Emerson Fluid Chiller Guía para resolver problemas descargar pdf (Pagina 48)

Regulators

Emerson Climate Technologies

Application Tips

• In systems that use a Venturi type distributor, the

bypass gas should be fed into the system between

the outlet of the expansion valve and the inlet to the

distributor. For pressure drop distributors that use an

orice, the inlet must be between the orice and the

inlet to the distributor.

• The hot gas bypass line should be insulated to mini-

mize system heat loss.

• In systems with sequential compressor unloading, the

valve should be set to start opening at two to three

pounds below the last stage of unloading, because

compressor unloading is considerably more efcient

and should be used before resorting to bypassing.

• For oil return considerations, the bypass line must

feed in ahead of the evaporator when the evaporator

is installed below the compressor.

• The hot gas bypass valve should be installed as close

as practical to the condensing unit, to reduce con-

densing ahead of it.

• In systems that operate on a pump down cycle, there

must be a solenoid valve or some other means of

shutoff in the bypass line.

Adjusting the Set Point

The suction pressure at which the valve opens is

selectable by increasing or decreasing the load on the

spring by turning an adjusting screw. To set it, the evap-

orator must be cooled down by shutting off the fans,

blocking off the airow, or some other means, until the

suction pressure drops to at least ve pounds below the

desired set point. Then, by allowing the pressure to be

raised by the bypass gas, the spring load can be varied

until the valve closes at precisely the desired set point.

The pressure is set to maintain an evaporator tem-

perature just above that at which frost forms.

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Emerson Fluid Chiller Guía para resolver problemas Pagina 48