Instruction, utility costs

How Can I Reduce My Risk of a Leak With My Fan Coil System?

If you are reading this, then I suspect that you’ve been the victim of a leak or flood that was the result of a faulty Fan Coil System. Let’s take a few minutes to explain what a Fan Coil System is, why they are such a high risk in your building, and what you can do to reduce your risk and exposure.

What’s a Fan Coil Unit System?

Fan Coil Units (FCU) are used to condition the local air to match the temperature requirements for an area in all types of buildings including commercial and multi-unit residential spaces. An FCU can contain an Air Handling Unit system (AHU) that supplies and returns fresh air around the building to all the rooms/units. The FCUs are connected to either a heating coil, a cooling coil, or both a heating and a cooling coil which will condition the air. A fan within the fan coil will then push the air out into some smaller localized ducts to strategically distribute the air within the room. Fresh air from the AHU is pushed into the back side, the inlet, of the fan coil unit, and a fan will suck the fresh air into the FCU. The fan will force the air across the heating and/or cooling coils before forcing it out into the area. The air will then take one of two routes: 1. It will be sucked into the return grille and be sucked back into the AHU via the return duct 2. It will be pulled back into the fan coil unit through a grille.

To learn more about the differences between Fan Coil Units and Water Source Heat Pumps, read our article here

Why are Fan Coil Units such high risk?

The coil heat exchangers will typically utilize a hot and/or chilled water supply which is distributed from the building’s boilers and chillers. That said, electrical heaters can be used for heating purposes and some coils use a direct expansion coil fed by a refrigeration system for cooling. If your system utilizes hot and cold water supply, this is where the risk comes into place.

Summer risk: You should keep an eye out if a cooling coil is used, as it can generate a lot of condensation where the warm moist air is condensing onto the cold surface of the coil. The cooling coil will remove the moisture from the air. This condensed liquid will run off the coil and collect in the drip tray at the bottom. The problem here is that in some cases the condensation (water) finds its way out of the drip pan and causes a leak that often goes unnoticed for long periods of time. In addition, a drain line from the pan is supposed to be connected to a nearby drain in theory; however, in many cases the drain line does not lead to a safe location that prevents potential damage.

Winter risk: You must keep an eye out for pipe bursts. In older buildings, the fan coil units were placed on the exterior walls. What we often see happening when a cold front settles in is some pipes burst as a result of a frosted line, which can cause significant damages. Pipe burst usually causes one of the largest losses from a dollar amount as it relates to leaks in the built environment.  In addition, older buildings and the hot water lines coming from the boiler over time erode and we have also seen pin holes occur.

All year round risk: You should always make sure to retain a qualified and reputable water treatment company that can offer a long term program where they test, track, and produce monthly records of your water and the glycol levels within your heating and cooling system to ensure longevity and integrity of your pipes. We’ve often found builds where the glycol levels were left unattended for long periods of time, corrosion was created within the system which created major infrastructure problems that resulted in leaks of all sizes. Following these, the necessary replacement of risers becomes inevitable.

How to reduce risk:
  1. For new buildings, start by ensuring the fan coil units are closer to the center of the building than the exterior walls.

  2. Install leak sensors in the drip pan to detect accumulation of water in the drip pan before it’s too late.

  3. If you are in an older building or newer building where the fan coil units are near the exterior wall, ensure that your leak detection system can also monitor temperature and give you early warnings of frost so you can install temporary heaters or add insulation where possible.

  4. In addition to leak detection sensors in the fan coil units, we also recommend installing leak detection sensors that come with a rope around the risers of the two pipe systems to detect pinholes or pipe burst.

  5. As discussed, retain a reputable water treatment partner that will ensure the integrity of your heating and cooling system.

  6. If you want to go the extra mile consider installing powered shut off valves to compliment the leak detection so that the water can be turned off if a leak within your system is detected.


As always, please don’t hesitate to reach out if you have any further questions as it relates to fan coil unit systems and the risks that are involved with them.
Your Connected Sensors Team.