I just installed a Tempstar oil fired furnace and the small transformer in the electric box hums all the time, does anyone know if this is normal,I can not find a number for Tempstar thanks Ron

have you checked voltages in and out of the transformer to make sure they are within ratings?

There is always a quiet hum from these transformers, however if it is loud, i would change it out. If you get the same noise from the new trans, then there isnt much you can do about it. Just the nature of the beast. Hope this helps and please let me know what you find.