Help with Fresh Air Intake Vent for Fireplace

[Dbla17]

I have a three sided fireplace in my basement family room. The fireplace is not very efficient since most of the hot air is escaping up the chimney and it is causing cold air to be sucked down my boiler exhaust that is in the basement as well. I would like to add a fresh air intake vent for the fireplace. I plan on running a 4 Inch vent from outside but do not know the best location to place the intake ven on the fireplace itself. The easiest location would be on the back wall of the fireplace. But i also have the ability to run the intake under the fireplace since that is where the ash pit resides. Any ideas on what the best location would be? Should i make one 4 inch vent? Or should i make a few smaller vents? Let me know if you need to see any pictures. Thanks

Antony

 

[DAKSY]

If you can do it, most masonry fireplaces with fresh
combustion air have the intake located at the front
middle, behind the hearth & just inside the fireplace
opening.

 

[Dbla17]

Thanks for the answer. However, since this is a three sided fireplace, it actually comes out to the room and has three doors, there really isn't a true "front". Should i make three different holes from underneath? And if so how big do you think each one should be?

Thaks