With all types and sizes available, replacing an HVAC coil can be intimidating. Keep in mind that 95% of the total cost of an HVAC coil is the area of the ribbed surface, the number of rows and fins per inch. The dimensions of the body, the depth of the coil, the size of the connections and the size of the headers make up only 5% of the total cost.
10 Simple HVAC Coil Information:
- If you eliminated the fins and used only tubes, you would get only about 30% of the performance compared to the same finned HVAC coils. The heat transfer of the fins is much larger than the pipes.
- Because steam is erosive, steam coils are often built differently than hot water coils. Water and steam coils may not always be used interchangeably. Some air reels can be used with hot water or steam. Keep in mind that steam should not be modulated through this type of coil if it is to be exposed below freezing temperature. As the valve modulates down, there is not enough pressure to force condensate through this type of coil. If you use steam in hot water rolls, you must select 2 position controls (on / off). Modular-type steam coils, so-called “non-freezing” steam coils, should not be used with hot water.
- The industry arbitrarily called 1 and 2 row coils "hot water HVAC coils" and 3-10 row coils "cooled water HVAC coils". Hot water coils and chilled water coils are constructed in the same way. The temperature of the hot water is much higher than the temperature of the air, which leads to a winding with fewer rows. The temperature of the chilled water is very close to the air temperature, which leads to a much deeper winding.
- Chilled water and DX (direct expansion). HVAC coils are identical except for the feed and return circuit. You cannot supply refrigerant through the MPT connection (external thread) and the connection to the damper. You must replace the standard coolant supply. A “spaghetti tube” connected to a distributor feeds as many tubes as you want it to feed. In addition, the chilled water and HVAC DX coils are identical.
- The Finns have corrugations that control the entire height and depth of each fin. Chips are not flat. Shirring promotes turbulence, increases surface area and coil efficiency. Shirring also helps prevent moisture transfer, which is very common with chilled water windings running at boundary speeds above 550 FPM.
- When you look at the HVAC coils, you can see that the fins alternate. This is another way to mix air, causing more turbulence, which creates more heat transfer, increasing the efficiency of the coil.
- Most HVAC coils last 15–20 years. HVAC coils can last up to 30 years if they are properly supported. Proper maintenance includes regular air cushion cleaning and proper treatment of fluid passing through the tubes.
- 5/8 "tubular windings with chilled water use more tubes per row than" tubular cooled water coils. "Tubular coils have a more ribbed surface area, but thicker 5/8" pipes take up more surface area. The performance of two different HVAC coils are similar. water pressure drop and thicker tube wall thickness.
- Since you pay for copper by the pound, you will pay more for a 5/8 "tubular coil than a 1/2" tubular coil. This is due to the fact that the wall thickness of the 5/8 "tubular coil is 10 - 15% larger than the same 1/2" tubular coil. Although the performance is the same, you will pay more for a 5/8 "tubular coil. One could argue that a 5/8" tubular coil would withstand a 1/2 "tubular coil.
- 95% of the total cost of HVAC coils is ribbed surface area, number of rows and fins per inch. The dimensions of the body, the depth of the coil, the size of the connections and the size of the headers make up only 5% of the total cost. Changing materials can have a huge impact on the total cost. Stainless steel cases and copper ribs are very common in aggressive environments. Material costs are higher, and the heat transfer properties of different materials will affect the size of the coil. If you change the fins to copper, you will lose about 15% of the capacity, which means that you will need a large coil.
