Emerson Fluid Chiller Instrukcja Naprawy Pobierz pdf (Strona 44)

Regulators

Emerson Climate Technologies

NOTE: Should the outdoor temperature fall below de-

sign conditions, more refrigerant will be required.

The total above is the total charge needed for satis-

factory system performance during the lowest expected

ambient air temperature conditions. During summer

operation the receiver must be sized to safely hold the

total system charge. Good refrigeration practice states

that the total system charge should not exceed 80% of

the receiver capacity.

CAUTION:

1. The HP control should not be used on a system

which does not have a liquid receiver or on one with

a receiver which is too small. If the receiver does not

have adequate storage space, the refrigerant will

back up in the condenser to produce excessively high

discharge pressures during high ambient air tempera-

tures, with could cause system damage or personal

injury.

2. The HP control should be used only on systems

which employ a Thermostatic Expansion Valve.

Installation of HP HeadMaster Series

Head pressure control systems are used on refrig-

eration systems that are temperature operated. The

compressor is started by a thermostat or the system

operates on a pump down cycle, where the thermostat

controls the liquid line solenoid valve and the compres-

sor starts on a rise in suction pressure with a low pres-

sure switch.

On systems that are pressure operated, migration of

the refrigerant to the cold condenser on the “off” cycle

should be prevented. If the system does not oper-

ate on a pump down cycle, migration can take place

through some compressors, from the suction line to the

condenser. Crankcase heaters will prevent liquid from

condensing in the crankcase, but will not stop migration

to the cold condenser. If the system is properly charged,

the lled condenser will permit the excess to remain in

the receiver and low side.

Under some conditions where the receiver is located

in a warm ambient, a check valve in the liquid drain line

between the HeadMaster control and the receiver may

be required to prevent the liquid receiver pressure from

equalizing to that of the condenser during the “off” cycle.

This enables the system to start on a pressure switch.

Some systems may require a time delay on the low

pressure switch. Condenser fans should not be cycled

when using the HeadMaster control. The sudden chang-

es in high side pressure caused by fan cycling will result

in erratic Thermostatic Expansion Valve performance,

and shortened head pressure control life. To prevent this

from happening, make sure fan controls are set to oper-

ate at pressures above the HP valve setting.

HP Series Capacity & Selection

The nominal HP control capacity in tons for various

refrigerants is shown in Table 1 for R134a, R22 and

R404A/R507A. The nominal capacity is based on 100°F

liquid, 40°F evaporator and the pressure drop shown.

To get capacities in tons at other liquid and evaporator

conditions, multiply the nominal capacity at the desired

pressure drop by the correction factor given in the

catalog for the liquid temperature and evaporator

temperature.

Pressure Drop – PSI

Valve Refrigerant 1 2 3 4 5

HP-5 2.0 2.9 3.6 4.1 4.6

HP-8 R-134a 5.5 7.8 9.6 11.0 12.4

HP-14 14.0 19.8 24.2 28.3 31.7

HP-5 2.2 3.2 3.9 4.5 5.0

HP-8 R-22 6.0 8.5 10.5 12.0 13.5

HP-14 14.7 20.8 25.6 29.7 33.8

HP-5 1.5 2.1 2.6 3.0 3.3

HP-8 3.9 5.5 6.7 7.8 8.7

HP-14 10.1 14.3 17.6 20.5 23.0

Based on 100°F liquid and 40°F evaporator

Table 1 – Nominal Capacity (tons)

R-404A

R-507A

NOTE: Not recommended for systems utilizing patented sub-

cooling coils in conjunction with low head pressure systems or

on sytems where the condensate line bypassses the receiver

in order to maintain subcooling effect in the liquid line.

NOTE: Do not select a valve for a capacity rating ex-

ceeding 5 psi pressure drop from Port C to Port B or for

a system with more than 20 psi pressure drop across

the condenser.

During normal ambient conditions, the available liquid

subcooling in the condenser will be adequate to cover

the pressure drop through the HeadMaster control.

If a valve is selected for a given ow rate, the result-

ing pressure drop must not cause the liquid pressure to

drop below saturation and produce ash gas. If enough

sub-cooling is not available to cover this pressure drop,

it is suggested that more than one valve be installed in

parallel to lower the pressure drop to tolerable limits.

Do not parallel valves of different capacities. Liquid

drain lines from the condenser to receiver are sized for a

velocity of 150 ft./min. or less.

1 2 ... 39 40 41 42 43 44 45 46 47 48 49 ... 71 72

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