Booster Coil FAQ’s


What is a Booster Coil?

Also known as Hot Water Duct Coils, the most common definition of a booster coil is any water coil with dimensions that fall somewhere between 6” x 6” – 30” x 60”.  Additionally, booster coils are only (1) or (2) rows.

Where Are They Found

Simply put, you’ll find them in just about every type of installation possible.

How Are They Built

One important factor to remember is that the coil is never the exact size of the ductwork. The coil is always larger than the duct to accommodate the correct air velocity, so the ductwork must be transitioned to the coil. A standard 1” casing is built on all (4) sides of the coil to allow the ductwork to transition to the coil flanges. For example, if you have a 12” x 24” fin dimension coil, the overall size of the coil, including the casing, is 14” x 26”.

Another common term that you might hear is “slip & drive”, which means there is no casing around the coil. There are only metal covers and end-plates to hold everything together. Slip & drive allows for the coil to be inserted into the ductwork with no transition or flange required.


Most booster coils are not headered coils. Typically, only (1), (2), or (3) tubes need to be fed, depending on the required GPM. Most other coils are fully headered due to a larger number of tubes that need to be fed.


You can select any number of fins per inch. Keep in mind – and this is true of all coils – that the more fins per inch you select, the more compact your fin area becomes. More compact means that the fins start to act as a filter, and are considerably harder to clean.

Tubes (Copper)

Whether you require 5/8” or ½” tubes, Capital Coil is your booster coil solution. 5/8” & ½” tubes are virtually interchangeable in booster coils, so you can easily substitute one for the other with no loss in performance.

CCA Booster Coil Availability

Capital Coil & Air can ship up to (10) booster coils within 3-5 business days! For quantities of up to (50) booster coils, CCA can ship in as little as 10 business days! You are essentially getting an expedited quick-ship for no additional charge. All of CCA’s coils, including boosters, are AHRI Certified, and we build them quicker than our competition.

Most coil manufacturers “cringe” when you send over a booster coil schedule. Based on our time and experience in the industry, we can tell you that most manufacturers do not want to spend the time engineering the job, and they certainly do not want booster coils tying up their production lines. Conversely, Capital Coil & Air wants the chance to earn all of your booster coil business! Send us your booster coil schedules, and you’ll receive same-day pricing and ultra-quick shipments.

We welcome the opportunity to do business with your company!


Stock Hot Water Booster Coils

Commercial Booster Coil Basics

Stock Hot Water Coils – Quick Buyers Guide