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Instruction, utility costs

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.
 
Sincerely,
Your Connected Sensors Team.


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Instruction

In multi-residential high-rise buildings, there are two types of HVAC systems: Water Source Heat Pumps, and Fan Coil Unit Systems. Read on to learn more about these two systems, and which option we believe is the best HVAC system for multi-residential high-rise buildings.

Water Source Heat Pumps vs. Fan Coil Unit System

 

When selecting the best HVAC system for multi-residential high-rise residential buildings, there are essentially two options for modern systems. The first option is the WSHP system and the alternative is the fan coil system. Both of these designs have benefits and challenges, but when making a decision one must consider how the decision affects all the interested parties over the life of the building, including the developer, contractors, building management, the owner, or the dwelling owner in the case of a condominium.  Ultimately, all these groups have common goals, but how they prioritize these goals may differ.  The developer is concerned with return on investment, the contractor is concerned with ease of installation and reduced call backs, the building management wants to reduce maintenance, and the owner wants a reliable and comfortable space.

Water Source Heat Pumps:

From our perspective, the choice is easy: a WSHP system meets all the stakeholders’ requirements.

How does a WSHP system work?

WSHP systems have individual packaged units that transfer heat via a single- or dual-pipe water loop. Each unit can be used in either heating or cooling mode year-round and loop temperature is maintained via a boiler/tower combination, where boilers are used for heating and towers for cooling. Each zone has complete control of its heating/cooling mode and each unit is independent from the others. This means if one unit goes down, the whole system is not affected. Controls can be as simple as one unit and one thermostat. WSHP systems are the most energy, cost, and space efficient of any system in the industry.

Why is this the best option?

From a developer standpoint the WSHP system provides a lower up-front cost than the traditional chilled water system.  For the contractor a WSHP system is less complex and easier to install.  Without the need for insulated pipes there are no worries of condensation causing leak issues and recalls. Generally, the modular design of WSHP makes it easy to service which makes the building management team happy and the added bonus for a condominium is that it can be relatively easy for each unit to be responsible for these costs. Finally, for the owner the WSHP system is efficient, reliable, quiet, and is more cost effective to operate. 

Fan Coil System:

How does a fan coil system work?

Fan coil systems are used to condition the local air to match the temperature requirements for areas as large as 150 cubic meters. As part of the fan coil system you can also find an air handling unit system (AHU) that supplies and returns fresh air around the building to all the rooms/units. In many cases, coming off the supply duct is a round duct supplying the fan coil units. The fan coil units are connected to either a heating coil, a cooling coil, or both a heating and a cooling coil. These 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. Since each room needs a certain amount of fresh air supply, the AHU which we touched upon earlier, is designed to feed fresh air into each room. This fresh air is pushed into the inlet of the fan coil unit. A fan will suck the fresh air into the fan coil unit. 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, or 2.  It will be pulled back into the fan coil unit via a grille.

Why is this not the best option?

As you can tell from the description above, the fan coil system is rather complex. These systems require complex chillers and boilers to provide a water loop in a particular temperature range. With complexity also comes additional maintenance cost. Besides, to compete with the WSHP you should stick to a two-pipe fan coils but they have a major disadvantage as control is substantially limited to whatever mode the system is currently in (i.e. cooling or heating). Alternatively, a four-pipe version requires both chilled and heated water to be available at the same time. The four-pipe systems also require twice the piping and twice the circulation equipment of a two-pipe system, which makes a four-pipe system one of the most expensive systems to install. Furthermore, with more pipes comes a greater risk of leaks which is one of the many reasons why we recommend the WHSP system.

While our preference is the WHSP systems, when it comes to residents, a four pipe fan coil system tends to provide a great deal of comfort because they can switch between heating and cooling very easily and the system responds rapidly, even for units located on the top floor but this comes with any other disadvantages as you can tell. 

In conclusion, from our perspective, a water source heat pumps (WSHP) system is the best HVAC system for multi-residential high-rise buildings that is an all-encompassing solution that is most advantageous to all parties involved. 
 
We hope that this article has helped you gain insight into the HVAC options, and which option may be best for your multi-residential high rise. 
 
Thank you,
 
The Connected Sensors Team
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