Sir jamman1125 . . .
. . . .
.My prior info was more related to why a person would be confused by imbalanced reading on a transformer with duplicate windings.
With a given, that unloaded transformers will potentially read higher voltages, than when being loaded down.
I am used to seeing a "Pwemium Bwewed" Amerikanski brands, like Thordarson / Merit / Triad transformers, only pull down ~ 10%
on a full spec load down.
Some of the "Cheapies(/cut corner units) will drop down upwards of up to ~20 % and run hot.
THEN we have some Mil Spec units are so good that they only load down in the order of 5%.
(Toroidal wound units can also fall in that last category. )
Lets refer back to the transformer manufacturers sheet that you gave us a link to.
Hey . . . . . it looks like you had added on a cable to it, in your voltage measuring .
Sooooooooo in just looking at the " naked" transformers, lets assign RED . . . .A-B-C-D
identifiers to their secondary winding terminals.
Ideally and probably being expected will be that if you put a wire jumper across terminals B-C that will establish connectin
between the two separate windings and thereby get yourself a common center tap between the units.
If that is correctly establishing a "series aiding " interconnect between the two windings, then in using your AC meter to
measure between a shared BC connection over to A terminal should read 18VAC, or additionally , BC connection
over to D terminal should read 18VAC. Then a final reading from A-D should reveal a totaled 36VAC.
Therefore those two windings were series connected in the correct phasing to add up to 36 volts.
IF you don't get this, then the windings would have been in opposed phasing wiring and you won't end up getting that 36 VAC additive voltage.
THEN, if finding that situation, to correct, go back and reinstall the jumper from terminal B-to-D and let that be the newly acquired
center tap. In testing with the new B-D center tap, it should read 18 VAC to either A or C and then, a final confirmation is made with
there being a full 36 VAC between terminals A and C.
Now hook it up to your system in that way.
A REAL TIME ANALOGY . . . . .
You are all of 4 years old and are exploring Uncle Bills pick up truck and are looking around in the glove compartment and find this flashlight.
You turn it on and off and on and off and play with it all that you can and than notice that the bottom end will turn.
You turn and turn and all of a sudden it pops apart and two long round thingys drop to the floor.
PANIC . . . . you find those two things and then rapidly stuff them back in the flashlight tube and with some musing, find that if you press hard,
the part you had come off on you, will go back on.
Of course, that's with some pressing and some early on self acquired / OTJ education of "Righty tighty and lefty loosey."
Finally that cap is tight and you immediately turn it on to play with it some more . . . . .but ALAS . . . . it no workee !
What a sinking feeling in the stomach . . . . .certainly your britches are in for a dusting !
You take it apart another time and this time . . . TOTALLY by chance . . . . a battery button end to a flat battery end is contacting,
and upon reassembly . . .
Behold ! . . .there was light.
Unknowingly you experienced "polarity" and "series voltage adding".
Definitely time to put that thing back where you got it and go in the back yard and play with the cat that walks up to greet you and
puts its paw up to shake your hand . . . .but that's another story . . . . . .
Now, with your transformer wiring just mentioned , there is a bit of both that polarity, and voltage adding aspect also being involved , but with the
additional complexity of it being an AC voltage.
Thasssit . . . . . . .
73's de Edd