Gas and Oil Home Heating Furnaces - return airs, how many?

My house is 1500sqft. In this 1500 is the family room which is a converted garage. I installed 2 heating/cooling vents in the room. The room is 25by12. Should i install 1 return air or 2? My heat pump is 2.5 tons.

How much return air does your system have already? The old rule of thumb for return air is one (1) square foot per ton of cooling. I prefer as much return as I can get (within reason, of course). I have a 2 ton system in my house and I have 3 square feet of return. If your system already has enough return air and the converted garage is wide open to the rest of the house, you may not need to install any more return. If the room is somewhat isolated and you plan to close the door often I, would install a 12x12 return vent in the room. My personal experience with converted garages is that they don't cool and heat as well and it is generally from lack of return air. I have a friend that built a house and he installed an 18x18 return in each of his four bedrooms. His system is extremely quiet due to the lower velocity of the air entering the grilles. The system works very well and with four filters, he doesn't have to replace them as often due to the increased filter surface area. Next question, what are the sizes of the grilles that you installed in the family room and do they get good airflow? Where did you connect to the supply ductwork? Each section of ductwork is sized to deliver a certain amount of CFM's, if you robbed air from the wrong place you may not be delivering the right amount of air to the family room not to mention taking airflow away from other areas. Let us know a little more information about the situation.

The vents I installed in the room are the standard 2in vents that you see often today. I used flex duct coming off of the trunk line that is nearest to the air handler. this is a downflow unit so the trunk is in my crawlspace and the return air trunk in my attic. there are 5 air returns in the house. One in each bedroom(3 bedrooms) and two in the living room. I had a little flow problem in one vent in the family room so installed a scoop in that particular duct so it would get more air. Flow is not as good in the living room now but I was planning on changing placement of the duct in the spring. With the 2 new vents in the family room there are a total of 12 vents now.