Dwyer 1900 User Manual download pdf (Page 2)

INSTALLATION

1. Select a location that is free from excessive vibration,

corrosive atmosphere and where the ambient temperature

is within the limits for these switches.

2. Mount standard switches with the diaphragm in a vertical

plane and with switch lettering and nameplate in an upright

position. Some switches are position sensitive and may not

reset properly unless they are mounted with the diaphragm

vertical. (Special units can be furnished for other than verti-

cal mounting arrangements if required.)

3. Connect switch to source of pressure, vacuum or differ-

ential pressure. Metal tubing with 1/4˝ O.D. is recommend-

ed, but any tubing which will not restrict the air flow can be

used. Connect to the two 1/8˝ female NPT pressure ports as

noted below:

• Differential pressures - connect pipes or tubes from source

of greater pressure to high pressure port marked HI-PR and

from source of lower pressure to low pressure port marked

LO-PR.

• Pressure only (above atmospheric) - connect tube from

source of pressure to high pressure port. The low pressure

port is left open to atmosphere.

• Vacuum only (below atmospheric pressure) - connect tube

from source of vacuum to low pressure port. The high pres-

sure port is left open to atmosphere.

4. Electrical connections to the standard single pole, double

throw snap switch are provided by means of screw termi-

nals marked “common”, “norm open”, and “norm closed”.

The normally open contacts close and the normally closed

contacts open when pressure increases beyond the set

point.

5. Switch loads should not exceed the maximum specified

current rating of 15 amps resistive. Switch capabilities

decrease with high load inductance or rapid cycle rates.

Whenever an application involves either of these factors,

the user may find it desireable to limit the switched current

to 10 amps or less in the interest of prolonging switch life.

OPERATION

Pressure acting on the power diaphragm rotates the ampli-

fying lever, which in turn extends the range spring and

rotates the snap switch input lever. When the set point is

reached, the snap switcch is actuated and the electrical con-

tacts make or break.

ADJUSTMENT

To change the set point, proceed as follows:

A. Remove the snap-on cover from the conduit enclosure by

loosening its retaining screw and pulling firmly at its bottom

end. Turn the slotted adjustment screw at the top of range

spring housing clockwise to raise the set point pressure and

counter-clockwise to lower the set point.

B. The recommended procedure for calibrating or checking

calibration is to use a “T” assembly with three rubber tubing

leads, all as short as possible and the entire assembly offer-

ing minimum flow restriction. Run one lead to the pressure

switch, another to the manometer of known accuracy and

appropriate range, and apply pressure through the third

tube. Make final approach to the set point very slowly. Note

that manometer and pressure switch will have different

response times due to different internal volumes, lengths of

tubing, fluid drainage etc. Be certain the switch is checked in

the position it will assume in use, i.e. with diaphragm in a

vertical plane and switch lettering and nameplate in an

upright position.

C. For highly critical applicaitons it is a good idea to check

the set point adjustment and reset it as necessary once or

twice in the first few months of operation. This will compen-

sate for any change in initial tension which may occur in the

spring and diaphragm. For most applications this change will

not be significant and no resetting will be required.

MAINTENANCE

Moving parts of these switches are sealed in and are per-

manently tamper proof. The single adjustment is that of the

set point. Care should be taken to keep the switch reason-

ably dry and free from dust or dirt. No lubrication or unusual

precautions are required for normal use.

Ø1/4 [6.350]

TYP

GROUND

SCREW

15/16 TYP

[23.81]

1-5/8

TYP

[41.28]

4-3/4 [120.65]

5-1/2 [139.70]

1-5/8

[41.28]

CLEARANCE

FOR COVER

REMOVAL

5-1/8

[130.18]

1-1/8

[28.58]

17/32

[13.49]

1-1/16

[26.97]

2-5/32

[54.76]

6-3/32

[154.78]

5-13/16

[147.64]

VENT

25/32

[19.83]

1/2 FEMALE NPT

CONDUIT CONNECTION TYP 2 PLACES

1/4 FEMALE NPT POSITIVE PRESSURE

1/4 FEMALE NPT NEGATIVE PRESSURE

ATEX Compliant Housing

Base number 1911 with -CN suffix.

DWYER INSTRUMENTS, INC.

Phone: 219/879-8000 www.dwyer-inst.com

P.O. BOX 373 • MICHIGAN CITY, IN 46361, U.S.A. Fax: 219/872-9057 e-mail: [email protected]

E-56 ATEX:E-56atex 2/11/10 10:04 AM Page 2

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DWYER INSTRUMENTS, INC 1

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Dwyer 1900 User Manual Page 2

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