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DIY Inline Heater with Temperature Controller

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15K views 21 replies 6 participants last post by  Le duke  
#1 ·
I'm currently in the early stages of a new tank project. The new aquarium is 130 gallons with canister filtration, and I want to have inline heat. Unfortunately, the inline heaters I have used in the past (Ista brand) have a new design that utilizes a staged 1/2"-5/8" barb that would be overly constrictive for a tank this size. I considered splitting the return line with a Y barb and doubling up on the heaters, but I thought I could maybe rig something up with some PVC and a standard probe/controller that would be more substantial and that could support whatever size plumbing I want.

I have seen DIY inline heaters that nest the body of the heater probe itself in a cable gland. I'm sure this works fine, but I really would prefer to have the entirety of the probe in the water, and I also want to be able to use a temperature controller like an Inkbird. So, I'm going in a slightly different direction here.

The basic design uses 2" fittings (a wye, a tee, and a union) with cable glands for the heater cord and the controller thermometer probe.

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Since the entire heater (500w) is going inside the PVC housing, I need to cut and re-splice the cord to be able to get it through the cable gland. I'm using wire nuts for the splice, but I will be enclosing the spliced portion of the cable in its own PVC housing (a 2" slip coupler with 2"x1/2" reducers and cable glands on the ends).

The end of the housing where the heater cord exits has a union (to make future changeouts of the heater probe simple). The cut heater cord is nested in a cable gland threaded into one side of the union:

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The controller's temperature probe is nested in a gland inserted into the tee:

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Once the heater cord was nested in the gland, I spliced it back together and enclosed it within its own waterproof housing. In addition to making it water proof, the cable glands at the ends of the housing will also prevent the wires from torquing which will immobilize the spliced portion of the power cord. From what I can tell, this is the same thing that Aqua Ultraviolet does with the power cords on their UV sterilizers.

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I've currently got it hooked up to a spare canister and the utility sink in the laundry room:

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So far so good!

One of the features that was important to me for this project was that the heater should shut itself off if the pump stopped circulating water. A temperature controller is no good for this if the temperature probe is in the tank - hence the placement in the body of the inline heater itself. To test, I shut off the canister and left the controller/heater on. It took about a minute for the temperature inside the housing to go from 72 to 78 and cut off power to the heater. After the controller shut off, the temperature in the housing continued to rise until leveling off at 85 degrees.

All in all, I'm pleased with how this came together, though I do want to trade out this old Hygger controller for a spare Inkbird I have laying around. With this controller, the probe itself is nested in the gland, and only about 2/3 of the probe is in the water. I think this is affecting the reliability of the temperature readings. Unfortunately the cord on the Inkbird's temperature probe is too small for the glands I have, but I have a plan to make it work. I'll follow up here when that's complete and tested.

Thanks for reading!
 
#2 ·
Nicely done! I hadn't heard of 'cable glands' before. I wish I had when I was designing my own equipment section of my big tank build. I definitely would have gone down this route instead of using inline heaters.
 
#4 ·
EmotionalFescue said:
@minorhero - has your UNS tank arrived yet? I got a stock alert for the 120S the other day. First time I've seen that one pop up in a year...
Click to expand...
Sadly no, I saw the 120s as well but so far no 120p. I've contacted both buce plant and the store I bought it from, no one has any real idea when it is coming.
 
#6 ·
Great project!

If the cable glands don't work out you could look into npt thermocouple plugs, but kind of expensive. You can also create your own version using a special fitting or using swage to npt adapters.

Of close this assumes the controller uses a thermocouple not some proprietary thermistor or RTD...
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Sent from my SM-G970U1 using Tapatalk
 
#7 ·
@Thenoob: nice - thanks for the tip!

I was able to switch out to the Inkbird controller by using a larger gland and nesting the temperature probe in some tubing filled with silicone (that's 1/2" clear pond tubing filled with black aquarium silicone).

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I seem to be getting much more reliable temperature readings with this arrangement. The Inkbird also allows me to dial in a correction factor, which is really nice since the temp in the housing seems to be about 3 degrees higher than in the 'tank'.

Another power off test with the Inkbird also yielded a much higher final temperature after the probe bled off all its heat into the housing. 97 degrees! Still cooler than a hot tub, so I think this should be fine. In any case, it's just meant to be a fail-safe - I plan to turn the controller off whenever I turn off the pump.

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#8 ·
Update.

This has been up and running for a couple weeks now with 1" line on a 130g tank, and it's working great. I installed it in a vertical orientation as shown below so that the thermometer is at the top of the housing and will be in the best position to measure rising heat when the pump shuts off. Speaking of which - I have tested the pump power off scenario (both intentionally and unintentionally!), and it works exactly as expected.

With the thermostat set to 78 degrees, and with the pump shut off while the element is heating, the temperature inside the housing rises to the upper 90s after the controller shuts off and the element bleeds its heat.

All in all, I would definitely recommend the DIY route for anyone who wants inline heat on a larger tank with canister filtration.
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M
#9 · (Edited)
Just to confirm, the gland's purpose is to allow you to get the entire heater into the unit because the cable end would be too fat to fit through threaded union, right? The last pic looks like a heater + reactor? (scratch that, I see it's an internal uv filter). What made you go with a cerges over rexx griggs?


I would like to combine your ideas with 150EH's here.

www.plantedtank.net

DIY Reactor Heater Combo

Scroll down to post 12 for a revised method of putting this together and you will avoid any pitfalls or leaks. I wanted to have a in-line heater and a reactor for my little 10 gallon build, this would give me heat and a super efficient reactor on a small tank and keep all the clutter out of the...
www.plantedtank.net www.plantedtank.net

I like the simplicity of his design but the safety of yours. Any reason not to do this?
 
#10 ·
I've honestly only ever made Cerges reactors. It's really easy to get big, clear housings to suit the reactor needs of just about any tank. Nothing against the RG style - I'm sure they work wonderfully. I think regardless of your reactor style, just be sure to install a bypass. If your reactor is on your only filtration loop, it's very difficult to optimize your co2 without a bypass.

I have thought about integrating a heater into a reactor, but have always settled on separate vessels with a pump powerful enough to deal with it all. There's really no single way to do this though, and I think designing my own equipment is super fun, so I'd encourage you to try whatever makes the most sense for you.

The cable glands allow you to run a cable (or really any cylindrical object) across a water boundary using threaded fittings. They're incredibly cheap, reliable, and easy to use. If you wanted to nest a heater body into a reactor vessel, I would encourage you to just get a cable gland big enough to fit the heater. like this:

Image


I personally wanted to use a temperature controller and have the entire heater element inside the vessel, but that was personal preference.
 
#16 ·
Homers said:
I know this is an old thread but thought id share the heater i made for my 500 turtle tank. Its a coolant heater from tractor supply tied to an inkbird
thermostat
Click to expand...
Interesting!

Do you have the Inkbird's thermometer in the tank? It looks like you would need to be careful to not turn the main pump off while leaving the heater on - is that right?
 
#21 ·
Le duke said:
Yet another question:

Any particular reason to go with a single-probe temperature controller over a double probe Inkbird?


Sent from my iPhone using Tapatalk
Click to expand...
I guess it could be more of a challenge getting two probes into the housing... Were you thinking they would go in at different points or right next to each other? If you used the same silicone-in-tubing trick I did to get them into a gland, you could run two just as easily as one.
 
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