There is no Outside Air Kit (OAK) available for the Hampton HI300... but that didn't stop me from trying. 
I'll attach pictures so you can see the install. Here's what I did...
Now I have outside air flowing through a 4 inch dryer hose to the ash-clean-out-door in my basement, up to the ash door in my fireplace(under my insert), to the rectangular dryer duct, to some custom bent ducting, to the right side air intake of my insert.
I know that this looks pretty messy, but it seems to be working. I can feel a good flow of air getting pulled into the 4 inch vent on the outside of my house.
Why do all this?
I'll attach pictures so you can see the install. Here's what I did...- My fireplace had an ash door in its floor that connects to a clean-out opening in the basement. so I ran a 4 inch dryer hose feeding outside air to that clean-out in the basement.
- Then I took a rectangular dryer duct which fit perfectly under my insert and fitted it to the ash door opening in the floor of the fire place. I did this without moving my insert.
- I bent, pop-riveted and high-heat-caulked some sheet metal to fit to the right side air intake of the insert. Then attached it using more high-heat-caulk.
- I bent more sheet metal to connect the insert intake connector to the end of the rectangular dryer duct. I used some more pop-rivets and a whole bunch of high-heat-caulk to make the connection.
- I closed off the left side air intake of the insert with a strip of metal and some high-heat-caulk.
Now I have outside air flowing through a 4 inch dryer hose to the ash-clean-out-door in my basement, up to the ash door in my fireplace(under my insert), to the rectangular dryer duct, to some custom bent ducting, to the right side air intake of my insert.
I know that this looks pretty messy, but it seems to be working. I can feel a good flow of air getting pulled into the 4 inch vent on the outside of my house.
Why do all this?
- You can supposedly get 20-30% improved efficiency burning unheated outside air vs inside air that you have already heated.
- Reduce drafting. Less air being pulled through cracks into the house for the purposes of burning.
- I like to tinker and couldn't help myself.
