Transformer Polarity

Hook 'em together and measure.

If you are connecting 2 transformers in series as mentioned in previous post if both transformers are of identical voltage output you will either have the sum of there voltages or zero volts. If the outputs are different voltages the you will have the sum or the difference of the two voltages.

If you are to connect them in parallel they must be identical units or circulating currents and poor power control will take place.Also to be safe to connect in parallel you should first check them in series , when you have the sum of the voltages the center tap connection of the second transformer can be removed and connected to the first connection of the fist transformer and the other end of the second transformer connected to what was the center tap, this will avoid connecting the transformers in reverse and creating a massive short circuit.

Take care and experiment with low voltage transformers.

If you have an oscilloscope with dual inputs it would be an easy task since the waveforms would be in-phase or out-of-phase and easily determined.

Using an AC meter and connecting the two secondaries in series and the AC meter placed on the outer terminals would also immediately reveal the connection polarity.

what effect would it have if there's a accidental connection of additive polarity to subtractive polarity in terms of transformer banking??

If your secondary is connected in Wye, it will result to unbalnce Line to line voltage.