Transformer output wiring question.

Thread Starter


Joined Apr 21, 2018
Is it safe to wire these two 12V outputs in series to obtain 24V?
And, if I wire them in parallel does that then give me double the current rating?



Joined Jan 29, 2010
hi PAK,
Welcome to AAC.
For 24V, link the two inner pins [ 12V 0]
For 12V at double current, link 0v to 0v and the other 12Vs together

Do you follow OK.?



Joined Jun 4, 2014
I'll just add a small proviso. In series there is no problem but in parallel there may be. The two secondary windings may not be well enough matched voltages for good parallel connection. Until recently I would have expected it to be OK to parallel connect them but I was looking at such a transformer and the data sheet specifically stated not to connect the windings in parallel. If possible check the data sheet for that transformer.


Joined Dec 29, 2008
... not completely sure about small transformers like these, but on larger power transformers it is necessary to check the transformer polarity. ... This is not too difficult. Just place the transformers in series, temporarily connecting the top secondary side of one to the bottom of the other secondary. Then measure the total AC secondary voltage ... between the bottom of the first transformer secondary to the top of the second ... No load is connected ... just an open circuit measurement. If everything is good, your voltage measurement will be the additive sum of the two secondary voltages. However, if for some reason the polarity of the transformers is not identical ... perhaps one of them is reversed, then you will measure zero total AC volts across the two in series, in other words the algebraic sum. ... It is a good idea to mark the polarity of each transformer secondary so that there is no confusion when connecting them in the future.
... note: the primary side of each transformer in the above series test is connected independently in a normal manner.
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Joined Jul 18, 2013
Ideally the two identical winding's should be wound Bifilar, and if they are, means they are closely matched.

The spec sheet states.
Chssis mounting low voltage mains transformers with a single 230Va.c. 50/60Hz primary winding. The two independent secondary windings may be connected in series or parallel to give a wide range of output voltage and current options.