User Guide

ManualsBrandsSporlan ManualsBF/EBF/SBF SeriesBFSE-A-Z 3/8" x 1/2" SAE Thermal Expansion Valve w/ 60" Capillary (1 Ton)

ing the evaporator, which is usually termed hunting or

cycling. The amount of hunting in a system is influenced by

the design of the evaporator coil, suction line piping at the

valve’s sensing bulb location, and the variability of the heat

load on the evaporator. Hunting may cause a reduction in

total system capacity, and a noticeable variation of evapora-

tor pressure on systems having one evaporator. If hunting is

severe, occasional floodback may result.

To help reduce or eliminate valve hunting, many Sporlan

pressure limiting thermostatic charges feature the

FLOWMASTER design introduced by Sporlan in 1948.

This design incorporates a thermal ballast with the charge

to help stabilize valve control.

Originally, it was felt that a highly temperature sensitive

TEV would best be able to reduce hunting. This concept

has proved to be incorrect for the majority of air condition-

ing and heat pump applications and, in fact, it was found

to often aggravate hunting problems. A less temperature

sensitive TEV using specifically designed pressure limiting

thermostatic charges has proven to be the best solution for

these applications.

Type VGA Thermostatic Charge — The VGA charge is

a specially designed pressure limiting charge for R-22 air

conditioning and heat pump applications. The constituents

and thermal ballast used with this thermostatic charge

provide exceptional anti-hunt characteristics, which makes

it the recommended charge for the majority of these applica-

tions. Due to its design, the MOP of the VGA charge is not

as defined as the VCP100 charge, our alternate standard

thermostatic charge for R-22 air conditioning and heat

pump applications. Therefore, if a defined MOP is not

required, the VGA charge may be used in place of the

VCP100 charge.

Maximum operating pressures for standard Sporlan pres-

sure limiting charges are listed in Table 3. The factory air

test pressure represents the valve MOP determined by a

Sporlan air test fixture. The nominal system pressure is the

actual system MOP. If an application requires a pressure

limiting charge with an MOP not shown, contact Sporlan for

assistance.

Due to the design of pressure limiting charges, the valve dia-

phragm and capillary tubing must be kept at a temperature

warmer than the bulb during system operation. Otherwise,

migration of the charge away from the bulb will occur, and

cause loss of valve control.

A properly selected and applied pressure drop type dis-

tributor is effective in preventing charge migration. Figure 7

illustrates how the pressure drop across this type of distribu-

tor keeps the TEV outlet pressure and temperature higher

than the suction gas temperature.

Pressure drop at the refrigerant distributor does not affect

system capacity. The refrigerant distributor simply lowers

the pressure drop across the TEV by a small amount. If the

TEV is properly sized, it will maintain desired superheat

(and system capacity) with the remaining pressure drop

available to the valve.

When applying a TEV and distributor, the two compo-

nents perform together to provide stable system operation.

Application of these components is much more critical on

systems that operate at part-load conditions much of their

operating time, e.g., variable air volume (VAV) systems

and refrigeration systems with compressor unloading. See

Bulletin 20-10 for complete information on refrigerant

distributors.

Refrigeration Applications

Ordinary refrigeration applications may be divided into the

following three categories: commercial refrigeration, low

temperature refrigeration, and extremely low temperature

refrigeration. For each of these categories, Sporlan has

developed a Selective Charge to provide optimum valve per-

formance. These charges are described below.

Type C Charges — The charges listed under the commer-

cial refrigeration section in the Recommended Thermostatic

Charges table on Page 18 are collectively known as C

Charges. These charges are liquid-cross charges and have

an operating range from an evaporating temperature of

50°F to –10°F. Figure 6 illustrates a typical superheat

characteristic curve of the C Charge. For comparison

purposes, the superheat characteristic curve of a straight

liquid charge is also shown. The flatter curve of the C

Charge allows the valve to respond in a more stable man-

ner to changes in evaporator pressure. Depending on the

static superheat requirements, the Type C Charge has been

applied by some manufacturers to display cases operating

at both medium and low temperature.

Types Z and ZP Charges — The charges listed under

the low temperature refrigeration section are the Types Z

and ZP Charges. The Z Charges (FZ, VZ, SZ, RZ, and PZ)

are liquid-cross charges having an operating range from an

evaporating temperature of 0°F to –40°F. A typical super-

heat characteristic curve of the Z Charge is illustrated in

Figure 6. Since the curve slopes upward to the right, the

valve will control at lower superheat values as evaporator

temperature decreases, providing operational advantages for

low temperature refrigeration. This characteristic prevents

Page 8 / BULLETIN 10-9

R-22

196 psig

(100°F)

= 94 psig

(56°F)

= 69 psig

(40°F)

66 psig (Superheat to 50°F)

66 psig

(38°F)

tnaregirfeR egrahCcitatsomrehT

-POM igsp

yrotcaF

tseTriA

lanimoN

metsyS

06PCF 60 50

PCF 40 30

PZF 20 12

001PCV 100 90

AGV

* *

PCV 65 55

04PZV 40 30

a431

06PCJ 60 50

PCJ 40 30

A404

511PCS 115 105

PCS 75 65

PZS 45 35

205

511PCR 115 105

PCR 75 65

PZR 45 35

705 PZP 45 35

* s.noitidnocgnitarepolamronevobA

Figure 7

Table 3