Fan-Coil Terminal vs Heat Pump

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7 comments

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    Tsai Tse Josh Lo (Edited )

    Angela,

     

    Fan coil unit is essentially a hydronic system which cools and heats air with chilled and hot water pipes. It can intake air through opening in the exterior wall (window unit), or used as part of an air-water system where tempered air is supplied by a central air handling unit, in which case air ducts are required. Air is often exhausted through the bathroom vent, or through windows.

     

    Heat pump cools and heats air with the compressive refrigerant cycle. In cooling mode, it withdraws heat from indoor air, and deposits it to the outdoor air (called air-to-air heat pump). In heating mode, the cycle is reversed with a switch of a button. Like fan coil unit, heat pump can be a window unit or part of an air-water system in which the heat pump deposits/withdraws heat to/from a water loop (called water loop heat pump).

     

    Josh

  • Avatar
    Tsai Tse Josh Lo

    Adelina,

    When heat pump is a package window unit, it has a fan built in the unit to circulate the air around the evaporator/condenser. Note that drainage is also provided inside to get rid of condensed water.

    When heat pump is part of an air-water system, it is often placed under window. Central AHU supplies tempered air (at the right humidity) to the heat pump, and the heat pump in turn heat/cool the air as required.

    Best,

    Josh

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    Adelina Koleva

    Hi Josh,

    Thanks for your answer, it's very helpful.

    Follow up question, how does a heat pump system work in terms of air distribution - does the unit itself have a fan? Or is it usually combined with another system in larger buildings?

    Thanks very much,

    Adelina

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    Adelina Koleva

    Cool - that's very clear. Thanks again Josh!

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    Samuel Stropes

    I had the same question and this is what my mechanical engineer had to say:


    "Sorry for the late response. I had to ask because I get these confused as well. They do the same thing basically, they both can heat and cool spaces.

    The fan coil has a cooling coil and a heating coil (see that on the PDF if has chilled water and hot water going to it). It switches off which coil to use when heating or cooling is needed.

    The heat pump contains a compressor inside of it while the fan coil’s compressor is in the chiller( that’s the main difference between the two). So the heat pump only has one coil and then the compressor can cool the air instead of a chiller cooling water to flow to it. The cooling tower gives a little more cooling capacity in the summer when it is needed but the heat pump can cool with the compressor."

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    ANGELA FERRIGAN

    Great explanations. That's makes a lot of sense. Now I have a follow up question. If we wanted to choose a cooling and heating system that would not be seen on the exterior façade we could immediately eliminate the fan coil and the heat pump, right?

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    Tsai Tse Josh Lo (Edited )

    Central AHU gives you minimal impact on the exterior façade because intake and exhaust are localized. However, cooling tower at roof top is required. Boiler and chiller are usually in the basement.

    Split system, VRV are also discrete, but only enough capacity for small building and recirculate room air, not great for air quality.

    Both fan coil and heat pump can be used as terminal unit in concert with the central AHU (ie. no opening in the exterior wall). This is called air-water system. AHU pumps fresh, filtered and humidified/dehumidified air into these units, and they in turn further heat or cool the air to the comfortable temperature before supplying it to the room.

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