An interesting converstation currently going on on Eribafolk Facebook which I though useful to add to the forum..

One of our Portugese members has modified his Truma chimney outlet thus:-

plastic exhaust pipe.jpg - Bild entfernt (keine Rechte)

Now I know nothing about the rights and the wrongs of this so perhaps some folk can enlighten me.

The debate that followed goes like this:-

Translated from Portugese.

It was a mistake you made, this old fireplace is from the heating and the other one is from the exhaust
The exhaust pipe can't stand the heat released by heating
There is going to be trouble

Also:-
How to kill yourself, mess with something you know nothing about. There is not enough “free space” on the terminal so the Products of combustion are not going to be able to disperse with that terminal. They will probably back up and smother the burner or the fumes will be released into space thereby killing you. You must only use the original as it has been designed specifically so you live

Correct , that chimney is to be used with exhaust because air is forced out of the engine
Besides that fireplace can't handle the heat of heating.