Selection Of Indoor Units - McQuay MDS030AR Applications Manual

Design & installation Guide For McQuay MDS Multi System
-54-

3.2 Selection of Indoor Units

The selection of indoor unit should be based on the several factors, including customer
s requirement, indoor air distribution, indoor decoration, etc. Ceiling concealed, ceiling
cassette, high pressure duct unit and ceiling exposed are available now.
The indoor unit should be selected to meet the actual indoor load demand. The nominal
cooling capacity should be is more than or equal to the actual indoor load demand.
As the indoor total capacity is different from the outdoor total capacity, the actual indoor
cooling capacity may be different from the nominal capacity, and it should be calculated
in accordance with the outdoor capacity table.
For ceiling concealed and duct unit, McQuay has several types such as standard unit,
auxiliary electric heater, auxiliary hot water heater, etc.
The selection is based on the following factors:
Cooling capacity/ heating capacity
Auxiliary heater capacity ( optional )
Air flow
External static pressure
Dimension
Power supply and others.
Selection step
Select the type of the indoor unit:
1. Are the units ceiling concealed, ceiling cassette, high pressure duct unit or ceiling exposed
?
2. Are the units cooling only, heat pump, auxiliary electric heater or auxiliary hot water
heater?
Calculate the cooling capacity and heating capacity
Confirm the model and the quantity
According to the cooling capacity, heating capacity, return air temp, ambient temp,
humidify and air flow, we can choose the model and confirm the quantity.
The ESP of the unit can be confirmed according to the air flow and the duct parameter.
Confirm the heating capacity. If the unit selected can meet the heating requirement,
then it is OK, but if can not, then we should select auxiliary hot water heater or
auxiliary electric heater.
For the cooling only unit, the actual total cooling capacity can be gotten through the
following formula: Actual total cooling capacity = Actual capacity x QTY
For the heating only unit, the actual total heating capacity can be gotten through the
following formula: Actual total heating capacity = Actual capacity x QTY + ( Auxiliary
heating capacity)
The best selection is that both the cooling capacity and the cooling capacity can meet
the requirement. Please note that the nominal cooling capacity and the nominal heat-
ing capacity is obtained in the standard condition. When the units run in nonstandard
condition, the actual cooling capacity and the actual heating capacity are different
from the nominal cooling capacity and the nominal heating capacity.