Carrier 37HS specifications 0.97+ 0.16 = 1.13 in. wg

Models: 37HS

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0.97+ 0.16 = 1.13 in. wg.

Fig. 22 Ð Air Series of Units of the Same Size and Capacity

FLEX DUCT IN AIR SERIES Ð Flexible duct is often used in air series to connect Moduline units. In calculating pres- sure requirements for units in air series, use the following guidelines:

1.For close-coupled units (either continuous diffuser or units in adjoining ceiling modules) where the ¯exible duct used is 6 to 8 in. in length, add 0.1 in. wg to unit requirement for minimum static pressure at control unit (Table 10).

For example, consider three 37HS2 units in air series, in adjoining modules, with 200 cfm per unit (Fig. 23). The minimum static pressure for multiple units is equal to 0.75 in. wg (from Table 10). Adding 0.1 in. wg for ¯exible duct, the total pressure downstream of run-out duct equals 0.85 in. wg.

2.For units in air series with extended ¯exible duct lengths, add DP from Table 11.

For example, consider four 37HS2 units in air series, 200 cfm per unit (Fig. 24). The units are in alternate series modules; 8-in. duct; 9- x 9-in. plenum. The

minimum static pressure for multiple units is equal to 0.75 in. wg. Three lengths of ¯ex duct at 4.5 ft equal 13.5 ft. From Table 11, read with 8-in. duct diam, DP is equal to

0.16in. wg for each 10 ft. of ¯ex duct. Therefore, for

13.5ft, DP is equal to 0.16 + 0.06 in. wg. The total DP downstream of run-out duct is equal to 0.75 + 0.22 = 0.97 in. wg.

3.Flexible duct, unsupported, tends to sag; this de¯ection increases the pressure drop. Whenever possible, support

the duct with wire between connections. Sagging will in- crease the DP as much as 0.06 in. wg in a 10-ft length; therefore rigid duct is recommended for lengths greater than 5.5 ft.

4.The use of ¯exible duct in air series run-out when 90 de- gree turns are required will also add DP. Table 12 pro- vides the additional pressure drop.

For example, refer to Fig. 25. The ``straight'' line DP is equal to 0.97 in. wg. If a bend is added to the run-out, the total pressure drop becomes:

0.97+ 0.16 = 1.13 in. wg.

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Carrier 37HS specifications 0.97+ 0.16 = 1.13 in. wg