Specifications

ManualsBrandsCarrier ManualsHeat Pump50DD028

null span, turn null adjusting screw (Fig. 41) clockwise to

decrease span and counterclockwise to increase span. All

switches leave factory with null span set at maximum po-

sition. The smaller the null span, the closer the pressure will

be maintained to desired set point.

DIFFERENTIAL PRESSURE SWITCH SET POINT AND

NULL SPAN (VAV Units Only When Equipped with Modu-

lating Power Exhaust Option) — See Fig. 36. The set point

range for this switch is −0.5 in. wg to 10.5 in. wg. Factory

setting is 10.1 in. wg. To adjust set point, turn set point ad-

justing screw (See Fig. 41) clockwise to decrease set point

and counterclockwise to increase set point. This switch also

has an adjustable null span. The null span is the pressure

change that can be made without contacts opening or clos-

ing. It is adjustable from 0.06 in. wg to 0.14 in. wg when set

point is at minimum position (−0.5 in wg) and 0.07 in. wg

to 0.14 in. wg when set point is at maximum position

(10.5 in. wg). To adjust null span, turn null adjusting screw

(Fig. 41) clockwise to decrease span and counterclockwise

to increase span. All switches leave factory with null span

set at maximum position. The smaller the null span, the closer

the pressure will be maintained to desired set point.

REFRIGERANT CHARGE — All units are shipped with a

complete operating charge of R-22. See unit nameplate and

Tables 1A and 1B for amount of charge. When charging re-

frigerant system, refer to Carrier Standard Service Tech-

niques, Refrigerants. When adding a complete charge, evacuate

system using standard evacuating procedures and weigh in

the speciﬁed amount of charge. All units have charging charts

for each refrigerant circuit. See Fig. 42-47.

Fig. 39 — Auxiliary Switch Stroke Adjustment

Fig. 40 — Auxiliary Switch Adjustment

NULL DECREASE

SET POINT

DECREASE

PLANE

SET

POINT

INDICATOR

SET

POINT

ADJUSTMENT

NULL

ADJUSTMENT

COM

N.C.

N.O.

CAPACITOR

Fig. 41 — Differential Pressure Switch for Inlet Guide

Vane and Static Pressure Control Option and

Modulating Power Exhaust Option