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Re: Dupla cables

My understanding was that both voltage and amps could kill you, if they were
high enough, and that the higher voltage of the Dupla system was a reasonable
compromise, as it allows a lower amperage.

As for overheating the aquarium, I'm not terribly worried about that as I plan
to use a temperature controller to turn off the cables when the water gets too
hot.  My hood is also well ventilated, so I don't run into problems with heat
due to that.  Also, is there really a good way to know how much water is cycling
through the substrate?  If there is, I would really, really like to know so I
can set up a couple of 10 gallon aquariums with just cables and and substrate
and spend a couple of days messing around with this stuff.  Basically what I'm
trying to find out is if there is a good reason to use a lower wattage cable
that is on more vs. a high wattage cable that may only be on half as much.

Also, the opinion you have expressed about $150 being too much for wire and
suction cups is just that.  I can rationalize it, seeing as I have a really
small desire to stick my hand in the tank one day and get a nasty shock because
I made a mistake assembling the cables.  $150 is minimal when compared to
personal safety.

Justin Collins

"Adam R. Novitt" wrote:

> Justin,
> One thing is that power is drawn, not pushed.  If you think about it, if you
> put a 40 watt light bulb in a socket it draws 40 watts even though the
> circuit will push 10 times that.  So the transformer has only to exceed the
> amount of amps being called.   My setup probably draws something like 4 amps
> and my transformer will put out like 10. This is good because the
> transformer never runs near capacity and consequently runs cool.
> As to the safety issue a car battery puts out 220 amps at 12 volts. A
> transformer to run your system using non Dupla cables will put out 10 amps
> at 12 volts. I have never heard of anyone being electrocuted by a car
> battery.  I asked the electrician on staff at the radio station I work at
> and he said it was absolutely not a dangerous current.  The Dupla system
> that uses a higher voltage is actually more current, and hence in theory
> more dangerous.
> For safety it is more important that the primary (house side) and secondary
> (tank side) windings are separated.  You could tape both live leads to your
> forehead with no I'll effect.  If you zip tied them to your tongue though it
> would most certainly be unpleasant.  Most all new transformers will have
> separate primary/secondary windings, my ACME transformer is made for outside
> use and does.
> I think that 150 watts in a 100-gallon are to many, especially if you are
> using powerful lights under a hood.  The combined effect will over heat the
> aquarium.  I really believe you only need to cycle the water through the
> substrate 1 or 2 times a day.
> I'm not sure if the analogy is totally accurate but... If electricity were
> water, amps would be pressure (PSI), and volts would be volume (GPH).
> Combine these to get Watts.  A light bulb or a stove or anything is kind of
> like forcing that water through a series of water wheels, only so much can
> get through at a given time.  In our case, with the heating cables, the AWG
> 30 wire is like a little tiny pipe.  Instead of having the electricity
> exhort pressure on the walls of the pipe, as say a pump would, it creates
> heat.   One weird thing is that as the length of the pipe or wire increase
> the wattage lost to pressure/heat actually decreases.  If you think of
> trying to blow up a tiny balloon vs. a big one.  Each breath added to the
> long balloon is a smaller percentage of the total volume and so exhorts less
> pressure on the surface of the balloon.
> The Dupla cable is just a bigger pipe so it needs a greater volume of
> electricity to expand/heat it.  Hence more power = more dangerous.
> I used to do irrigation for a big, big farm.  I used to set up green house
> irrigation too.  This is an easy way for me to think about this.
> $150 is too much for suction cups and wire, even if you do have the money.
> Regards,
> Adam R. Novitt