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Re: BIG tank heating cables -- efficiency vs tube heaters

"S. Hieber" <shieber at yahoo_com> wrote:
 
>  Ivo Busko noted that:
> 
> > There might be another factor that compounds with the one you
> > described: 
> > contact area. A tube heater has a few square inches of very hot glass
> > in 
> > contact with water. A cable heater provides a large mass of mildly 
> > warm gravel in simultanous contact with a large mass of water. The
> > water in
> > contact with the tube heater may get very warm, but as you said, a
> > good
> > part of this heat is going to escape at the surface. Setting a
> > powerhead 
> > or filter output jet to blow right over a tube heater should increase
> > 
> > its effectiveness by a lot, I think.
> > 
> I think you are right.  The powerhead/filter output helps to increase
> the disitribution of heat from the tube, getting it closer to what a
> substrate cable achieves.  How close is close enough.  Hard to say
> without objective measurements that can be applied to a specific
> situation -- but when heating 1,000 gallons (which started this thread)
> small efficiencies can add up to big savings, maybe even enough to pay
> for the heating cables if you by ready made cables.
> 
> Ivo, you make your own cables do you not?  About what do you think it
> would it cost you to make up a heater for a 1,000 gallon tank?
> 
> Scott H.
> 

No, I didn't make my cable. I got a 200 Watt Azoo cable from m3 for
about $60. It's length is OK for the 120 gal footprint. It's being 
operated now at effectively 100 Watt, since it is cycled on/off every 
1/2 hour by a timer. Based on this only setup that I observed so far, 
I would guesstimate that a 1,000 gal tank would require something in 
the range of 600-800 Watt if the cables are to be left on all the 
time. If one wants to cycle them, more power will be required. I would 
consider installing two 300 Watt cables, maybe an extra 100 or 200 
Watter if it fits in the footprint. About $200 - 250 total. Adding 
complementary heating via some other means is always possible later on, 
if the cables turn out not to be enough, or if one wants to cycle then. 
Multiple cables also provide more redundancy, a good thing IMO.

Also, insulating the unseen tank surfaces (at least the back and bottom)
would help to keep the heat inside.

- Ivo Busko
  Baltimore, MD

  "Buy a fish, Save a tree !"
  Project Piaba: http://www.angelfire.com/pq/piaba/