Carrier GTR040-420 Dokumentacja Pobierz pdf (Strona 49)

Cooling Set Point (4 to 20 mA) —

A field supplied

and generated, externally powered 4 to 20 mA signal can be

used to provide the leaving fluid temperature set point. Connect

the signal to TB6-3,5 (+,–). See Table 29 for instructions to

enable the function. Figure 26 shows how the 4 to 20 mA sig-

nal is linearly calculated on an overall 10 F to 80 F range for

fluid types (Configuration mode, sub-mode OPT1, item

FLUD) 1 or 2. The set point will be limited by the fluid

(FLUD) type. Be sure that the chilled water loop is protected at

the lowest temperature.

234

TEMPERATURE DIFFERENCE (EWT-LWT) DEGREES F

TEMPERATURE DIFFERENCE (EWT-LWT) DEGREES C

.55

1.1

1.7

2.2

2.8

3.3

3.9

4.4

5.0

5.5

DESIGN RISE

RESET

AMOUNT

RESET AMOUNT DEGREES F

RESET AMOUNT DEGREES C

5.5

5.0

4.4

3.8

3.3

2.8

2.2

1.7

1.1

.55

CHANGE IN

LWT SET

POINT

FULL COOL

RESET T

∆

NO COOL

RESET T

∆

LEGEND

Fig. 25 — Return Water Reset

EWT —

Entering Water (Fluid) Temperature

LWT —

Leaving Water (Fluid) Temperature

100

(38)

(27)

(15)

(4.4)

(-7)

(-17)

4 6.3 8.6 10.9 13.1 15.4 17.7 20

4 TO 20 mA SIGNAL TO EMM

SET POINT, F (C)

(32)

(21)

(10)

(-1)

(-12)

(FLUD = 2) MINIMUM

SET POINT 14 F (-10 C)

(FLUD = 1) MINIMUM

SET POINT 38 F (3.3 C)

MAXIMUM

SET POINT

70 F (21.1 C)

Fig. 26 — Cooling Set Point (4 to 20 mA)

EMM —

Energy Management Module

1 2 ... 44 45 46 47 48 49 50 51 52 53 54 ... 103 104

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