Is It Possible To Have Too Much Wattage On A Heater?

ythao01

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so I'm thinking about buying a new heater for my 20 long and was looking at the 100-150w heaters but then I found a 250w heater for the same price. Would more wattage be better or would it heat the water too fast? or get the water to hot? is it an advantage or disadvantage?
 
I have an over sized heater in my tank. Long as its working shouldn't be a problem.
 
Not a question of it heating water too fast. The main problem with an oversized heater is that if the thermostat packs up and sticks on, a high output heater will keep heating and you will have poached fish. With a lower output if the same thing occurs, the danger to the fish is much less as it may not be able to over-heat the water due to heat dissipation by the tank. Plus a more powerful heater is also bigger and may look out of place in a smaller tank.
 
Higher wattage also causes less stability over time. It's hysteresis if you want to google it.
 
I have over sized heaters in all 3 of my tanks but they aren't too overkill.  For instance I have a 200 watt in a 55 gallon, a 150 watt in my 36 gallon and a 100 watt in the 20 high.  
 
I just re read your post and a 250 watt heater would be ridiculously overkill for a 20 long in my humble opinion.
 
I also agree that it's best not to go with an oversized heater in the event of the heater breaking.

What I like to do is get two heaters in my tank that are slightly undersized and have them both running at the same time. This way, if one breaks, the other heater can still keep up well enough until I notice the problem. And if one of them does break and over heats, it shouldn't be enough to cause harm to the fish. It also helps to keep the heat distribution fairly even if they're situated at two different ends of the tank.

Of course, if they both broke at the same time, it could be bad.. But I feel like those chances are slim enough that the benefits outweigh the risks.
 
Total wpg cause fluctuating temperature due to rapid heat up, be it via 1, 2 or 10 heaters. But a pair of 100w would be better than 1 200w especially if controlled from a common stat, independent stats would lead to a single heater carrying 90% of the duty due to the impossibility of setting two stats at an identical temperature, not to mention their different positions in the tank, different hysteresis curves, temperature float of the stat setting over time and not forgetting Sod's law. Bit saying bad idea, just not as perfect as it could be.

A pair of heaters in parallel set to say 27 degrees. And a series connected stat at 26.5 switching both would be better, the common stat would cleanly control both as the built in stats would never reach 27 to shut off unless the control stat fails, at this point the bck up stats will click out at 27 to prevent over heating. I have used that set up for many years, a little more complex in my case (temp control is kinda what I do for a living) but it's very stable. Reality is it depend how sensitive your fish are to fluctuations. If your that anal you could use a pair of any sized heaters via a pid controler for no fluctuation at all, bit silly but if you got cash and a desire....
 
So, MrBarry, can you recommend a reasonably-priced temperature controller? I have a six foot tank with two heaters and although they seem to be pretty well balanced at the moment I doubt it will stay that way.
 
In one of my tanks I use a 50 watt controller I picked up from a LFS, it's so old I can't read the brand I'm afraid. I use it to switch a 240v relay in a control panel in the stand, the relay switches the heaters, In actual fact it switches a 4 way trailing socket and the heaters are plugged into that, makes it easy to swap out a heater should one go south.
I use a 50watt controller because it was around £15, a 600w controller was £300 at the time. The relay was £5 and panel £5 and trailing socket £5. Easy to see why I made that choose then ;) I very much recommend either this approach or a standard heater stat switching a relay/heaters. Cheap, effective. Be safe however, electricity isn't everyone's thing!!

In the other I have a Allen Bradley 1200 plc with additional system clock, it has 3 k type couples it references with one as a control and the others as reference in case one goes bad. The program in that cascades the 3 200w heaters on and off as needed, closer to set point less heaters, more deviation more heaters. I use this system because it also controls auto water changes every Saturday via a header tank in my loft, a dosing pump that adds water safe to the header tank and an over flow from the tank to drain. It has alarms for heater failure and other stuff like water level in header tank and low water safe (I buy it in bulk and add it to a bottle on the dosing unit) it's lazy but trouble free fish keeping. I know what time it water changes Saturdays and Hoover before hand. I wouldn't recommend it to most people but I do similar control for a living and program the plc my self. Oh, it also does light control. This system has been retired a few years but is out and will be in use again very soon.
 

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