sheet metal gauge?????

[dookits13]

does the gauge of the plenum or duct work make a difference in heating efficientcy??? also does the size of your plenum make a difference???? i have a 20x20 in. plenum x 24 in. high. would a bigger plenum be better ??

 

[Hogwildz]

does the gauge of the plenum or duct work make a difference in heating efficientcy??? also does the size of your plenum make a difference???? i have a 20x20 in. plenum x 24 in. high. would a bigger plenum be better ??

Not sure if we have any HVAC guys here. But I'll take a stab at it.....
The gauge of the sheetmetal won't make a difference , but the insulation wrapping or not around it will.
The plenum if installed by a knowledgeable mechanic, should be sized according to the duct & blower CFM rating I believe.
The duct itself is the biggest heat loss factor. In un conditioned space, it should be well insulated. And the joints should be tight and not leak. Thats where the most heat loss occurs, and thus less efficiency.

 

[Corie]

Sheet metal gauge hardly matters. Plenum size DOES matter.

Remember the plenum carries the full CFM of the furnace until it begins branching off. You need to have the HVAC calculations performed to be certain it's properly sized or you'll have pressure loss too high and not get enough air to the furthest ducts.

 

[begreen]

Well, gauge sort of matters a little. It determines how rigid the duct will be and burn resistant. From what I remember, in commercial work, light gauge stuff is allowed for ventilation only, not heating. Heavier gauge helps stiffness to reduce rumbling and popping on startup and when running. It's good for large plenums and long runs.