How Do You Set Up Your Ranco Controllers for Redundant Heating?

[DiscoStuart]

General temperature control advice seems to focus on two key principles:

Redundancy – Use two heaters, each capable of handling part of the load.
Failsafes – Have at least one, if not two, layers of protection to shut off heaters if something goes wrong.

A common recommendation is using two 150W heaters (for a system requiring 200-300W) plugged into an Inkbird, which some then plug into an Apex for an additional layer of redundancy.

At the same time, I often hear that “Rancos are bulletproof” while “Inkbirds suck” (though plenty of people seem happy with Inkbirds too).

For those using Ranco controllers, I’m trying to understand your setup:


Two heaters, each with its own Ranco?
• If so, do you set them to the same temp to share the load, or does one sit slightly lower as a backup?

Two heaters, controlled by a single Ranco?
• Is this possible, and if so, how well does it work?

One heater + one Ranco, with a spare heater ready to go?


And regardless of your approach—do you use an additional failsafe beyond the Ranco?
• For example, do you plug the Ranco into an Inkbird or Apex in case the Ranco fails?

Would love to hear what’s working for you. Thanks!

 

[KStatefan]

Primary Ranco Setpoint 78° F Differential 1°F

Secondary Ranco Setpoint 78° F Differential 2°F

Each heater on a different electrical circuit.

 

[DiscoStuart]

Primary Ranco Setpoint 78° F Differential 1°F

Secondary Ranco Setpoint 78° F Differential 2°F

Each heater on a different electrical circuit.

Thanks! Am I right in understanding with that setup, both units will be on at the same time typically? (Not sure how Ranco differentials work!)

 

[KStatefan]

Thanks! Am I right in understanding with that setup, both units will be on at the same time typically? (Not sure how Ranco differentials work!)

No

With a setpoint of 78° F and a differential of 1°F the heater will turn on at 77°F and off at 78°F . The secondary will only come on when the temp drops to 76°F so if the primary can maintain the secondary never come on. Graph below shows what happens when the primary heater failed and was replaced. I increased the wattage of the heater is why the cycles increased also.

 

[DiscoStuart]

I increased the wattage of the heater is why the cycles increased also.

Got it - so you have two heaters that can independently fully heat the tank - and the backup should rarely, if ever be used until the primary fails. And with a higher wattage unit, it's faster to get up to temp - hence shorter, but more cycles (though potentially bad for heater lifespan, no?)

Out of interest what are you using to track temp and alert you? (as I don't believe the Ranco's have data feeds that would let you plot like that).

 

[KStatefan]

Yes. I am getting ready to replace a mag drive pump with a DC so my heater requirements is going up is why I went with the larger heater. Prior the primary was big enough for all but the worst days when dew point went way down.

The graph is from my GHL P4