Can these supply grills effectively be used as dampers??
#1
06-20-17, 12:48 PM
Can these supply grills effectively be used as dampers??
When I moved into my current home someone cut and mounted 12 x 8 supply grills directly on into the main duct to heat the half finished basement ( I'm assuming home owners but possibly HVAC guys as the unit was new) .
I have since knocked down a wall to expand the half finished basement into a 3/4 finished basement. the other 1/4 of the basement is the coldest area and had no heat supply so I went ahead and added another register and cut out the same size hole.
By the calculations I have seen a 12 x 8 hole is equal to a 10 in and 400cmf. My system is 88,000 btu with a 1/3 hp blower so there is no way I am going to get 1200 cmf out of those 3 supplies.
My question is, can these supply grills effectively be used as dampers so I do not drain all the CMF from the rest of the house?
Or should I put in a real damper above the grill like this?
Dampers|Dampers|Air Balance Rectangular Balancing Damper
OR should I cut a piece of sheet metal like this and place it flush with the duct basically turning the wood frame that the grill mounts to into a duct boot?
Below is a picture of the vent I cut out ( all three look like this ).
I have since knocked down a wall to expand the half finished basement into a 3/4 finished basement. the other 1/4 of the basement is the coldest area and had no heat supply so I went ahead and added another register and cut out the same size hole.
By the calculations I have seen a 12 x 8 hole is equal to a 10 in and 400cmf. My system is 88,000 btu with a 1/3 hp blower so there is no way I am going to get 1200 cmf out of those 3 supplies.
My question is, can these supply grills effectively be used as dampers so I do not drain all the CMF from the rest of the house?
Or should I put in a real damper above the grill like this?
Dampers|Dampers|Air Balance Rectangular Balancing Damper
OR should I cut a piece of sheet metal like this and place it flush with the duct basically turning the wood frame that the grill mounts to into a duct boot?
Below is a picture of the vent I cut out ( all three look like this ).
Last edited by PJmax; 06-20-17 at 01:22 PM. Reason: added pic
#2
06-20-17, 01:20 PM
Group Moderator
An adjustable register would work fine for that application.
Very easy to adjust once the ceiling is finished too.
Very easy to adjust once the ceiling is finished too.
#4
06-20-17, 03:20 PM
Ok I was a little worried after I put another big hole in the supply because 4 of the upstairs supplies lost a ton of CMF.
I have yet to buy a register for this hole though. So as it stands, it is a 12 x 8 hole with no damper. I assume it is because it is so close to the 4 supplies upstairs that lost all that CMF therefore there is basically no static pressure in that area?
- Registers upstairs that lost CMF are RED
- Registers upstairs with no or minimal loss in CMF are GREEN
- Hole downstairs that I just cut is BLUE
I have yet to buy a register for this hole though. So as it stands, it is a 12 x 8 hole with no damper. I assume it is because it is so close to the 4 supplies upstairs that lost all that CMF therefore there is basically no static pressure in that area?
- Registers upstairs that lost CMF are RED
- Registers upstairs with no or minimal loss in CMF are GREEN
- Hole downstairs that I just cut is BLUE
#5
06-20-17, 03:39 PM
Group Moderator
You can't just have open holes. The system must be pressurized or the air will not travel to the ends of the system.
Cover the holes until you get the registers on them. You will only be opening the registers slightly. You should need very little cool air in the summer down there. More needed in the winter.
Cover the holes until you get the registers on them. You will only be opening the registers slightly. You should need very little cool air in the summer down there. More needed in the winter.
#6
06-20-17, 03:43 PM
Thanks Pjmax, I should have mentioned I do not have central air yet just forced hot air. It is over 80 f today so the system isn't being used ( only the short period for testing). Weird thing is, the the supplies further down the duct still seem to have sufficient CMF even with the huge hole. Its just the ones in the direct vicinity that dropped off.
