Steam coils need to be divided into two general categories: Steam distributing coils and standard steam coils.

Steam distributing coils are also referred to as “non-freeze” steam (a misnomer!), tube-within-a-tube, and IDT (inner distributing tube). Steam distributing coils do not have any return bends. Where the return bends would normally be located you will find a stub end of the tube. It might be crimped, capped, or sealed in another way. When you look at a steam distributing coil that has supply and return connections on the same side, you will only see one header and the supply connection will be directly above the return connection (if the header is copper or steel).

Standard steam coils might also be termed “u-bend” steam coils. For the most part they look like a hot water coil in that they have two headers, one for the steam supply and one for the condensate return. Frequently the connection on the supply header will be halfway up the header whereas on a hot water coil the supply will usually be at the bottom of the header. The condensate connection must be at the very bottom of the return header in order to not trap steam inside the header. Assuming that the supply and condensate connection s are both on the same side, the end of the coil opposite the headers will have return bends just like a water coil.

For commercial applications, the most commonly used tube material is copper, and there are a variety of tube wall thickness options to handle different applications. We recommend a minimum tube wall of .025” copper for good coil longevity. Aluminum is the most commonly used material for the fins on a coil, because of good heat transfer characteristics and low cost. There are many different fin designs that will either enhance heat transfer or reduce air pressure drop, depending on the requirement. Coil frames (or casings, flanges, whatever you might call them) are normally galvanized.. Coil connections are typically copper, steel, or brass.

Keep in mind that although there are a huge variety of material options available for coil designs, unless there is a design reason to specify something special, most coils will be purchased based on the cost alone, so using the “standard” coil material is generally the approach to take.