NT-30MA to NT-30SP furnace change '79 Excella 500

[SafeHarbor]

Hi, folks,

Over the weekend and the next few days untill it's done, I'm going to be changing out the furnace in my '79 Excella from the original 1979 NT-30MA to a modern NT-30SP. The "A" nomenclature appears to mean that the heater is a variant of the NT-30M made for Airstream. There may be other differences, but the main one I see is that the old heater has an opening in the bottom from for flexible ducting to the forward holding tank.

The NT-30M is described in the 1979 service manual, and it is a thermostatically controlled pilotless model. I am replacing it because it's been operating a little bit erractically and because it is twenty-seven years old.

The furnaces are not exactly identical, although they do share very close dimensions. The outside end does fit in the existing cutout in the interior skin, but the inside end needs to be raised about half an inch to make the inlet and outlet pipes line up.

Here's a picture of the new furnace pushed into place.

Lamar