Blue Flame heater won't stay lit
I just recently got a vent free 20k btu Mr Heater blue flame for my greenhouse. Problem is it won't stay lit. This originally happened the very first night I set it up. Figured it was a oxygen problem so ran a 4" pipe to underside of heater and taped up the rest of the intakes as suggested by another post on here. It worked good for one night and then back to not being reliable. It will sometimes only stay on for 10 minutes and other times it would go all night. I also used compressed air and cleaned it out per the manual (though I didn't think this would help as it was brand new). This didn't seem to make much of a difference. I also have my doubts as it being a dirty thermocouple issue as well being how it is new.
The pilot flame is just blue as it should be and does not show any orange or otherwise which would indicate it being dirty. I have a 100# tank with a 10ft hose attached. I don't think it is a draft either as the wind does not blow much here and when it does it doesn't seem to make a diff on performance anyway. My greenhouse is very air tight and insulated. Is it possible a 4" supply is not enough or maybe the oxygen is just not being pulled in enough (I am running less than 30" from heater to outside in a straight shot)? The outside of my pipe has a dryer vent attachment without the flappers installed. I have taken this completely off to just leave the pipe wide open but this also doesn't seem to make a diff.
Any new ideas would be appreciated. I've searched and searched on here and can't seem to find my solution. Thanks so much in advance.