Pro and Con of multiple heaters in one tank

[George]

I keep hearing people suggesting multiple, small heaters in a tank to minimize the impact of heater malfunction. Well, it may slow down your temperature going up in the event of one or more heaters malfunction. BUT, with three heaters in your tank running parallel, now you have three times the chance of getting a malfunction heater.

It may be a better idea to hook your heater to a temperature controller. If the tank temperature hitting a set point, you can instruct the controller to shut down the heater. Then again, I haven't seen a stand-alone heater controller for water. Most aqua controllers are expensive due to all-in-one design.
If someone can design a heater controller, I don't think it will cost more than two heaters. Or can it? hint, hint...

I don't know. I am just throwing ideas for discussion here.

Thanks for your time.
George

[Son Of Skyline]

Basically what you're say is that you could have a backup thermostat in case your heaters' internal thermostat goes nutty? That would be pretty good idea if one could get it to work.

[StirCrazy]

I am looking into trying a safty shut off by using this senser (http://www.smarthome.com/1523.html) in conjumction with my X-10 controler. this would basicly kill the power to the heater if it hits a preset temp. I am also looking at a reversal also by having a second heater that is always off and willcome on if the tank temp falls below a preset temp.

Steve

[Jack]

This is actually a pretty cool subject. I would buy one if it was available. We have all heard nightmare stories from some of you on the board about stupid heaters getting stuck on or off. I wish an Aquarium company would get off there butts and make something like you say, Or get someone ingenious enough to make one... hint, hint Steve :D

What makes me mad is how cheap heaters are, compaired to all other equipment in reef keeping and I am getting really worried. I run a single Ebo Jager 250 watt :mad:

I only have one softy coral so far, and look at me, Im panicking! :rolleyes:

[ 10 April 2002, 11:48: Message edited by: Jack ]

[Delphinus]

Hi, cool topic, I don't really have anything to add to the controls side of the conversation, but ...

BUT, with three heaters in your tank running parallel, now you have three times the chance of getting a malfunction heater.

'tis true, but I think what is important to realize is that if any ONE heater fails, it is not going to do any damage (or at least "not as much"). So, the risk of a failure is more, but the risk of potential damage is mitigated. So goes the theory, anyways. Unfortunately there is never any way to make the risk an absolute zero, it's all in the way we play the risk management game.

But that said, I agree that it would be VERY nice to see an inexpensive solution that could be applied to heater control without a multiple-hundred-dollar investment.

[DJ88]

Jack,

I am in the process of building a PIC(Programmable Interrupt Controller) based Control system for home use. Once I write my calculus midterm this week I will be prototyping it to see how things go. If that goes well I will try making one. I am planning on using this summer to get this and a couple other projects going.

It will measure the tank temp and then control; fans(variable speed deepndant on tank temp), lighting, heaters and if I can get one large enough a pelltier device to do cooling as well as heating.

So there will be some available in the future. I don't have a cost yet. It will be cheaper than others out there I hope. But very small quantities produced.

Just so ya know.

[Troy F]

I am eagerly awaiting Darren's temp controller but in the meantime if you can't wait Ranco make a temperature control. It's available through Ackland-Grainger and, if memory serves me, is in the neighbourhood of $100Cdn. Reviews of this product were predominantly positive. A search on Reefcentral will give you more information.

[Son Of Skyline]

Originally posted by delphinus:

'tis true, but I think what is important to realize is that if any ONE heater fails, it is not going to do any damage (or at least "not as much"). So, the risk of a failure is more, but the risk of potential damage is mitigated. So goes the theory, anyways.
<font size="2" face="Verdana, Helvetica, sans-serif">I agree. If you have 3 heaters in your tank and one of them fails, the other 2 will simply work overtime to keep the temp correct. Unless of course one of them gets stuck ON. Then that's why we'd need this safety system regardless of how many heaters you have.

Multiple heaters:
Great safety net if one fails and shuts down
Useless if one fails and stays on

[StirCrazy]

Originally posted by Son Of Skyline:
Multiple heaters:
Great safety net if one fails and shuts down
Useless if one fails and stays on[/QB]<font size="2" face="Verdana, Helvetica, sans-serif">this is just the point of having small heaters than cannot keep up by themselves. lets say you need 250 watts to just hold your tank at 82 degrees. now you go and get three 100 watt heaters.. if one of them sticks on it will not be enuf to over heat your tank.. the other two will still cycle on and off.. just not as much as when all three were working.. if two stick on.. big deal you have already determand that a 250 watt will barly get your tank to 82 so 200 will only get it to say....80. your third will still cycle on and off. the problem is that on the other hand if you are using a Tronic (solid state and fails off) the other two won't be able to keep up.. so if that is the case you have to use two heaters that are capable of heating your tank. I had a Tronic fail on me on my angel tank.. (out of the 6 tronics I have that is the only one that has failed.) luckaly I caught it wwhen it was down to 78 and that fish are more forgiving than coral hehe..

Steve

[Jack Rainville]

"Multiple heaters:
Great safety net if one fails and shuts down
Useless if one fails and stays on "

The point is, one of them is far too weak to ever over heat your tank. Get it? If one is stuck on, the others will simply not turn on as often. The only problem with the multiple heater setup is you actually have to check the heaters from time to time to make sure they're functioning. You might not even know if one is stuck on or stuck off because the temperature of the tank might not fluctuate much.

Seems to me, an expensive controller is just back to having all of your eggs in one basket again. If the controller described above fails while you're away, then you have no heat control, no lights, no fans, etc. Right?

[StirCrazy]

they do make one Jack, it is called the aquacontroler LOL.. but that is to expensive for my blood right now. mind you I do sit and drool when I see al the stuff it can do .. hehe

Steve

[Jack]

Haha, I know. I just finished browsing at them on J&L's site. 400$ for just the basic one. To much money...

[Delphinus]

Steve and Jack explained perfectly what I meant. The risk of "a failure of some kind" is greater but the risk of "what damage is going to be done" is mitigated (ie, limited). Thinking of process control there are concepts such as "fault-tolerance" and "fail-safe" and "single point of failure." "Fail-safe" means we recognize the possibility of a failure, but if a failure happens, it is left in a safe state. "Fault-tolerant" means that a failure might happen, but the process will be able to continue unaffected. Since a heater cannot be guaranteed "fail-safe" then you want to use a heater such that that if it suffers a worst-case scenario failure (and Murphy's Law dictates that the possibility of this is darn near 100%), then you want to be able to know that it won't cook your tank all by itself. I.e, NOT a "single point of failure." If you use TWO heaters then they both have to fail on to cook your tank, and the possibility of THAT is (theoretically) half that of a single heater failing on. Thus the multiple heater scenario is closer to a "fault tolerant" design.

This only makes sense if you're using heaters that by themselves are underpowered for the tank. If you are using fully redundantly sized heaters then indeed you are just doubling the risk of a meltdown. This is an important assumption to be pointed out.

Don't get me wrong: I'm not knocking the secondary controller idea. The reason THAT is good idea is that using a secondary controller (as well as the thermostat in the heater) is that in that scenario, you don't have "single point of failure." No one item failing is enough to shut you down.

There you go. Next lesson will be "programming in a real-time dual-redundant semi-fault-tolerant environment." Oh wait .... That's my job not my reefing hobby. Forget that! :D

[Jack]

Very well explained you guys, I am now thinking of changing to more smaller heaters than one big 250w. I am just to worried about loosing any livestock, seeing as I live on the island(no saltwater stores for miles and miles and miles...) so I want to keep what I get.

How many heaters?
2,3?
100w, 150w, ?

112gallon tank.
33 gallon tank as sump.

[Reefmaster]

hey all.
i recently had a 300W fail (off position) and am now in the market for a new one. i run 3 heaters and can't say enough about doing so. i would pay cash/trade for w.h.y. if anyone is looking to replace a big 'un with a smaller unit. actually, i also have a 50W i think that is 1.5yrs old i would trade if anyone wanted. (moderators, i know, not the trading post but fits with the discussion...)
shane