Re: Frogs, Cables, Vacation

> From: Erik Olson <olson at phys_washington.edu>
> Date: Thu, 27 Apr 1995 19:36:22 -0700 (PDT)
> Subject: FROG
> George, the FROG is a little better than that, because it does have a
> little pop-out thing that tells when the tank is running low.  The label
> says "10 minutes left when it pops in".  But this is for welders who are
> not running it through a needle valve, so I'd guess you probably have a
> week before you have to actually replace the tank. 

A local store sells their own version fo CO2 injection using these
FROG things and 5# bottles and they report that they have *never* seen
the button do its thing.  FWIW.

> From: jsprag at srv_net (John Sprague)
> Date: Thu, 27 Apr 95 22:46:51 -0600
> Subject: Re:  Temp controlled DIY heating cables
> Ideally the system would be designed so that the cables could be on at
> all times and just provide the required heat with no supplemental
> heater.  

Keep in mind the main purpose of the coils: provide slow circulation
in the substrate.  The substrate heating thing is secondary and the
tank water heating thing is just a useful side effect.  The "ideal" 
(as far as we understand it) is continuous slow circulation in the

> For various reasons this obviously won't work.  The two options then
> are to 1) Make a system designed to provide less heat than required
> and have an additional, thermostatically controlled heater to make up
> the difference (the typical DIY design) and 2) Place a controller on
> cables that will provide more heat than necessary (the typical
> commercial design).

The Dennerle system ("low watt" school) is to have a smart controller
that runs the lower wattage cables as much as possible.  If the cable
heat is not sufficient to maintain the water temp, it switches on the
aux heater until water temp is OK.  A "perfect" design will have the
cables sized so that they are on all the time and the aux heater is
just used in winter.

In our "low watt" tanks, we have an UltraLife temp controller set at
78 F running the cables and a Ebo-Jaeger set at 76 F providing aux
heat.  If the cables can't supply enough heat, the Ebo-Jaeger kicks
on.  The cables are on most of the time.  They tend to be off towards
the end of the day when the MH lights have pushed the water temp just
over the cable temp threshold. 


I'll be on vacation for the next two weeks.  I bet I'll have a lot of
reading to catch up on when I get back!