208x240 buck boost transformer putting out 260v

[dewhite04]

I recently installed a buck-boost transformer in a building with 208Y/120v service to support a 1hp submersible well pump rated for 230v.

The transformer is a GE 9T51B0158 which is labeled for 208v primary x 240v secondary, up to 500va.

Per the label diagram, I connected 208v nom. (210v measured at the transformer) to X1 & X2, tied H2 to H3, and then took a meter reading at H1 & H4 before connecting to the well-pump control. I measured 259v at H1 & H4, unloaded. Is there some reason to expect this kind of over-voltage? Would you expect the secondary to drop down closer to 240v under some load? Or is it more likely that I have either misunderstood the wiring diagram or acquired a dud unit?

Any thoughts are appreciated.

Thanks,

Dan

 

[Dennis Alwon]

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