Heaters.....

[jimmyringo]

I had a good brand(can't remember which offhand) heater in my tank for ages.But to keep a steady temp of 26C i had to set the heater to 22C.i assumed the heater was just a bit off.Anyway,a few months ago i bought a new Hydor heater.Now my tank temp is at a steady 26C.......even though the heater is set to 18C.The heater still comes on regularly.If i turn the heater off ,the temp will gradually drop to about 20C(room temp).But as soon as i turn it back on,up it goes to about 26C even though its set to 18C.
It seems that no matter what heater i have in my tank at whatever setting,the temp will always rise to about 26C.I'm not that fussed ,as its a steady 26 ,but i'm curious as to why?Anybody?

 

[SuperColey1]

I've found that almost every heater I have never recognises the printed heat on the dial. Not a problem though if you have a thermomenter as you can set the dial to the correct place that you know will get the desired temperature and as long as it is heating to the desired temp it doesn't really matter what the 'printed number says'

AC

 

[smegforbrains]

You may also want to consider the fact that, unless you heater is in the flow of the filter and thus circulating heated water, you will have possible cold spots in the tank.


If you are not taking the measurement in exactly the same place every time, you will get inconsistencies in your readings.

 

[jimmyringo]

I have 2 thermometers ,one on the top right of the tank(stick on),and one in the bottom left(glass submersible).They both read the same.

 

[onebto]

By trade I am a refrigeration engineer and had a lot of dealings with thermostats of varying shapes and sizes in my time . The adjuster on the top of the heater used in aquarium applications is a thermostat but working in the opposite to the refrigeration process.

Very rarely would I find a thermostat that its markings would marry up with the temperature actuations unless they were digital and relay operated (expensive), so I found that I had to set each individual analogue thermostat (cheaper) up to its individual application I think this is the case with the temperature controls on the top of the heaters maybe .

Contacts making an electrical circuit thus making the heater work if they are on for to long will start sticking the components are probably the cheapest available to the manufacturer and this will be a factor.

There is a saying that apply's today to a lot of things and applications " they do not make them like they used to" time is money and money unfortunately is KING in business.

My humble 2 cents worth

 

[raptorrex]

I had a good brand(can't remember which offhand) heater in my tank for ages.But to keep a steady temp of 26C i had to set the heater to 22C.i assumed the heater was just a bit off.Anyway,a few months ago i bought a new Hydor heater.Now my tank temp is at a steady 26C.......even though the heater is set to 18C.The heater still comes on regularly.If i turn the heater off ,the temp will gradually drop to about 20C(room temp).But as soon as i turn it back on,up it goes to about 26C even though its set to 18C.
It seems that no matter what heater i have in my tank at whatever setting,the temp will always rise to about 26C.I'm not that fussed ,as its a steady 26 ,but i'm curious as to why?Anybody?

Though the dial temperature, seems, to have no correlation to the real temp, i have always found adjusting, up or down, had an effect. though a good quality thermometer is needed to find the true temperature. mind you, i only have experience of 4 or 5 heaters to go by!

 

[jimmyringo]

My humble 2 cents worth

And much appreciated.

 

[StrontiumDog]

The three heaters I have are all set lower than what my thermometers read, I also have 4 digital thermometers that read different to the glass ones I have.

Having been in a Tannery job where thermometers, PH meters, and weighing scales are used every day, that all have varing readings and no 2 will read the same. I all comes down to as some one has mentioned money, and the tolerance that is set for that item.

IE: Tolerance on some digital termometers can be + or - 2 deg C, unless you pay mega money.

 

[three-fingers]

None of the 3 heaters I'm using atm actually heat to the temperature they are set to . One of them has even stuck on in the past (though I unplugged it and left it for nearly a year as a spare and it's working OK now).
And I just had a heater stop working on me again.

I really don't like heaters, most of them just seem to stop working normally after 1-2 years.

I just got a couple of eheim jagers though, and they look promising. Quite big (very big compared to other brands of the same wattage) and robust feeling, and you can calibrate them so they actually heat to the temperature they are set to. They are quite cheap (only cost me about £10 each), but the 3-year warrenty is promising. Really hope they turn out OK.

 

[keenonfish]

It comes down to the use of a mechanical device to control the temperature it is basically two pieces of metal glued together with different thermal properties i.e. one metal expands quicker than the other and bends the arm due to the slower moving metal and making / breaking contact. The main problems are that it is a rather inaccurate system and it doesn't (and cannot) have direct contact with water which only adds to the problems. It also fatigues so the value may drift over time I assume it may weaken which will contribute toward the dreadful stuck on effect. Of course the main culprit here is arcin gof the contacts eventually the weld together.
Incidentally, have you ever used a max / min digital thermometer in your aquarium? Another thing with bimetal and other similar operating stats (onebto will be familiar with stats with a coiled bit of stiff metal works on a similar principle unless it is a thermocouple) is that they have a very wide hysteresis, i.e. they will say, cut out at 26 c and the water might drop down to 24 - 25 c before the stat senses this and turns back on.

On a similar note, if you have ever had your mum complain about her new oven not being the same as the old one then you know why, basically the means used to detect temperature is about as basic as you get, but arguably just about adequate!

As I keep saying there is really no excuse as to why thermometers are not digital except I suspect digital ones are available and cost serious $$$$ for marketing reasons. Basically companies love to rip us all off

My Visi-therm thermometers are probably the most accurate that I have got not sure what the general consensus is on this make but I like them!

 

[SuperColey1]

I remember when I used to use a Fluval Tronic in my tank that I used to set it to 81ºF(27.5ºC) to get 77ºF(25ºC).

These days I use a Hydor inline and it is probs ½ºC out so not a problem really.

I use the glass thermometers form Wilkos as they cost 99p and both of them read the same.

To the poster that said about cold spots. I am running at over 10x volume lph so I don't think there is going to be too much difference in temp anywhere . I will be running at 17x volume lph very soon!!!.

AC

 

[Schmill]

I guess I just got a lucky pairing with mine

EDIT
Following AC's comment later in the thread I realised I hadn't mentioned this and I should have really. The reason that this is so 'warm' at the moment is because it is just at the end of a fishless cycle, so has been running at an elevated temperature. I will be turning it down in the next day or so

 

[keenonfish]

I guess I just got a lucky pairing with mine

One thing I have noticed using those thermometers is that they tend to always show the average temperature of the tank whereas digital ones adjust pretty quickly. My identical therm to yours is always showing the same temp more or less whereas there is an obvious swing with the digital ones (and mine are quite accurate too!).

Not that any of this matters I don't think the fish generally complain about any fluctuations but could some hard to spawn fish or certain fry be more sensitive?

 

[Schmill]

Is it not the average tank temperature that we WANT to measure rather than the temperature of the particular peice of water that happens to be flowing past that fraction of a second?
Certainly after a water change I can watch this thermometer drop as the fresh water goes in, and then gradually climb over a few hours as the water heats again, (of course I don't know how much dealy is involved, but testing it in a cup of water it seems to react within a few seconds of change).

 

[elaine128]

i`v got the hydor external heater which i think is an excellent,heater set at 25 , cheap thermometer from wilko`s reads 25,expensive high precision thermometer reads 25, digital reads 28 and it doesnt seem to matter where i place the thermometers,the digital reading is always higher,