Attaching temp sensor in PVC pipe.

[Ed van Willegen]

I want to add a temp sensor to the pool pipes and was a bit unsure how to do that.

I ended up with simply drilling a hole in the pipe, putting the sensor in and trying my best to glue it up with PVC glue. But to be honest I'm not feeling very secure about this.. Any one else who have done something similar?

View attachment 74649 View attachment 74650

I have seen a few others using some sort of threaded insert, but I have no threading bits to cut that with.

What I have done is a so-called inox cable gland tapped in the pvc pipe. No glue or silicon requiredand it gives a perfect fit.

 

[Alexr54]

Don’t they sell Tee’s that fit temp sensors?
Like this?
wouldn’t this be easier?

 

[Ed van Willegen]

Sure that will work as well. Still you need a plug for the sensor. Plus cutting and glueing to get the T piece in. It’s a choice.

 

[Dirk]

Hope you don't mind me sayin'... I'm not lovin' a tap into a PVC pipe wall. It's the kind of thing that will work at first, and for a while, with even a slim chance of working for a long while. But there's a lot that can go wrong. Firstly, it's SOP to thread plastic (male) into metal (female), not the other way around. Secondly, the tap is only offering a few threads (turns), which is not ideal. You've also got some forces in play: you've got two different materials (metal and plastic), subject to different expansion/contraction rates, with a full range of temps bombarding it, both from the inside (water) and the outside (weather). And you've got a metal "fulcrum" that is just asking to get knocked into, which could weaken or even strip out those few threads. Then there's the o-ring, sandwiched between a flat surface and a round one, also not ideal.

Previously in this thread you were advised how to use a T, and even though that's still metal threads inside PVC threads, it would give you a whole lot more threads. And then there's the setup that uses a SS band to bind the sensor to the pipe (that's how mine is). Either of those methods would be far superior than the tap, IMO. Not only would the original install be more reliable, but subsequent replacements would also be less prone to failure (like when you have to take out the sensor and thread a new one in, further weakening the PVC threads each time you do).

It's not about what will work "OK" when you first put it together, it's about how well, and how long, it will work after being subjected to foreseeable and unforeseeable forces.

Do it right, do it once...

 

[Ed van Willegen]

Hope you don't mind me sayin'... I'm not lovin' a tap into a PVC pipe wall. It's the kind of thing that will work at first, and for a while, with even a slim chance of working for a long while. But there's a lot that can go wrong. Firstly, it's SOP to thread plastic (male) into metal (female), not the other way around. Secondly, the tap is only offering a few threads (turns), which is not ideal. You've also got some forces in play: you've got two different materials (metal and plastic), subject to different expansion/contraction rates, with a full range of temps bombarding it, both from the inside (water) and the outside (weather). And you've got a metal "fulcrum" that is just asking to get knocked into, which could weaken or even strip out those few threads. Then there's the o-ring, sandwiched between a flat surface and a round one, also not ideal.

Previously in this thread you were advised how to use a T, and even though that's still metal threads inside PVC threads, it would give you a whole lot more threads. And then there's the setup that uses a SS band to bind the sensor to the pipe (that's how mine is). Either of those methods would be far superior than the tap, IMO. Not only would the original install be more reliable, but subsequent replacements would also be less prone to failure (like when you have to take out the sensor and thread a new one in, further weakening the PVC threads each time you do).

It's not about what will work "OK" when you first put it together, it's about how well, and how long, it will work after being subjected to foreseeable and unforeseeable forces.

Do it right, do it once...

Yes I did it right and once. It’s running for some months now without a single issue ( both on the pressure and suction side of the pump)!
I cut the thread into the pvc. To get some thickness I glued an additional layer on top of the location for the sensor and fitted the cable clamp with some Teflon tape. Beautiful tight fit. Never has to come out again. If I need to replace the sensor I only have to loosen the clamp and remove the sensor. The clamp itself stays nicely in position. It is cheap, easy and fast and it will last. But do what you like!

 

[Dirk]

I was commenting on your pictures, not on what you are now describing, which is not the same thing, and may or may not be better, I can't tell from your description. No matter, as you say: "do what you like!"

More importantly, I stand by my comments, for others that might happen by and see those pic's as a good idea. It is not.

 

[Ed van Willegen]

Thank you Dirk!!

 

[balajibv]

Thanks for all your inputs, I have a "version 2.0" which I'm feeling a bit better about:

I figured out how to cut a thread with a tap I think it's called. Together with an IP68 coupling of some sort that fits very tight to the probe and finished with some glue:
View attachment 74917

Although I figured out the T should probably have been pointing down instead, hoping it will work fine regardless.

/Kim

Can you share the parts you have used here. Especially the white ones. I'm planning to use the Dallas Sensor in similar method.

 

[keenskelly]

And I want to experiment with solar heating on the pool. What are you using for a panel design? What I want to try to get working is a photo-voltaic panel running a bilge pump (or multiples). When the sun isn't strong enough to run the pump it will shut off by itself. Sort of like what you are doing with the delta T control. But that way I can claim I am 100% solar!

Hello! Did you already dive into this? I planned, procured, and installed my own Solar thermal pool heater this year. The supplies that I picked up were selected and sized for the roof of our garage which is directly above the pool pump room from solarpoolsupply.com. If you read the ratings on the panels, I think you will find that a bilge pump is not going to cut it. The panels require 4GPM each, and I have 5 panels, so that's a full 20GPM flowing through 2" pipes for the complete rig. I also want to drive my pool pump with solar photovoltaics... but I am planning to size the system to run the full 1HP main pump with a battery and inverter strong enough to take the startup surge hit.

 

[Rattus Suffocatus]

I was going to do this at ground level. So it might have worked, actually.. especially because I would have run multiple pumps with smaller panels. The head loss is what the pump has to overcome ultimately. Yes there are "ultimate" flow rate levels, etc for maximum efficiency but I wasn't concerned with that.

This spring, I started to come up with a test system that would have initially used a 110V utility pump..just enough initially that I could quantify some heat gain. I had a bunch of family emergencies this year that stopped that project right as I was about to hook a coil up-- and in general saw the pool get very little use this season, unfortunately. And one of my dogs chewed up a part of my homemade test coil... so... I'll try again next year. My problem is that my house isn't oriented so putting panels on the roof would be too feasible, so I was going to try to make something that had good south facing exposure on my back block fence, hidden from the neighbors... Long and narrow along the fence line...

 

[keenskelly]

... I would have run multiple pumps with smaller panels. The head loss is what the pump has to overcome ultimately. Yes there are "ultimate" flow rate levels, etc for maximum efficiency but I wasn't concerned with that... family emergencies this year that stopped that project right as I was about to hook a coil up...

Ugh yes, it's been a rough couple years - sorry to hear that. For us it was important to get the pool heat working so that we could bear it while cooped up at the house - soon as the wifey endorsed the project, I was off to the races. I guess I would simply suggest that, if you can get close to flow rate specs for a commercial panel with your pump, you should try to hit it - having this dialed could be more than just fine tuning, it could make a significant dent in your ability to raise the temperature of the pool. You will definitely see a higher temperature if you slow the flow rate... but then with the slower flow rate you get less volume of heated water, and it could be to the point where you can't out-pace radiant losses. I sure would like to automate our own for this purpose - I have to hand-tune it every day at the moment, but I don't mind as it has been a hands-on learning exercise!