18x20 / 144,000 BTUs / 100 PSI For use in your hot air furnace plenum.***Not recommended for air compressors*** Information about our heat exchangersThis heat exchanger is ideal for a 18"x 21" plenum or larger.The outlets come out on the 18" side (shown as the vertical side in the picture above)The fin area is 18"x 20"GPM 15 CFM 1756 Outside Dimensions 18”(width)x23.5”(Length from Manifold to Base)x3.5”(Thickness) There is a 1" frame on the end opposite the outlets that covers the copper elbows. This makes the area inside of your plenum 1" longer.All exchangers are 3 1/2" thick.Aluminum fins are installed at 12 fines per inch.All exchangers are triple pass design.Tubing is 1/4" copper.All our exchangers include the flat front face mounting for easier installation and increased plenum strength. Our exchangers have 1" copper outlets and can be installed with either sweat fittings or push fit type fittings like sharkbite's.Exchangers from us come with a lifetime warranty, including shipping. Exchangers will work with chilled water also.We stock many sizes, always order the largest size that will fit into your plenum.Installation brackets, sold separately, for installing water to air heat exchangers inside of furnace plenums. This easy to install kit takes all of the work out of installing a coil. Great for the do it yourselfer or the seasoned installerThis kit will work with most coils being sold on other sites that are 3.5" wide. Check before you buy, but that will cov