Heater Size Head Scratcher

[Larry L]

it really depends on how warm the room is and how much above room temp you need to heat the water

^^^ This. One formula I've seen online that takes this into account is:

HEATER MATCHING FORMULA: (© Carl Strohmeyer)
As for heating requirements, I recommend 25 watts of heater for every 10 degrees of ambient temperature per 10 gallons you need to raise your aquarium temperature.
EXAMPLE: If your home is 68 degrees and you have a 40 gallon aquarium, to reach a temperature of 78 degrees you would need a 100 watt heater.​

I run two heaters that I originally chose using the heater manufacturer's wattage recommendations. Since I only looked at the tank temperature during the day I assumed everything was fine. It wasn't until I got an Apex that I saw that the tank temp was dropping overnight, and realized the heaters were actually undersized and couldn't keep up when the furnace turned down at night.

 

[Forsaken77]

I recently replied to a post talking about heaters, and I suggested using two under-sized heaters instead of just one proper sized heater. With Eheim's being the longest heaters, I inluded this table so that they could see if the heater would fit. As I stared at this table I noticed that watts to tank size didn't add up. Let me explain with an example.

...Tank Size....Power Needed....Heater Length
7–16 gallons.........50 watt.................9"
16–26 gallons.......75 watt...............10.2"
26–40 gallons.....100 watt..............12.2"
40–53 gallons.....125 watt...............12.2"
53–79 gallons......150 watt..............13.4"
79–106 gallons....200 watt.............15.7"
106–159 gallons..250 watt..............17.3"
159-264 gallons...300 watt.............19.6"


Let's say I have 106 gallons of water. According to the table, I'd need one 200W heater. Now if I wanted to use two heaters, you'd divided 200W by 2 and you come up with 100W....so two 100W heaters. But now when I look at the recommendations, that only totals to (40G + 40G) 80 gallons? You still have a total of 200W, so why doesn't it add up. According to that table, to now get to 106 gallons I'd need two 125W heaters (53 + 53 = 106gallons), for a total of 250W. Why!

These are the little things that bother my overly anal mind!

Well, 106 is at the end of that range, so it'll take the longest to reach the necessary temperature. So I would use the size above, the 250 watt.

Now splitting it in two doesn't necessarily mean getting back to 250 watts. In the example you provided I would use two 150 watt heaters.

The idea is to be able to still maintain the water temp if one heater fails, and it's also not high enough to boil the tank on its own if one gets stuck (or at least it would have to be on for a very long time to overheat the tank).

Those are pretty much just guidelines for what size heater to use. It's not written in stone. This is also why a temperature controller (a good one) is a necessity. So you don't rely on the heater to operate on its own. The controller will prevent a stuck-on heater from boiling the tank and keep the secondary heater running if the other fails.

 

[Forsaken77]

As far as people buying temperature controllers, I've noticed that some choose to buy a controller that is actually cheaper than the heaters themselves, like the $20 Inkbird. Needless to say, these controllers are just as prone to failure as the heaters they're controlling. I also would avoid heaters with the built-in controllers because if one fails, you lose the whole package (unless replacements are sold individually).

 

[ca1ore]

What typically happens with two undersized heaters is one of the two heaters ends up doing most of the work because its thermostat is slightly off from the other. This causes it to burn out quicker as well. The "fix" to this is to put both heaters on one controller which for some strange reason people do all the time but that means if the controller goes off or malfunctions, the tank could experience a wild temp swing.

The two undersized heaters philosophy more or less assumes that two small heaters reach max temp as fast as one large one, that both heaters are "dead on" accurate with each other, that two units uniformly heat as well as one and that all wattage consumed by a heater is transferred to the water column with the same efficiency.

In my experience, having two properly sized heaters that have built in temp controllers paired with external temp controllers is a better option. For example on a 100g tank with a target temp of 78, use two temp controllers (such as Inkbird and an Apex or RK) dialed in using the "ice water" method. Pair each with a 300w heater (depends on climate) dialed in by using a 5 gallon bucket or similar. Set the primary temp controller to 78 and its heater to 80. Set the backup temp controller to 76 and its heater to 80. For an expensive tank the backup controller and heater should be on a separate breaker preferably one with a generator hookup. I suggest when using a controller, to set alarms at 76 and 80 degrees (depending on climate and setup). This is the safest setup I know of. The only downside is $50 or so bucks more expensive. Given that a great number of tank failures track back to heaters, money well spent IMO.

Not sure I completely agree, but good that you've taken the time to think it through. As an additional data point (though not statistically significant due to sample size), I'm not all that confident in the inkbird. Bought two for my kids tanks and one of them failed. I much prefer the Ranco as my backup controller to apex on my big tank. I suppose anything/everything can fail, I just 'trust' the Ranco more.

 

[Sleepydoc]

Larger heaters with more surface area bring the water column to heat much faster and are more efficient. ... Better to use two heaters with two separate backup controllers. In the long run, it is cheaper and safer.

What typically happens with two undersized heaters is one of the two heaters ends up doing most of the work because its thermostat is slightly off from the other. This causes it to burn out quicker as well. The "fix" to this is to put both heaters on one controller which for some strange reason people do all the time but that means if the controller goes off or malfunctions, the tank could experience a wild temp swing.
...

Assuming identical heating elements, etc, two heaters will either be equally efficient or more efficient than one heater due to the simple fact that they will have more surface area in contact with the water and heat transfer is directly proportional to surface area.

As far as you concerns about having 2 heaters, you are correct that one heater will typically switch on first and get more wear due to having 2 separate thermostats. I think that your conclusion that this is worse is wrong, though. If you think about the two options of having 2 smaller heaters vs one large heater, the single large heater will switch on and off just as frequently as the smaller heater that switches on first. The remaining small heater will either switch on slightly later or not at all if the first heater is adequate, meaning the element will get less wear and the thermostat switch either fewer cycles or the same number.

There are two sources of wear and tear in heaters - the element itself, and the thermostat. Of these two, the thermostat is generally the bigger issue, as they have a tendency to fail in the 'on' position. Since failure is generally a function of the number of cycles, the large heater and small heater #1 are equally likely to fail. The difference being, if the small heater fails it is less likely to cause a problem. As far as the heating element goes, the larger heating element will be on just as much as the element in small heater #1. Again, the advantage with two heaters being if one of them fails, you are note completely without heat.

Regardless, I completely agree that the safer and best option is to use a separate (quality) controller and have the heater thermostats set slightly above the controller set point so they serve as a backup. This uses the more reliable controller switch as the primary and prevents any wear and tear on the heater thermostat switch unless the controller fails.

 

[Sleepydoc]

How about the fact that the charts don't include ambient temperature, desired temperature, or surface area of the tank? Not factoring in those parameters or even what solids are in the tank like rock and sand along with sea water having different properties than fresh water, I stick to guidelines like @NowGlazeIT shared.

This. There are many factors influencing heating watts required including

• Volume of water to be heated
• Ambient temperature
• Surface area of the tank
• Evaporation (a function of exposed water surface area, ambient humidity, temperature and air flow over the tank)
• Other equipment adding heat to the system (submerged vs external pump, skimmers, LED vs halide lighting, etc...)

My system (120 gallon + 40b sump, T5x6 lighting) needs fans in the summer time to keep it from overheating and 400w of heaters in the winter to keep it from dropping too low.

 

[revhtree]

I'm running one 800w heater on my whole system and it keeps the temp perfect. The total water volume without sand and rock is around 450-475g.

 

[Fudsey]

OK explain this:

300 watt Finex Titanium heater with analog controller 81-100 gallons
300 watt Finex Titanium heater element without controller 40-80 gallons

To get the same heating with just the element you have to step up to a 500 watt unit???
This make no sense to me...

 

[Sleepydoc]

maybe one is imperial gallons? ;Smuggrin

 

[LJLKRL05]

I would prefer to use two correctly sized or a little larger than needed and connect them to a controller. They will both work less to keep up.

 

[vedau]

What happens if the return pump fails? The heaters are in the sump.

if the return pump fails and heaters are in the sump and if you not around. Livestocks could die from the cold

 

[Daltrey]

if the return pump fails and heaters are in the sump and if you not around. Livestocks could die from the cold

Lol, no kidding. I was asking the guy that had 10 failsafes.

 

[Sleepydoc]

But your sump would be nice and toasty....

Intrinsic to the decision to have a sump with all your equipment in it is the fact that you are then dependent on your return pump to keep the water circulating. Because the return pump is such a critical piece of equipment is why many people buy backup pumps and perform routine preventative maintenance on their pumps.

How quickly it would be an issue depends on your system. In general, livestock can deal with cold much better than heat. The heater on my QT accidentally came unplugged and the temp dropped to about 68º F. I noticed the next day when I came down to feed the fish and the water felt really cold, but aside from that the fish actually seemed quite content and were eating as well as ever. Corals are a bit more sensitive, but if it were a gradual temperature drop and not prolonged you should be fine. (Out of curiosity, I wonder what the temperature is in the water by the time corals arrive after being shipped.) The other advantage of a temperature drop is that livestock use less oxygen and cold water can hold more oxygen. Of course oxygenation is drastically reduced when the water quits moving, which is a bigger issue.

(or was this just a long answer to what was supposed to be a tongue in cheek question? )

 

[[Cameron]]

What happens if the return pump fails? The heaters are in the sump.

I suggest having two return pumps rather than one. On expensive setups, put each one on a separate breaker. Bit more plumbing but return pumps eventually die like all mechanical equipment. The good news is it takes a good long time for a return pump failure to knock out a tank. Heaters can do it in a few hours. Even better news is that two return pumps aren't much more expensive than one big one. I think BRS uses the same method. I also suggest using a different brand and model. Pumps from the same lot often fail around the same duty cycle.

Heater failures are one of the most common tank killers so it makes sense to be extra cautious when using them. Dual returns make sense mainly because setting up a flow alarm isn't always easy or cheap so a return pump being out can be easily missed in many tanks. Cheap insurance on both counts IMO.

 

[[Cameron]]

Not sure I completely agree, but good that you've taken the time to think it through. As an additional data point (though not statistically significant due to sample size), I'm not all that confident in the inkbird. Bought two for my kids tanks and one of them failed. I much prefer the Ranco as my backup controller to apex on my big tank. I suppose anything/everything can fail, I just 'trust' the Ranco more.

I agree that Ranco's are better but some are not comfortable with the slight DIY aspect with them. There are some really nice brewer oriented temperature controllers now.

 

[Daltrey]

I run two seperate eheim jager heaters. I am changing them out to two finnex titanium heaters next week and plan on using a profilux 4 as the controller. I thought about running one in my sump and one in my overflow box.

I already run two seperate 20 amp breakers to the tank and split everything that is considered life support.

I am just making sure everything is covered as I need this tank to basically run itself when I am gone.

My build thread.

https://www.reef2reef.com/threads/daltreys-red-sea-reefer-750-xxl-build.351366/

 

[mcarroll]

Not sure I completely agree, but good that you've taken the time to think it through. As an additional data point (though not statistically significant due to sample size), I'm not all that confident in the inkbird. Bought two for my kids tanks and one of them failed. I much prefer the Ranco as my backup controller to apex on my big tank. I suppose anything/everything can fail, I just 'trust' the Ranco more.

The Inkbird is too new I've never seen one in action....but I've seen plenty of the other one over time and I can say I've seen more controller failures than I've seen heater failures.

And more titanium heater failures than glass heater failures.

I do use a backup controller, but it's a Reefkeeper Lite....also used for other things.

And to recap, I keep one right-sized glass heater (Marineland; Lifetime warranty) per tank, with a little wintertime "backup wattage" in the sump for the coldest days of winter. At least in my experience (over q fair amount of time) they are bulletproof as long as you treat them well.

All of the non-glass heaters (the flat or round plastic covered ones) I've used failed pretty quick.

By contrast I still have a glass heater that dates back to the 1990's.

And a backup return pump is really the only gear that I recommend to keep a spare for on hand. Worth the expense – they never EVER fail when stores are open. (Ever.)

If the return is all that failed on my system, it wold be OK....only loss would be the skimmer and top-off. Important but not world-ending. It's not depended upon for heat or flow, thankfully. I still keep a spare. (Two actually.)

 

[Fudsey]

Funny @mcarroll, I've had both fail miserably. 1st glass one stuck on in a fresh water tank, cooked everything. Early version of Titanium back in the mid 90's just stopped working. Also had another glass one just crack completely around and drop the bottom 1/2 of the glass to the bottom of the tank.

I have also had other glass ones get stuck on. The one I have now the temp is not even close to correct but it's now on a Finnex controller set at 78 with the temp on the heater at 76. Problem is at 76 the heater will heat to at least 80. I religiously check the temp in my tank now every morning and night

 

[mcarroll]

I consider that I take care of mine as the reason for their longevity, if it was anything I did at all. They dont get bumped or exposed or lifted by the cords, etc - and other "environmental factors" that many heaters are commonly exposed to.

And I do not say that based on anyone else's experience, only my own. Aside from utterly keaving them alone, I don't do anything special for them, other than maybe sticking with the same brand. So I just don't have anything else to attribute the "success" to.

(It doesn't really even seem like "my success" that my heaters are all still working... all I really did was take them out of the box and adjust the dial.)

As I noted, even with all that said I still use what I see as maximum redundancy. Five heaters would have to stick on and the controller would have to fail on for my tank to be cooked.

It seems like if I were you I would still consider the Marineland heaters since they have a lifetime warranty. They are very no questions asked about honoring it IME.

 

[leahfiish]

Hey there, how did the two 200w neo therms works for you? I have a 120g DT as well, but a little more water in the sump, probably 140-150g total, and am looking at new heaters.

So far working great, no issues.