Mitsubishi 20-MYA Specifications download pdf (Page 9)

1. Model Selection (With actual examples)

First step, to select the approximate model:

Based on the cooling load and the cooling capacity listed in the capacity table, select the applicable model.

Notes:

*1. The correct WB is required since it has a serious effect on the capacity.

*2. The cooling capacity decreases as the outdoor temperature increases. Therefore, the estimated highest

temperature during an air conditioning time frame is the “designed outdoor temperature”. However, it is

recommended that the abnormal outdoor temperature which may occur once or twice a year be excluded from

the calculation to avoid selection of an excessively large capacity model.

*3. The wind pressure loss of an air duct should be calculated correctly. If a value having an excessive allowance is

used, an excessively large model will be selected. Moreover, an excessively high air flow will be induced during

actual operation causing the generation of high operating sounds and carry-over of condensed water.

(Step-1) Confirmation of operation range

Confirm that the conditions given above for the model to be selected are within the operation

range listed on Page 18.

(Step-2) Calculation of actual air flow, external static pressure, and fan motor input

Based on the designed air flow and external static pressure, obtain the actual air flow and fan motor

power from the fan performance table for the model input selected. For an explanation of how to

use the fan performance table, see the following examples.

Example: PRHG-10, 50Hz

Example 1. (To operate with values near to the designed air flow and external static pressure.)

Condition : Designed air flow 100CMM

Designed external static pressure 60Pa

Calculation : The designed point is A. Therefore, duct

resistance line passing A is dotted line.

Therefore, actual point is B for

fan speed 1088rpm.

(Select a pulley near A point to fan speed.)

Actual air flow = 110CMM

Second step, to select the model:

To select the model, the following conditions must be known:

(1) Total cooling load or sensible cooling load

(2) Indoor conditioned temperature (WB*1, DB)

(3) Designed outdoor temperature (DB)*2

(4) Designed air flow

(5) Designed external static pressure (= Wind pressure loss of air duct)*3

internal static pressure

Air flow

1500

90 95 100 105

1670

(CMM)

(L/S)

1.5kw

2.2kw

900

1000

1100

1200

1300

1400

100

200

300

400

500

Total static pressure (Pa)

Fan speed

<rpm>

1500

110 115

1830

120

2000

600

700

800

1600

1700

SELECTION PROCEDURE

60Pa

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Mitsubishi 20-MYA Specifications Page 9

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