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Hot Water Coils

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In a central air system, heating coils are connected to air handlers as a means of providing forced-air heating. This type of setup enables the combination of heating and cooling systems for the purposes of saving space, as well as reducing energy and installation costs. A complete system includes the hot water coil, an air handler/direct expansion coil assembly, a condenser and/or furnace, and a water heater or boiler. The coil may also contain a pump to keep water circulating for space heating, leaving the pump in the water heater to be used to provide usable hot water for taps and nonheating residential devices.

Types Of Hot Water Coils

There are many variables to consider when recognizing what to replace your existing hot water coil with. Among them are:

  • Casings: Available in 16-gauge galvanized or stainless steel, aluminum or copper
  • Connections: DX, Condenser & Heat Reclaim connections are copper sweated, while DX distributor connections are either standard or hot gas. In addition, certain optional steel connections are threaded--either in MPT or FPT variety. Supply connections are set on both ends of steam distributing coils, while copper MPT connections are used for the water and steam coils.
  • Fins: Made of either 6- or 10-gauge aluminum or 6-gauge copper, and spaced using three-eighths, one -half inch or five-eighths inch OD tubing, which provide, respectively 10 to 22 fins per inch, 10 to 16 fins per inch or 4 to 16 fins per inch.

In addition, all joints are hand-brazed. Brazing is a bonding method by which a filler material or alloy is melted and distributed between parts via capillary action. Special coatings and intertwined circuitry are among other variable options, depending on the hot water coil setup.

Replacing A Hot Water Coil

Slight differences may be encountered depending on the model, but the following instructions are taken from Carrier Corp.'s instructions on replacement of their LT40 Hot Water Coil. Remove the access panel from both sides of the cabinet. Then take out the knockouts for the coil's stubouts. Remove two galvanized strips from the package, and install an angle strip with notches resting in the drain pan and the half-inch flange pointing toward the blower. Install the other angle strip at the top of the coil, with the half-inch flange resting atop the cooling coil, pointing to the rear of the unit. Place the clip as high as possible on this strip, securing it to the end plate of the cooling coil. These strips are used to prevent air from bypassing the heating coil and also serve as support. Then install the coil through the access door on the opposite side of the connections. The coil should be raised slightly in the drain pan, letting the stubouts align with the cabinet's knockout holes. The hot water coil may now be secured to the cooling coil by fastening two clips over the cooling coil and hot water coil end plates.

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