[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

RE: Duplamat 300w transformer replacement

Jon Wilson wrote:
>Subject: Duplamat 300w transformer replacement

>I realize this is a long shot, but my Dupla 300w transformer died this
weekend. I have been scouring the net and my local electronics places
looking for a replacement. After reading all the FAQs on DIY cable heat, it
seemed that I should be able to make my own replacement, but I can't find a
24v 12.5A transformer anywhere.

>As a sanity check, I'm hoping someone more electronically inclined than I
can make sure I am looking for the right thing and/or point out a source
that I have overlooked.

>The Dupla transformer says:
Primary 115V 50-60Hz, 2.9A
Secondary 24V Max, 12.5A

>If I had to, I'd be willing to spend the $270 for another Duplamat 300
transformer, but I can't find anyone selling them in the US either. (You'd
think they'd last more than 3 years at that price:)

>Any clues would be appreciated.

>Jon Wilson

The new Dupla importer is Hawaiian Marine Imports.  They are also the Eheim
importer.  Phone them at 800-993-4346 or www.hawaiianmarine.com or
Sales at hawaiianmarine_com.  They are just got started with the Dupla stuff at
the first of the year and are still learning about it.  Some of the product
will be imported and some will not, particularly the foods (mad cow).  If
the demand is there I would imagine that all the product line will be
available eventually.

From what I understand Dupla is currently refusing to make the transformers
for the US market (in other words no 120V 60Hz transformers) probably
because of the volume needed to justify a production run.  However they have
provided Hawaiian Marine with the tech specs to get one made here.  I
believe they have something now or they might direct you to the transformer
mfg.  I'm not sure about the price.  The list I have may be from before the
decision on importing the transformers was made so I don't want to mislead
anyone.  Check with Hawaiian Marine to be sure.

If you decide to make your own, I want say that I am not an expert in this
stuff but I studied the communications and controls end of EE.  I remember a
little about transformers (though I sure studied them) so consult with the
manufacturer before you buy.  They should help you make a good decision.  Be
careful - electricity can be hazardous.  I worked primarily with lower power
control circuits but I still got burned pretty good a few times, even after
working with it for years.  My pride usually suffered the worst injury but I
often had a little burn on a finger that reminded me every time I picked
something up for the next couple of weeks.  Just last week I watched my
electrician zap himself working on an outlet in the backyard.  And don't
forget what happened to George Booth a year ago the first of last month.  As
I recall (I have a couple of small children so my mind has gotten feeble :))
it only takes about 250mA (1/4 Amp) to electrocute you.  Anything above that
and you may be held to the circuit.

First, you will want a transformer with a 5 to 1 turns ratio to step down
the voltage.  The Dupla cables run on 24V and the power outlet is 120V
(120/24 = 5).  Second, make sure the transformer is capable of handling the
power.  You mentioned 300W.  You might also tell them the primary and
secondary specs from the Dupla transformer.  Third, I would imagine that you
would want to find a transformer where the primary and secondary windings
are completely isolated physically.  In the event of a short on either side
(primary or secondary) the insulating material could melt away allowing the
conductors in one of the windings to make contact.  If the primary (connects
to the wall outlet) and secondary (runs into the tank) coils are physically
touching I would almost guarantee that a short or some other melt down would
bypass the electromagnetic coupling of the primary and secondary windings
and you might end up with primary voltage in your tank.  This would be sort
of like cutting a cord off an appliance, sticking the cut end in your tank
and plugging the other end in and outlet.  Needless to say, don't try this
at home kiddies :)

If you make it yourself, you will need electrical connectors for the Dupla
cables (I think they are banana plugs) and you will have to wire the primary
to a power cord.  You might also want to consider potting it in a proper
waterproof housing and an indicator light to see when its on (depending upon
your control scheme).

IMHO, I would check with Hawaiian Marine first.  I do not know what they
intend to sell them for, but if you can handle the price (it may be cheap
for all I know) it would save a lot of time and it would be done correctly.
I sort of am the type who would prefer to let someone else do it, mostly
because I don't have the time to hunt down all the stuff to build it and
make it look nice.  I used to R&D and manufacture electrical stuff and I
have had enough messing with potting compounds and the cleanup to last a
lifetime or two.  That sort of adds to my off-the-shelf bias too.

Good luck!