How to Calculate fan coil unit's capacity

Fan Coil Unit is one of the most widely used air conditioning equipment, used for cooling and heating residential, office, commercial, hospitals, hotels, etc. (ceiling-mounted, roof-mounted, floor-mounted and duct-mounted) depending on the location and use.

Before choosing a Fan Coil Unit, it is necessary to consider the type and arrangement of the coils, whether the Fan Coil Unit is 2-pipe or 4-pipe, the dimensions of the fan coil and the location where it will be installed, but most important thing is to determine the capacity of the fan coil by calculating the heating and cooling load for each room in the desired premises.

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Accurate fan coil unit capacity calculation

To accurately calculate the capacity of the fan coil unit, the cooling load of the space to be cooled must first be determined, which is usually done by the facilities' engineering consultants. You can contact the air conditioning experts at the Heating Equipment Specialist Group during office hours to estimate the cooling load of your space and receive advice.

The ventilation capacity of the fan coil unit is calculated using the following formula, based on the cooling load of the building:

Q = m.C.ΔT

where Q is the cooling load of the building in Btu/min, m is the airflow of the fan coil in cubic feet per minute (cfm), cp is the specific heat of the air at constant pressure (which is a number equivalent to btu/lb. ᵒF is 0.24), ΔT is the temperature difference between the inlet and outlet air of the fan coil in degrees Fahrenheit.

To calculate the airflow in cfm, the specific heat of the air must be multiplied by the density of the air (equivalent to 0.075 lb/ft3), the product of which is btu/ft3. ᵒF becomes 0.018. Therefore, the above formula can be simplified as follows:

Formula for calculating fan coil capacity

For example, if the cooling load of a space is calculated as 6000 Btu/hr, using the above formula, we will have:

The formula for optimal calculation of the capacity of the fan coil 2

Therefore, in this space, a fan coil with a capacity of 300 cfm will be a suitable choice.

Accurate calculation of the capacity of the fan coil unit

To calculate the exact capacity of the fan coil, first of all, to estimate the cooling load of the desired space, we divide its surface (m2) by a constant number between 25 and 30. The warmer the climatic conditions of the region, the closer the denominator will be to 25; also, the cooler the weather, the closer the denominator will be to 30.

For example, let us consider a space of 70 metres. The cooling load in this environment will be equivalent to 2.3 tonnes of cooling or 8088 W or 27600 BTU/hr. In this case, the capacity of the fan coil unit is obtained by dividing it by the number 27, as follows:

Accurate calculation of the capacity of the fan coil unit

Therefore, it can be roughly said that the cfm 1000 fan coil is the right choice for a 70-meter space; To make it easier to calculate the capacity of the fan coil according to the size, the following table has been prepared:

Fan Coil Unit Capacity(CFM)	Maximum used infrastructure
200 CFM	Till 12 m2
CFM 300	Till 20 m2
400 CFM	Till 28 m2
600 CFM	Till 40 m2
800 CFM	Till 56 m2
1000 CFM	Till 70 m2
1200 CFM	Till 80 m2

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Final Speech

This article has attempted to calculate the capacity of the fan coil unit. We hope that the material presented in this article was useful and practical for you.

You can see and compare different types of fan coil units of different brands and power levels, and find updated prices on DamaTajhiz HVAC Group's website (the first and most reliable group in building equipment and all air conditioners sector since 2013 with 3 valid business permits).

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