Dwyer A3000 - Manual (Page 4)

©Copyright 2009 Dwyer Instruments, Inc. Printed in U.S.A. 7/09 FR# 13-440202-04 Rev. 5
DWYER INSTRUMENTS, INC.
Phone: 219/879-8000 www.dwyer-inst.com
P.O. BOX 373 • MICHIGAN CITY, INDIANA 46361, U.S.A. Fax: 219/872-9057 e-mail: [email protected]
Bulletin B-33-A
Circuit style LL is used for manual reset applications which require
that contact be maintained following pressure decrease below the
set point. Load connections are made to the appropriate terminals
in Sections A and D. A normally open type manual reset switch
such as Dwyer
® Instruments, Inc. Part No. A-601 is connected to
the terminals in Sections B and C. The circuit must be “armed by
momentarily closing the switch while the black pointer is to the
right of the set point. From that point on, the circuit will latch on
pressure decrease below the set point and remain latched on
pressure increase until manually reset with the optional switch.
7. Dual Set Point Automatic and Manual Reset
Combinations: Circuit Style HH may be used with either set point
wired and operating as in paragraph 5 above and the other set
point wired and operating as in paragraph 6.
8. High Low Limit Control - Dual Set Point: Circuit Style HH
may be used to control fans, dampers, pumps, etc., between the
set points of a PHOTOHELIC
® Switch/Gage. To accomplish this,
use one set point relay to reset the other as shown in the wiring
diagram Fig. L. In this typical application, the load (for instance a
fan) would be connected to the N.C. contacts for the right set
point relay Section A (Fig. H). On pressure rise to the right set
point, its relay would pull in and hold even though pressure might
then fall below that set point . I the pressure continued to fall to
the left set point, its relay would automatically be DE-ENERGIZED,
return to its normal position and in so doing, open the holding coil
circuit from Section B (Fig. H). The right set point relay would thus
be reset and the cycle could repeat.
9. Dual Set Point Special Purpose Circuits: Circuit Style LL
may be used where manual reset following maintained contact on
pressure decrease to either set point is required. Circuit Styles HL
and LH are combination units. For special combinations of fea-
tures, special units, and detailed instructions regarding their use,
consult the factory.
10. Single Set Point PHOTOHELIC ® : The single set point PHO-
TOHELIC ® Switch/Gage is furnished with the right set point only.
Terminals in Sections A and B (Fig. H) are connected to this relay.
Circuit Style SRH is wired for automatic reset as in paragraph 5
above. Manual reset is accomplished by adding a normally closed
reset switch or push button to the circuit as described in para-
graph 6 above.
11. Single Set Point Special: Manual reset after actuation on
falling pressure can be obtained by using Circuit Style SRL.
Consult the factory for special units and detailed instructions
regarding their use.
12. Placing in Service: In normal operation each relay is de-ener-
gized when the pressure applied to the instrument is below its set
point. Special low-latching units will ordinarily have to be reset
before placing on the line in normal operation.
13. Failure Mode: The PHOTOHELIC ® Switch/Gage circuit design
provides certain protection in the event of a loss of pressure or
electrical power. In either case, both relays will de-energize, return-
ing to their normal “zero pressure” state. The exceptions to this are
models with center zero ranges. Because the relays on all standard
models are always energized when the indicating (black) pointer is
to the right of their respective set points, the relay action on loss of
pressure will depend on set point position, since either of them
could be located to the left of zero. As an example; if the left point-
er were set at -2 in. w.c. and negative pressure was -3 in. w.c., a
loss of that pressure would allow the black pointer to return to the
center and thus cause the low set point relay to energize.
If the LED should burn out, only the left-low relay will de-energize.
The right-high relay will react as if pressure were above its set point
and will remain energized even though pressure might be below
that setting. In this situation, only termination of electrical power will
allow the right-high relay to de-energize.
MAINTENANCE AND SERVICE
Dwyer Instruments, Inc. PHOTOHELIC
® Switch/Gages are preci-
sion instruments, expertly assembled and calibrated at the factory.
They require no lubrication or periodic servicing. If the interior is
protected from dust, dirt, corrosive gases and fluids, years of trou-
ble-free service may be expected. Zero adjustment should be
checked and reset occasionally to maintain accuracy. The PHO-
TOHELIC
® Switch/Gage is not field serviceable and should be
returned if repair is needed (field repair should not be attempted
and may void warranty). Be sure to include a brief description of
the problem plus any relevant application notes. Contact customer
service to receive a return goods authorization (RGA) number
before shipping.
RESET
NC
NO
RESET
NC
NO
HI LO
C NO NC NC NO C
C NO NC NC NO C
L 2 L 1
1/3 HP*
120 V
LOAD
RESET JUMPERS
*Note: For larger motors, use the Photohelic ®
Switch/Gage in a maintained contact, 120 Volt
Control or Push Button Circuit of the motor
Fig. L
CAUTION: Do not apply electrical current to ter-
minals in Sections B and C.
Manual Reset with Circuit HH
Fig. K
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