Heater controller

[Randys]

I had the same issues with my Ranco and have replaced the probe two times.
The first time I didn't realize the probe was not water proof and the controller went crazy after a couple of months.
I bought a new probe from Grainger and the recommended shrink wrap from ETC Supply. Even though I thought I had a good water tight seal with the tubing the same thing happened after another couple of months. At this point I wasn't sure if it was the unit or the probe again because the shrink tubing still looked water tight so I did some testing with the unit for a couple of weeks. I would run it with the probe in water and then not in water. I came to the conclusion it was definitely the probe again. THIS time I replaced the probe and bought a thermowell from a brewery supply company. Now the probe NEVER touches water and it's been working great for several months.
They're expensive but I was really impressed with the quality. Well worth the money in my opinion.

 

[Randys]

Here's the link to the thermowell I purchased.
https://www.brewershardware.com/Weldless-Thermowells/

 

[DN328]

How does the probe work with the thermalwell? Does it change the accuracy in anyway?

 

[jaws7777]

In case you were wondering about the specifics jaws. I have 3 Jaeger heaters on my heater controller set to 88 or 90F. When the ranco is at the desired temp a relay stops the power from flowing into the heaters. When the temp falls the ranco will put power through to the heaters. Since they are all set to 88 they all kick on at the same time. Once the temp rises back over the set temp the power cuts off so they all shut off at the same time. I have my heaters at the end of my sump right before the pumps, and the probe upstream but in the same chamber. (no baffles in between) This forces the water to heat through basically the entire tank until it heats up the water at the beginning of the sump. With the Jaeger they will kick off once they hit 88, so if the ranco were to fail and remain on it wouldn't cook the fish. I've had one unit fail due to water getting into the probe, fortunately it read way above my actual temp (reading 100F and beyond in 70F water) so that if I had used a titanium heater my fish would still not have been cooked. Neither of my units have been shrink wrapped.

Thx for the detailed explanation. Why would the titanium heater have made a difference?

 

[DN328]

In the case described above, since the controller was inaccurately reading high, it never would turn on any heater. So having the titanium type, with no built in thermostat, would not make you worse off than one with its own therm.

I get lazy typing on mobile so was a bit vague earlier

 

[Randys]

How does the probe work with the thermalwell? Does it change the accuracy in anyway?

You mount the thermowell so the end of it is in the water and then slide the probe inside and push it down to the end.
The thermowell is made to fit a 1/4" diameter probe so it's a pretty good fit between the ID of the thermowell and OD of the probe. The water temp transfers through the stainless steel to the probe.
I wouldn't think it would change the accuracy.

 

[Woefulrelic]

Thx for the detailed explanation. Why would the titanium heater have made a difference?

Like DN said in my scenario a titanium heater would not have resulted in any losses. Had the opposite happened and the probe read low the glass heaters I use would stop at 88, the titanium heaters wouldn't stop at all because they have no internal thermometer as they are meant to be used with ETC.

 

[tarheel96]

Does anyone know if there are external controllers designed so that, instead of turning the heaters completely on or off at certain temperatures, the current or voltage to the heaters is varied (the voltage/current is increased or decreased depending on the temperature)? This seems like a better approach to me. A simple way it might operate would be when the water temperature reaches a set high temperature, the power to the heating elements is decreased; when the water temperature reaches a set low temp, the power is increased. But I'd think the controller could dial-in on a small voltage-range which would keep the temperature fairly steady. With the maximum current being limited, I'd think the heating elements would last much longer especially if a higher power heater is used.

E.g., You have 3x 300 watt heaters and a 220 gallon. Instead of switching all 3 heaters on or off with 120 volts, 2.5 amps (300 watts each, 900 total), the controller varies the voltage/current somewhere between 75 volts, 1.33 amps to 90 volts, 1.66 (100 - 150 watts each, 300-450 watts total) so the tank temperature matches the high/low temperatures set on the controller.