"Chris_S" wrote in message
...
I've got several EBOs. As far as I know you can put them under water.
It's
just not too easy getting to the temp knob when you do that.

I always thought highly of the EBOs in the past, but recently I'm not
so
sure anymore. For all their claims about their temp accuracy, they
just
don't bare out. Recently I got a digital temp thermometer. I verified
it
was correct by checking it against another of my lab grade digitals.
It was
within 0.25C. Very good.

But my EBO's were way off. One was 5F high and the other was 3F high.
You
set for 80F and the water temp was 85F. I had to set it down to 75F to
get
the water at 80F were I wanted it.

Virtually all of the built-in temp gauges on heaters I have tested are
wrong. I just don't trust any of them anymore. My advice is to invest
$15
in a digital temp thermometer and just use the heater gauges for
adjusting
them. Their accuracy is just too questionable.

Chris.
snip

I see heaters having 3 parameters of interest, absolute accuracy,
relative accuracy and drift.

Absolute accuracy is defined as how close the water temp. is to the set
point (on the dial). Analogs thermostat heaters are between infinity (no
number on dial) and about 4-6F (ie:Thermals). I find the digital
thermostat equipped heaters are better, at around 3-4F accuracy. This
factory adjustment is done in a high speed manufacturing environment,
probably in the atmosphere, instead of submerged with a long dwell time.
Fortunately, it's your least important parameter, as the heater should be
adjusted to a thermometer.

Relative accuracy is your most important parameter, which is how much
does the temperature bounce around. Typically, you can see about 2F
bounce, and the doctrine is that a 3F change in 24 hours is fine for
fish, so heaters are generally well within that range. Compare the tank
temperature early in the AM to late in the day to compare. More than 2F
drift might be your lights warming the tank beyond the heater's set point
though.

Drift is..- drift ). Your setpoint wasn't changed, but the tank's
temperature is slowly (over months) going up or down. This is an ailment
of digital thermostat heaters, related to solid state fatigue, especially
the earlier models. As long as the range of your dial still lets you
adjust up or down, you have a bit of time to buy another heater, but
eventually you run out of adjustment range, and beware that drift can
accelerate quickly. Contact the manufacturer as they might be able to
help.

If your EBOs are relatively accurate and not drifting, then your fish are
happy, so you can be too ).

NetMax