WD Catalog 2018

4-14

Chapter 4

– Air Conditioner Components

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Table of Contents

Index

The valve opens and closes depending on system need for refrigerant at

the inlet to the evaporator. Figure 4-10 shows an internally equalized

valve.

Note:

Insulating material is wrapped around the expansion

valve, and coil or bulb where it attaches to the evapo-

rator outlet. This is done to improve heat energy

conduction and prevent condensation forming on the

valve.

2. Expansion Tubes

Expansion tubes are also called fixed orifice tubes. They are used in some

systems, always in combination with an accumulator instead of a re-

ceiver-drier. The tubes have no moving parts and are not adjustable.

When used, an expansion tube is located inside the inlet tube of the

evaporator. It restricts but allows a continuous flow of refrigerant to the

evaporator coil.

An expansion tube is shown in Figure 4-11. When an expansion tube is

used in place of a valve, liquid refrigerant may pass through the evapora-

tor before it can change to a gas. The accumulator prevents liquid refriger-

ant from reaching the compressor. When an expansion tube is defective it

must be replaced using a special tool.

O-RING

EXPANSION TUBES FIT INSIDE

THE EVAPORATOR INLET FITTING

ORIFICE TUBE

INTERNALLY EQUALIZED VALVE

PRESSURE

OUTLET

PRESSURE

FROM

CAPILLARY

Figure 4-10

The internally equalized

TXV is shown. This valve is

designed with either tem-

perature sensing coils or

bulbs at the end of its capil-

lary tubes.

Figure 4-11

The expansion (fixed orifice)

tube is used in place of an

expansion valve. There are

no moving parts.