recently purchased a fabco night fire pellet stove insert. i understand that this is a outdated model and that fabco went out of business years ago. the stoves fan and auger both work perfectly. ive tried to run this unit outside to test it before i install it in the fireplace. however , the unit wont keep the fire going and goes out in about 5 minutes .ive read that this is a positve venting stove and needs to be installed in the fireplace to work properly, can any one out there confirm this ? also, would any one know the approximate btu rating on this unit ?thanks.