In the funny, non-logical wire gauge sizing, up means smaller number (larger diameter wire, not up as in bigger number. If it actually pulls the stated 37A, then it's a surprise that the breaker didn't trip. Plus, if the thing actually was left on for awhile, it could burn up the wiring. It depends on how it was run how easy it is for the wire to dissapate the heat. Run it tight in a wall with lots of insulation verses stapled to the joist, sitting in the open will make a difference in how hot the wires actually get. if this was ever inspected, it would fail...you should follow the manufacturer's instructions.
Is the data plate for the old one state exactly the same values as the new one? The same model doesn't necessarily mean the same thing after 25-years.