Why Use Insulated Chilled Water Coil Cabinets in Duct Systems?

by Dan Jacobs, March 26, 2019

Coil cabinets are one of the HVAC world’s best kept secrets. Almost any facility has hot water duct reheat coils in their buildings. They are small (1) or (2) row coils that are approximately the size of the ductwork, and are meant to reheat the air to anInsulated Coil Cabinets acceptable temperature. Although in many cases, these coils cannot be built exactly to the duct size, they are still pretty close because the coil face velocities are usually close to the air duct velocities. Coil velocities are usually in the 600 Ft/min – 1,000 Ft/min range.

So what does any of this mean? This means that if you have 2,000 CFM, a coil is required to be 12” x 24” (2 Sq. Ft – 1,000 Ft/min), or 12” x 30” (2.5 Sq. Ft – 800 Ft/min). The idea is to build the coil as closely to the duct size as possible, while keeping the velocity between 600 Ft/min – 1,000 Ft/min.

What is less well known is that you can also design the same kind of duct coil for chilled water coils. The MAJOR DIFFERENCE is that the face velocity across the coil cannot exceed 550 Ft/min! Face velocities larger than 550 Ft/min will cause water carryover off of a wet coil, and the water is then carried down the ductwork and past any drain pans. This means that the height and length of the coil need to be substantially larger than the size of the ductwork. While this may seem annoying and/or difficult, there really is an easy solution to this kind of installation. Capital Coil builds chilled water cooling sections as cabinets that include the Chilled Water or DX Coil. Capital Coil’s cabinets are fully insulated, and the coil is placed within the cabinet to allow the air to use the coil’s entire face area. The coil is sealed within the cabinet, and there is a stainless steel drain pan that extends to the leaving air side of the coil. Basically, you are only required to hook up the ductwork on the entering and leaving side of the coil section, as well as hook up the piping to the drain connection on the drain pan. This is easily the fastest and most economical method to install any cooling coil system in ductwork.

CCA’s coil sections can be built from 12” x 12” (500 CFM) to 54” x 90” (18,000 CFM). Capital Coil can build the coils in either 5/8” O.D. tubes, ½” O.D. tubes, or 3/8” O.D. tubes. The sizes are custom to match the size of your ductwork, or your CFM. An important point to remember is that allowable duct velocities are much higher than allowable coil velocities, so a transition will be required.

Capital Coil & Air realizes that our customers are looking to upgrade their equipment solutions whenever possible, and if those solutions involve easy installation, then so much the better. Here are some of the main features of Capital Coil’s coil cooling section:

  • 1 ½” flanged connection on the entering and leaving air sides of the coil housing for easy duct connections.
  • 16 Ga. or 18 Ga. galvanized sheet metal housing.
  • 1” insulation with 4.2 R value.
  • 18 Ga. stainless steel drainpan with 1” stainless steel MPT drain connection. The draIN pan is double-pitched.
  • 5” connection sub-outs on all coilS.
  • Chilled Water or DX (Evaporator) Coil custom designed for your application.

All insulated cabinets are available in 3 – 4 weeks, as well as both (5) & (10) day quick-ships. Capital Coil can build double wall insulated or stainless housings if needed. Our sole purpose is to make your job as quick and easy as possible, and there is nothing faster or easier than cabinet cooling coils by Capital Coil & Air. We look forward to working with you on future projects!

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