On Sat, 26 Dec 2015 03:59:28 -0600, wrote:

On Sat, 26 Dec 2015 00:58:19 -0500, wrote:

Clare pegged it, You haver a loose neutral. Try checking it at the
main lugs. If it is bad there call the PoCo. If it is bad at your sub,
investigate your neutral connections or look for a serious load
imbalance.

It's possible there is a neutral problem, but you could just have a pole
transformer that is not exactly center tapped. There could also be some
load on one leg, pulling down the voltage. Measure the voltage at the
MAINS on both legs with everything turned on. Then do it again with
everything turned Off.

If it's still unbalanced with everything OFF, it's just a transformer
that's a little unbalanced. Not to be worried about, if that's all it
is.


Huh?
They don't arbitrarily "center tap" the transformer wherever they
want,. It is wound at the factory and it will be tapped exactly at the
center.
This looks more like a 5-6% voltage drop in the neutral.
That is far beyond the NEC recommendation and the utility standard.