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Re: Transformers for Dupla heating cable

>> >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.
>> This is very hazardous.  Most inexpensive transformers do not have
>> secondaries that are isolated from the primaries (transformers that
>> do are called isolation transformers).  Connect the secondaries
>> together at all may be dangerous.
>Could you elaborate?  I have been told by several local transformer
>suppliers that connecting two lower powered transformers in series "Will
>not work" but I do not understand the problem.  As I understand
>transformers, current in the secondary comes from the magnetic field of the
>primary and there is no electrical path between the two.  What is the
>difference between a regular transformer and an isolation transformer?
>What consequence does one risk when connecting transformer secondaries in

There is some misinformation here:

1) First of all the reference to 42 volt heating coils was a typo, it
should have been 24.

2) 24 volt transformers are easily available in a wide variety of wattages,
so you shouldn't have to use multiple transformers.

3) Most transformers are isolation transformers, very few are not. The full
specification will give a rating for the isolation insulation.

4) When you use a transformer, use it within the rated power limits. You
can connect transformers in series, provided you don't exceed the power
requirements. Exceeding the power requirements will cause the transformer
to overheat and release smoke. As most of us know, it is the smoke that
makes electrical and electronic components work, because once smoke
escapes, they don't work any more.


Paul Nicholson               Electronic Imaging Systems, Inc.
TEL 805 532 1068             5148 Commerce Avenue, Unit F
FAX 805 532 1065             Moorpark, CA 93021 U.S.A.
paul at eisusa_com		     http://www.eisusa.com