Gas heater

[thosoneill]

Is a carver sb1800 heater interchangeable with a truma s3004 heater

 

[ProfJohnL]

Simple answer NO

However there are similarities which means it may be possible to up grade, but this will need work on the floor hole cutout, and the means to root the flue pipe to the roof.

I suggest you have a professional check out and to do the fitting.