Dwyer Instruments 490A Operating Manual

Series 490A Hydronic Differential Pressure Manometer

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Specications - Installation and Operating Instructions

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Bulletin D-24A

Series 490A Hydronic Differential Pressure Manometer are versatile, hand-held,
battery operated manometers available in several basic ranges for positive or positive
differential pressure measurement and can tolerate most liquid media compatible
with 316LSS. A memory function allows storage of up to 40 readings for later recall
and a backlight provides auxiliary lighting for hard-to-see locations. Standard are a
hold feature and both visual and audible overpressure alarms. A new feature added

to the Series 490A is a eld adjustable damping, independent viewable high/low

pressure readings, and low range increased resolution. This allows the user to choose

the level of display averaging rate corresponding to the uctuation level common in

many applications. A 9 V alkaline battery is included that provides up to 100 hours of
operation.

MODEL CHART
Model English Range Metric Range Maximum Pressure Available Engineering Units
490A-1
490A-2
490A-3
490A-4
490A-5
490A-6

0 to 15 psi
0 to 30 psi
0 to 50 psi
0 to 100 psi
0 to 500 psi
0 to 200 psi

0 to 103.4 kPa
0 to 206.9 kPa
0 to 344.8 kPa
0 to 689.5 kPa
0 to 3448 kPa
0 to 1379 kPa

30 psi (2.7 bar)
60 psi (4.13 bar)
100 psi (6.89 bar)
200 psi (13.78 bar)
1000 psi (68.9 bar)
400 psi (27.57 bar)

psi, in w.c., in Hg, cm w.c., mm Hg, kPa, hPa, mbar, bar, oz/in
psi, in w.c., in Hg, cm w.c., mm Hg, kPa, hPa, mbar, bar, oz/in
psi, in w.c., in Hg, cm w.c., mm Hg, kPa, hPa, mbar, bar, oz/in
psi, in w.c., in Hg, cm w.c., mm Hg, kPa, hPa, mbar, bar, oz/in
psi, in w.c., in Hg, cm w.c., mm Hg, kPa, hPa, mbar, bar, oz/in
psi, in w.c., in Hg, cm w.c., mm Hg, kPa, hPa, mbar, bar, oz/in

SPECIFICATIONS

Service: Compatible gases & liquids.
Wetted Materials: 316 SS; -3V option: 316LSS, Buna-N, silicone, grease, PTFE,

brass 360, copper, reinforced acetal copolymer; -HKIT option: 316LSS, PTFE,
brass, copper.
Accuracy: ±0.5% FS from 60 to 78°F (15.6 to 25.6°C); ±1.5% FS from 32 to 60°F
and 78 to 104°F (0 to 15.6°C and 25.6 to 40°C).

Pressure Hysteresis: ±0.1% FS.
Pressure Limits: See chart

Temperature Limits: Operating: 0 to 140°F (-17.8 to 60°C); Process with -HKIT
option: -20 to 180°F (-29 to 82°C); Storage: -4 to 176°F (-20 to 80°C).

Display: 4-digit LCD (.425˝ H x .234˝ W digits).
Resolution: See chart.
Process Connections: Two 1/8˝ (3.18 mm) female NPT; -HKIT option: Two 1/4˝

male 45° are ttings.

Power Requirements: 9 V alkaline battery, installed non-functional, user
replaceable.

Weight: 14.1 oz (400 g); -HKIT option: 3.6 lb (1.63 kg).
Agency Approvals: CE.

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DWYER INSTRUMENTS, INC.

P.O. BOX 373 • MICHIGAN CITY, INDIANA 46360, U.S.A.

Phone: [phone]

Fax: [phone]

www.dwyer-inst.com

e-mail: [e-mail]

BATTERY INSTALLATION

The unit is shipped with a separate 9 volt alkaline battery which must be installed
before operation. Remove the two screws holding the bottom endcap in place and
remove the endcap. Connect the battery to the enclosed battery clip, making sure to
observe correct polarity. Be careful not to trap wires between the battery, case, or foam

pads which retain the battery. This could make it difcult to install the battery or remove

it later for replacement. Be sure that the rubber gasket is properly seated in the gasket

channel of the endcap and replace endcap. Note that the endcap will only t one way

because the holes are slightly off-center. Place the Z shaped wrist strap clip in one of
the screw recesses and replace the screws. Do not over tighten the screws. Attach
the wrist strap to the clip. Note: On –HKIT option 490A, the rubber boot will have to be
pulled back to have access to the battery compartment.

When battery replacement becomes necessary, use only a 9 volt alkaline type such as

a Duracell

®

MN 1604, Eveready® 522, or equivalent. Zinc-carbon types, often labeled
heavy-duty are not recommended because of the increased potential for leakage.
Alkaline batteries are also a better value because they last up to three times longer
in this device.

Low Battery Indicator

A weak battery can cause improper operation or inaccurate measurements. A
low battery indicator is provided on the display to show when the battery needs
replacement.

NOTICE

Although the unit might appear to function and indicate properly,

the accuracy of readings cannot be guaranteed when the LOW

BAT indicator is illuminated. Replace the battery with a new one. Do not leave an
exhausted battery in the unit due to potential leakage.

ON-OFF OPERATION

Press the ON/OFF button once to turn the unit on. Once on, press the ON/OFF button

for more than 5 seconds to turn the unit off. If the manometer is left on with no activity
for approximately 20 minutes, the unit will turn itself off to conserve the battery.

ZEROING PRESSURE READING

Potential inaccuracy due to temperature effects can be minimized by re-zeroing
immediately before use. To zero the display, vent both ports to the atmosphere so

no pressure is applied to either port. Press the ZERO/STORE button and ---- will be

momentarily displayed as zeroing occurs. Zeroing is not possible when the memory
mode is in use. It must be done before selecting that function.

If the unit is accidentally zeroed with pressure applied to one of the ports, the pressure
reading might display incorrectly. To correct, vent the pressure ports to atmosphere

and press the ZERO/STORE button to zero the unit.

BACKLIGHT

The Model 490A includes a display backlight to allow use in the dark or in poor lighting

conditions. Pressing the ON/OFF button toggles the backlight on or off. With the 490A
on, press the ON/OFF button to toggle the backlight on or off. The backlight will remain

lit for approximately 2 minutes after which it will turn itself off to conserve battery life.

AUTOMATIC RESOLUTION ADJUSTMENT

For all ranges, the series 490A will automatically move the decimal place one point to
the left when reading in the bottom 10% of its calibrated range. This allows the user
to gain a higher resolution reading for lower static or differential pressure readings.

SELECTING PRESSURE UNITS

Up to seven pressure units are available. The display will indicate the current

selection. To change to different units, use the UNITS/LOC button. Each press of the

button will cause an advance to the next choice. The selected units will remain in the
memory even when the power is shut off. This way, the user preferences will always
be displayed after the initial selection.

DISPLAY HOLD

In situations where a reading needs to be temporarily retained, the Model 490A
includes a display hold feature which freezes the current reading and holds it on the

display until it is cleared. To activate this operation, press the HOLD/MEMORY button

when the desired pressure is displayed. A HOLD indicator will appear on the display
to indicate that the reading shown is frozen. To return to normal operation, press the

HOLD/MEMORY button again. The HOLD indicator will disappear and the current

pressure will be shown.

MEMORY FUNCTION

A memory function is included in the Model 490A that allows users to store up to 40
pressure readings for later review or recording. The readings are stored in non-volatile
memory so they will be retained even if the unit is shut off or the battery is removed.

Storing Pressure Readings

To store a reading, press and hold the HOLD/MEMORY button until ST01 displayed.
Next, press the ZERO/STORE button to safe the current reading to the ST01 memory

location. A beep will sound indicating that the reading has been saved. As each
reading is saved, the memory location display will advance to the next number. To

resume pressure measurement, press the HOLD/MEMORY button again. Note that in

the memory mode, the display zero function is not available. To zero the display, exit

the memory mode and then press the ZERO/STORE button.

Viewing Stored Readings – Selecting a Location

To view the contents of the memory, press and hold the HOLD/MEMORY button
until RD01 is displayed. Next, press UNITS/LOC to view other memory locations. To
resume pressure measurement, press the HOLD/MEMORY button again.

Clearing Memory

To clear the contents of the memory, press and hold the HOLD/MEMORY button until
CLR is displayed. Next, press the ZERO/STORE button to clear all previously stored

readings. During this operation --- will be displayed. Once the memory is cleared, the
current pressure will be displayed.

Exiting Memory Mode

To exit the memory mode, press the HOLD/MEMORY button again and the unit will

return to normal operation.

PRESSURE CONNECTION

Measuring Single Pressure

To measure single positive pressure, connect the tubing to the port marked “High
Pressure” and vent the opposite port to the atmosphere.

Measuring Differential Pressure

To measure differential pressure, connect the higher positive pressure to the port
marked “High Pressure” and the lower positive pressure to the port marked “Low
Pressure”. The manometer will indicate the difference between the two.

Overpressure Alarm

A visual indicator and audible alarm are provided to alert the user that pressure has
exceeded the operating range of the unit. Exceeding the range will not damage it
or affect calibration as long as the maximum rated pressure is not exceeded. The
maximum pressure for all units is shown on the rear label and on page 1 of these
instructions.

CAUTION

Do not exceed the maximum rated pressure of the manometer.
Doing so will cause permanent damage to the sensor, may rupture

the housing, and/or cause personal injury.

DAMPENING FUNCTION

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The dampening feature allows users to enter a dampening number from 1 to 16
(default value = 2). Entering a larger number increases the amount of readings that
are averaged for each display update.

In order to access the dampening feature:

1. Press and hold the HOLD/MEMORY button for 7 seconds until DAMP is displayed.

2. Once DAMP is selected, a number is shown in the upper right portion of the
LCD, along with the current pressure reading. This number is the dampening

number. Adjust the number up by pressing the ZERO/STORE button or down by
pressing the UNITS/LOC button. The LCD update rate slows as the number

increases from 1 to 16. Therefore, for best results, choose the smallest number that
provides a stable pressure reading.

3. Once the pressure reading is stable, press the HOLD/MEMORY button to store the

dampening value.

INDEPENDENT HIGH OR LOW STATIC PRESSURE READINGS

This feature allows the user to select the pressure source to be shown on the LCD.

The selections are LOW (-), HIGH (+), or DIFF (HIGH – LOW) without disconnecting

any process connections.

OPTIONAL 3-WAY VALVE

For certain hydronic applications, it is benecial to measure the differential pressure

with the assistance of the optional attached 3-way valve. (See Figure A)

Begin with valve V1 open and valves V2 and V3 closed. (See Figure B) Slowly open
V2 and V3. Once the pressure has stabilized and is equal on the high and low side,
V1 can be closed and normal operation can proceed. To ensure proper pressures will

be detected by the 490A, use the bleed tting provided with this valve package. (See

Figure A) Before applying pressure to the process connections, turn V1 to the open

position and back off the bleed screw. Next apply pressure. After the owing liquid
is free of bubbles, retighten the bleed screw. Before taking the 490A ofine from the

process, open V1 then close V2 and V3.

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1. Press and hold the HOLD/MEMORY button for 9 seconds until SRCE is displayed,

then release.

2. Next, press the UNITS/LOC button to change the source to the one desired.

3. Press the ZERO/STORE, or ON/OFF or HOLD/MEMORY button to store the

source and resume pressure measurement. To return to any other pressure source
reading, please return to step 1. Note: The unit will default to DIFF when powered

on, to return to a differential pressure reading DIFF (HIGH-LOW) simply turn the

unit off and then back on.

BLEED

FITTING

Figure A

Figure B

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OPTIONAL HYDRONIC KIT (-HKIT Option)

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V2 V3

For hydronic valve balancing, Dwyer offers a full comprehensive kit of components to
be able read pressure across valves by tapping the pressure test ports on either side

of the valve or pump. The kit is comprised of two sets of 60˝ hoses with integral ball

valves, 3 pairs of various size gage piercing adapters, adapters for various installations
and a 3 way valve. The 3 way valve allows for isolation of pressure, equalization

between high /low and bleeding of lines to evacuate air or particulate.

(See Figure C). Please use following procedure as a guide when reading differential
pressure across a hydronic valve or pump.

1. Begin with valve V1 open and valves V2 and V3 closed. (See Figure D) Verify the
integral ball valves on the red and blue hoses are in the open position. Then slowly
open valves V2 and V3.

2. Once the pressure has stabilized and is equal on the high and low side, valve V1
can be closed and normal operation can proceed.

3. To ensure proper pressures will be detected by the 490A, use the bleed ttings \

for the high & low pressure sources on either side of the 3-valve manifold assembly.

(See Figure D) These can be adjusted with the use of the adjustable wrench in the
kit. PVC tubing has also been provided for connection to the bleed tting giving the

ability to control the bleeding into a container or reservoir. Once the lines are clear

of pockets of air, close each bleed tting with the wrench provided.

4. With valve V1 closed, bleed ttings tightened, valves V2 and V3 open, take the

necessary readings.

5. Once the readings are completed, it is best practice to close off the integral ball
valves in the red and blue hoses and leave valves V2 and V3 open. Then using

the bleed ttings once more, loosen and bleed out the pressurized uid or gases.
The PVC tubing can be used once more to control the bleeding of the uid into a

container or reservoir.

6. Maintaining the integral hose ball valves in the closed position, disconnect from the
pressure test ports.

490-X-HKIT Field Replacement Parts

Model Description

A-HKIT-AFIT

A-HKIT-BFIT
A-HKIT-HOSES

A-HKIT-500
A-HKIT-500XL
A-HKIT-510
UHH-STRAP
A-47X-BOOT
A-203

Please call our customer service for pricing and availability at 219-879-8000 or
email: [e-mail]

Adapter tting replacement kit including:
Straight adapter, 1/4˝ Male NPT X 1/4˝ - 45° are (2 per kit)
1/4˝ SAE 45° are seal cap and gasket (2 per kit)
90° union elbow, 1/4˝ - 45° are X 1/4˝ - 45° are (2 per kit)
90° male elbow, 1/4˝ male NPT X 1/4˝ - 45° are (2 per kit)
Bleed tting assembly (2 per kit)
60˝ blue charging hose with valve
60˝ red charging hose with valve
Piercing gauge adapter 1/8˝ DIA x 1-1/2˝ Length (2 per kit)
Piercing gauge adapter 1/8˝ DIA x 3˝ Length (2 per kit)
Piercing gauge adapter 1/16˝ x 1-1/2˝ Length (2 per kit)

Pipe or carry strap
Rubber boot

PVC tubing 1/4˝ OD x 1/8˝ ID. Ordered per foot

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Figure C

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MAINTENANCE/REPAIR

Upon nal installation of the Series 490A, no routine maintenance is required. The
Series 490A is not eld serviceable and should be returned if repair is needed. Field

repair should not be attempted and may void warranty.

This symbol indicates waste electrical products should not be disposed
of with household waste. Please recycle where facilities exist. Check with
your Local Authority or retailer for recycling advice.

WARRANTY/RETURN

Refer to “Terms and Conditions of Sale” in our catalog and on our website. Contact

customer service to receive a Return Goods Authorization Number before shipping the

product back for repair. Be sure to include a brief description of the problem plus any
additional application notes.

HIGH PRESSURE

Figure D

DWYER INSTRUMENTS, INC.

P.O. BOX 373 • MICHIGAN CITY, INDIANA 46360, U.S.A.

V1

LOW PRESSURE

BLEED FITTING

Printed in U.S.A. 1/19 FR# 443142-51 Rev. 5©Copyright 2019 Dwyer Instruments, Inc.

Phone: [phone]

Fax: [phone]

www.dwyer-inst.com

e-mail: [e-mail]