flow was going through housing.

You might want to contact the manufacturer to see what kind of heat you might be looking at with the unit full of water. That said, I don't know why they don't make these things to automatically shut-off if it gets to a certain temperature.

I just had another idea... you could position the outlet to where it empties on to a temperature probe and see what kind of temperature you are getting (should be a good bit warmer than your tank). Set a failsafe to where the UV bulb turns-off if that probe's temperature is < X degrees. if the pump stops, the probe's temperature would quickly go down as the warm water would be gone and evaporation would start very quickly. I bet you could set to where your bulb would shut-off in less than a minute.

 

[BZOFIQ]

I thought to strap a temp probe to the unit and set it some degrees above what I find is the normal operating range.

That would definitely be the cheapest solution.

 

[BZOFIQ]

You might want to contact the manufacturer to see what kind of heat you might be looking at with the unit full of water. That said, I don't know why they don't make these things to automatically shut-off if it gets to a certain temperature.

It's too simple a device. It's a vessel with water flow through with a bulb in an environment it's not supposed to be in.

That said, I don't think it would be too hard to incorporate a small temp sensor into the housing connected to the driver for monitoring. So simple, yet nobody's done it.

 

[BZOFIQ]

I'm going to create a temporary loop in a bin and test how it behaves when i slow/cut the flow before I plumb the thing into its final location.

 

[Crashjack]

It's too simple a device. It's a vessel with water flow through with a bulb in an environment it's not supposed to be in.

Agreed. They're expensive anyway so a few more bucks for a simple auto-shut-off would be money well spent.

I'm not industrious enough to modify the actual unit. However, the outflow has to run back into the sump anyway, so if you set it to where it emptied above the waterline, you could easily insert a temperature probe into the outflow tube/pipe (at least you could with my temperature probes), and then strap the probe’s cord to the outflow tube such that the probe couldn’t come out. You could also just find a way to mount the probe right below the outflow tube and accomplish the same thing as long as you mounted your outflow tube to where it couldn't move. it might even work keeping the outflow tubing below the water surface; I just don't know how fast the temperature would drop. it would really depend on how warm the water was coming out of the UV.

 

[BZOFIQ]

.... it would really depend on how warm the water was coming out of the UV.

And this is what I want to test with a model setup.

I don't think the water coming out of the UV is much hotter than normal tank temperature and so there isn't enough delta to make it work using your method. I know however that water will rise in temperature substantially enough in the housing if there is no flow through it - allowing possible use of an external temp probe mounted to the housing.

 

[Crashjack]

And this is what I want to test with a model setup.

I don't think the water coming out of the UV is much hotter than normal tank temperature and so there isn't enough delta to make it work using your method. I know however that water will rise in temperature substantially enough in the housing if there is no flow through it - allowing possible use of an external temp probe mounted to the housing.

I have a Pentair 40w UV, and I estimate my actual water volume to be around 125 gallons. Running my UV makes about a .5 degree Fahrenheit difference in my overall tank temperature during the afternoon with no heaters running (also, UV empties into sump and main temperature probe is in display). I have my UV bulb programmed as a heater in my controller to where it shuts off when the tank gets to a certain temperature. I've never actually taken the temperature of the water coming out of the UV, which I guess I should do. All of that said, The output probably doesn't have to be any warmer than the tank temp if you empty on to the probe above the water surface. Once the water stops, air temperature and evaporation will drop the probe's temperature a few degrees if not more.

I'm very interested to see what you discover and come up with, so please keep the thread updated.

 

[tehmadreefer]

 

[Gp!]

Just a thought but if I was going to do this I would keep the reading related to flow not temperature.

For example, route the output into a container with a hole in the bottom and use a float or optical sensor to detect when the container is full. Allow it to overflow into the sump.

 

[Gp!]

You could also go a different direction and use a pump like the cor-20 or something similar and use the RPM reading to turn the UV on