While there are many different types of heating and cooling coils all HVAC coils typically fall into one of the four general categories outlined below.
Standard Steam Coil
A standard steam coil can be identified by having the supply and return headers on opposite sides. Used for heating, a steam coil features a “straight through” steam path, where steam enters on one side of the coil, travels through a single row of tubes (sometimes two rows) to the opposite side, where it leaves as condensate (water). These coils will usually be pitched toward the return side. These coils are typically used in applications above 40°F.
Distributing Steam Coil
Unlike standard steam coils, distributing steam coils have the supply and return headers on the same side. The steam enters on one side, is distributed across the coil through small-diameter inner tubes. The steam is “sprayed” against the inside of the outer tube (which is connected to the fins) and then leaves as condensate (water) on the same side of the coil. These coils are typically pitched toward the supply/return side to allow drainage. Distributing steam coils are sometimes referred to as “freeze proof” coils and are used in applications where the temperatures can be below 40°F.
Fluid Coils
Most fluid coils either use chilled water for cooling or hot water for heating, although glycol and other special fluids can also be used in certain applications. In most cases, fluid coils have multiple rows of tubes and have both the supply and return headers located on the same side. Connections are typically Male Pipe Thread (MPT), but can be flanged, Female Pipe Thread (FPT), or plain end to accommodate a wide variety of installation requirements.
Direct Expansion (DX) Coils
Also referred to as evaporator coils, direct expansion coils are typically used for cooling (but can sometimes be used for heating in hot gas bypass applications). DX coils utilize refrigerant, which flows through multiple rows of tubes. As the refrigerant passes through either a Thermal Expansion Valve (TXV) or distributor, it expands and changes from a liquid to a vapor, which cools the refrigerant and absorbs heat from the air moving through the coil. In a hot gas bypass application, the heated refrigerant vapor coming off the compressor is recirculated through the tubes to heat the air moving through the coil.
Within these four general types of coils, Marlo Heat Transfer Solutions offers an almost infinite number of possible products. As a custom coil manufacturer, we can design and build your solution with your choice of tube sizes, number of fins, fin type, materials, connection type and location, and many other features.
Where to Buy
Contact your local Marlo Independent Manufacturer’s Representative to discuss your coil needs and to get a fast quote using our Marlo Metrics coil selection software.
Coil Products
All Marlo Heat Transfer Solutions’ commercial coils are engineered to meet our customer’s specific parameters. We prefer to design our equipment around your project.
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