Emerson Fluid Chiller Anleitung zur Fehlerbehebung PDF herunterladen (Seite 47)

Regulators

Emerson Climate Technologies

Thermal Valves for Liquid Injection

When hot gas is bypassed directly into the suction

line, it is necessary to make some provision for desuper-

heating the gas returning to the compressor. Without a

small Thermal valve to lower suction gas temperature to

tolerable limits, compressor damage may occur. Stan-

dard Thermal Valves cannot be adjusted for control over

20°F superheat and, therefore, are not recommended.

Liquid Injection Thermal Valves with special adjustment

ranges are used to conform to compressor manufacturer

temperature recommendations.

To simplify selection, Emerson has developed Liquid

Injection Thermal Valves with four basic adjustment

ranges. These are designated as models A, B, C and D.

The adjustable superheat range chart (page 11) shows

the proper power assembly charge symbol sufx for a

given saturated suction temperature and a given super-

heated suction gas temperature entering the compres-

sor.

Nearly all Thermal valves for liquid injection may be

internally equalized. However, if pressure drop occurs

at the valve outlet due to a distributor, spray nozzle or

other restrictive device, externally equalized valves may

be needed.

Model LER and LIR valves are furnished with a 1/4”

SAE male are external equalizer as standard. Other

models must include the code letter “E” to specify the

1/4” SAE male are external equalizer connection.

Example: LCLE and LJLE.

Application and Installation

Liquid injected into a gas to be desuperheated should

be injected in a way which provides a homogeneous

mixing of the liquid and superheated gas. Desuperheat-

ing hot gas bypass in the suction line may be accom-

plished in several ways.

The preferred method is to bullhead the hot gas and

liquid injection in a tee to permit good mixing before it

enters the suction line. A good mix with the suction gas

may be gained by injecting the liquid/hot gas mixture

into the suction line at a 45° angle against the ow of

suction gas to the compressor. See gure 6.

For suction lines 7/8” OD and smaller, the bypass

mixture may be introduced into a tee rather than an

angle connection. For lines larger than 2-5/8” OD, intro-

duce the desuperheated bypass mixture into a 90° ell

inserted against the ow of suction gas to the compres-

sor.

Arranging a bypass directly into a suction accumula-

tor is often a convenient way to get proper desuperheat-

ing of suction gas.

Introducing the hot gas and liquid into the suction line

with separate connections is not recommended.

NOTE: Excessive suction gas superheat can cause

serious damage to the compressor. As a safety precau-

tion, the bypass line solenoid valve should be wired in

series with a discharge line thermostat.

Special Applications

On systems where evaporator pressure regulators

are used, better control can be reached by installing

the bypass regulator equalizer line on the downstream

(outlet) side of the EPR so it responds to compressor

suction pressure, not evaporator pressure. This results

in nearly constant evaporator load balance. See gure 8.

Figure 8

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