# Dupla Heating Cables

```There is yet another "solution" to the 42 volt power supply dilemma.

_TWO_  (or more) transformers secondaries may be hooked in series (they MUST
be "in phase!!!") to produce any given voltage.

Thus, you could hook a 24 volt and a 12 volt transformer correctly, and get
36 volts. This is still under the 42 volt rating, but if you do the
calculations, it will give you _significantly more_ heat.

You could also hook 24 volt, 12 volt, and 6 volt transformers together and
get 42 volts.

Or, you could use two, 24 volt transformers, and get 48 volts. That could get
you into trouble, because at that voltage you would be driving the cables a
bit heavy. First, they might not handle the current safely, second, you are
now at a high enough EMF to really zap yourself! (EMF = Electro Motive
Force.)

When hooking transformer secondary windings together, they MUST be "in
phase," or instead of adding, they will SUBTRACT from each other. Not good.
Also, you must consider whether the CURRENT ratings of all the transformer sec
ondary windings are adequate, and whether the secondary windings are
sufficiently insulated for the increased EMF. In this case, the 6-volt
transformer would have a 42 volt EMF working quite hard to puncture the
insulation.

To try this, attach the PRIMARIES of the two transformers in PARALLEL, attach
the secondaries of TWO transformers in series, then check the resultant
voltage. If it is not correct, REVERSE the connections of ONE of the two
transformer secondaries. Now it should be correct. Then, if you are
connecting three transformer secondaries, check the voltage after adding the
third. Same criteria, same solution.

I am _not recommending_ any of these "solutions," just noting that "there is
more than one way to skin a cat."

(Or, you could just spring for the Dupla Transformer!! :-))

Cheers!

Jean Olson
JOlson8590 at AOL_com
Out in the Boonies, near
Cambridge, Iowa
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