What is this thing in the return plenum box?

What’s wrong, missing, not working?

I have never seen this in SSM On.
I think you are missing the return to some area not served on that direct return plenum.
Purhaps an office or addition added.:smiley:

Not enough info:D:D:D:D:D:D:D:D

Charley, I don’t want YOU spilling the beans!!!

OK, Hint…

Supply air pressure 97 pa. (97 pascal = 0.389 419 186 31 inch of water [4 °C])
Turn off 2nd floor thermostat and pressure goes to 179 pa.
179 pascal = 0.718 618 910 81 inch of water [4 °C]

75pa = .3" wg ; residential system design duct pressure (static).

Sounds like there is a zoned forced air supply system…which is quite a rare bird in residences.

What are you showing in the first picture other than a couple of
plenum/duct takeoffs? Still not a great picture in the second photo…I’m thinking a duct damper control arm…but in the return?

Pretty common here in residences over 35K

Do you mean 35,000 ft2 or 3,500ft2?

I can see it being used in cooling climes…need to get that cooling upstairs. Predominantly heating climate here- 95%+. I used to see it in larger 1950-1960’s homes and in the odd other one…but we haven’t had much cooling in houses here until the last 5-10 years…HP/AC units being seen more and more.

Hows the filter?

House is 2,563 sf.

Had zoned HVAC in a 3 story townhouse last week.
Cat 4 with 3 thermostats.
Had a damper controlled vent to the garage to boot.

Was it listed as a fire-damper?

I find thermostatically controlled dampers in homes of all shapes and sizes. The dampers, however, usually include control boxes and balancers :stuck_out_tongue:



I had this on the forum last week asking about it if it was OK in the heating section.


[quote=“Brian_A.MacNeish, post:7, topic:59042”]

Do you mean 35,000 ft2 or 3,500ft2?


3500Sq Ft My Bad was in a hurry

Jeff & Bob, you both posted pics of the missing parts…


I don’t recall that, but the duct to the garage would require a listed smoke-and-fire damper in my jurisdiction.

Honestly never heard that before ,so where would I find this?


Are you asking about the equipment, or are you asking about the code reference?


In Canada, no forced air registers (return or supply) from central system to a residential garage. Forced air ducting going to other rooms, can go through the garage if it is at least 26 gauge (I believe) provided that it is sealed at the joints and well supported.

They don’t want smoke, CO or other vapours re-circulated through the central system.