Can these supply grills effectively be used as dampers??

Reply

  #1  
Old 06-20-17, 12:48 PM
R
Member
Thread Starter
Join Date: Sep 2008
Location: MA
Posts: 591
Received 0 Votes on 0 Posts
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?

Name:  register.jpg
Views: 202
Size:  27.8 KB

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?

Name:  vent hole.jpg
Views: 173
Size:  8.1 KB
Below is a picture of the vent I cut out ( all three look like this ).
 
Attached Images  

Last edited by PJmax; 06-20-17 at 01:22 PM. Reason: added pic
Sponsored Links
  #2  
Old 06-20-17, 01:20 PM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Northern NJ - USA
Posts: 59,052
Received 1,108 Votes on 1,028 Posts
An adjustable register would work fine for that application.
Very easy to adjust once the ceiling is finished too.
 
  #3  
Old 06-20-17, 02:05 PM
S
Group Moderator
Join Date: Oct 2004
Location: WI/MN
Posts: 19,573
Received 94 Votes on 83 Posts
I just use adjustable registers to balance my house between summer and winter.
 
  #4  
Old 06-20-17, 03:20 PM
R
Member
Thread Starter
Join Date: Sep 2008
Location: MA
Posts: 591
Received 0 Votes on 0 Posts
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

Name:  Untitled.jpg
Views: 126
Size:  7.4 KB
 
  #5  
Old 06-20-17, 03:39 PM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Northern NJ - USA
Posts: 59,052
Received 1,108 Votes on 1,028 Posts
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.
 
  #6  
Old 06-20-17, 03:43 PM
R
Member
Thread Starter
Join Date: Sep 2008
Location: MA
Posts: 591
Received 0 Votes on 0 Posts
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.
 
Reply
Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description:
Your question will be posted in: