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Unidad fancoil

¿Qué es una unidad de fan and coil (FCU)?

Una unidad de fan and coil (FCU) calienta o refrigera el aire en el interior de un ambiente. Un ventilador integrado aspira el aire en la FCU y lo guía a través del intercambiador de calor para el acondicionamiento de la temperatura. El aire sale de la FCU más frío o más caliente que antes. Las FCU cuentan por lo general con un serpentín de agua fría para la refrigeración y con un serpentín de agua caliente o un elemento eléctrico para la calefacción. En aplicaciones comerciales, el control de unidades de fan and coil varía considerablemente, desde un termostato que simplemente abre y cierra una válvula, hasta unidades controladas con DDC que varían de forma ilimitada los flujos de aire y modulan las válvulas.

Esquema

La imagen muestra el esquema de una aplicación típica en una sala con dos unidades de fan and coil, cada una de ellas con una Belimo Energy Valve™, encargadas de la gestión de la potencia térmica suministrada a la unidad fancoil. El uso de válvulas EV ofrece las siguientes ventajas:

  • Balanceo hidráulico dinámico (en cualquier condición de carga) del flujo de agua alcanzado mediante la válvula de control presión-independiente
  • Utilizando las posiciones físicas de las Energy Valves™ de un edificio, puede optimizarse la velocidad de la bomba para proporcionar solo la presión suficiente para satisfacer la unidad de indexación.
  • Transparencia total del sistema (flujo volumétrico, temperaturas, salida de frío/calor, etc.) mediante el registro de datos en la EV o, de forma opcional, en la Nube de Belimo

 

 



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Energy Valve



Problemas comunes con las unidades de fan and coil y por qué debería elegir la Belimo Energy Valve™

For optimum heat exchange and occupant comfort while remaining energy efficient, Fan Coils require good control of air volumes and water flow rates. However, manufacturers of FCUs often only publish flow requirements for maximum load conditions. What is unknown is the optimum water flow when air volumes are adjusted by the occupant or the DDC controller. Also, when using non-PI valves, differential pressure fluctuation in the hydronic system will impact the flow-rate through the fan coil and therefore the thermal energy supplied to the room.
Reciprocal influence with several consumers is eliminated due to the dynamic balancing. Dynamic balancing is carried out automatically at each operating point. Changes in differential pressure cause minimal changes in the flow rate.

Dynamic Balancing of a Fan Coil Unit


A FCU is commissioned to the following values, design water flow is set to 0.11 l/s (0.029 GPM), with 23 °C (73 °F) air entering the unit. As the system is dynamic after a short period of time, the pressure in the system increases due to changes in other locations of the hyrdonic system. In this specific FCU, the increase in pressure has caused the flow to increase which results in overflow of the FCU, consequently lowering the delta T and lowering the efficiency of heat transfer.

As a result an occupant of the space may have found the air flow bothersome and manually set the fan speed at low, as space temperatures rise the valve is commanded further open by the controller until the air is simply unable to remove any more energy from the heat exchanger. This results in the return water temperature being cooler than expected. With the water flowing too quickly for the air flow we have a classic recipe for low delta T, this is effecting not only this unit, but is reducing the capacity of the central plant, and the overflow is significant point of consumption for the pumps with our flow now at 0.14 l/s (0.037 GPM).



Fan Coil Unit at Design Operation    Fan Coil Unit with valve overflowing
We have the same FCU working as expected; design water flow is set to 0.11 l/s +/10% [0.029 GPM], with 23 °C [73 °F] air entering. Even if the pressure rises from 2 bar to 3 bar, the flow rate hardly increases. Flow rate inaccuracy is vastly improved offering some plant savings, but not as accurate as an electronic valve. User fan speed adjustments still effect the optimum heat exchange which will result in low delta T and poor off coil conditions.

Fan Coil Unit at Design Operation

There is the same FCU working as expected, design water flow is set to 0.11 l/s [0.029 GPM], with 23 °C [73 °F] air entering. Again the system delivers a pressure increase due to changes in other locations. The electronic flow sensor in the EV detects the flow increase before the room sensor can register an increase in space temperature and allows the valve to close slightly to avoid reaching the saturation zone.

If the FCU has been held on low fan speed again. As space temperatures rise the valve is commanded further open by the controller which would have resulted in the air being unable to remove any more energy from the heat exchanger. The EV‘s fixed Delta T Manager recognizes the diminishing delta T and overrides the control signal and does not allow the valve to open further, this eliminates the over flow condition.

The EV continually measures the flow and calculates if it needs to compensate or not, based on the control signal input as well on the Delta T Manager set point. The Delta T Manager has slowed the water down to ensure the heat exchange is optimal for the air volume set by the user. This saves pump energy and keeps the system permanently optimized.



Fan Coil Unit without water overflow
In the age of easily controlled EC/DC fans, variable air volume FCUs represents one of the most energy efficient methods of air conditioning a space. However, the control of fan speed vs valve position is a matter of debate.The energy valve when configured for power control provides a completely linear response, meaning fan speeds can be directly tied to the valve output, simplifying the controls process dramatically.

Fan Coil Unit with delta T-optimised valve flow

Historia de éxito: 5 estrellas a la eficiencia energética en el Hotel Marriott Al Jaddaf en Dubái

La cadena de hoteles Marriott abrió su experiencia hotelera el 15 de enero de 2014 en Dubái, Emiratos Árabes Unidos.
Con su brillante diseño y su perfecta ubicación en Al Jaddaf, este hotel de 5 estrellas tiene un gran número de comodidades y servicios bien pensados.

Algunos de ellos son habitaciones de lujo totalmente automatizadas y suites que fomentan la relajación, con ropa de cama de lujo, baños de mármol, Internet de alta velocidad y televisores de pantalla plana, que también ofrecen vistas del horizonte de Dubai. El hotel ofrece 352 habitaciones de lujo y 128 apartamentos.

Los productos Belimo pudieron implementarse de manera eficiente y permiten un sistema sostenible y libre de mantenimiento.