Thakn you guys for yours answer.
That is exactly what happend, the owner of the place call me to fix his heater, after changing the fuse, the heater is still no working, so i found that the transformer for the control voltage is burn, i replaced it and after work for a minute, the transformer is...
i have a dayton 2yu74 electrical heater, in the plate said 15Kw, 60 Hz, control voltage 24v, 208V, 1/3 fase.
could this unit works fine if is connected to 240 v?