The simple answer is "no". We strongly recommend that Building Regulations and manufacturer’s guidelines (as per your stove’s installation manual) are strictly adhered to.
It’s true that many wood pellet stoves have been terminated in this way and that often, they work, but it’s wrong and it's dangerous. A natural draught is very important for your wood pellet stove, especially in the event of a power cut. This protects you from smoke and gases existing the appliance and carbon monoxide poisoning.
Incorrect flue installation may also invalidate your stove warranty. We strongly recommend that you always engage a professional, registered and insured installer when having any stove fitted. This should ensure that all correct procedures are followed, give you peace of mind and protect you in the case of an incident.