Thank you all for your interest in my request. I tried this forum hoping to see someone with same model as mine unfortunately the reply did not help me enough. I sent an email to Newmar with same request and here's what they say:
There is no way to turn the heat off to just to the basement in your coach. On the gas coaches, all we did is drill some holes in the heat run to allow residual heat to the basement when the furnace is running. On the diesel coaches, we would have run a heat line to the basement with a fan that you could turn off and on by the switch in the water service bay. No problems should develop from running the furnace while traveling. Some customers have a great fear of using any type of LP when they travel in case of a possible accident.
Hope this will help futur Newmar Mountain aire owner in ther request for help.
Thank you all formyour support.