# Heater lesson learned and questionsÃ¢â‚¬Â¦



## cdavitt (Apr 4, 2011)

So I learned my first heater lesson last night. I figure I'd share....
The lesson learned is when the package says "glass may break if plugged in and not fully submerged" it is true! I was doing a water change in a 20H that has a small 50 watt glass heater in it. Usually I flip the switch on the surge protector to turn everything off during a water change. Well I guess this time I was in a rush and only unplugged the HOB. The heater couldn't have been above the waterline more than 3-4 minutes. I am looking away and I hear POP! At first I thought maybe a light bulb went out, or one cracked due to heat and water splashing on it. Nope! The top of the heater blew off sending about 5 billion almost microscopic pieces of the metal 'glitter' fragments all over the place. The (now 1/4 full tank) looked like it was raining silver. The top of the water was covered in the substance as well.

Needless to say, emergency mode kicked in. Grabbed and empty 10 gallon and filled it. Strained as much surface metal fragments as I could and immediately started netting and moving over the livestock (class N endlers, ABN plecos, and RCS). Moved everything over and rinsed the old tank thoroughly. I also learned a lesson on never wanting substrate in a shrimp tank again (took way too long to catch them all) but I digress. Tank, decor, sponge filters all rinsed. Everything moved back and AOK this morning. I am going to continue large daily water changes...

I guess the only question I have is if this has happened to anyone before? Is the metal dust-like material inside of heaters toxic in any way? I would think not, since I am sure exploding heaters is a regular occurrence. I just wanted to double check. Anyone else have advice for monitoring/cleanup? BTW the new heater is only 1" off the base of the tank now. I will be looking into stealth heaters in the future.

Thanks for letting me rant.


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## PfunMo (Jul 30, 2009)

What brand and type of heater was this? Most say not to run out of water but we all forget somehow. I can't think which might have anything like you describe as tiny metal particles.

Why do you say you will be looking into stealth heaters? Do they advert some feature that appeals to you over others?


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## prov356 (Sep 20, 2006)

> I will be looking into stealth heaters in the future.


Maybe because they're not glass? I had a stealth with a huge bulge in it one time. I believe it was leaking something that was killing my fish, but not positive. Keep in mind they had a huge recall on stealths due to their tendency to explode and blow out tanks. So, it could have been worse.

If you want unbreakable, look into the titanium models.


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## cdavitt (Apr 4, 2011)

FWIW it was a Deep Blue Professional 60 Watt Mini Heat Stick. Inside the glass looks like it is stuffed with silver glitter....

I wanted to look into stealth heaters because they arenÃ¢â‚¬â„¢t made of glass and wonÃ¢â‚¬â„¢t break. I understand this instance was my fault, but if better equipment helps I am all about it.

I did stay away from stealth heaters at first since every forum I am on had multiple posts about all the recalls. I guess when it comes down to it, cleaning out a tank of hopefully nontoxic heater shrapnel is better than a heater sticking and boiling my fish.

Anyone have advice on a good stealth heater? What was the brand that was recalled? IÃ¢â‚¬â„¢d think now would be a good time to buy that brand because their quality control should be elevated after such a large $$ loss due to recall.


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## prov356 (Sep 20, 2006)

> Anyone have advice on a good stealth heater? What was the brand that was recalled?


The source I purchased from took back all stealths and stealth pros even though all the instances of exploding heaters that I'd heard of were stealth pros. They actually just gave me store credit for the stealths as I had purchased them a few years back and didn't even have them any more.



> IÃ¢â‚¬â„¢d think now would be a good time to buy that brand because their quality control should be elevated after such a large $$ loss due to recall.


You have much faith in mankind and his abilities. More than I have.


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## PfunMo (Jul 30, 2009)

Faith is running pretty thin in my part of the world for sure.

I'm still deciding what heaters are going to work out best. I had settled on a semi-cheap Via-Aqua heater that seemed to have all the basic design items covered but as I got into them I found they had major quality control questions. I had 2 out of 5 come out of the package with defects but I was fortunate that I had bought them from a dealer who was super about backing the product even when it was not his fault. I currently have 5 of these and they have worked quite well for about a year but now I see they have changed the design and gone digital. Does that make it better or does it mean they have to learn how to make them all over again?

Via-Aqua titanium is my current choice do to price, a remote sensing bulb, and controls outside the tank. These features remove some major failures in that they can make bigger, better contacts as well as better seal the heater tube against leaks. Whether the new digitals will be good is still an open question.


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## jerry11 (Aug 25, 2011)

Last time I checked, marineland was only selling Visitherm models due to the lawsuits, recalls, etc... I sent back my 5 stealth pro's for refunds directly from marineland.

Visitherms are okay but don't heat as much water as many other brands. I'm buying eheim heaters now. Big but they seem to be working well n


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## jason_nj (Feb 24, 2010)

My favorite heater is Catalina Aquarium titanium heaters. I have them in 4 different tanks ranging from 150 watt to 500 watt and they seem to be really accurate. Whatever temp I set the external dial for, is usually where my tank temp is, give or take 1 degree.


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## The King Crabb (Jun 28, 2011)

+1. I'll be picking up a 500Watt one for my 125G.


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## iwade4fish (Jan 5, 2009)

You certainly get what you pay for when it comes to heaters.
They aren't fail-safe, meaning when they fail, they stay 'on'!
Major flaw.

Titanium is the best bet now-a-days, and I'm sure the future will bring even more peace of mind regarding these.

As a hypocrite, I use a lot of el-cheapos, but have taken them apart and modded them a bit for peace of mind. Usually, the heater element-to-thermostat connection gets compriomised and either won't turn on, or the opposite, won't turn off. Drop of epoxy goes there.

25watter got stuck on last night in a 55gallon, it was 85, but prolly wouldn't go above that w/that volume of water.

Which is another point; big heater in big tanks, or built-in redundancy with two, smaller wattage heaters?
opcorn:


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## The King Crabb (Jun 28, 2011)

2 smaller heaters are best, but like iwade4fish, I'm a cheapo :lol: I always just buy 1! Would the 500W titanium be too much for the 125G?


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## jason_nj (Feb 24, 2010)

I'm using the Catalina heeater 500w in my 125G right now. It's been working great so far, no issues with it and more than adequate to heat the whole tank.

I had an outbreak of ich because I didn't quarantine some new fish and I was able to get the temp in my tank to about 88 degrees.


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## Number6 (Mar 13, 2003)

500W in a 125g??? Unless you keep your house real chilly, then it's cooked fish waiting to happen in my opinion. 

I use a 150W in my 125g and it's plenty... house isn't drafty, stays nice and warm so I only need to bump up the heat slightly all winter. You might need a more powerful heater... depends on how much you need to warm the tank up.


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## PfunMo (Jul 30, 2009)

The question of whether a heater breaks the glass or not when it is running out of the water is kind of a feel good thing in many cases. While several advertise that they will shut down when out of the water, there may be more to the story. Do the internal parts work the same after overheating?


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## jason_nj (Feb 24, 2010)

I went with the 500 watt following the 3-5watt per gallon. Also my tank is in the basement so can get a little chilly.


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## Number6 (Mar 13, 2003)

jason_nj said:


> I went with the 500 watt following the 3-5watt per gallon. Also my tank is in the basement so can get a little chilly.


that's why I despise "rules of thumb". 3 to 5 W per gallon is power consumption only... nothing about that tells you what you really need to raise your tank for each 1 degree above the ambient room temp. It leaves folks panicking that they need 5W per gallon. :roll:


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## juststayinthecave (Dec 23, 2010)

I have a 250 watt in my 180 gallon tank in the basement and it keeps the water at a steady 80 deg F. Temp in the room is around 68 - 70.


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## jason_nj (Feb 24, 2010)

juststayinthecave said:


> I have a 250 watt in my 180 gallon tank in the basement and it keeps the water at a steady 80 deg F. Temp in the room is around 68 - 70.


Ok good to know. I have a 250 watt heater I can downsize to.


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## The King Crabb (Jun 28, 2011)

Number6 said:


> I use a 150W in my 125g and it's plenty... house isn't drafty, stays nice and warm so I only need to bump up the heat slightly all winter.


Keep in mind you live in Florida, Sunny Tampa even. Where as here in Utah it's not unheard of to hit 0 degrees several times a year, wake up to 8" of snow, and even find your 1/2" of ice covering the entire North side of your house. Very different climate :wink:

Although thinking it over, 500W does sound like a lot...


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## Number6 (Mar 13, 2003)

The King Crabb said:


> Keep in mind you live in Florida, Sunny Tampa even. Where as here in Utah it's not unheard of to hit 0 degrees several times a year, wake up to 8" of snow, and even find your 1/2" of ice covering the entire North side of your house.


That doesnt happen in your house.... :lol: 
Seriously though.... The 150w heater was purchased in Ontario for use in my living room. In my basement fish room, i needed a 200w heater. In my other reply, I hazarded a guess that between 200 and 300w would be wisest depending on quality/efficiency of heater and how chilly you keep the house.


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## PfunMo (Jul 30, 2009)

To me there is one really big thing to keep in mind. As we all have different setups, there is little way to judge how much may be enough so that leaves us to try to guess and then correct if we are wrong. 
There are two ways to be wrong on size. Too large and the fish can die in 8 hours or less. Too small and the water will slowly get too cool. Maybe if there is a really cold spell out and the room temperature drops ten degrees the tank may take three days to cool to a level that bothers the fish. Which do you feel is safer? Taking the risk of being too small and having a week to get another heater or going to work and finding a heater is stuck on and your fish are dead when you come home?

Hot water holds less O2 and that kills fish quick. Cool water can create a bad case of ich!


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## The King Crabb (Jun 28, 2011)

Number6 said:


> That doesnt happen in your house.... :lol:
> Seriously though.... The 150w heater was purchased in Ontario for use in my living room. In my basement fish room, i needed a 200w heater. In my other reply, I hazarded a guess that between 200 and 300w would be wisest depending on quality/efficiency of heater and how chilly you keep the house.


That's a good point. The place I'm going to put the 125G will be ~70 all year, so you think 300 will be good?


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## Number6 (Mar 13, 2003)

*The King Crabb*
Prov is a believer in one single "undersized" heater where I like the minor benefit of having two with a really good thermometer. I like to put the heaters in a spot with plenty of water movement... The sump being my favorite place... And what i find is that as small as a 200w heater can bring a tank in a room at 70 up to 78 and keep it there. I usually go for two 200w heaters... I am guessing but I think the folks like Prov would say 1 300w heater. Buy quality whichever way you go. I admit that if i bought a heater from a chain store, i would probably buy a higher wattage than if i buy one of my favorite makes.

I once ran a 100g tank on a broken 100w heater... With ot stuck in the on positoon, it kept a 100g tank at the right temp in a basement... It just goes to show that there is no one rule as pfunmo points out.


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## prov356 (Sep 20, 2006)

> Prov is a believer in one single "undersized" heater where I like the minor benefit of having two with a really good thermometer.


No, one 'properly' sized. I'd go with a single heater that can only take the tank up to upper 80's when stuck on. That'd be properly sized.



> I am guessing but I think the folks like Prov would say 1 300w heater.


300w is probably too much. I'd start with 200-250.

If using two heaters, I'd always put them on one controller. Getting two heaters to work efficiently and properly in tandem on their own controllers is more difficult than setting the dial on each and plugging them in. The heat from each can affect the other and cause it to cycle more rapidly than it would otherwise, and increase the likelihood that it will stick on. And if one goes out of calibration (very common), you may find in time that one no longer comes on at all. If going with two, consider one a backup and set the dial two degrees less than the primary so it doesn't come on at all unless the primary fails. And if you need both to heat the tank, again, I'd get them on one controller. But, then you've taken away the 'if one sticks on' scenario.


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## Number6 (Mar 13, 2003)

Thanks Prov... I was thinking about firing you off a PM to weigh in on this one. Glad you saw and jumped in. :thumb: 
By the by, the "undersized" was in reference to the packaging labels, not at all directed towards your practices.

*The King Crabb*
there you have it... IMO, try the 250W quality heater.


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## PfunMo (Jul 30, 2009)

While we often think of big tanks as needing more to keep them running, heat in big tanks is much simpler than small tanks. A 125 tank takes a whole lot longer to heat or cool than a ten gallon tank. The 125 may take a week to steady out when you are first heating it but it will also stay warm much longerif a heater stops heating. A ten gallon really needs more careful study than the large as they heat and cool so much quicker. But due to human nature that is not the way we look at things. Our first ten gallon tank we just throw some stuff in but when we get around to a big tank we feel we need to study it carefully.

That leaves the new guy with his first tank in the worst position to deal with problems! Bummer!


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## The King Crabb (Jun 28, 2011)

Some excellent advice, thank you everyone who chimed in! I'm going to go with a 200 Watt titanium heater, and if that's not enough I have a spare 50 Watt to throw in there. Thanks again :thumb:


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## PfunMo (Jul 30, 2009)

I've not had a heater in my tank all summer but as time goes on my tank is now slipping down to about 74 degrees and I like it close to 78. I've added a 200 Watt on a 125 gallon and set it to 78. Even though I know it will probably not wind up on 78, it is a place to start. In five hours the heater has brought the temp up 2 degrees and that is about what I want. If the fish can stand 94 before it gets fatal, that gives me 16 degrees of rise before it gets fatal. Rising two degrees in five hours gives me something like 40 hours to see the problem and correct it. That is if the rise was a straight line, which it isn't but it makes the figures easier. In 40 hours I should see it but if I used a 500 watt, the time would be much less.


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## The King Crabb (Jun 28, 2011)

That's a good point Pfunmo, so the 200 Watt is heating the 125G nicely?


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## PfunMo (Jul 30, 2009)

Heating it okay but very slowly. I can't tell that there is that much change from my earlier post. The numbers on heaters are usually pretty much a guess so I may need to bump the temperature a bit higher but I want it to go up slow so I'm happy so far. The heater is cycling on and off frequently right now as it works it's way up but I will be watching to see it stop that once we reach the set temperature. This is one of the newer digital that Via-Aqua is putting out and I'm not sure I like seeing the temperature in that much detail. There is a lot of current in that tank and it carries the heat away so that the thermostat is working pretty heavy right now. I should know more by morning.


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## prov356 (Sep 20, 2006)

So, it's set at 78, the tank water is still under that, and it's cycling on and off?


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## 13razorbackfan (Sep 28, 2011)

PfunMo said:


> Heating it okay but very slowly. I can't tell that there is that much change from my earlier post. The numbers on heaters are usually pretty much a guess so I may need to bump the temperature a bit higher but I want it to go up slow so I'm happy so far. The heater is cycling on and off frequently right now as it works it's way up but I will be watching to see it stop that once we reach the set temperature. This is one of the newer digital that Via-Aqua is putting out and I'm not sure I like seeing the temperature in that much detail. There is a lot of current in that tank and it carries the heat away so that the thermostat is working pretty heavy right now. I should know more by morning.


While I am no expert in these matters what does come to mind is maybe not enough circulation of the newly heated water thus triggering the heater to think the tank is up to set temperature even though it is not? While the water right near the heater maybe warmer than the opposite side of the tank. When the cooler water finally mixes with the warmer water it brings the temp down thus triggering the heater to come on again. Only thing I can think of.


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## PfunMo (Jul 30, 2009)

The heater will cycle on and off numerous times when raising the temperature. It has to do this regardless of the current. Heat builds up very quickly inside a small tube when you turn a 200 watt heater on. It can't stay on for long as the temperature inside the tube would get too hot. If the tube were a better conductor of heat so that the heat was passed instantly to the water, the heater could stay on. That is why titanium is used in the better heaters rather than some cheaper material. Titanium conducts heat much better but still not as well as a perfect material might. How hot is a red heater coil? Something like 400-600 degrees? It can't stay on very long confined in that small space so it has to cycle on/off.

If we could build heaters that only opened/closed the contacts when the tank temperature reached a set point, they would last much longer, but so far that doesn't work.


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## prov356 (Sep 20, 2006)

PfunMo said:


> The heater will cycle on and off numerous times when raising the temperature. It has to do this regardless of the current. Heat builds up very quickly inside a small tube when you turn a 200 watt heater on. It can't stay on for long as the temperature inside the tube would get too hot. If the tube were a better conductor of heat so that the heat was passed instantly to the water, the heater could stay on. That is why titanium is used in the better heaters rather than some cheaper material. Titanium conducts heat much better but still not as well as a perfect material might. How hot is a red heater coil? Something like 400-600 degrees? It can't stay on very long confined in that small space so it has to cycle on/off.
> 
> If we could build heaters that only opened/closed the contacts when the tank temperature reached a set point, they would last much longer, but so far that doesn't work.


My experience differs quite a bit. I've monitored these things. They can take up to an hour to cycle. If this is how some cheap heaters have to work, I'd steer clear of them entirely. That's a ticking timb bomb.


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## PfunMo (Jul 30, 2009)

What type heater do you find which doesn't cycle on and off as it tries to raise the temperature? I can't imagine one which could let the heating coil run full time and not expect to damage the internal electronics. How do you monitor your heaters? As far as I know the titanium is considered the best material available for heaters.


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## prov356 (Sep 20, 2006)

I put a digital thermometer on my 180 one day and sat and watched it. This was a few years ago. I will do some more testing.

I've sort of got the flipside thinking though. Why would they make a heater that had to shut off to avoid damaging itself? Is there an internal temp sensor that tells the heater to turn off when it's getting too hot? That sounds expensive and it sounds like something prone to fail and cause the heater to overheat and fail.


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## PfunMo (Jul 30, 2009)

> Why would they make a heater that had to shut off to avoid damaging itself?


Its may be matter of how to design a heater coil that will give adequate heat, small enough to fit the tube and still thick enough to stand the heating/cooling. It is really hard to get this all done in the size and price we want. Running on 120 AC which we all want to use, makes the coil heat so fast, it can't be run full time so it has to cycle. Otherwise it would be like a toaster! It would work okay but not many would want it hanging in the tank!



> Is there an internal temp sensor that tells the heater to turn off when it's getting too hot?


Yes, there is an internal sensor that turns the heater on/ off. It is the set of bimetal springs that you can see looking through glass heaters that have the controls in the tube.



> That sounds expensive and it sounds like something prone to fail and cause the heater to overheat and fail.


No, they are not expensive and yes they do fail often on the normal heater we see.

When the controls are moved out of the glass tube, they can use as much space as they want and not worry about the heater cooking the gizmos. Thermistors are very cheap but do a good job in the right situation. Much better than bi-metal springs. 
Part of my reason for using heaters with controls not in the tube is that I know electronics last longer if they are not exposed to high heat. If the controls are inside the tube and less than an inch from the heating coil, they get cooked every time the heat comes on. I feel it is far better to have the electronics and controls outside and away from heat and water. You are not cooking them nor letting them get wet.

For my heater cycling as it raises the temperature, I would expect it to stop once it gets to the set point. Then I would expect it to come on to bump the temp up slightly but then stay off for a much longer time as the tank will cool slowly. It is the amount of the temperature increase that is making it cycle so often now. By this afternoon it had stopped but I wanted the temp a couple degrees higher and clicked it up two degrees.


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## prov356 (Sep 20, 2006)

I don't think you see my question. I know there's a sensor that turns the heater on and off at setpoints, usually +/- 1 degree, but you're talking about another sensor besides that one that measures the temp in the tube? What you're describing isn't making sense to me. The heater turns off because it reaches max point inside the tube even though the water is not at set point? What tells it to do that, the same sensor that tells it the water is at setpoint? How can that be??


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## PfunMo (Jul 30, 2009)

If we are speaking of the style with controls in the tube, it is the same thing. When the metal gets hot, it pulls the contacts open. When the inside of the tube cools, it bends back and the contacts make so that current flows to the heater coil. This is part of my complaint with this type heater. Calling them controls is pretty much overstating things. The "control" is a screw which forces the flat springs to a position which is calculated to bring the water temp to a number. As the heater heats up, there is no way to measure the water temperature but it just relies on the metal spring bending at the correct time/temperature to open and close. That temperature inside the tube might reach 200 degrees which is then expected to transfer to the water and bring the water to the set point of maybe 75. I think I need to tear down an old heater and take some pictures to show what happens. It has so many faults in the design that it is really pretty amazing they work as well as they do. But then most of us are not really too happy with heaters, are we? We keep thinking we can buy a better heater but if most are made the same way, they will all have the same defects with only minor differences in the operation.


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## prov356 (Sep 20, 2006)

Mine just don't work that way. A heater that cycles too frequently is either defective or of poor design and shouldn't be used IMO. The heat is transferred to the water, not back up into the tube if designed properly. If any amount of heat is allowed back up to those contacts directly. no way the heater functions properly. The water temp alone has to affect those contacts. It's also important to position a heater properly and have adequate current. You don't want heated water passing up past the area of the tube that houses those contacts nearest the cord.


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## Number6 (Mar 13, 2003)

Prov, I had a heater once (Hagen I think?) that worked best when mounted at a 45 degree angle on the back wall. Now I think I know why... very useful thread! :thumb: very useful info. Thanks...

You know you're a fish geek when...
"I put a digital thermometer on my 180 one day and sat and watched it."

:lol:


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## PfunMo (Jul 30, 2009)

What you are saying about the design is mostly true. What you are missing is that my main point is not to defend the design but to point out that it is faulty. When you put a heating coil in a tube and put the controls inside that same tube less than an inch away, there is no way the heat is not going to pass through the little bit of fiber insulation stuffed in the tube between the heater and the controls. It's like holding a sheet of paper between you and a blowtorch.

I don't see that watching a digital thermometer in the tank does much to tell you what the heater is doing inside the tube. How can you tell if the heater is cycling on/off by watching the tank temperaure? That would seem to only tell you that the heater is working but not whether it is working in a steady stream or an interupted pattern. One would need to monitor the current being drawn by the heater, actually watch the contacts, or use some other way to tell if the heater coil is staying on or cycling. You could hold your hand on the heater while it works but that is a good way to burn your hand! It often gets too hot to hold. It does not cut off when it reachs a set point like 78.

Your house often has the same situation if designed poorly. If you put your thermostat where a heat duct blows on it, the furnace will cycle erratically and give you really weird cycles. If one were to compare a tank heater with a home heating thermostat, it is as if they put the thermostat IN the heat duct.



> You don't want heated water passing up past the area of the tube that houses those contacts nearest the cord.


This is in conflict with the design of many heaters and the instructions they provide. Many heaters are designed to clamp on the tank side in an upright position so that the heated water will go up past the controls. Turning them over or submerging the top of many heaters is NOT recommended in the instructions. They do not want the controls to be in the water so if they can't touch the water, they can't directly sense the water temperature. The water temperature is monitored by the controls sensing the temperature of the AIR inside the tube, not the water temperature directly.

That is why I favor a heater with the temperature sensing in a bulb that is located OUTSIDE and away from the heating coil. It can sense the water temperature as it is truly in the water. The heating coil does not heat the temperature sensing bulb but only the surrounding water which then at some point changes the water temperature around the sensing bulb.

It is like locating the house thermostat in a hallway away from direct heat from the furnace ducts. It just works better. Most heaters we buy are poorly designed, made very cheaply, and perform badly with frequent failures.


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## PfunMo (Jul 30, 2009)

Some pictures of what I'm talking about.

This is a Hydor Theo 50 watt that I use in my reserve water supply as it has failed and I now run it but don't expect it to cycle but just run full time when plugged in. 
First is the heater before I pulled it apart. It is covered in limestone due to the hard alkaline water it sets in. As it sets and cooks it developes the deposits much as a tea pot might. 









When you pull the glass tube off, this is what you find. Pretty much standard stuff for heaters with the exception that this heater uses a micro-switch instead of the contacts on the metal plate which many heaters use. It also uses a foil heating element rather than a wire wrapped around ceramic that many use. Notice that there is nothing to isolate the heat from the controls. The heating foil is wrapped around the controls.









This is the bimetal spring which controls the heater. When it gets hot one metal expands more than the metal on the other side. This makes the metal warp or bend to close the contacts on the micro-switch. You can also see the glass indicator bulb and a couple resisters. There may also be some other items tucked in to hold down the arcing as the contacts open and close. May not because they have used the micro switch which may last longer than the other contacts would. I did not dig deeper as I still plan to use this heater for my reserve water. 








Terrible choice of colors for the labels but they show left to right, the control, the bimetal spring and the micro-switch with the small white switch button. When this button is pushed it turns the heater on/ off. As the metal heats or cools, it warps and the button is pushed or released which controls the heat element.

For setting the temperature, a screw is run through the plastic top, down through the rubber seal, and riding on a tapered plastic piece on the metal spring. Screwing this in or out changes the amount of tension it takes to open or close the micro switch. 









Problems that I see? 
1. The shaft moves and is really hard to seal. This lets any water that gets on top seep down inside. Not good for electronics that carry 120 AC. 
2.The heater element heats the bimetal spring real hot. Heat tends to make metal distort over time and do funky things. It certainly throws any thoughts of precise control out the window. 
3. The screw through plastic is not a real durable operation. Plastic wears pretty quick and your setting gets bad. There really isn't a precise way to calibrate this to start with as it depends on the length of the screw as well as the width of the plastic at the end. 
4. The metal spring reacts to the temperature inside the glass tube rather than the water temperature. This makes it cycle and wear out much more often than if it was outside the tube sensing the water temperature.

Bottom line is we should not expect to get much for the prices we are willing to pay. And we don't???


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## prov356 (Sep 20, 2006)

> The metal spring reacts to the temperature inside the glass tube rather than the water temperature.


Just talking off the top of my head here. If the water doesn't affect the 'on/off' mechanism, then why does the heater respond to the temp of the water and turn on and off? I can see where it might respond to both, if poorly sealed from the heating coil, and turn off too soon. But, the metal spring has to also react to water temperature, even if indirectly. That water is transferring heat or cold to that air in the 'contact' chamber while heat is escaping from the 'coil' chamber to the water. Water is also acting to cool the glass covering the coil chamber. A heater under water only feels warm to the touch. Out of water, it'll burn your hand. I'm guessing, and only guessing, that it doesn't get incredibly hot inside the coil chamber, so the insulation in the better heaters does ok at keeping the coil chamber heat from affecting the contacts. And I acknowledge that I may be very wrong. I've got some old heaters laying around at home, so I know what I'm doing tonight. This is becoming an intriguing topic.


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## PfunMo (Jul 30, 2009)

The on/off cycle does react to the water temperature but only indirectly through the air temperature. It can't react to water temperature if it is not in water. Your house thermostat reacts to the outside air temperature but not directly. It reacts to the air temperature inside which is affected by the outside temperature. If there were perfect insulation between the heat coil portion and the control portion it might be possible but that is not possible with a single glass tube with little to no insulation between the two. Some heaters are better, some worse. Some have a bit of fiber insulation between the heat and the controls but once water leaks in and the insulation gets soggy is has little advantage over one with no insulation. With a different design that had two parts to the glass tube, one end could be the heater temperature and one end could be the water temperature, at least in theory. But with a single piece of glass, the two ends have to be near the same temperature or the glass would break. Evidence of this is spraying cold water from a hose on a hot car window. Car windows are much stronger and don't do this too often but if one has a defect like a chip, it can definitely crack big time.

I know it sounds unreasonable and hard to believe but in my opinion, the heaters sold most often are all a very poor design. That may be the reason we are constantly asked where one can buy a good heater at a reasonable price. There just isn't one!


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