Dual/Redundant heater control tips

McDam

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As most reefers know and to those that should know, having multiple heaters as back up and or redundancy is a must.

I have always had two heaters, each one sufficient on its own to maintain the desired temperature of the system. Heater #1 would operate as the primary and Heater#2 as a backup, just in case Heater#1 failed.
The fact of the matter is, heaters will fail.
But the issues with this setup are:
- If the primary heater fails and the secondary pick's up the slack and maintains the temperature, then you might not know that the primary heater has failed until the secondary also fails.
- If you are always operating with your primary heater, you don't know if the backup heater is even going to work when it is needed.
- and the primary heater is also more susceptible to failure as it is doing all the work and is turned on and off all day long while the secondary sits idle possibly for months at a time.

For all these reasons I decided to change my heating philosophy and thought I should share. I have always controlled my heaters with my apex for higher accuracy and controllability purposes (and that is not going to change, no lecture required, I am fully aware of the risks and they are acceptable to me). I keep a pretty tight tolerance on the temperature range so the heaters cycle on and off frequently. So I wanted a way to share the work between the two heaters and the outlets they are plugged into. What I decided to try was to alternate which heater is the primary and which heater is the secondary. This will help share the duty and help with ware and tear and reliability.

Heater#1 will be the Primary and Heater #2 Secondary on Monday's, Wednesday's, and Friday's
then Heater#2 will be the Primary and Heater #1 Secondary for Sunday, Tuesday, Thursday, and Saturday

The heaters are both set to 80 deg F using the dial on the heater as protection from overheating in the event the outlet controlling them gets stuck on.

Typically/previously I would have the primary set to maintain a temperature of 78 deg F. and the secondary to kick in if the temperature drops below 77.8 deg F (Set these values to whatever temperature levels you like, these are just what I use)

The added benefit of this is also being able to tell which heater is failed. If you notice that your temperature is low on certain days of the week, then the primary heater for that day has failed or is failing and alarms and such can be set.

The code looks like this.

Heater #1
1580225267183.png




Heater#2

1580225573637.png


Happy Reefing.
 
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reef lover

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I myself like to use 2 heaters but i use 2 smaller ones to add up to what i would need to heat the tank in case one malfunctions and stays on. Coming home to a tank full of fried fish is never fun.
 
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McDam

McDam

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I used to run two smaller ones (150W) but what I found was they would have to work harder and would fail more frequently because they were both always on, working hard to maintain temps. Especially in the winter. I found by doubling the heater size I have better temperature control and less failure.
It could have been an improper heater size choice for my system as well. I am much happier with the 300W's.
 
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