20" x 20" x 18" HVAC Plenum Box — $92.43
- Width: 20"
- Depth: 20"
- Length: 18"
- Gauge: 22 ga
- Material: Galvanized Steel
- Connections: Slip & drive
- Fabrication: Made to order in Pittsburgh, PA
- Lead time: Ships in 1 business day
- Returns: Made to order, not returnable
Custom fabricated 20" x 20" x 18" supply or return plenum box in 22-gauge galvanized steel, slip-and-drive connections. Sized to your furnace or air handler, made to order.
20" x 20" x 18" HVAC Plenum Box: sizing numbers
Worked out from this size's dimensions, so you can check it against your duct design before you order.
| Cross-section free area | 2.78 sq ft (20" x 20") |
| Internal volume | 4.2 cu ft |
| Side-wall area for take-offs | about 10.0 sq ft |
| 2-ton system (800 CFM) | 290 fpm through the plenum |
| 3-ton system (1,200 CFM) | 430 fpm through the plenum |
| 4-ton system (1,600 CFM) | 580 fpm through the plenum |
| 5-ton system (2,000 CFM) | 720 fpm through the plenum |
Airflow by velocity
| Air velocity | Cross-section (2.78 sq ft) |
|---|---|
| 600 fpm | 1,665 CFM |
| 700 fpm | 1,945 CFM |
| 900 fpm | 2,500 CFM |
| 1,200 fpm | 3,335 CFM |
Airflow is free area times air velocity. Pick the row that matches the velocity your design uses; these figures are capacity at that velocity, not a pressure-loss calculation.
Questions about this size
What size system does a 20" x 20" plenum suit?
Size it to the supply or return opening on the furnace, air handler or coil first. For airflow, at the usual 400 CFM per ton a 3-ton system (1,200 CFM) moves through this 2.78 sq ft cross-section at about 430 fpm and a 5-ton system (2,000 CFM) at about 720 fpm.
How much room is there for take-offs on a 20" x 20" x 18" plenum box?
The four side walls total about 10.0 sq ft: two 20" x 18" faces and two 20" x 18" faces. The box holds 4.2 cu ft of air.
What gauge is a 20" x 20" x 18" plenum box made in?
22-gauge galvanized steel. PMX picks the gauge from the distance around the largest opening: the 20" x 20" cross-section is 80" around, and openings that measure over 54" up to 84" around are built in 22 gauge. The configurator on this page lets you choose 26, 24, 22 or 20 gauge and re-prices it.
How much does a 20" x 20" x 18" plenum box cost?
$92.43 as configured on this page: 22-gauge galvanized steel, made to order. The price comes from the same quoting engine that prices the cart, and changing any dimension in the configurator re-prices it. The same size is $141.18 in aluminum and $189.93 in stainless steel. In galvanized steel, the 12" long version is $83.07, the 24" long version is $102.02, the 36" long version is $134.28, the 48" long version is $166.54.
Can I order a plenum box in a different size?
Yes. This page is one published size; the configurator above is loaded with these dimensions and every one of them can be changed to the size you measured, in galvanized steel, aluminum or stainless steel. Each fitting is cut and formed for the order in Pittsburgh, PA.
How fast does a 20" x 20" x 18" plenum box ship, and can it be returned?
It ships in 1 business day from our Pittsburgh, PA shop, by UPS or by LTL freight for large orders, anywhere in the continental US. Shipping is calculated at checkout from the order's weight and destination. Because it is made to the dimensions you order, it is not returnable.
About this size
This page is the 20" x 20" x 18" HVAC Plenum Box configuration of our hvac plenum box. It is cut and formed for this order — nothing here is a stock import part. The configurator above is loaded with these exact dimensions, so you can add it to the cart as-is, or change a dimension and it re-prices instantly.