Benefit of two heaters

[HarleyC]

Hi,
I have two 250W heaters in my sump for my 120G.
There are controlled by an aqualogic controller.
My question is is there any real benefit to having two heaters in the sump, apart from warming quicker? Which once you are up to temp is negligible.
I could understand two in a large DT tank, at opposite ends.
Cheers,
Harley

[daplatapus]

I have 3- 300W heaters in my 150 gal sump/77gal DT.
Redundancy, Redundancy, Redundancy.
Usually I have only ever seen 2 heaters on at a time, but if 1 ever fails, not that big a deal, 2 heaters go - you're in trouble but not dead... yet.
When I get my 210 going, I'll probably get another 3 - 300W heaters and have all 6 in there.

[HarleyC]

Thanks. I guess if you are ever away for several hours/days, you could get a few degrees temp drop. So, a back up isn't a bad idea there.
But, how many degrees and over what period are we talking before it's a major issue?
If I understand correctly, it's more of a sudden temp jump that's an issue.

[subman]

I lost $$$$ when I ran 1 heater because it failed. If i would have had 2 (like I do now and will forever) the second would have picked up the slack. I rarely check temps (even though I know I should) so the redundancy is key. Also my tank is in the basement so it dropped rather quickly to a chilly 68f over the weekend.

[sphelps]

It would take a while for a tank to cool off enough to cause problems, however for some reason heaters rarely fail in the off position. For this reason two small heaters is better than one large heater, however two large heaters is worse than one large heater. Hopefully that makes sense but ideally if a heater fails in the on position it shouldn't be able to cook the tank. Not so much an issue with external controllers.

[sphelps]

BTW I also agree with redundancy like others have talked about but don't forget about control redundancy as well. If you run multiple heaters all large enough to do damage an external controller for temp control would be a wise addition.

[Azzkr]

I run two heaters my self as well i keep one a couple degrees colder just incase the primary one fails, the tank will only be a couple degrees colder than until the primary one gets replaced,

[HarleyC]

I think I see what your saying sphelps - basically if you have 2 large and they somehow both fail, then you get a rapid rise. However, I do have the temp controller, so the odds of all 3 devices failing would be more in line with the lottery odds - no?

[sphelps]

I think I see what your saying sphelps - basically if you have 2 large and they somehow both fail, then you get a rapid rise. However, I do have the temp controller, so the odds of all 3 devices failing would be more in line with the lottery odds - no?

With two large heaters only one would have to fail on to cook the tank which can happen faster than it cooling off and livestock tends to be sensitive to heat vs cold. Also two heaters means twice the chance of this failure mode. And yes external controller can help prevent it. Usually people set heater temp slightly higher than the external controller temp for added safety.

[daplatapus]

Yeah, that's why in my mind I prefer several (3-4) smaller heaters. I also have a basement sump that sucks the heat out of my system. If one fails on or off, no big deal. On a 200-300 gallon system, if one or 2 even, get stuck on, definitely needs fixing, but shouldn't cause a catastrophic failure.
But that also means you have to pay attention to your system. You don't want one broken heater to be doing all the heating :) You should know if they're switching on and off.

[HarleyC]

Gotcha.
Cheers!!

[subman]

BTW I also agree with redundancy like others have talked about but don't forget about control redundancy as well. If you run multiple heaters all large enough to do damage an external controller for temp control would be a wise addition.

yes! +1 I actually run 2 large heaters but they are controlled separate controllers

[HarleyC]

Good point subman. I have both mine coming off the controller through a splitter. Which basically means one heater. My thought was, if one fails, it will still control the other. If the controller fails, I guess that could be an issue as you would have no power to either heater.
Is that why you use two controllers.
tks

[subman]

I actually only use one heater the other is set to wait 45min before kicking in. If it fails off the temp has to be below the set point for that period of time before turning on. I can't actually see the controller failing to shut the outlet off, but I've been wrong before lol

[HarleyC]

Man! the multiple scenarios we have to put our brains through , just for some piece of mind and there are some companies making some nice coin out of our paranoia LOL

[gregzz4]

I'm kinda crazy on heaters, as others will tell you ... :surprise: :crazy:
Just look at my build thread
I have 3 x 200W on my RKE, and a pair of 250W on a Ranco, just in case :rolleyes:
All in a 75g tank ( 110g total with sump )

I agree with everyone on the idea of using multiple smaller heaters, instead of one or two larger ones;

With one or two large ones, if one fails on, it may cook your tank
With one or two large ones, if you rely on them both, and they both fail, your tank is doomed

With two or three smaller ones, if one or even two fail, one will still be adequate to keep your tank going short-term
With two or three smaller ones, if one fails on, it will take longer for it to cook your tank

I set all my heaters in a bucket so they are max 81 degrees F
This way, if a controller fails, they won't cook my tank
Next, I installed 3 x 200W heaters controlled by my RKE
Next, I installed a Ranco controller, with 2 x 250W heaters set for one degree below my target temp, in case the RKE or such fails

Hope that helps :wink:

[The Guy]

It would take a while for a tank to cool off enough to cause problems, however for some reason heaters rarely fail in the off position. For this reason two small heaters is better than one large heater, however two large heaters is worse than one large heater. Hopefully that makes sense but ideally if a heater fails in the on position it shouldn't be able to cook the tank. Not so much an issue with external controllers.
I totally agree with this thinking and have never had a heater fail off when it dies, I only run a 125w and a 100w in my 90g with a 50g sump and it keeps my system at 80f. I plan on putting an external controller and make everything safer though. So I would say bigger isn't better in this case.

[spit.fire]

I run 3 300w because anything less they have a hard time maintaining the temp on my system in the winter. Also if 1 fails it cannot overheat my system

[asylumdown]

I've got 2 300 watt heaters controlled by an Apex on my tank, which is about 375 gallons of overall water volume. I ran my display tank disconnected from my sump for 5 weeks once (i.e. with no heater of any kind), and on the main floor of my house I never had a problem.

I've never had heater issues on salt water tanks, but I would concur that they don't fail in the off position. I lost two entire planted freshwater tanks to that very problem. It's why I won't use any one heater that by itself could cook my tank